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Nitrogen removal and mass balance in newly-formed Myriophyllum aquaticum mesocosm during a single 28-day incubation with swine wastewater treatment
... Chinese scientists have also assessed the performance of watermilfoil species in removing nutrient in the treatment systems and found that watermilfoil species (e.g. M. aquaticum, M. spicatum, and M. verticillatum) can survive under high pollutant levels and remove large amounts of N in high N-loaded wastewater Liu et al., 2016Liu et al., , 2018bZhang et al., 2017b). Generally, macrophytes can assimilate large quantities of nutrients; the excess nutrients could make the aquatic plants exposed to a toxic stress. ...
... Although SAPs can assimilate N, bacterial nitrification/denitrification is the predominant nitrogen removal mechanism. Based on the previous reports, more than 60% of the total N removal contributed by the bacterial nitrification and denitrification (Liu et al., 2016). M. aquaticum improves simultaneous growth of nitrifying and denitrifying bacteria (Collins et al., 2004;Souza et al., 2013). ...
... M. spicatum was found to increase simultaneous growth of nitrifying and denitrifying organisms (Souza et al., 2013). Liu et al. (2016) found that the N removed via nitrification and denitrification processes could account for about 60% TN reduction in M. spicatum mesocosm. Putting all the mentioned mechanisms together tends to lead to a higher degradation efficiency of pollutants in microbe-plant combination than microbe or plant alone systems. ...
Watermilfoil (Myriophyllum) is one of the world's most troublesome invasive aquatic weeds. Although current management practices may inhibit its expansion, it also impacts not only the quality of water but habitat deterioration. Therefore, the need for developing highly efficient and low-cost biotechnologies with resource recovery into the agriculture field as a complementary management strategy cannot be overstated. Here, we reviewed the scientific/grey literature to offer readers a precise and panoramic view of the invasive watermilfoil ecology, regional problems, impacts, ecosystem services, and management. In this regard, an in-depth review aimed to assess the potential for reducing non-point source inorganic and organic pollutants using invasive watermilfoil, with the sustainable approaches, while offering other services and mitigating ecological trade-offs is presented. Global distributions, growth, and current progress on the management and utilization of invasive watermilfoil biomass are summarized to develop the aim, which is to convey challenges during the implementation of large-scale weed use. In short, pollutant assimilation in plant and bacterial communities linked to this weed considerably contribute to the reduction and degradation of pollutants from both natural and artificial systems. Although several considerations in recycling and reusing biomass need to be considered, the potential reuse of the harvested material for livestock feed, compost and direct use in farming systems offer an additional strategy to achieve sustainable ecosystem restoration. Further research and development may focus on a more detailed economic modeling approach that integrates the costs (worker's wage, harvesting, transportation, and energy consumption), legal and regulatory barriers, health risks and ecosystem service benefits (biodiversity improvement, and pollutant removal) to holistically evaluate the economic, environmental, and societal value of reusing and recycling this waste material.
... However, E. crassipes has been found to be an exotic species without natural enemies, which will likely deteriorate the ecosystems in the long term [25]. On the contrary, the risks of M. aquaticum spreading into other ecosystems could be manageable [26,27]. ...
... Inspired by previous studies [27,42], a laboratory-scale surface flow CW (LSCW) was designed aiming to determine (a) the best pollutant removal efficiencies by different treatments including E. crassipes, M. aquaticum, and PFs; (b) the optimal operational conditions for this LSCW; and (c) the closest match of removal results with the simulations of kinetic models. The simulation results showed that pollutant removal was best simulated with the Monod kinetics model combined with the plug flow pattern. ...
... The results collectively indicated that M. aquaticum planted in the LSCW was a better macrophyte for removing these pollutants from wastewater. The mechanism of pollutant removal may be attributed to plant uptake for growth and proliferation as reported in other studies [27,42,53]. For instance, mass balance analyses in these studies showed that M. aquaticum can uptake 1.06-1.44 ...
Water pollution caused by various eutrophic nutrients such as nitrogen (N) and phosphorus (P), such as outbreaks of eutrophication in rivers and lakes, has become a serious environmental problem in China. Such problems have spurred extensive studies aiming at finding environmentally friendly solutions. Various constructed wetlands (CWs), planted with different macrophytes, have been considered as environmentally safe technologies to treat various wastewaters for several decades. Due to their low energy and operational requirements, CWs are promising alternative solutions to water eutrophication problems. Within the CWs, macrophytes, sediments, and the microbial community are indispensable constituents of such an ecosystem. In this study, a laboratory-scale surface flow CW (LSCW) was constructed to investigate the effects of two different plants, Eichhornia (E.) crassipes (Mart.) Solms and Myriophyllum (M.) aquaticum, on the removal of eutrophic N and P. The results showed that both plants could significantly reduce these nutrients, especially ammonium (NH4+), and LSCW planted with M. aquaticum performed better (82.1% NH4+ removal) than that with E. crassipes (66.4% NH4+ removal). A Monod model with a plug flow pattern was used to simulate the relationship of influent and effluent concentrations with the kinetic parameters of this LSCW. Based on the model, a pilot-scale surface flow CW (PSCW) was designed, aiming to further enhance N and P removal. The treatment with M. aquaticum and polyethylene materials showed the best removal efficiency on NH4+ as well as on total nitrogen and phosphorus. In general, the enlarged PSCW can be a promising solution to the eutrophication problems occurring in aquatic environments.
... Herein, we hypothesize that selected wetland plants might have greater nutrient recovery potential if they could tolerate high-concentration swine wastewater. We have previously demonstrated that M. aquaticum is able to tolerate high-strength swine wastewater (> 200 mg N L −1 ) and has high nutrient uptake capacity from swine wastewater under lab and field conditions (Liu et al., 2016a;Luo et al., 2017;Zhang et al., 2017b). Therefore, it is considered appropriate to investigate the use of M. aquaticum as the wetland plant in CWs system for N recovery from swine wastewater under sustainable plant harvesting management. ...
... The freeze-dried sediment was prepared for TN analysis according to the National Standard Methods of China (GB7173-87). Plant samples were dried, ground, and then digested with hydrogen peroxide and sulfuric acid before the final determination of TN (Liu et al., 2016a). Potential nitrification and denitrification rates and abundance of functional genes including ammonia-oxidizing archaea (AOA) ammonia monooxygenase α-subunit A (amoA), ammonia-oxidizing bacteria (AOB) amoA, narG, nirK, nirS, and nosZ genes of the fresh sediments were analyzed according to methods described in our previous studies (Li et al., 2018;Zhang et al., 2017a). ...
... Therefore, the ammonia volatilization mass could be neglected in terms of N removal in the SFCWs. In addition, our previous study indicated that TN removed via ammonia volatilization from M. aquaticum mesocosm CWs accounted for < 4% of the TN removal mass (Liu et al., 2016a). Poach et al. (2002) also observed ammonia volatilization was responsible for 7-16% of the N load during summer in continuous-marsh systems treating swine wastewater. ...
Pilot-scale three-stage surface flow constructed wetlands (SFCWs) planted with Myriophyllum aquaticum were constructed to study the organics removal performance from lagoon-pretreated swine wastewater. The removal performance of organics in the SFCWs was evaluated using deterministic and probabilistic methods and the results were consistent. The SFCWs achieved a relatively high removal efficiency (79.0-82.7%) for a wide influent COD concentration range (456-1010 mg L-1). No significant difference (p > 0.05) of COD removal efficiency and first-order removal rate constant among the various strengths of influent suggested that the present loading rates (2.74-6.06 g m-2 d-1) have not yet reached the maximum removal capacity of the SFCWs. The mean emission fluxes of methane from the SFCW units fed with different strengths of wastewater were 25-1210 mg m-2 d-1. A significantly positive correlation (p < 0.01) between methane emission fluxes and COD loading rates indicated that the anaerobic digestion of organics was an important process for organics removal in the SFCWs. No significant organics accumulation in the sediment over time suggested that plant harvest could be in favor of reducing the organics accumulation in the substrate and should be considered important during management of constructed wetlands.
... Evidence suggests that algae can quickly and efficiently remove dissolved nitrogen, typically in either the form of ammonia or nitrate, from an aqueous system under a variety of conditions [4][5][6][7][8]. Complete nitrogen removal is often reported in algae-based wastewater treatment systems [9][10][11][12]; however nitrogen budgets of these systems are rarely able to attribute 100% of the nitrogen removed from the liquid portion of a system to biomass growth, even in axenic conditions [13][14][15][16][17][18][19]. Coupling algal growth with the treatment of waste streams has been studied but very few have evaluated the nitrogen budget of this system [20]. ...
... While the production of nitrous oxide (N 2 O) and nitric oxide (NO) is only rarely reported, some studies have shown that this pathway of nitrogen conversion is possible in wastewater treatment [24]. Ammonia oxidizing bacteria/archaea (AOB/AOA), nitrite oxidizing bacteria (NOB), Anammox, and denitrifying bacteria have all been found to play an important role in nitrogen removal in wastewater treatment systems [14,16,21,25]. The sorption of ammonia on to particulates within engineered system is frequently observed in phytoremediation systems where soil or gravel is used as a medium for rooting plants but is also applicable to any system with particulate matter that could act as a sorbent [14,16,25]. ...
... Ammonia oxidizing bacteria/archaea (AOB/AOA), nitrite oxidizing bacteria (NOB), Anammox, and denitrifying bacteria have all been found to play an important role in nitrogen removal in wastewater treatment systems [14,16,21,25]. The sorption of ammonia on to particulates within engineered system is frequently observed in phytoremediation systems where soil or gravel is used as a medium for rooting plants but is also applicable to any system with particulate matter that could act as a sorbent [14,16,25]. The nitrogen transformation pathways introduced here are a representative but not exhaustive list of the possible nitrogen conversions that could occur in an engineered biological wastewater treatment system. ...
Nitrogen was tracked though an algae-based landfill leachate remediation system. This system was designed to remove nutrients from the liquid waste via nitrogen assimilation into new algae biomass. While the nitrogen removal pathway of bio-assimilation was present, it was not the only nitrogen removal pathway in the treatment system. Weekly measurements of the dissolved inorganic nitrogen (ammonia-N, nitrate-N, and nitrite-N) and the nitrogen content of the biomass were used to track nitrogen transformation pathways during this yearlong study. During a major part of the study (83.4% of the observed weeks), all nitrogen could not be accounted for in the dissolved inorganic nitrogen or biomass portions of the system. It is hypothesized that some of the unaccounted-for nitrogen was lost due to volatilization of gaseous nitrogen species. Based upon characteristic distribution of measured dissolved inorganic nitrogen and the nitrogen content of the biomass for each week and prior metagenomic analysis of the microbial community in the treatment system, we have postulated potential scenarios of the fate of nitrogen in this algae-based wastewater treatment system. Further research is needed to identify all pathways of nitrogen conversion in algae-based wastewater remediation systems and verify our proposed scenarios.
... Each water sample was divided into two parts, with one part being filtered through the 0.45 µm membrane for determination of NH + 4 -N and NO − 3 -N and the other part being used for direct determination of TN and COD. The concentrations of NH + 4 -N and NO − 3 -N in the water samples were analyzed using a fully automated flow-injection system (AA3, SEAL, Norderstedt), while TN and COD were quantified using the alkaline potassium persulfate digestion-UV spectrophotometric method and potassium dichromate titration, respectively [21]. Other forms of nitrogen in the water samples were calculated by subtracting the concentrations of NH + 4 -N and NO − 3 -N from the TN concentration [22]. ...
... Surface sediment samples (0-5 cm depth) were collected and homogenized using a cylindrical stainless auger (diameter: 2 cm) from various sampling points within the same Water 2024, 16, 308 4 of 14 system on days 30, 60, and 90 during the experimental period. After the extraction of fresh sediments with a 0.5 M K 2 SO 4 solution, the SOC and dissolved organic carbon (DOC) contents in the sediments were determined using the previously described methods [9,21]. ...
This study designed surface flow constructed wetlands (SFCWs) with Myriophyllum aquaticum (M. aquaticum) to evaluate how different influent C/N ratios (0:1 (C0N), 5:1 (C5N), 10:1 (C10N), and 15:1 (C15N)) affect pollutant removal, greenhouse gas (GHG) emissions, and microbial communities. The results showed that effluent ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), and total nitrogen (TN) concentrations decreased, but effluent chemical oxygen demand (COD) concentration increased with increasing influent C/N ratios. The highest removal rates of TN (73.17%) and COD (74.56%) were observed with C5N. Regarding GHG emissions, a few changes in CO2 fluxes were caused by the influent C/N ratio, whereas CH4 fluxes obviously increased with the increasing influent C/N ratio. The highest N2O emission occurred with C0N (211.03 ± 44.38 mg-N·m−2·h−1), decreasing significantly with higher C/N ratios. High-throughput sequencing revealed that different influent C/N ratios directly influenced the microbial distribution and composition related to CH4 and N2O metabolism in SFCWs. The highest abundance (46.24%) of denitrifying bacteria (DNB) was observed with C5N, which helped to achieve efficient nitrogen removal with a simultaneous reduction in N2O emissions. Methanogen abundance rose with higher C/N ratios, whereas methanotrophs peaked under C5N and C10N conditions. Additionally, the random forest model identified influent C/N ratio and Rhodopseudomonas as primary factors influencing CH4 and N2O emissions, respectively. This highlights the importance of the influent C/N ratio in regulating both pollutant removal and GHG emissions in constructed wetlands.
... Constructed wetlands (CWs) are recognized as the dominant technology for improving water the quality of polluted waters, due to their low cost, high efficiency and relatively simply management (Zhang et al., 2009;Piwpuan et al., 2014). Aquatic macrophytes, as the main body of CWs, play an important role in bioremediation through nutrient assimilation and promoting water purification by microbial community functions and structures (Shelef et al., 2013;Li et al., 2015;Liu et al., 2016Liu et al., , 2018. ...
... Thus, CWs planted with M. aquaticum can be used to treat a variety of wastewaters, highly efficiently removing N Zhang et al., 2016;Liu et al., 2016Liu et al., , 2018. Our findings may help develop management strategies for CWs-for example, by adjusting NH 4 + concentrations in influent wastewater or by adjusting the loading rate according to the treatment requirements. ...
Myriophyllum aquaticum (M. aquaticum) can be used in constructed wetlands (CWs) to effectively purify swine wastewater with high-ammonia nitrogen (NH3–N and NH4⁺-N) concentrations. However, the understanding of its tolerance mechanism to ammonia nitrogen is limited. The physiological response and tolerance mechanism of M. aquaticum to a wide range of NH4⁺ concentrations (0–35 mM) were investigated in the present study. The results indicated that M. aquaticum can tolerate NH4⁺ concentrations of up to 30 mM for 21 days and grow well with high nutrient (N, P) uptake. A suitable concentration of NH4⁺ for a better growth of M. aquaticum was 0.5–20 mM. The free NH4⁺ content was no obviously increase at NH4⁺ concentration below 15 mM, indicated there was no obviously ammonium accumulation. Exogenous NH4⁺ inhibited K⁺ absorption and improved Ca²⁺ absorption, indicating mineral cation could mediate NH4⁺ homeostasis under NH4⁺ stress. Moreover, comparison with those in the control group, the activities of glutamine synthetase (GS), glutamate synthetase (GOGAT) in M. aquaticum increased by 52.7%−115% at 1–20 mM NH4⁺, and superoxide dismutase (SOD) increased by 29.2–143% at 1–35 mM NH4⁺. This indicated that the high NH4⁺ tolerance of M. aquaticum was mainly due to the balance of free NH4⁺ content in tissues, as well as improved nitrogen metabolism and antioxidant system. This could be attributed to the role of the GS-GOGAT cycle and SOD. In conclusion, M. aquaticum, which tolerates high NH4⁺ concentration and has a high N uptake ability, can be used as a good candidate specie to help develop more efficient management strategies for treating high-NH4⁺ wastewater in CW systems.
... In addition, some research has shown that, in effluents with nitrogen concentrations not higher than 20 mg L −1 , M. aquaticum can both absorb nitrogen and phosphorus from sediments through their roots and utilize nutrients from the water through their stems and leaves. Nitrogen and phosphorus are absorbed and used for plant growth, while some organic compounds and heavy metals that are toxic to M. aquaticum may be degraded or immobilized in their bodies [4][5][6]. This macrophyte can store a variety of essential nutrients at high concentrations within the tissues, such as proteins with a relatively balanced amino acid composition, various trace elements, and vitamins and essential fatty acids. ...
... This macrophyte can store a variety of essential nutrients at high concentrations within the tissues, such as proteins with a relatively balanced amino acid composition, various trace elements, and vitamins and essential fatty acids. Therefore, these properties make it an ideal food for farming livestock [4][5][6][7]. ...
Myriophyllum aquaticum (M. aquaticum) is a commonly used aquatic macrophyte for water purification and could be utilized as animal food. However, the high water content of M. aquaticum makes it difficult for long-term preservation, which leads to challenges as an ideal animal feed ingredient. The storage of Silage for long periods may be a proper method to solve the problem. In the present paper, we assess the effects of lactic acid bacteria Lactobacillus buchneri (LB), Lactobacillus plantarum (LP), or their combination on fermentation and microbial communities during the ensiling of M. aquaticum silage. The results show that the LP-treated silage displays a higher lactic acid concentration than that in the control silage. Both LB and LP increased the abundance of Lactobacillus, but decreased the abundance of Serratia and Prevotella_9 in M. aquaticum silage after 60 days of ensiling. Both LB and LP increased the diversity and richness of fungi. Therefore, the inoculation of LP improved silage fermentation during ensiling. These results show that the inoculation of lactic acid bacteria improves the fermentation quality of M. aquaticum silage, which makes it possible for the application of M. aquaticum to animal forage in the future.
... Much research in the field of agriculture and environmental protection fields has focused on identifying plants with a strong nutrient purification ability that can be conveniently harvested and recycled for the treatment of LW as well as overcoming the problem of "ammonia toxicity" and the seasonal restrictions of plants. Spirodela polyrhiza can remove 89.4% and 83.7% of TP and TN from a 6% swine wastewater lagoon in 8 weeks, respectively, but the plants need to be harvested twice a week [45]. Lemna sp. ...
... In a simulated experiment, water hyacinth removed 63.74% of TN and 19.05% of TP from 10% swine wastewater in 21 days [46]. Myriophyllum aquaticum removed more than 97% of NH 4 + -N and 94% of TN from swine wastewater in 28 days [45]. However, water hyacinth and Myriophyllum aquaticum are invasive plants in China that lead to the local extinction of macrophytes and decrease the native aquatic macrophyte diversity [48,49]. ...
The rapid growth of the livestock and poultry industries has resulted in the production of a large amount of wastewater, and the treatment of this wastewater requires sustainable and environmentally friendly approaches such as phytoremediation. A substrate-free floating wetland planted with water dropwort (Oenanthe javanica), a common vegetable in Southeast China, was constructed to purify a lagoon with anaerobically and aerobically treated swine wastewater in Suqian, China. The average removal rates of total nitrogen, ammonium nitrogen, nitrite nitrogen, and chemical oxygen demand were 79.96%, 95.04%, 86.14%, and 59.91%, respectively, after 40 days of treatment. A total of 98.18 g∙m−2 nitrogen and 19.84 g∙m−2 phosphorus were absorbed into plants per harvest through the rapid growth of water dropwort biomass, and the nitrogen accumulation ability was similar to that observed of other plants, such as water hyacinth. In addition, the edible part of water dropwort was shown to comply with the Chinese National Food Sanitation Standards and be safe for human consumption. Its low soluble sugar content also makes it a suitable addition to the daily diet. Overall, substrate-free floating constructed wetlands planted with water dropwort could be more widely used for livestock wastewater purification and could be integrated with plant–livestock production in China because of its high removal efficiency and recycling utilization of water dropwort biomass.
... Various hydrophytes with different species have been utilized for the management of LW, for example, Spirodela polyrhiza, Lemna minor, Polygonum hydropiper, Lemna gibba, Eichhornia crassipes, Pistia stratiotes, Scenedesmus quadricauda, Typha latifolia, Phragmites australis, Limnobium laevigatum, Chlamydomonas reinhardtii, Myriophyllum aquaticum, Coelastrella sp., Lemna aequinoctialis Ekperusi et al., 2019;Hu et al., 2019;Kumari and Tripathi, 2015;Liu et al., 2016;Luo et al., 2016;Mishra and Tripathi, 2009;Sudiarto et al., 2019;Zheng et al., 2013;Zhou et al., 2018). Researches on phytoremediation of LW are rapidly developing, and this review would like to furnish a comprehensive catalogue of available information on this interesting topic. ...
... Meanwhile, nitrification and denitrification should be the most essential methods for TN removal than other microbial processes. As indicated via Liu et al. (2016) that 55-65% of nitrogen can be removed by nitrification and denitrification from LW, and the increased NO 3 − -N in the effluent was constituted as one of the evidence (Luo et al., 2018b). Finally, a large amount of nitrogen was adsorbed by the sediment of CWs at initial, but with the extension of purification, the saturation of adsorption, and blockage caused by SS, the removal efficiency of nitrogen by matrix gradually reduced (Luo et al., 2018b). ...
Phytoremediation, the application of vegetation and microorganisms for recovery of nutrients and decontamination of the environment, has emerged as a low-cost, eco-friendly, and sustainable approach compared to traditional biological and physico-chemical processes. Livestock wastewater is one of the most severe pollution sources to the environment and water resources. When properly handled, livestock wastewater could be an important alternative water resource in water-scarce regions. This review discussed the characteristics and hazards of livestock wastewater and available methods for the treatment. Meanwhile, the current status of investigations on phytoremediation of livestock wastewater via different hydrophyte systems such as microalgae, duckweed, water hyacinth, and other hydrophytes is reviewed, and the utilization of hydrophytes after management also discussed. Furthermore, challenges of phytotechnologies for livestock wastewater management and the possible settle perspectives are also emphasized. At last, gene-editing technology such as CRISPR systems should be focused in the future.
... We previously found high nitrification and denitrification rates in SFCWs vegetated with Myriophyllum (M.) aquaticum, which facilitate the rapid removal of N from high-strength NH 4 + -N wastewater ( Liu et al., 2016;Luo et al., 2018). However, whether the selection of optimal influent C:N ratios may further improve N removal from SFCWs remains unclear. ...
... Each sediment sample was collected and homogenized from different sampling points within same system using a cylindrical stainless auger (diameter: 2 cm). Fresh sediments were extracted using 0.5 M K 2 SO 4 solution to measure their NH 4 + -N, NO 3 − -N, and dissolved organic carbon (DOC) content by previously described methods ( Liu et al., 2016;Shen et al., 2014). The freeze-dried sediment samples were prepared for soil TN analysis in accordance with the National Standard Methods of China (GB 7173-87). ...
Exploring optimal C:N ratio is necessary to ensure balanced microbial nitrification and denitrification in constructed wetlands (CWs), which has become an important management practice for more efficient nitrogen removal and sustainability of CWs. Surface flow constructed wetlands (SFCWs) vegetated with Myriophyllum aquaticum were designed to investigate the effects of five different influent C:N ratios (0:1, 2.5:1, 5:1, 10:1, and 15:1) on nitrogen removal performance and microbial communities over a 175-day experimental period. Compared to the influent C:N ratios of 0:1, higher NH4+-N, NO3--N, and total nitrogen (TN) removal efficiencies and lower NO3--N accumulation were observed at influent C:N ratios higher than 5:1. In addition, the highest TN removal efficiency (70.4%) and the lowest nitrous oxide emission flux (4.12 mg m-2 d-1) were obtained at the influent C:N ratio of 5:1. High-throughput sequencing revealed that influent C:N ratios altered the distribution and composition of microbial communities in the sediment, which resulted in a dynamic interplay between N-transforming functional microbes and NH4+-N and NO3--N removal. In particular, the dominant denitrifiers, including Desulfovibrio, Zoogloea, and Dechloromonas, were more abundant in the sediment with an influent C:N ratio of 5:1, which contributed to the high N removal rate. These findings may be used to screen for an optimum influent C:N ratio to maintain the sustainability of SFCWs with higher N removal efficiency.
... In CWs, macrophytes play important roles in nitrogen removal since macrophytes can absorb and assimilate the nitrogen nutrients to constitute amino acids and proteins in tissues [8,9]. Meanwhile, as economic plant species, many wetlands plant species show rapid growth, produce a large amount of aboveground biomass, and own the potential to be used as a source of feed and biomaterials as well as bioenergy [4,10]. However, ammonium of high concentrations in wastewaters were usually toxic to most macrophytes, which influenced the treatment effects of CWs [4,6]. ...
... The introduction of C4-like traits into C3 plants, such as wheat and rice, therefore, has been a favored approach to improve the photosynthetic efficiency of C3 plants and enhance crop yield [21]. Additionally, studies have shown that M. aquaticum is easy to harvest, and its high growth rate makes it a suitable candidate used in CWs for nitrogen-rich wastewater treatment [7,9,10]. Compared with other aquatic plants such as Canna indica, Hydrocotyle verticillata, and economic crops such as corn, rice, and soybeans, M. aquaticum had a much higher crude protein and key amino acids content [4,13,23], which indicated that M. aquaticum could be used as a suitable forage for livestock. ...
Massively input and accumulated ammonium is one of the main causes of eutrophication in aquatic ecosystems, which severely deteriorates water quality. Previous studies showed that one of the commonly used macrophytes, Myriophyllum aquaticum, was capable of not only withstanding ammonium of high concentration, but also efficiently assimilating extracellular ammonium to constitutive amino acids and proteins. However, the genetic mechanism regulating such efficient nitrogen metabolism in M. aquaticum is still poorly understood. Therefore, RNA-based analysis was performed in this study to understand the ammonium regulatory mechanism in M. aquaticum in response to various concentrations of ammonium. A total of 7721 genes were differentially expressed, of which those related to nitrogen-transport, assimilation, and remobilization were highly-regulated in response to various concentrations of ammonium. We have also identified transcription factors and protein kinases that were rapidly induced in response to ammonium, which suggests their involvement in ammonium-mediated signalling. Meanwhile, secondary metabolism including phenolics and anthocyanins biosynthesis was also activated in response to various concentrations of ammonium, especially at high ammonium concentrations. These results proposed a complex physiological and genetic regulation network related to nitrogen, carbohydrate, transcription factors, and secondary metabolism for nitrogen use efficiency in M. aquaticum.
... Wolffia arrhiza exhibited higher tolerance to NH 4 + up to 4 mM 23 . However, Myriophyllum aquaticum, an important wetland plant species for biomass accumulation and nutrient removal 18,24 , is entirely different from Myriophyllum spicatum, which is used in ecological engineering for aquatic ecosystem restoration and is sensitive to NH 4 + 25 . M. aquaticum shows strong potential to resist NH 4 + toxicity since it can grow in constructed wetlands with high concentrations of NH 4 + (up to 26 mM) [24][25][26] . ...
... However, Myriophyllum aquaticum, an important wetland plant species for biomass accumulation and nutrient removal 18,24 , is entirely different from Myriophyllum spicatum, which is used in ecological engineering for aquatic ecosystem restoration and is sensitive to NH 4 + 25 . M. aquaticum shows strong potential to resist NH 4 + toxicity since it can grow in constructed wetlands with high concentrations of NH 4 + (up to 26 mM) [24][25][26] . For coping with NH 4 + toxicity, M. aquaticum has a specialized pathway that can achieve detoxification, and this pathway is highly distinct from that in sensitive species 5 . ...
Plants easily experience ammonia (NH4+) toxicity, especially aquatic plants. However, a unique wetland plant species, Myriophyllum aquaticum, can survive in livestock wastewater with more than 26 mM NH4+. In this study, the mechanisms of the M. aquaticum response to NH4+ toxicity were analysed with RNA-seq. Preliminary analysis of enzyme activities indicated that key enzymes involved in nitrogen metabolism were activated to assimilate toxic NH4+ into amino acids and proteins. In response to photosystem damage, M. aquaticum seemed to remobilize starch and cellulose for greater carbon and energy supplies to resist NH4+ toxicity. Antioxidative enzyme activity and the secondary metabolite content were significantly elevated for reactive oxygen species removal. Transcriptomic analyses also revealed that genes involved in diverse functions (e.g., nitrogen, carbon and secondary metabolisms) were highly responsive to NH4+ stress. These results suggested that a complex physiological and genetic regulatory network in M. aquaticum contributes to its NH4+ tolerance.
... These findings align with the studies by Thongtha et al. [41] and Su et al. [42]. However, the purification effect of different mosaic systems on water bodies exhibited some variations, likely due to the response of microorganisms in the water body to different plant combinations [43]. Microbial nitrification and denitrification reactions represent the main denitrification pathways within the three microcosms studied [44,45]. ...
Aquatic plants play a crucial role in the sustainable management of eutrophic water bodies, serving as a valuable tool for water purification. However, the effectiveness of using aquatic plants for improving water quality is influenced by landscape considerations. In practical applications, challenges arise concerning low purification efficiency and compromised aesthetic appeal when utilizing plants for water purification. To address these issues, this study aimed to examine the impact of aquatic plants on the purification of simulated landscape water bodies, specifically focusing on the effectiveness of the mosaic system of submerged–emerged plants in remediating eutrophic water bodies. Our findings indicated that individual aquatic plants exhibited limited efficacy in pollutant (total nitrogen, total phosphorus, ammonia nitrogen, and chemical oxygen demand) removal. However, when combined in appropriate proportions, submerged plants could enhance species growth and improve the purification efficiency of polluted water bodies. Notably, the mosaic system of submerged–emerged plants neither significantly promoted nor inhibited the growth of each other, but it effectively removed pollutants from the simulated water bodies and inhibited turbidity increase. The comprehensive evaluation ranked the purification capacity as Canna indica-submerged plants combination (C + S) > Thalia dealbata-submerged plants combination (T + S) > Iris pseudacorus-submerged plants combination (I + S) > Lythrum salicaria-submerged plants combination (L + S). Both C + S and T + S configurations effectively mitigated the rise of water turbidity and offered appealing landscape benefits, making them viable options for practical applications in urban landscape water bodies. Our study highlights that a submerged–emerged mosaic combination is a means of water purification that combines landscape aesthetics and purification efficiency.
... Myriophyllum aquaticum is an aquatic angiosperm distributed worldwide with rapid growth and large biomass (Li et al., 2020) and is often planted as a remediation plant to effectively reduce nonpoint pollutants (e.g., nitrogen and phosphorous) from river channels or drainage ditches (Luo et al., 2020;Wersal & Madsen, 2011). Previous studies have found that M. aquaticum can tolerate highstrength swine wastewater with an NH 4 + -N concentration greater than 400 mg·L −1 (Liu et al., 2016), and reduce the toxicity of NH 4 + -N in tissues by converting ammonium nitrogen into internal nitrogen in the form of nitrates (Zhou et al., 2017). Meritorious plants of M. aquaticum with relatively large biomasses after eutrophication reduction deserve proper disposal. ...
To clarify the sorption mechanism and removal efficiency of PAHs by waste biomass-based magnetic sorbents, the sorption performance of magnetic Myriophyllum aquaticum biomass (MMaB) for PAHs was studied. The structural characteristics and magnetic properties of MMaB were measured by FTIR, SEM–EDS, XRD and VSM. Batch experiments were carried out to evaluate the effects of contact time, initial concentration and properties of PAHs, pH, ionic strength and temperature on PAH sorption. The results showed that the sorption of seven PAHs achieved equilibrium at approximately 4–6 h, which fit well to the pseudo-second-order kinetic model. The isotherms followed the Freundlich model and linear model well, indicating that the sorption process was controlled by chemisorption. The distribution parameter (Kd) values were 91.3, 563.7, 1010.5, 2917.8, 2706.6, 9046.8 and 15969.0 L·kg⁻¹ for naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, pyrene, and fluoranthene on MMaB, respectively, following the order of their hydrophobicity (e.g., Kow). A positive correlation was obtained: logKd = 0.8091logKow + 1.7034. Water chemical properties such as pH and ionic strength had no obvious effect on PAH removal. The spontaneity, feasibility and exothermic properties of PAH removal by MMaB were explained from thermodynamic point of view. The as-prepared MMaB sorbent underwent four consecutive sorption cycles and had good cycling performance. These studies indicate that MMaB has great potential as an easily-prepared, easy-to-operate and efficient biosorbent to remove PAHs from wastewater.
... However, it has been difficult to reach ideal efficiency in pollutant removal. TP and NH 3 -N removal efficiency in practical engineering applications has been less than 50% and 60%, respectively, due to magnification effects, geography, climate, seasons, and filler saturation (Reddy et al., 2001;Liu et al., 2016;Wang et al., 2018). It has been found that CWs that used Typha latifolia for RDS treatment had low TP and TN efficiencies of 11% and 18%, respectively (Saha et al., 2015). ...
Constructed wetlands (CWs) have been widely used in tailwater treatment. However, it is difficult to achieve considerable removal efficiency of nitrogen and phosphorus in tailwater solely by CWs-an efficient green wetland filler is also important. This study investigated 160 domestic sewage treatment facilities (DSTFs) in rural areas from two urban areas in Jiaxing for TP and NH3-N and found that TP and NH3-N concentrations in rural domestic sewage (RDS) in this plain river network are still high. Therefore, we selected a new synthetic filler (FA-SFe) to enhance nitrogen and phosphorus reduction, and we discuss the importance of filler in constructed wetlands. Experiments revealed the adsorption capacity of the new filler: the maximum adsorption amounts of TP and NH3-N reached 0.47 g m-2 d-1 and 0.91 g m-2 d-1, respectively. The application potential of FA-SFe was verified in actual wastewater treatment, with the removal rates of ammonia nitrogen and TP reaching 71.3% and 62.7%, respectively. This study provides a promising pathway for nitrogen and phosphorus removal from rural tailwaters.
... According to previous research, low phosphorus stress can impact photosynthesis, slow plant growth, and changes morphology, whereas a high phosphorus environment causes plant phosphorus poisoning and decreases agricultural product productivity and quality [13,29,30]. The results of influences of different phosphorus concentrations on M. aquaticum's growth rate in this study indicated that low phosphorus stress had a greater impact on the growth of M. aquaticum than high phosphorus stress, which was consist with previous studies showing that M. aquaticum preferred nutrient-rich conditions and high phosphorous treatment could significantly increase its branch number and length [31][32][33]. Moreover, previous studies also revealed that shoot porosity was higher in nutrient-rich substrate than in nutrient-low substrate, and the effect of low phosphorous stress was greater in the later period of the growing season of M. aquaticum [13,34]. ...
Through excellent absorption and transformation, the macrophyte Myriophyllum (M.) aquaticum can considerably remove phosphorus from wastewater. The results of changes in growth rate, chlorophyll content, and roots number and length showed that M. aquaticum could cope better with high phosphorus stress compared with low phosphorus stress. Transcriptome and differentially expressed genes (DEGs) analyses revealed that, when exposed to phosphorus stresses at various concentrations, the roots were more active than the leaves, with more DEGs regulated. M. aquaticum also showed different gene expression and pathway regulatory patterns when exposed to low phosphorus and high phosphorus stresses. M. aquaticum’s capacity to cope with phosphorus stress was maybe due to its improved ability to regulate metabolic pathways such as photosynthesis, oxidative stress reduction, phosphorus metabolism, signal transduction, secondary metabolites biosynthesis, and energy metabolism. In general, M. aquaticum has a complex and interconnected regulatory network that deals efficiently with phosphorus stress to varying degrees. This is the first time that the mechanisms of M. aquaticum in sustaining phosphorus stress have been fully examined at the transcriptome level using high-throughput sequencing analysis, which may indicate the direction of follow-up research and have some guiding value for its future applications.
... Hence, it is necessary to modify the system accordingly by diluting the nutrient concentration or using selected plant species that thrive in wastewaters with high nutrient concentrations [103]. Myriophyllum aquaticum was able to flourish in the presence of swine wastewater with high nutrient concentrations (nitrogen content >200 mg/L) both in controlled lab conditions and field conditions [227]. Myriophyllum aquaticum can convert NH 4 -N to NO 3 -N in its cell and assimilate it to enhance biomass production [102]. ...
Nutrient removal and recovery from nutrient-rich wastewater have recently gained significant attention because of their potential to contribute to sustainable development. Numerous treatment technologies have been implemented to tackle nutrient-rich wastewater, but high cost, low adaptability to varying organic loading, and undesirable effluent quality are a few factors that have significantly limited their applications. On the other hand, constructed wetlands (CWs) are robust, cost-effective processes with a high degree of nutrient removal and recovery. In this review, the role of various biotic and abiotic components that affect the performance of CWs has been discussed. It was found that vertical flow CWs were more efficient in removing total phosphorus (64.6 ± 30%), while horizontal flow CWs were efficient in removing the total nitrogen (67.6 ± 20%). Furthermore, the introduction of artificial aeration, external carbon sources, variation of plant species and substrate, and bioaugmentation significantly improved the performance of the CWs. Hybrid CWs have also been used to achieve enhanced total nitrogen removal and recovery (89%). However, phosphorus removal was not significantly affected by the hybridization of the CW-based systems. Hence, several recommendations have been suggested to enhance nutrient removal and recovery, such as incorporating hydrochar and oyster shells as substrate modifications, providing suitable pre-treatment, and others. This review circumscribes the different aspects of nitrogen and phosphorous recovery and removal from nutrient-rich wastewater treatment using CWs and may be instrumental in achieving a circular economy.
... Verdc is a perennial aquatic or emergent plant, widely distributed in tropical and subtropical regions . It is a promising phytoremediation agent that can absorb nutrients, heavy metals and organic pollutants in water with fast growth and strong environmental adaptability (Liu et al. 2016;Guo et al. 2019). This experiment was conducted to investigate the growth and physiological responses of M. aquaticum to individual and combined levels of CTC and OTC at different concentrations (1, 10, 50 mg/L) after 7 days (7 D) and 14 days (14 D). ...
As two typical tetracyclines, chlortetracycline (CTC) and oxytetracycline (OTC) coexist widely in water. In the experiment, Myriophyllum aquaticum (Vell.) Verdc was exposed to the orthogonal hydroponic environment with the concentrations of CTC and OTC at 1, 10, and 50 mg/L for 7 days (7 D) and 14 days (14 D). The results showed that the plant height, relative growth rates (RGR), and photosynthetic pigment contents of M. aquaticum decreased significantly after 14 D of CTC/ OTC, which was stronger than that after 7 D, and the toxicity of CTC was stronger than OTC. The combined toxicity of the two on the RGR and total chlorophyll content was mainly synergistic or additive after 7 D. After 14 D, the interaction changed to antagonism or addition, and the response of total chlorophyll content was more obvious than that of RGR. After 7 D of combined treatments, the malondialdehyde (MDA) content decreased significantly, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities responded to different combined concentrations, respectively, and CAT was the main protective enzyme of M. aquaticum . After 14 D of combined treatments, the hydrogen peroxide (H 2 O 2 ) content increased significantly, the MDA content increased first and then decreased, and POD was the main protective enzyme among the three antioxidant enzymes. Overall, this study provided the first insight into the single and combined toxicity of CTC and OTC on the growth and physiology of M. aquaticum at different time periods, revealing the reversal of the combined toxicity with time of exposure.
... Organic and N compounds are removed in CWs of the SSF type by a combination of adsorption, nitrification/denitrification, volatilization, and ionic exchange [3]. Nitrification and denitrification are considered essential mechanisms for N removal [1,37], having an efficiency of more than 60% [55]. According to Vidal et al. (2018) [3], denitrification is the most effective process to remove nitrogen in CWs, and the aerated and non-aerated treatments prior to CW in the experimental plant have been beneficial for these processes. ...
This study evaluates the depuration efficiency of a combined system consisting of lagoons (with aerated and non-aerated tanks) and CWs (with Typha latifolia L.) working at pilot scale for treating SW under two recirculation rates (RRs, 4:1 and 10:1) of the CW effluent. The combined system removed about 99% of the total suspended solids and organic matter, and from 80% to 95% of the total nitrogen at both tested RRs. The lagoon system was effective as a pre-treatment of SW, particularly for nitrogen removal. It is convenient to adopt the higher RR, since nitrogen removal can be increased by approximately 20%. The irrigation of the CWs with SW did not generally determine the phyto-toxic effects on Typha latifolia L., except at the start of the experiment and under the lower RR. Despite the limited spatial and temporal scale of this investigation, these results provide a starting point for the use of V-SSF CWs to treat livestock wastewater with a high pollution potential (such as SW).
... The gravel bed and calcite bed platform with a top width of 19 m and a total vertical thickness of 80 cm were added in the coastal zone around the deep purification area to strengthen the contact oxidation and adsorption function of water flow with the shore media ( Wang et al., 2015a ). (6) JID: JES [m7;March 26, 2021;19:18 ] ture period ( Liu et al., 2016 ;Luo et al., 2017 ). However, attention should be paid to the control of excessive spread and regular vegetation harvesting management of Myriophyllum aquaticum ( Chen, 2012 ;Kumwimba et al., 2020 ). ...
Jiaxing created a precedent using bypass riparian marshes to purify micro-polluted water sources in China. Pond-wetland complex with constructed root channel technology becomes a paradigm which can be analogized as “human-body wetland model” based on bionics or biomimetics. Heterogeneous plant-bed/ditch system with highly active land/water ecotone interfaces, especially meandering boundaries, breeds many biochemical reactions “living areas”. Optimization of hydraulic regulation promotes redox environment alternations and wetland treatment efficiency. Here we reported a series of upgrades and performances in Guanjinggang wetland after the Shijiuyang prototype. Morphological reform of plant-bed/ditch system played a vital role. Spatially root channel zone was main force of wetland purification, and temporally the treatment effect was higher in low-temperature seasons indicating non-temperature dependent mechanisms worked. Water pollution comprehensive index improved steadily from IV to III, and comprehensive pollution load was reduced by ca. 40%–60%. Comprehensive evaluation function value further showed the gradients purification effect of the upgraded wetland. Ecological wetlands ameliorated source water quality, and reduced drinking water treatment reagents, thereby bringing about economic benefits. Through wetlands operation, people can see how the micro-polluted surface water becomes clear and clean, so promoting a significant social benefit. As a viable component of urban green space, wetlands could beautify regional eco-environment, freshen the air, increase urban ecological taste, and enhance the eco-environmental protection publicity. Thus, the multifunctional service values and indirect benefits are substantial. Jiaxing ecological wetlands provide a typical paradigm for water pollution remediation in developing countries and plays a leading role in technology engineering radiation effect.
... This was much higher than ever reported values in the M. aquaticum CWs treating swine wastewater (e.g. 0.88 g N/m 2 /d in Sun et al. (2017) and 0.16 g N/m 2 /d in Liu et al. (2016)). Compared to CWUU, the overall NH 4 + -N and TN removal efficiency within CWFM was enhanced by 76.3% and 65.4%, respectively. ...
Despite of low operation costs and convenient maintenance, the application of natural systems for swine wastewater treatment has been limited by large construction area and unsatisfactory effluent quality. Introducing ammonium high uptake aquatic plants and shifting nitrogen removal pathway from nitrate to nitrite in constructed wetlands (CWs) has been regarded as promising approach to promote their performances. This study aimed to establish nitrite pathway and enhance N removal via free nitrous acid (FNA)-sediment treatment and Myriophyllum aquaticum vegetation in the CWs treating anaerobically digested swine wastewater. Nitrite pathway was successfully and stably achieved in the M. aquaticum CW with FNA-treated sediment. The overall removal efficiencies of ammonium nitrogen and total nitrogen were 42.3 ± 10.2% and 37.7 ± 9.3% in the planted CWs with FNA-treated sediment, which were 76.3% and 65.4% higher than those in the conventional oxidation pond system, respectively. Microbial community analysis (qPCR and metagenomics) suggested that the nitrite pathway established through FNA-sediment treatment was based on the inactivation of nitrite oxidizing bacteria (lower nxrA gene abundance) and the reduction of relative abundances of NOB (especially Nitrobacter and Nitrospira). During the denitrification processes, the integration of M. aquaticum vegetation with FNA-sediment treatment can lower the nitrate reduction by decreasing narG gene abundances and decreasing the relative abundances of napA affiliated bacteria (especially Bradyrhizobium), while strengthening reduction of nitrite and nitrous oxide by increasing nirK and nosZ gene abundances and enriching the corresponding affiliated microbial taxa, Mycobacterium and Bacillus, respectively. Our findings suggest that applying FNA-based technology in CW systems is technically and economically feasible, which holds promise for upgrading current CW systems treating swine wastewater to meet future water quality requirements.
... Effluent nitrate concentration (C; mg L − 1 ) over time (t) fitted to harmonic regression equation (n = 91) and as a function of water quality parameters including temperature (Temp; • C), pH, dissolved oxygen (DO; mg L − 1 ), and oxidation reduction potential (ORP; mV) using a multivariate linear regression equation ( AOB than of AOA shows the AOB plays a more important role in the microbial nitrification process, especially in ammonia-rich soils or sediments (Di et al., 2009;Liu et al., 2016). In wetlands, microbial driven denitrification is the most important nitrogen removal process (Uusheimo et al., 2018). ...
Nitrogen dynamics were studied over 3 years in pilot-scale surface flow constructed wetlands (SFCWs) treating three strengths of ammonium-rich swine wastewater. A high removal rate of ammonium (1.2–2.9 g m⁻² d⁻¹) and total nitrogen (1.5–3.5 g m⁻² d⁻¹) was achieved from highstrength wastewater in the SFCWs. Nitrate concentration was significantly higher (p < 0.01) in the effluent than in the influent, and the increased nitrate concentration did not significantly affect ammonium removal in the SFCWs. The effluent nitrate concentration showed annual cyclical changes and could be described using a harmonic regression equation over time (y = a + b sin (2π/365.25 t + c); R² = 0.152–0.566). The multiple regression equation (R² = 0.200–0.551) indicated that water temperature and oxidation reduction potential were the primary factors affecting nitrate accumulation in the SFCWs. The abundance of nitrification functional genes (amoA in ammonia-oxidizing archaea and bacteria) was higher in spring and winter than in summer. The abundance of denitrification functional genes (narG, nirK, nirS, and nosZ) was higher in summer than in spring and winter. At cold temperatures (5–10 °C), nitrate accumulated significantly in the water column rather than in the sediments and the potential nitrification rates increased slightly, suggesting the importance of nitrogen transformation in the water column during nitrogen removal. These results are helpful for selecting targeted seasonal intensification strategies to improve the SFCWs performance.
... For these reasons, an eco-friendly alternative treatment was introduced that employed phytoremediation (Barbafieri et al. 2017). By using aquatic plants to remove pollutants from the environment, this method is less hazardous, more cost-effective, and generate fewer secondary pollutants than conventional wastewater treatments (Holkar et al. 2016;Jeevanantham et al. 2019;Liu et al. 2016Liu et al. , 2019Rasheed et al. 2018). Srivastava et al. (2008) revealed that treatment of wastewater with aquatic plants mitigated level of a variety of pollutants. ...
Phytoremediation and bioremediation are eco-friendly methods of wastewater treatment that are widely used throughout the world to reduce anthropogenic water contamination. This study was conducted to assess the effectiveness of symbiotic bacteria in phytoremediation using two aquatic plants, Echinodorus cordifolius and Lepironia articulata, that were tested in sterilized and unsterilized groups. The results showed that unsterilized plants removed more phosphate, ammonium, nitrate and nitrite than the sterilized plants. In untreated and unsterilized E. cordifolius groups, the dominant bacterium was Calothrix (46.90 and 49.69%, respectively), which was higher than in the sterilized E. cordifolius group (38.88%). In untreated and unsterilized groups of L. articulata, Clostridium was a dominant bacterium. The proportion of Clostridium was much lower in the sterilized L. articulata group (1.31%) than in the untreated (13.71%) and unsterilized (49.02%) groups. Our results suggested that root-associated bacteria in E. cordifolius and L. articulata were effective in the removal of phosphorus and nitrogen from domestic wastewater.
... The influence of water column nutrient concentration, water level and light intensity on the growth of M. aquaticum have been well studied (Hussner et al., 2009;Madsen, 2011a,b, 2013;Souza et al., 2013). In China, studies have also been performed to test their nutrient removal capacity in the floating bed system and demonstrated that M. aquaticum can survive and remove large amounts of nitrogen (N) in high N-loaded wastewater (Liu et al., 2016a;Zhang et al., 2017). The question remains whether the floating beds of M. aquaticum is an effective tool for the remediation of eutrophic waters where nutrient concentrations are lower than that in wastewaters under various light intensities. ...
In recent years, Myriophyllum aquaticum grown on floating beds has been widely applied to the treatment of the malodorous black river water with high nutrient concentrations. This is due to the ability of the effective removal of nutrients by this plant. However, environmental factors such as light and nutrients influence plant growth, which may negatively affect the results of ecological restoration. To test the effects of nutrient levels and light intensity on the growth of M. aquaticum, a 21-day outdoor two-factorial experiment (three levels of nutrient loadings and three light intensities) was conducted from September 3 to September 30, 2016. Results showed that the addition of nutrients had no significant effects on the growth of M. aquaticum. Reduced light intensity led to a decrease in Chlorophyll a concentration in the water column and the growth of M. aquaticum. All growth indicators in the full sunlight treatment were significantly higher than in the shading treatments. The lowest growth was found in the 60% shading treatment. The mean plant height and the number of roots responded significantly to the interaction between light intensity and nutrient level. This study reveals that M. aquaticum planted on the floating beds could grow normally in eutrophic waters and can be used as a restoration technique to treat eutrophic water. However, shading (e.g., riparian trees) may be a major limiting environmental factor to M. aquaticum.
... Taking the areas overgrown with overwintering ditch plant species into account, TN and TP sequestered in the biomass accounted for 29.3% and 19.7% of the total removed loads. These percentages fall within the range of 10.0-85.6% reported for other ditch or wetland plant species (Jiang et al., 2007;Keizer-Vlek et al., 2014;Kumwimba et al., 2017b;Liu et al., 2016;Nsenga Kumwimba, 2017;Wu et al., 2011;Zhang et al., 2020;Zhang et al., 2016). Mean reduction efficiencies of nutrients were lower compared to those found for the warm season (e.g. ...
Vegetated agricultural drainage ditches (VDs) are a relatively new best management practice for pesticide and nutrient mitigation that is receiving increasing global interest. However, VDs are seldom used during winter due to considerable deterioration of pollutants reduction efficiencies driven by low-temperature effects. Limited knowledge on the internal loading of nutrient in VDs due to vegetation decomposition calls for further evaluation. Here, we assessed plants growth characteristics and nutrient dynamics in a field-scale VD receiving nutrient-rich sewage and planted with the overwintering plants: Acorus gramineus, Myriophyllum aquaticum and Iris sibirica. Water purification performance showed average TN, NH4-N, NO3-N, TP and PO4-P reduction efficiencies of 44, 46, 43, 52 and 46%, respectively, over the winter period. Maximum reduction rates of TN and TP were 5.31 and 0.34 g⁻² d⁻¹, respectively. Of the total nutrient removal by plants of 5.37 × 10³ kg N y⁻¹ and 0.65 × 10³ kg P y⁻¹ from the VD system, A. gramineus contributed 65.7% and 72.1%, respectively. Nonetheless, substantial amounts of N and P retained within the aboveground biomass were released into the water column as ditch plant shoots decayed to deteriorate the water quality. All three species, A. gramineus, M. aquaticum and I. sibirica demonstrated considerable nutrient accumulation during winter and facilitated nutrient retention in the VD system. Consequently, they can be considered effective overwintering species of choice in VDs for purifying nutrient-rich water and potentially appropriate for vulgarizing elsewhere, particularly throughout the winter season.
... Nitrogen uptake by M. aquaticum was responsible for 12.4%, 16.4%, and 21.5% of the influent TN loading, which was within the range of 10.0-51.9% reported in other wetland plants ( Wu et al., 2011;Liu et al., 2016a;Zhang et al., 2016a). M. aquaticum is hardy and can reach considerable height and biomass at low temperatures ( Liu et al., 2018). ...
Vegetated ditches are widely used to treat agricultural wastewater, but effective nitrogen removal at low temperatures remains a challenge because plants wilt in the winter. In this study, three simulated drainage ditches vegetated with Myriophyllum aquaticum were operated with low, medium, and high water levels to study ammonium nitrogen (NH4+-N) removal under cold temperatures. The M. aquaticum ditches had a mean NH4+-N removal efficiency of 75.8-86.8% throughout cold period. Based on nitrogen mass balance, plant uptake, sediment adsorption, and microbial removal accounted for 12.4-21.5%, 0.0-8.1%, and 38.9-54.6% of the influent total nitrogen loading, respectively. The accumulation of nitrate confirmed that intense microbial nitrification occurred in M. aquaticum ditches even at low temperature. These results suggest that M. aquaticum is appropriate as a cold-tolerant plant for NH4+-N removal in drainage ditches.
... A submerged macrophyte from a genus that can release oxygen (Myriophyllum aquaticum) ( Laskov et al., 2006) was included. M. aquaticum is a widespread macrophyte that can tolerate high-strength wastewater and effectively remove N from polluted waters in laboratory and pilot scales ( Li et al., 2018;Liu et al., 2016a). M. aquaticumbased treatment systems are extensively reported to be beneficial to the remediation of polluted ecosystems owing to their technical feasibility, ecological benefits and economic advantages ( Liu et al., 2018;Wang et al., 2003). ...
... The input-output accumulation of heavy metal in different depths of soil column via the mass balance of influent and effluent is ascertained in view of the following formula where M out in is the accumulated heavy metal in SAT column during recharging of the secondary effluent, C in represents the average concentration of heavy metal in secondary effluent obtained from upper water sampling ports, C out represents the average concentration of heavy metal in SAT effluent obtained from lower water sampling ports and V water denotes the volume of the recharged secondary effluent. In the packed soil, the linear expression of net accumulation of the heavy metals is expressed in the following equation (Liu et al. 2016) where accumulation of estimated heavy metals in the packed soil of SAT column can be represented as M acc , average concentration of heavy metals in the different depths of soil can be referred as C soil , average concentration of heavy metals before secondary effluent recharging of the packed soil can be specified as C original soil , radius of the SAT column and ...
Soil aquifer treatment (SAT) is a most proficient innovation which depends on broad physical and biogeochemical forms in the underground water and aquifer for water quality change. In this investigation, the conveyance, quantitative changes and, in addition, the speciation qualities of heavy metals in various depths of soils of a 2-year worked laboratory-scale SAT are investigated. A greater part of the heavy metals in the energized secondary effluent are effectively caught by the consistent state worked SAT. Here, the removal efficiency of SAT with and without adsorbent is conveyed for parameters like pH, total dissolved solids, total solids, chloride, COD, TKN, potassium, phosphate, copper, zinc, nickel and hexavalent chromium. The investigations are completed by utilizing toxic wastewater and fluctuating adsorbents, for example, eucalyptus leaves, sawdust and mosambi peel (MP). Here, the soil types of clayey sand, inorganic silt with sand (MI SAND) and silty sand are utilized and their properties are resolved. To enhance the removal efficiency of SAT for expulsion of heavy metals, distinctive adsorbents and, in addition, different soil tests are utilized. In the light of investigation, the SAT system with adsorbent is more effective in treating toxic wastewater.
... In most small rural areas of developing Countries with fewer population densities, wastewater is treated using on-site sanitation system such as septic tanks connected to drain fields, on-site sewage system (OSS), and so on. An alternative solution to domestic wastewater treatment is HSSF-CW technology; it is built, smooth operations, low cost, and maintenance and higher efficiency in treating different types of wastewater [9][10][11][12][13] and appropriate technology for removing different types of nutrients [14]. An environmental problem in some parts of the world is water bodies enriched with nutrients, the of nutrients removal such as phosphorous and nitrogen from the water bodies is of vital importance. ...
This study assessed the performance of a small-scale horizontal sub-surface flow constructed wetland (HSSF-CWs) for rural domestic wastewater treatment with different species of vegetative plants capsicum annum (A), Allium sativum (B), Apium graveolens (C), Spinacia oleracea (X), Apium graveolens (Y) & cilantro (Z).The system operational time was over three months as a tertiary treatment for both summer and winter season to improve the effluent quality before disposal. The average temperatures during the experimental operation were 27°C and 11.6°C in summer and winter respectively. The average pH value ranges between 6.98-7.19 and 6.72-6.98 respectively. The average hydraulic residence time (HRT) of 2 and three days with the hydraulic loading rate (HLR) set to 180ml/min in summer and winter respectively. The average removal efficiency (RE) concentrations for plants A, B & C in summer were 77.2%, 77.2%, 81.4% & 93% for TN, NO3-N, NH4+N & TP. Whereas in the winter season the RE were 67.6%, 65%, 69.4% & 86.6% for TN, NO3-N, NH4+N & TP for plants X,Y,& Z respectively. All the vegetative plants almost performed similarly in nutrient removal under HRT of two and three days with the best performance revealed in summer. HSSF-CW successfully achieved high removal efficiency due to its self-adaptability, low-cost, secure operations and maintenance and above all is high effluent quality reuses and self-remediation. HSSF-CW is a good alternative for wastewater treatment system.
The release of nutrients back into the water column due to macrophyte litter decay could offset the benefits of nutrient removal by hydrophytes within urban streams. However, the influence of this internal nutrient cycling on the overlying water quality and bacterial community structure is still an open question. Hence, litter decomposition trials using six hydrophytes, Typha latifolia (TL), Phragmites australis (PAU), Hydrilla verticillata (HV), Oenanthe javanica (OJ), Myriophyllum aquaticum (MA), and Potamogeton crispus (PC), were performed using the litterbag approach to mimic a 150-day plant litter decay in sediment-water systems. Field assessment using simple in/out mass balances and uptake by plant species was carried out to show the potential for phytoremediation and its mechanisms. Results from two years of monitoring (2020-2021) indicated mean total nitrogen (TN) retention efficiencies of 7.2-60.14 % and 9.5-55.6 % for total phosphorus (TP) in the studied vegetated urban streams. Nutrient retention efficiencies showed temporal variations, which depended on seasonal temperature. Mass balance analysis indicated that macrophyte assimilation, sediment adsorption, and microbial transformation accounted for 10.31-41.74 %, 0.84-3.00 %, and 6.92-48.24 % removal of the inlet TN loading, respectively. Hydrophyte detritus decay induced alterations in physicochemical parameters while significantly increasing the N and P levels in the overlying water and sediment. Decay rates varied among macrophytes in the order of HV (0.00436 g day-1) > MA (0.00284 g day-1) > PC (0.00251 g day-1) > OJ (0.00135 g day-1) > TL (0.00095 g day-1) > PAU (0.00057 g day-1). 16S rRNA gene sequencing analysis showed an increase in microbial species richness and diversity in the early phase of litter decay. The abundances of denitrification (nirS and nirK) and nitrification (AOA and AOB) genes also increased in the early stage and then decreased during the decay process. Results of this study conducted in seven urban streams in northern China demonstrate the direct effects of hydrophytes in encouraging nutrient transformation and stream self-purification. Results also demonstrate that macrophyte detritus decay could drive not only the nutrient conversions but also the microbial community structure and activities in sediment-water systems. Consequently, to manage internal sources and conversions of nutrients, hydrophytic detritus (e.g., floating/submerged macrophytes) must be suppressed and harvested.
With the rapid expansion of livestock production, the amount of livestock wastewater accumulated rapidly. Lack of biodegradable organic matter makes denitrification of livestock wastewater after anaerobic digestion more difficult. In this study, Myriophyllum aquaticum constructed wetlands (CWs) with efficient nitrogen removal performance were established under different carbon/nitrogen (C/N) ratios. Analysis of community composition reveals the change of M. aquaticum CWs in microbial community structure with C/N ratios. The proportion of Proteobacteria which is one of the dominant phyla among denitrifier communities increased significantly under low C/N ratio conditions. Besides, to obtain cultivable denitrifier that could be added into CWs in situ, 33 strains belonging to phylum Proteobacteria were isolated from efficient M. aquaticum CWs, while the best-performing denitrification strain M3-1 was identified as Bacillus velezensis JT3-1 (GenBank No. CP032506.1). Redundancy analysis and quadratic models showed that C/N ratio had significant effects on disposal of nitrate (NO3⁻-N) and the strains isolated could perform well in denitrification when C/N ratio is relatively low. In addition, they have relatively wide ranges of carbon sources, temperature and a high NO3⁻ removal rate of 9.12 mg/(L·hr) at elevated concentrations of 800 mg/L nitrate. Thus, strains isolated from M. aquaticum CWs with low C/N ratio have a practical application value in the treatment of nitrate-containing wastewater. These denitrifying bacteria could be added to CWs to enhance nitrogen removal efficiency of CWs for livestock wastewater with low C/N ratio in the future.
The use of phytoremediation technology in urban and rural landscapes can permit both aesthetic and water purification functions to be achieved sustainably. Here, the ability of three ornamental aquatic plant species (Lythrum salicaria L., Sagittaria trifolia L., and Typha orientalis C. Presl) to remove nutrients from simulated contaminated water over 35 days and the structure of their rhizosphere microorganism populations were evaluated to examine their potential to be used for landscape phytoremediation as well as determine the mechanism of nutrient removal. L. salicaria had the highest nutrient removal ability (86.91–96.96% removal efficiency of total nitrogen and 46.04–66.70% removal efficiency of total phosphorus). The population structure of rhizosphere microorganisms was mainly affected by plant species and not the nutrient level of the water body according to principal coordinates analysis and non-metric multi-dimensional scaling. Betaproteobacteriales and Chitinophagales were highly correlated with the content of nutrients in water according to redundancy analysis. The accumulation of the two orders by L. salicaria and higher biomass might explain the stronger removal ability of L. salicaria. The findings of this study indicate that these plants could enhance urban and rural water landscape design; our results also shed new light on the mechanism of phytoremediation by rhizosphere microorganisms.
The utilization of livestock waste has attracted increasing attention in recent years. The presence of high levels of heavy metals is a major obstacle to the utilization of biogas as a fertilizer resource. In this study, the heavy metal contents in biogas residue, slurry, and discharged sewage from three representative farms of gooseries, henneries, and dairy farms in the Yangtze River Basin were investigated and assessed. The results demonstrated that heavy metals, including Cd, Mn, As, Cu, Pb, Cr, Zn, etc., could be detected in all biogas residues, with significantly different contents between farm types (p < 0.005). Specifically, biogas residues from the goosery and the dairy farms met “China’s Organic Fertilizer Standards” (COF Standards); however, Cd concentrations in biogas residues from hennery farms exceeded the limits by five times. The concentrations of Cd and Pb in biogas slurries from all of the farms exceeded the limits of the “China Farmland Irrigation Water Quality Standard” (CFIWQ Standard). In particular, the Pb concentrations in biogas slurry from the dairy farms exceeded the limits by 29 times, and the discharged sewage from all three farm types complied with the comprehensive sewage discharge standards in China; however, only that from the goosery farms was suitable for irrigation. Thus, it is recommended to increase the feed selection, biogas engineering, and biological-purification-supporting technology, and to carry out regular sampling inspections of the biogas residue, slurry, and discharged sewage for heavy metals, so that environmental and crop pollution risks can be reduced when they are used as sources of nutrients for eco-friendly agriculture.
The loss of N from aquaculture has caused eutrophication of freshwater systems. A multistage surface flow constructed wetland (SFCW) with Myriophyllum (M.) aquaticum was engineered to treat lagoon swine wastewater from a large-scale hoggery. The mean removal efficiency of TN and NH4⁺-N were 9.92 and 7.64 g·m⁻²·d⁻¹, respectively. The plant and sediment absorption were 1.89 and 1.96 g·m⁻²·d⁻¹, respectively. The dynamics of the NO3⁻-N concentrations and the abundance of nitrifiers (AOA and AOB) and denitrifiers (nirK and nirS) revealed strong nitrification and denitrification processes occurring in the SFCW, with a mean N removal of 6.07 g·m⁻²·d⁻¹. Moreover, AOB and nirK could be the main participants for nitrifiers and denitrifiers, respectively. The combination of quantitative polymerase chain reaction (qPCR), the potential nitrification rate (PNR), and the potential denitrification rate (PDR) showed that the microbial abundance and activity was significantly positively with N concentrations and water temperature (P < 0.05). Factors like PDR, DO, plant N uptake, sediment N adsorption, and pH may play an important role on N removal. These results showed that the M. aquaticum SFCW can efficiently treat swine wastewater and reduce the discharge of pollutants downstream in situ.
A packed-bed anaerobic-aerobic reactor (PBAOR) with two anaerobic and two aerobic compartments was constructed to treat manure-free piggery wastewater which was characterized by high ammonium (NH4⁺-N) and low ratio of chemical oxygen demand (COD) to total nitrogen (TN). Performed for 60 days at the normal atmospheric temperature of 25℃ with a constant hydraulic retention time of 32 h and reflux ratio of 2.0, a stable state in pollutants removal was obtained in the PBAOR. Within the next routine operation process, the removal of COD, NH4⁺-N and TN was above 85.7%, 98.2% and 85.8%, with a residual less than 81.7, 7.2 and 39.9 mg L⁻¹ in effluent, respectively. Twelve veterinary antibiotics classified into tetracyclines (TCs), sulfonamides (SAs) and fluoroquinolones (FQs) were detected from the piggery wastewater. and the PBAOR was effective in removing TCs and SAs with an average removal of 74.8% and 93.3%, respectively, but presented a negative removal for FQs. Most COD in the piggery wastewater was mainly removed in the first two anaerobic compartments along with an obvious removal of TCs and SAs, while the TN were mainly removed in the last two aerobic compartments with the negative removal of FQs.
This study examined the performances of Acorus calamus, Pontederia cordata, and Alisma plantagoaquatica in removing nitrogen (N) from farmland wastewater. P. cordata showed the fastest rate of N removal, followed by A. plantagoaquatica, whereas that of A. calamus was slowest. P. cordata and A. plantagoaquatica achieving a greater rate of TN reduction in soil than that by A. calamus. A. plantagoaquatica demonstrated the highest N adsorption capacity, 32.6% and 392.1% higher than that of P. cordata and A. calamus, respectively. The higher potential nitrification and denitrification rate, and abundance of functional genes in the P. cordata microcosm resulted in a stronger process of nitrification-denitrification, which accounted for 65.99% of TN loss. Plant uptake and nitrification-denitrification were responsible for 50.06% and 49.94% of TN removed within the A. plantagoaquatica. Nitrification-denitrification accounted for 86.35% of TN loss in A. calamus. These findings helped to insight into N removal mechanisms in different plants.
Swine wastewater (SW) treatment by Myriophyllum aquaticum is an important biotechnology for its resource utilization. However, some knowledge gaps remain in compound-pollutant removal in SW, especially in practical applications. To clarify the responses of M. aquaticum to the compound pollutants as well as the related operational parameters in SW treatment, three initial doses (0.5, 1.0, and 1.5 kg per pond in 150 L simulated SW) of M. aquaticum and a control (no plant; CK) were allocated to 12 ponds under a plastic roof in Nanjing city of Eastern China during 75 days in the summer of 2019. Results showed that M. aquaticum could be used as a pioneer plant to efficiently remove compounded pollutants of nitrogen (N), phosphorus (P), and especially for heavy metals in simulated SW. Compared with CK, M. aquaticum assisted in improving the total N, NH4⁺–N, NO3⁻–N, NO2⁻–N, and dissolved organic N by 30.1%, 100%, 100%, 97.6%, 20.2%, 39.8% whereas Cu, Zn, and Cd by 50.4%, 36.4% and 47.9% on average during the 75-day experiment in summer, respectively. Moreover, concentrations of Cu and Cd at day 75 were in the ranges of 1.92–2.82 and 0.64–1.47 g kg⁻¹ DW, respectively, exceeding the corresponding limits of the heavy-metal hyperaccumulator. For the operational parameters, the optimized initial dose was 1.0 kg per pond with M. aquaticum harvested after 45 summer days, respectively. Given that M. aquaticum has been widely used as animal feed in recent years and limit values for Cu and Zn in animal feed are not set in China, the toxicities of Cu and Zn should be assessed and the guideline of their limit values needs to be established for safe feed production. Interestingly, NH4⁺–N could dominate the removal of heavy metals especially Cd in the simulated SW, however, related mechanisms are needed for further study.
Integrated effects of three different combination of aquatic macrophytes community (emergent, floating-leaved and submerged species) on river ecological restoration were investigated. LNH (Lythrum salicaria L, Nymphaea L and Hydrilla varticillata) showed the best performance in terms of COD removal yet LNV (Lythrum salicaria L, Nymphaea L and Vallisneria natans (Lour.) Hara) ranked first in terms of TN removal and TP removal. Due to the significant distinction of LNV on TN removal, LNV was suggested as the best option for river ecological restoration using combination of aquatic macrophytes community. A drastic reduction of pollutants in the early phase of treatment was observed for both COD and nutrition removal process. However, the timing of drastic reduction for COD was Day 5, while that of TN and TP was Day 17. Absorbtion and phytoremediation were the main process that contribute to the rapid removal of pollutants.
An innovative hybrid process was designed using an integrated bio-reactor based on an anoxic / aerobic process that combined a fixed bed and a fluidized-moving bed with a constructed wetland (A/OFMCW) to enhance the removal of organic material and nitrogen. The goal was to achieve stringent discharge standards for rural domestic wastewater treatment. A preliminary lab-scale investigation of about 130 days obtained an average COD (Chemical Oxygen Demand) removal rate as high as 92.2% at an average influent concentration of 319.5 mg/L. The average TN (Total Nitrogen) removal efficiency positively correlated with the attached-growth biofilm as observed by SEM (Scanning Electron Microscope), and declined from 79.1% to 53.2%. The was accompanied by a gradual increase in the average influent concentration from 16.73 to 52.01 mg/L despite the relative nitrification rate fluctuating between 92.5% and 97.9%. The entire integrated system improved the COD removal efficiency by nearly 36% and the TN by 14–28%. Classical autotrophic nitrification and heterotrophic denitrification were the main mechanisms responsible for the elimination of pollutants, and the latter was determined to be the limiting step. Overall, this study provides an effective and less expensive alternative method to apply or upgrade DWWT (Decentralized Wastewater Treatment).
Constructed wetlands (CWs) have received increasing attentions for their N removal performances, especially regarding NH4⁺-N. Different influent NH4⁺-N concentration may influence N removal efficiency in practice, while the effects of different NH4⁺-N concentrations on microorganisms removing N in CWs are poorly understood. In this study, surface flow CWs planted with Myriophyllum (M). aquaticum were established to investigate the influences of different NH4⁺-N concentrations on the composition, structure, and interactions of microbial community. Our findings suggested 105 mg/L NH4⁺-N CWs achieved highest N removal rate, removing 89.30% NH4⁺-N and 92.34% TN from the influent. The results of real-time quantitative polymerase chain reactions (qPCR) indicated abundances of nitrifying genes (nxrA) and denitrifying genes (narG, nirS, nirK, and nosZ) were increased by increasing NH4⁺-N concentrations, and the strongest effects were observed in narG (8-fold) and nosZ genes (11-fold). Different NH4⁺-N concentrations was proved to alter composition and structure of microbial communities via high-throughput sequencing, e.g. denitrifiers including Brevendomonas.sp, Dokdonella.sp and Rhodococcus.sp were enriched obviously with increasing NH4⁺-N concentrations. In addition, network showed interactions among microbial populations and positive interactions were dramatically shifted and enhanced by increasing NH4⁺-N concentrations.
Endophytic bacteria are generally helpful for plant growth and protection. Strain WSE01, which was identified as bacillus cereus, was isolated from the stem of Myriophyllum verticillatum and it displayed a high tolerance to Mn (1500 mg/L). The strain was found to be able to produce indole-3-acetic acid (IAA) and siderophores, fix the atmospheric nitrogen and dissolve potassium from insoluble K-bearing minerals. In hydroponic culture experiments, the inoculation of strain WSE01 significantly promoted the growth and increased the leaf enzyme activity in the inoculated plant M. verticillatum. Furthermore, the manganese content was increased by 36.4% in stems and by 54.7% in leaves of the inoculated plant under Mn stress at 400 mg/L, compared to the non-inoculated group. This study suggests that the strain WSE01 has the potential to be used as biocontrol and/or biofertilizing agents for application in macrophyte M. verticillatum and conduces to achieving more effective phytoremediation of metal-contaminated waters.
A novel hybrid anaerobic-aerobic baffled reactor (HAOBR) with four compartments was constructed to treat manure-free piggery wastewater with an average COD/TN ratio as low as 0.98, without any supplement of external carbon source. Inoculated with aerobic activated sludge and operated at hydraulic retention time 36 h, 32 °C and reflux ratio 2.0, the reactor could perform steadily within 24 days. The removal of COD, NH4+-N and TN within the 21-days steady phase averaged 87.0%, 100% and 91.3%, respectively. Analysis of stoichiometry and results of high-throughput pyrosequencing revealed that the excellent nitrogen removal in the HAOBR was achieved by the cooperation of heterotrophic and autotrophic denitrification with anammox as the dominant approach. Compared with the previously developed microaerobic treatment processes and the recently reported modified A/O process, the HAOBR was more cost-efficient in treating manure-free piggery wastewater because of the less energy consumption, rapid startup process and efficient nutrients removal.
As a floating plant, Myriophyllum aquaticum provides a large surface area under water, and thus has high potential for the removal of pollutants through adsorption. The aim of this study was to evaluate the potential adsorption of tetracycline (TC) by M. aquaticum, and examine the underlying mechanisms. M. aquaticum exhibited a high potential for TC removal from water. Adsorption was the main mechanism for rapid TC removal by live M. aquaticum plants, due to its large contact area and ion exchange, accounting for about 99% and 54% of the total amount of TC removed within 2 h and 5 d, respectively. Further, the roots of M. aquaticum exhibited a higher adsorption capacity than the stems or leaves, as the roots had the largest specific surface area. Fourier transform infrared spectroscopy analysis and identification of functional groups showed that -OH, -COOH, and -NH2 groups are involved in the adsorption process. The use of M. aquaticum may be a promising approach for TC removal from aquatic environments, especially in terms of shortening reaction times.
Rice straw was applied often as a carbon source to improve nitrogen removal; however, few studies have considered the effect of rice straw on nitrous oxide (N 2 O) emission during nitrogen removal in constructed wetlands (CWs). We constructed eighteen combined systems, consisting of rice straw ponds and surface flow CWs to investigate the effect of rice straw application on N 2 O emission in three strengths of swine wastewater treatments. The results showed rice straw (RS) treatment increased 131.5% of N 2 O emission factor from low strength CWs, but decreased 37.2–43.7% of N 2 O emission factors for medium and high strengths compared with no rice straw (NRS) treatment. The RS application led to an average 10.7% increase in the potential denitrification rate, and simultaneously enhanced gene abundances of the total bacteria (16S rRNA), ammonia-oxidising archaea, ammonia-oxidising bacteria, nitrate reductase, and N 2 O reductase (nosZ) for all strengths CWs. The multiple regression model revealed N 2 O emissions were strongly related to water temperature, nitrate, chemical oxygen demand, and denitrification genes. The proportion of nosZ gene abundance in 16S rRNA was higher in RS (0.7–1.3%) than NRS (0.4–0.9%) for medium and high strengths, while an opposite trend was observed for low strength. The discrepancy was responsible for increasing or decreasing N 2 O emission by RS application among different strengths. These findings indicated the effectiveness of RS application to control N 2 O emissions from the surface flow CWs was related to the pollution level of wastewater.
Although Myriophyllum aquaticum exhibits efficient nitrogen and phosphorus removal from wastewater, it has poor performance on organic matter removal. Here, a wastewater treatment system combining M. aquaticum and activated sludge was developed to improve its removal of organic matter. The Box–Behnken response surface methodology was used to optimize the construction conditions of the system, and the effects of time, temperature, illumination intensity, pollutant load, and dissolved oxygen (DO) on plant mass increment (PMI) and microbial biomass (MB) of the system were investigated. The wastewater remediation potential of the system was then evaluated. The results show that temperature and illumination intensity significantly affected PMI (p < 0.01), and that time, pollutant load, and DO were the most significant factors affecting MB (p < 0.01). The optimal construction conditions were 18.77 days in length, a temperature of 20.42 °C, an illumination intensity of 5827.61 Lx, a pollutant load of 120.61 mg/g plant, and a DO of 3.21 mg/L. The inoculation of activated sludge caused MB of the system to increase by four times relative to the non-inoculated system, suggesting successful formation of biofilms on M. aquaticum. Additionally, the removal of chemical oxygen demand (COD) from wastewater was significantly enhanced by the combined approach compared with a system relying solely on M. aquaticum. This study provides a new method for improving the remediation efficiency of M. aquaticum by combining the use of this species and activated sludge.
Domestic wastewater and agricultural runoff are increasingly viewed as major threats to both aquatic and terrestrial ecosystems due to the introduction of non-point source inorganic (e.g., nitrogen, phosphorus and metals) and organic (e.g., pesticides and pharmaceutical residues) pollutants. With rapid economic growth and social change in rural regions, it is important to examine the treatment systems in rural and remote areas for high efficiency, low running costs, and minimal maintenance in order to minimize its influence on water bodies and biodiversity. Recently, the use of vegetated drainage ditches (VDDs) has been employed in treatment of domestic sewage and agricultural runoff, but information on the performance of VDDs for treating these pollutants with various new management practices is still not sufficiently summarized. This paper aims to outline and review current knowledge related to the use of VDDs in mitigating these pollutants from domestic sewage and agricultural runoff. Literature analysis has suggested that further research should be carried out to improve ditch characteristics and management strategies inside ditches in order to ensure their effectiveness. Firstly, the reported major ditch characteristics with the most effect on pollutant removal processes (e.g., plant species, weirs, biofilms, and substrates selection) were summarized. The second focus concerns the function of ditch characteristics in VDDs for pollutant removal and identification of possible removal mechanisms involved. Thirdly, we examined factors to consider for establishing appropriate management strategies within ditches and how these could influence the whole ditch design process. The current review promotes areas where future research is needed and highlights clear and sufficient evidence regarding performance and application of this overlooked ditch system to reduce pollutants.
So far, the contribution of ammonia-oxidizing archaea (AOA) to ammonia oxidation in wastewater treatment processes has not been well understood. In this study, two soil aquifer treatment (SATs) systems were built up to treat synthetic domestic wastewater (column 1) and secondary effluent (column 4), accomplishing an average of 95 % ammonia removal during over 550 days of operation. Except at day 322, archaeal amoA genes always outnumbered bacterial amoA genes in both SATs as determined by using quantitative polymerase chain reaction (q-PCR). The ratios of archaeal amoA to 16S rRNA gene averaged at 0.70 ± 0.56 and 0.82 ± 0.62 in column 1 and column 4, respectively, indicating that all the archaea could be AOA carrying amoA gene in the SATs. The results of MiSeq-pyrosequencing targeting on archaeal and bacterial 16S rRNA genes with the primer pair of modified 515R/806R indicated that Nitrososphaera cluster affiliated with thaumarchaeal group I.1b was the dominant AOA species, while Nitrosospira cluster was the dominant ammonia-oxidizing bacteria (AOB). The statistical analysis showed significant relationship between AOA abundance (compared to AOB abundance) and inorganic and total nitrogen concentrations. Based on the mathematical model calculation for microbial growth, AOA had much greater capacity of ammonia oxidation as compared to the specific influent ammonia loading for AOA in the SATs, implying that a small fraction of the total AOA would actively work to oxidize ammonia chemoautotrophically whereas most of AOA would exhibit some level of functional redundancy. These results all pointed that AOA involved in microbial ammonia oxidation in the SATs.
The annual dynamics of N2O emissions from a tea field in southern subtropical China was observed in situ weekly in 2010 using a static closed chamber - GC method for three treatments: non-fertilised (CK), conventional (CON) and rice straw mulching (SM). The annual N2O emissions for CK, CON and SM were 7.1, 17.2 and 16.7 kg N/ha/yr, respectively. The N2O emission factors for the CON and SM treatments were estimated as 2.23% and 1.91% of the total fertiliser N applied, respectively. Rice straw mulching exhibited a potential to reduce the N2O emissions from the tea field, but not statistically significant (p=0.82). The daily N2O fluxes were positively correlated with the air temperature. The cumulative precipitation of the previous five days was significantly correlated with the daily N2O fluxes of CON. The soil water contents were significantly correlated with the daily N2O fluxes in the three treatments. The N2O fluxes from CON had a more significant correlation with the soil NH4+-N contents than with the soil NO3--N contents, while the N2O fluxes from SM showed an inverse pattern. The N2O fluxes from CK did not show any significant relationship with the soil mineral N content.
Myriophyllum aquaticum (Vell.) Verdc. is native of South America and has a pantropical distribution. This species has been cited as dioecious, monoecious and polygamous. The purpose of this paper was to contribute to the discussion of its sexual condition, based on herbarium material, and supported by field observations. Herbarium material from Argentina was examined. Also, twenty branches from the Punta Lara Nature Reserve (Buenos Aires, Argentina) were periodically sampled to record the sex of flowers present on each whorl during the flowering period of 2002. Both in herbarium material and in field, we observed specimens with branches bearing either female or male, and specimens with female and male flowers on the same branch. Some of these materials have also fruits. Our observations support the idea that M. aquaticum is not a strictly dioecious species, at least in Argentina.
The oxidation of ammonia to nitrate, nitrification, is a key process in the nitrogen cycle. Ammonia-oxidizing archaea are present in large numbers in the ocean and soils, suggesting a potential role for archaea, in addition to bacteria, in the global nitrogen cycle. However, the importance of archaea to nitrification in agricultural soils is not well understood. Here, we examine the contribution of ammonia-oxidizing archaea and bacteria to nitrification in six grassland soils in New Zealand using a quantitative polymerase chain reaction. We show that although ammonia-oxidizing archaea are present in large numbers in these soils, neither their abundance nor their activity increased with the application of an ammonia substrate, suggesting that their abundance was not related to the rate of nitrification. In contrast, the number of ammonia-oxidizing bacteria increased 3.2-10.4-fold and their activity increased 177-fold, in response to ammonia additions. Indeed, we find a significant relationship between the abundance of ammonia-oxidizing bacteria and the rate of nitrification. We suggest that nitrification is driven by bacteria rather than archaea in these nitrogen-rich grassland soils.
The larger aquatic plants growing in wetlands are usually called macrophytes. These include aquatic vascular plants, aquatic mosses and some larger algae. The presence or absence of aquatic macrophytes is one of the characteristics used to define wetlands, and as such macrophytes are an indispensable component of these ecosystems. As the most important removal processes in constructed treatment wetlands are based on physical and microbial processes, the role of the macrophytes in these has been questioned. This paper summarizes how macrophytes influence the treatment processes in wetlands.
The most important functions of the macrophytes in relation to the treatment of wastewater are the physical effects the presence of the plants gives rise to. The macrophytes stabilise the surface of the beds, provide good conditions for physical filtration, prevent vertical flow systems from clogging, insulate the surface against frost during winter, and provide a huge surface area for attached microbial growth. Contrary to earlier belief, the growth of macrophytes does not increase the hydraulic conductivity of the substrate in soil-based subsurface flow constructed wetlands. The metabolism of the macrophytes affects the treatment processes to different extents depending on the type of the constructed wetland. Plant uptake of nutrients is only of quantitative importance in low-loaded systems (surface flow systems). Macrophyte mediated transfer of oxygen to the rhizosphere by leakage from roots increases aerobic degradation of organic matter and nitrification. The macrophytes have additional site-specific values by providing habitat for wildlife and making wastewater treatment systems aesthetically pleasing. (C) 1997 IAWQ.
In the Chesapeake Bay drainage basin, wastewater from animal operations laden with nutrients, sediment, and biochemical oxygen demand (BOD) contributes to the degradation of surface water quality. A constructed wetland system was built to treat wastewater from a dairy farm in Frederick County, Maryland to evaluate the use of wetland technology as a best management practice for dairy waste. To assess treatment effects, we sampled water once a month at several sites through the system, which consists of two settling basins, two cells, and a vegetated filter strip. Samples were analyzed for total nitrogen, ammonia, nitrate/nitrite, total phosphorus, ortho-phosphate, total suspended solids, biochemical oxygen demand, dissolved oxygen, temperature, conductivity, and pH. Flow through the wetland system resulted in significant reductions in concentrations of all analytes except nitrate/nitrite. Relative to initial concentrations, total nitrogen was reduced 98%, ammonia 56%, total phosphorus 96%, ortho-phosphate 84%, suspended solids 96%, and biochemical oxygen demand 97%. Nitrate/nitrite increase by 82%, although mean concentrations were much lower than concentrations of ammonia or total nitrogen. The increase in nitrate/nitrite is probably due to the oxidation of ammonia via nitrification in the vegetated filter strip. Our results suggest that while reductions are large, further removal is necessary to meet design requirements. This may be possible through the addition of another anaerobic wetland cell downstream of the system or recirculation of wastewater through the wetland cells to promote denitrification and uptake of nutrients by plants.
Bacterial denitrification results in the loss of fertilizer nitrogen and greenhouse gas emissions as nitrous oxides, but ecological factors in soil influencing denitrifier communities are not well understood, impeding the potential for mitigation by land management. Communities vary in the relative abundance of the alternative dissimilatory nitrite reductase genes nirK and nirS, and the nitrous oxide reductase gene nosZ; however, the significance for nitrous oxide emissions is unclear. We assessed the influence of different long-term fertilization and cultivation treatments in a 160-year-old field experiment, comparing the potential for denitrification by soil samples with the size and diversity of their denitrifier communities. Denitrification potential was much higher in soil from an area left to develop from arable into woodland than from a farmyard manure-fertilized arable treatment, which in turn was significantly higher than inorganic nitrogen-fertilized and unfertilized arable plots. This correlated with abundance of nirK but not nirS, the least abundant of the genes tested in all soils, showing an inverse relationship with nirK. Most genetic variation was seen in nirK, where sequences resolved into separate groups according to soil treatment. We conclude that bacteria containing nirK are most probably responsible for the increased denitrification potential associated with nitrogen and organic carbon in this soil.
Animal waste management is a national concern that demands effective and affordable methods of treatment. We investigated constructed wetlands from 1993 through 1997 at a swine production facility in North Carolina for their effectiveness in treatment of swine wastewater from an anaerobic lagoon. We used four wetland cells (3.6 × 33.5 m) with two cells connected in series. The cells were constructed by removing topsoil, sealing cell bottoms with 0.30 m of compacted clay, and covering with 0.25 m of loamy sand topsoil. One set of cells was planted with bulrushes (Scirpus americanus, Scirpus cyperinus, and Scirpus validus) and rush (Juncus effusus). The other set of cells was planted with bur-reed (Sparganium americanum)and cattails (Typha angustifolia and Typha latifolia). Wastewater flow and concentrations were measured at the inlet of the first and second cells and at the exit of the second cell for both the bulrush and cattail wetlands. Nitrogen was effectively removed at mean monthly loading rates of 3 to 40 kg N ha-1 day-1; removals were generally >75% when loadings were <25 kg ha-1 day-1. In contrast, P was not consistently removed. Neither plant growth nor plant litter/soil accumulation was a major factor in N removal after the loading rates exceeded 10 kg N ha-1 day-1 However, the soil-plant-litter matrix was important because it provided carbon and reaction sites for denitrification, the likely major treatment component. Soil Eh (oxidative/reductive potential) values were in the reduced range (<300 mV), and nitrate was generally absent from the wetlands. Furthermore, the wetlands had the capacity to remove more nitrate-N according to denitrification enzyme activity determinations. Our results show that constructed wetlands can be very effective in the removal of N from anaerobic lagoon-treated swine wastewater. However, wetlands will need to be augmented with some form of enhanced P removal to be effective in both P and N treatments at high loading rates.
Shifts in nitrifying community structure and function in response to different ammonium concentrations (50, 500, 1,000, and 3,000 mg of N liter-1), pH values (pH 6.0, 7.0, and 8.2), and oxygen concentrations (1, 7, and 21%) were studied in experimental reactors inoculated with nitrifying bacteria from a wastewater treatment plant. The abilities of the communities selected for these conditions to regain their original structures after conditions were returned to the original conditions were also determined. Changes in nitrifying community structure were determined by performing an amplified ribosomal DNA (rDNA) restriction analysis of PCR products obtained with ammonia oxidizer-specific rDNA primers, by phylogenetic probing, by small-subunit (SSU) rDNA sequencing, and by performing a cellular fatty acid analysis. Digestion of ammonia-oxidizer SSU rDNA with five restriction enzymes showed that a high ammonium level resulted in a great community structure change that was reversible once the ammonium concentration was returned to its original level. The smaller changes in community structure brought about by the two pH extremes, however, were irreversible. Sequence analysis revealed that the highest ammonium environment stimulated growth of a nitrifier strain that exhibited 92.6% similarity in a partial SSU rRNA sequence to its nearest relative, Nitrosomonas eutropha C-91, although the PCR product did not hybridize with a general phylogenetic probe for ammonia oxidizers belonging to the beta subgroup of the class Proteobacteria. A principal-component analysis of fatty acid methyl ester data detected changes from the starter culture in all communities under the new selective conditions, but after the standard conditions were restored, all communities produced the original fatty acid profiles.
Constructed wetlands are a natural alternative to technical methods of wastewater treatment. However, our understanding of the complex processes caused by the plants, microorganisms, soil matrix and substances in the wastewater, and how they all interact with each other, is still rather incomplete. In this article, a closer look will be taken at the mechanisms of both plants in constructed wetlands and the microorganisms in the root zone which come into play when they remove contaminants from wastewater. The supply of oxygen plays a crucial role in the activity and type of metabolism performed by microorganisms in the root zone. Plants' involvement in the input of oxygen into the root zone, in the uptake of nutrients and in the direct degradation of pollutants as well as the role of microorganisms are all examined in more detail. The ways in which these processes act to treat wastewater are dealt with in the following order: Technological aspects; The effect of root growth on the soil matrix; Gas transport in helophytes and the release of oxygen into the rhizosphere; The uptake of inorganic compounds by plants; The uptake of organic pollutants by plants and their metabolism; The release of carbon compounds by plants; Factors affecting the elimination of pathogenic germs.
A pilot-scale wetland was constructed to assess the feasibility of treating the wastewater from a tool industry in Santo Tomé, Santa Fe, Argentina. The wastewater had high conductivity and pH, and contained Cr, Ni and Zn. This paper describes the growth of vegetation in the experimental wetland and the nutrient and metal removal. The wetland was 6 x 3 x 0.4 m. Water discharge was 1000 l d(-1) and residence time was 7d. After the wetland was rendered impermeable, macrophytes from Middle Paraná River floodplain were transplanted. Influent and effluent quality was analyzed every 15 d. TP, Cr, Ni and Zn concentrations in leaves, roots and sediment (inlet and outlet) were measured monthly. Cover and biomass of predominant species were estimated. Also, greenhouse experiments were carried out to measure the effects of conductivity and pH on floating species. The variables measured in the influent were significantly higher than those in the effluent, except for HCO(3)(-) and NH(4)(+). TP and metal concentrations in sediment at the inlet were significantly higher than those at the outlet. Conductivity and pH of the incoming wastewater were toxic for the floating species. Typha domingensis displaced the other species and reached positive relative cover rate and biomass greater than those at the undisturbed natural environment. T. domingensis proved to be highly efficient for the treatment of wastewater. For that reason, it is the advisable species for the treatment of wastewater of high conductivity and pH enriched with metals, characteristic of many industrial processes.
Quantitative PCR of denitrification genes encoding the nitrate, nitrite, and nitrous oxide reductases was used to study denitrifiers
across a glacier foreland. Environmental samples collected at different distances from a receding glacier contained amounts
of 16S rRNA target molecules ranging from 4.9 × 105 to 8.9 × 105 copies per nanogram of DNA but smaller amounts of narG, nirK, and nosZ target molecules. Thus, numbers of narG, nirK, nirS, and nosZ copies per nanogram of DNA ranged from 2.1 × 103 to 2.6 × 104, 7.4 × 102 to 1.4 × 103, 2.5 × 102 to 6.4 × 103, and 1.2 × 103 to 5.5 × 103, respectively. The densities of 16S rRNA genes per gram of soil increased with progressing soil development. The densities
as well as relative abundances of different denitrification genes provide evidence that different denitrifier communities
develop under primary succession: higher percentages of narG and nirS versus 16S rRNA genes were observed in the early stage of primary succession, while the percentages of nirK and nosZ genes showed no significant increase or decrease with soil age. Statistical analyses revealed that the amount of organic
substances was the most important factor in the abundance of eubacteria as well as of nirK and nosZ communities, and copy numbers of these two genes were the most important drivers changing the denitrifying community along
the chronosequence. This study yields an initial insight into the ecology of bacteria carrying genes for the denitrification
pathway in a newly developing alpine environment.
The processes that affect removal and retention of nitrogen during wastewater treatment in constructed wetlands (CWs) are manifold and include NH(3) volatilization, nitrification, denitrification, nitrogen fixation, plant and microbial uptake, mineralization (ammonification), nitrate reduction to ammonium (nitrate-ammonification), anaerobic ammonia oxidation (ANAMMOX), fragmentation, sorption, desorption, burial, and leaching. However, only few processes ultimately remove total nitrogen from the wastewater while most processes just convert nitrogen to its various forms. Removal of total nitrogen in studied types of constructed wetlands varied between 40 and 55% with removed load ranging between 250 and 630 g N m(-2) yr(-1) depending on CWs type and inflow loading. However, the processes responsible for the removal differ in magnitude among systems. Single-stage constructed wetlands cannot achieve high removal of total nitrogen due to their inability to provide both aerobic and anaerobic conditions at the same time. Vertical flow constructed wetlands remove successfully ammonia-N but very limited denitrification takes place in these systems. On the other hand, horizontal-flow constructed wetlands provide good conditions for denitrification but the ability of these system to nitrify ammonia is very limited. Therefore, various types of constructed wetlands may be combined with each other in order to exploit the specific advantages of the individual systems. The soil phosphorus cycle is fundamentally different from the N cycle. There are no valency changes during biotic assimilation of inorganic P or during decomposition of organic P by microorganisms. Phosphorus transformations during wastewater treatment in CWs include adsorption, desorption, precipitation, dissolution, plant and microbial uptake, fragmentation, leaching, mineralization, sedimentation (peat accretion) and burial. The major phosphorus removal processes are sorption, precipitation, plant uptake (with subsequent harvest) and peat/soil accretion. However, the first three processes are saturable and soil accretion occurs only in FWS CWs. Removal of phosphorus in all types of constructed wetlands is low unless special substrates with high sorption capacity are used. Removal of total phosphorus varied between 40 and 60% in all types of constructed wetlands with removed load ranging between 45 and 75 g N m(-2) yr(-1) depending on CWs type and inflow loading. Removal of both nitrogen and phosphorus via harvesting of aboveground biomass of emergent vegetation is low but it could be substantial for lightly loaded systems (cca 100-200 g N m(-2) yr(-1) and 10-20 g P m(-2) yr(-1)). Systems with free-floating plants may achieve higher removal of nitrogen via harvesting due to multiple harvesting schedule.
The larger aquatic plants growing in wetlands are usually called macrophytes. These include aquatic vascular plants, aquatic mosses and some larger algae. The presence or absence of aquatic macrophytes is one of the characteristics used to define wetlands, and as such macrophytes are an indispensable component of these ecosystems. As the most important removal processes in constructed treatment wetlands are based on physical and microbial processes, the role of the macrophytes in these has been questioned. This paper summarizes how macrophytes influence the treatment processes in wetlands.
The most important functions of the macrophytes in relation to the treatment of wastewater are the physical effects the presence of the plants gives rise to. The macrophytes stabilise the surface of the beds, provide good conditions for physical filtration, prevent vertical flow systems from clogging, insulate the surface against frost during winter, and provide a huge surface area for attached microbial growth. Contrary to earlier belief, the growth of macrophytes does not increase the hydraulic conductivity of the substrate in soil-based subsurface flow constructed wetlands. The metabolism of the macrophytes affects the treatment processes to different extents depending on the type of the constructed wetland. Plant uptake of nutrients is only of quantitative importance in low-loaded systems (surface flow systems). Macrophyte mediated transfer of oxygen to the rhizosphere by leakage from roots increases aerobic degradation of organic matter and nitrification. The macrophytes have additional site-specific values by providing habitat for wildlife and making wastewater treatment systems aesthetically pleasing.
We report on the observations of two ultra metal-poor (UMP) stars with
[Fe/H]~-4.0 including one new discovery. The two stars are studied in the
on-going and quite efficient project to search for extremely metal-poor (EMP)
stars with LAMOST and Subaru. Detailed abundances or upper limits of abundances
have been derived for 15 elements from Li to Eu based on high-resolution
spectra obtained with Subaru/HDS. The abundance patterns of both UMP stars are
consistent with the "normal-population" among the low-metallicity stars. Both
of the two program stars show carbon-enhancement without any excess of heavy
neutron-capture elements, indicating that they belong to the subclass of
CEMP-no stars, as is the case of most UMP stars previously studied. The [Sr/Ba]
ratios of both CEMP-no UMP stars are above [Sr/Ba]~-0.4, suggesting the origin
of the carbon-excess is not compatible with the mass transfer from an AGB
companion where the s-process has operated. Lithium abundance is measured in
the newly discovered UMP star LAMOST J125346.09+075343.1, making it the second
UMP turnoff star with Li detection. The Li abundance of LAMOST
J125346.09+075343.1 is slightly lower than the values obtained for less
metal-poor stars with similar temperature, and provides a unique data point at
[Fe/H]~-4.2 to support the "meltdown" of the Li Spite-plateau at extremely low
metallicity. Comparison with the other two UMP and HMP (hyper metal-poor with
[Fe/H]<-5.0) turnoff stars suggests that the difference in lighter elements
such as CNO and Na might cause notable difference in lithium abundances among
CEMP-no stars.
Plant vegetation has been reported to be one of the best management practices to control the transport of nutrient pollutants in agricultural drainage. In this study, soil samples were collected from a novel constructed drainage ditch (ND) vegetated with strips of Indica canna, Hydrocotyle vulgaris, Sparganium stoloniferum, Myriophyllum aquaticum, and Juncus effusus, from an upstream ordinary agricultural drainage ditch (OD), and from an adjacent paddy field (PD), at the 0-5 and 5-15 cm layers, to compare phosphorus (P) sorption capacity. In the ND, there was a great difference in the properties of ditch soils between at the 0-5 cm and 5-15 cm layers. For instance, total organic carbon (TOC) at the 0-5 cm layer increased rapidly with the growth of Indica canna, Hydrocotyle vulgaris, and Myriophyllum aquaticum in the ND for approximately 3 years. Correspondingly, those three plants elevated the P sorption maximums (S-max) of the ditch soil, which were determined to be 521, 612, and 552 mg kg(-1), respectively. The equilibrium phosphorus concentration (EPC0) and the degree of P saturation (DSP) of the ditch soils in the ND were also shown to be lower than those in the OD, which may be attributed to efficient ditch clearance in the ND. The Pearson's correlation analysis revealed significant correlations of TOC with the key parameters of the P sorption isothermal curves, such as the Freundlich adsorption constant (K-F), S-max, EPC0, and DSP. Furthermore, the multivariate regression analysis showed that TOC explained more than 50% of the variability of S-max and DPS, suggesting that the vegetated drainage ditch played an important role in regulating the P adsorption capacity of the ditch soils. Our collective results indicated that plant vegetation and ditch clearance can be optimized to enhance the P retention capacity of ditch soils via robust and re-vegetated drainage ditch systems, such as the ND, and have a great potential to reduce the P loss from agricultural headwater catchments.
Plants are an indispensable component of a constructed wetland; however, the eco-physiological characteristics of wetland plants and their influences on wastewater treatment efficiency are still unclear. In this study, we investigated the growth features of six commonly used wetland plants, namely, Canna indica (Ci), Iris pseudacorus (Ip), Pontederia cordata (Pc), Cyperus alternifolius (Ca), Vetiveria zizanioides (Vz), and Pennisetum purpureum (Pp) that were treated with sewage. After 50 days of treatment, plants treated with diluted sewage, especially Ci and Ip, had a better growth rate than those receiving undiluted sewage. The abilities of different wetland plants to directly take up nitrogen (9.28-17.26 mg g−1 DW) and phosphorus (0.89-2.18 mg g−1 DW) were species-specific, but within each species, uptake was similar between diluted and undiluted sewage. Total biomass determined the total accumulation of N and P in plant tissues. The removal of pollutants, except nitrate and organic matter, was dependent on both plant species and sewage dilution. The first-order rate constants (K) for nitrate and organic matter were similar between diluted and undiluted sewage. Differences in the removal of nitrate and biochemical oxygen demand among plant species were due to differences in chlorophyll fluorescence, a photosynthetic characteristic, leading to different root lengths. The amounts of oxygen release to the rhizosphere (radial oxygen loss [ROL]) by wetland plant was directly governed by total root biomass and significantly influenced the removal of ammonia and total dissolved phosphorus via processes such as plant uptake and nitrification. The removal of total phosphorus and chemical oxygen demand resulted from the filtration by root systems. A non-species-specific significant positive correlation was found between ROL (12.50-205.25 μmol O2 d−1 g−1 DWroot) and root porosity (9.95-32.49%). These results suggest that the root features and photosynthetic characteristic of wetland plants are important determinants of sewage treatment efficiency and could be used to select appropriate plants for constructed wetland systems.
Constructed wetlands with free water surface (FWS CWs) have been used for many purposes worldwide. Emergent macrophytes play important roles in FWS CWs; they reduce wind speed and thus support sedimentation and prevent re-suspension, provide substrate for periphyton and bacteria, take up nutrients and in carbon-limited systems provide carbon for denitrification during biomass decomposition. It has been reported that treatment performance of planted FWS CWs is superior to unvegetated lagoons. However, treatment performance of FWS CWs could be affected by plant species used. The literature survey of 643 FWS CWs from 43 countries recorded 150 plant species and revealed that the most commonly used macrophyte genera were Typha, Scirpus (Schoenoplectus), Phragmites, Juncus and Eleocharis. In terms of species, most frequently used species were Typha latifolia, Phragmites australis, Typha angustifolia, Juncus effusus, Scirpus lacustris, Scirpus californicus and Phalaris arundinacea. In terms of continents, P. australis is the most frequent species in Europe and Asia, T. latifolia in North America, Cyperus papyrus in Africa, P. australis and Typha domingensis in Central/South Americas and Scirpus validus (S. tabernaemontani) in Oceania.
Water eutrophication in subtropical regions of southern China threatens watershed health and is of major concern. However, annual phosphorus (P) loading and its dominant causes are still unclear, especially at the watershed scale. In this study, we investigated dynamic P loadings and associated factors (e.g., land use, livestock production, and runoff depth) in ten watersheds that varied in area from 9 to 5,212 ha in a hilly area of Hunan Province, China. A flowmeter was installed at the outlet of each watershed, and total P (TP) and soluble P (SP) concentrations were monitored periodically from June 2010 to October 2012. The results showed that annual P loadings (APLs) in the ten watersheds ranged from 22.8 to 247.8 kg P/km(2) and that P loss primarily occurred from April to June of each year during the main rainfall season in the study area. In addition, the average eutrophication (>0.05 mg P/L) ratio for stream waters was 86.7 % during the study period, which was indicative of a potentially serious condition for the local water environments. Annual P loadings were linearly related to livestock density (LD; R = 0.92, p < 0.01), whereas the eutrophication ratio of stream water was significantly (p < 0.05) correlated with LD (R = 0.61), percentage cropland (R = 0.71), and percentage forest cover (R = -0.68). Thus, it is concluded that the control of livestock production has the greatest potential for reducing P loadings in watersheds in this subtropical area. This will be beneficial to the amelioration and protection of local environment.
An experimental continuous Circular-Flow Corridor (CFC) wetland was developed for the secondary treatment of high-strength swine wastewater. The removal performances of ammonium and phosphorus were investigated, and their mass balance was quantified. CFC wetland shows high efficiency toward the removal of COD, NH4-N and TP, with the average efficiency of which was all above 93.9%. CFC wetland exhibits promising efficiency even in winter, and as low as 5% decrease of the removal efficiency was observed in winter. In high temperature period (20–25 °C), nitrification and the adsorption of zeolite dominates in the removal of NH4-N with the average contribution of 45.1% and 31.3%, respectively. However, in low temperature period (3–7.5 °C), zeolite adsorption contributes to as high as 87.9% of the removal of NH4-N. The removal of phosphorus is achieved in the front of the wetland, mainly through the co-precipitation with Ca2+ and Mg2+ substituted from zeolite. The effect not only delays the clogging of porous media, but also increases the utility of released Ca2+ and Mg2+. Furthermore, to achieve the long-term treatment stability of the CFC wetland, only the regeneration of zeolite at intervals of 0.5 year is required. This CFC wetland is a reliable, cheap and effective treatment process for the treatment of high-strength swine wastewater.
The hybrid systems were developed in the 1960s but their use increased only during the late 1990s and in the 2000s mostly because of more stringent discharge limits for nitrogen and also more complex wastewaters treated in constructed wetlands (CWs). The early hybrid CWs consisted of several stages of vertical flow (VF) followed by several stages of horizontal flow (HF) beds. During the 1990s, HF-VF and VF-HF hybrid systems were introduced. However, to achieve higher removal of total nitrogen or to treat more complex industrial and agricultural wastewaters other types of hybrid constructed wetlands including free water surface (FWS) CWs and multistage CWs have recently been used as well. The survey of 60 hybrid constructed wetlands from 24 countries reported after 2003 revealed that hybrid constructed wetlands are primarily used on Europe and in Asia while in other continents their use is limited. The most commonly used hybrid system is a VF-HF constructed wetland which has been used for treatment of both sewage and industrial wastewaters. On the other hand, the use of a HF-VF system has been reported only for treatment of municipal sewage. Out of 60 surveyed hybrid systems, 38 have been designed to treat municipal sewage while 22 hybrid systems were designed to treat various industrial and agricultural wastewaters. The more detailed analysis revealed that VF-HF hybrid constructed wetlands are slightly more efficient in ammonia removal than hybrid systems with FWS CWs, HF-VF systems or multistage VF and HF hybrid CWs. All types of hybrid CWs are comparable with single VF CWs in terms of NH4-N removal rates. On the other hand, CWs with FWS units remove substantially more total nitrogen as compared to other types of hybrid constructed wetlands. However, all types of hybrid constructed wetlands are more efficient in total nitrogen removal than single HF or VF constructed wetlands.
Understanding the sorption and desorption behavior of NH4+ in soils associated with animal waste is important because of the potential for the formation of NO3- and subsequent leaching that affects ground water quality. Batch equilibration experiments were conducted to evaluate the sorption and desorption of NH4+ in two soils exposed to a complex matrix (liquid swine waste) and a simple matrix [aqueous solution of 0.01 M CaCl2 containing (NH4)(2)SO4]. Kennebec silt loam (fine-silty, mixed, mesic Cumulic Hapludolls) and Haynie very fine sandy loam (coarse-silty, mixed, calcareous, mesic Mollic Udifluvents) were used. This study revealed that the sorption and desorption behavior of NH4+ in soils exposed to (NH4)(2)SO4 Solutions with a 0.01 M CaCl2 matrix is significantly different from that in soils exposed to liquid swine waste. Faster sorption rate, lower sorption capacity, and higher desorption capability were observed for NH4+ in soils exposed to the (NH4)(2)SO4 Solution compared with soils exposed to the liquid swine waste. Sequential extraction could not extract nonexchangeable NH4+ in both soils exposed to liquid swine waste, while a significant amount of nonexchangeable NH4+ was extracted from the two soils that were initially exposed to the (NH4)(2)SO4 solutions. The high dissolved organic C (DOC) content coupled with the high pH in swine waste appears to stimulate the sorption and retard desorption of NH4+ in the two soils. This study revealed that batch equilibrium studies using solutions with simple matrixes may underestimate the sorption or overestimate desorption of NH4+ in soils associated with swine waste.
Nitrate removal rates and dissolved oxygen (DO) levels were evaluated in small batch-mode wetland mesocosms with two different plant species, cattail (Typha spp.) and bulrush (Scirpus spp.), and associated mineral-dominated sediment collected from a mature treatment wetland. Nitrate loss in both cattail and bulrush mesocosms was first-order in nature. First-order volumetric rate constants (kV) were 0.30d−1 for cattail and 0.21d−1 for bulrush and rates of nitrate loss were significantly different between plant treatments (p 15mgN/L). Areal removal rates were on average 25% higher in cattail versus bulrush mesocosms. DO in mesocosm water was significantly higher in bulrush versus cattail (p
Ammonia oxidation plays a pivotal role in the cycling and removal of nitrogen in aquatic ecosystems. Recent findings have expanded the known ammonia-oxidizing prokaryotes from Bacteria to Archaea. However, the relative importance of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in nitrification is still debated. Here we showed that, in two large eutrophic lakes in China (Lake Taihu and Lake Chaohu), the abundance of AOA and AOB varied in opposite patterns according to the trophic state, although both AOA and AOB were abundant. In detail, from mesotrophic to eutrophic sites, the AOA abundance decreased, while the AOB increased in abundance and outnumbered the AOA at hypertrophic sites. In parallel, the nitrification rate increased along these trophic gradients and was significantly correlated with both the AOB abundance and the numerical ratio of AOB to AOA. Phylogenetic analysis of bacterial amoA sequences showed that Nitrosomonas oligotropha- and Nitrosospira-affiliated AOB dominated in both lakes, while Nitrosomonas communis-related AOB were only detected at the eutrophic sites. The diversity of AOB increased from mesotrophic to eutrophic sites and was positively correlated with the nitrification rate. Overall, this study enhances our understanding of the ecology of ammonia-oxidizing prokaryotes by elucidating conditions that AOB may numerically predominated over AOA, and indicated that AOA may play a less important role than AOB in the nitrification process of eutrophic lakes.
The difference between the molar concentrations of simultaneously extracted metals (SEM) and acid volatile sulfides (AVS) is widely used to predict metal availability toward invertebrates in hypoxic sediments. However, this model is poorly investigated for macrophytes. The present study evaluates metal accumulation in roots and stems of the macrophyte Myriophyllum aquaticum during a 54 day lab experiment. The macrophytes, rooting in metal contaminated, hypoxic, and sulfide rich field sediments were exposed to surface water with 40% or 90% oxygen. High oxygen concentrations in the 90% treatment resulted in dissolution of the metal-sulfide complexes and a gradual increase in labile metal concentrations during the experiment. However, the general trend of increasing availability in the sediment with time was not translated in rising M. aquaticum metal concentrations. Processes at the root-sediment interface, e.g., radial oxygen loss (ROL) or the release of organic compounds by plant roots and their effect on metal availability in the rhizosphere may be of larger importance for metal accumulation than the bulk metal mobility predicted by the SEM-AVS model.
Ecological treatment systems, which rely on renewable resources, have successfully treated municipal and industrial effluents with reduced costs compared to conventional methods, but their capacity to treat dairy wastewater is unknown. In order for ecological treatment systems to be practical for agriculture they must be able to treat a significant portion of a dairy's daily wastewater production. In this study, the impact of three strengths of dairy wastewater on effluent water quality was assessed. Three ratios of wastewater and city water—(1) one part wastewater:three parts city water, (2) one part wastewater:one part city water, and (3) two parts wastewater:one part city water—were each pumped into an ecological treatment system. Influent and effluent water samples were analyzed for PO4-P, TP, TN, NH4-N, NO3-N, total suspended solids (TSS), and carbonaceous biochemical oxygen demand (CBOD5). Influent dairy wastewater volumetric loading rates were much greater than those of municipal wastewater. Regardless of influent wastewater strength, concentrations of all measured variables were significantly reduced between the influent and effluent of the ecological treatment system. At the lowest wastewater strength, PO4-P was reduced 39%, TN 83%, and NH4-N 89%, while at the highest wastewater strength, PO4-P was reduced 41%, TN 79%, and NH4-N 70%. Increased wastewater strength required greater aerobic treatment volume to reduce concentrations of NH4-N and CBOD5.
Constructed wetlands are gaining increased attention for treatment of nonpoint sources of water pollution. Although constructed wetlands have been utilized for wastewater treatment in warm climates, their performance in cold climates has been questioned. A surface-flow wetland, designed to treat 2.65 m3 d−1 of milkhouse wastewater, was constructed on the University of Connecticut’s Storrs campus in 1994. The purpose of the project was to determine the efficiency of the system in reducing nitrogen, phosphorus, five-day biochemical oxygen demand (BOD5), total suspended solids (TSS), and fecal coliform bacteria (FC). The wetland was designed to process an estimated BOD5 loading rate of 7.3 g m−2 d−1, which was less than half of the average actual loading rate. The overall percentage of mass retention was 94, 85, 68, 60 and 53% for TSS, BOD5, total phosphorus, nitrate–nitrite and total Kjeldahl-nitrogen, respectively. Although the wetland became a net source of ammonia nitrogen (NH3–N) following plant die back in fall 1994, NH3–N outflow concentrations have gradually declined over time. Mass retention was significantly greater (P<0.05) during the summer than during the winter for all variables except FC. Denitrification rates measured using the acetylene block method have shown denitrification to be a minor removal mechanism (<1%) for nitrogen in this wetland. The mass balance indicated that settling and increased storage was the largest removal mechanism. The treatment of wastewater in this wetland did not meet design outflow concentration criteria, most likely due to BOD5 overloading.
The effect of influent loading rate on mass removal of nitrogen and phosphorus from dairy parlour wastewaters was compared in four pairs of planted (Schoenoplectus validus) and unplanted gravel-bed wetlands (each 19 m2). The wetlands were operated at nominal retention times of 7, 5.5, 3 and 2 days, with in and outflows sampled fortnightly over a 20 month period. Hydraulic flows were monitored to enable calculation of the mass flows of nutrients, and plant biomass and tissue nutrient levels sampled to evaluate plant nutrient uptake. Influent water quality varied markedly during the trial period (TN, 10–110; NH4-N, 5–70; and TP 8–18 g m−3). As theoretical wastewater retention times increased from 2 to 7 days, mean reduction of TN increased from 12 to 41% and 48 to 75% in the unplanted wetlands and planted wetlands, respectively, and TP removal increased from 12 to 36% and 37 to 74%, respectively. In the planted wetlands, mean annual removal rates of TN (0.15–1.4 g m−2 d−1) and TP (0.13–0.32 g m−2 d−1), increased gradually with mass loading rates. The unplanted wetlands showed a marked decline in TN and TP removal at high loadings. Net storage by plants in the first year of monitoring accounted for between 3 and 20% of the greater N removal and between 3 and 60% of the greater P removal in the planted wetlands.
Nitrogen removal processes were investigated at three frequencies of water level fluctuation, static, low and high (0, 2 and 6 d−1), in duplicate gravel-bed constructed wetland mesocosms (0.145 m3) with and without plants (Schoenoplectus tabernaemontani). Fluctuation was achieved by temporarily pumping wastewater into a separate tank (total drain time ∼35 min). Intensive sampling of the mesocosms, batch-fed weekly with ammonium-rich (∼100 g m−3 NH4-N) farm dairy wastewaters, showed rates of chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal increased markedly with fluctuation frequency and in the presence of plants. Nearly complete removal of NH4-N was recorded over the 7 day batch period at the highest level of fluctuation, with minimal enhancement by plants. Redox potentials (Eh) at 100 mm depth rose from initial levels of around −100 to >350 mV and oxidised forms of N (NO2 and NO3) increased to ∼40 g m−3, suggesting conditions were conducive to microbial nitrification at this level of fluctuation. In the unplanted mesocosms with low or zero fluctuation, mean NH4-N removals were only 28 and 10%, respectively, and redox potentials in the media remained low for a substantial part of the batch periods (mid-batch Eh ∼+100 and −100 mV, respectively). In the presence of wetland plants, mean NH4-N removal in the mesocosms with low or zero fluctuation rose to 71 and 54%, respectively, and COD removal (>70%) and redox potential (mid-batch Eh>200 mV) were markedly higher than in the unplanted mesocosms. Negligible increases in oxidised N were recorded at these fluctuation frequencies, but total nitrogen levels declined at mean rates of 2.4 and 1.8 g m−2 d−1, respectively. NH4-N removal from the bulk water in the mesocosms was well described (R2=0.97–0.99) by a sorption-plant uptake-microbial model. First-order volumetric removal rate constants (kv) rose with increasing fluctuation frequency from 0.026 to 0.46 d−1 without plants and from 0.042 to 0.62 d−1 with plants. As fluctuation frequency increased, reversible sorption of NH4-N to the media, and associated biofilms and organic matter, became an increasingly important moderator of bulk water concentrations during the batch periods. TN mass balances for the full batch periods suggested that measured plant uptake estimates of between 0.52 and 1.07 g N m−2 d−1 (inversely related to fluctuation frequency) could fully account for the increased overall removal of TN recorded in the planted systems. By difference, microbial nitrification-denitrification losses were therefore estimated to be approximately doubled by low-level fluctuation from 0.7 to 1.4 g N m−2 d−1 (both with and without plants), rising to a maximum rate of 2.1 g N m−2 d−1 at high fluctuation, in the absence of competitive uptake by plants.
In this study, the performance of a combined subsurface vertical and horizontal flow constructed wetlands system, designed for rural domestic wastewaters treatment and with theoretical hydraulic retention time of 2 d and 3.6 d, respectively, was investigated. Several water quality parameters including pH, BOD5, COD, TSS, TKN and TP, and faecal bacteria’s number in both raw and treated wastewaters were monitored during a macrophytes life cycle. At the same time, the growth of the rooted plants, reeds and cattails was investigated through the measurement of the height and leaves number. The average influent characteristics were as follows: pH (7.98 ± 0.27), BOD5 (420 ± 144 mg/L), COD (1339 ± 352 mg/L), TSS (798 ± 302 mg/L), TKN (205 ± 70 mg/L), TP (30.7 ± 12.4 mg/L), faecal coliforms ([2.69 ± 4.14] × 107 CFU/100 mL) and faecal streptococci ([9.35 ± 1.81] × 106 CFU/100 mL). The main treatment performance results showed the following average removal rates: BOD5 (93 ± 2%), COD (89 ± 3%), TSS (98 ± 1.5%), TKN (38 ± 19%), TP (72 ± 16%). The average bacterial reduction between the inlet and the outlet was of the order of 4 ± 1 logarithmic units for faecal coliforms and 3 ± 1 logarithmic units for faecal streptococci. Analysis of the results reveals a temporal variation in the system’s performance depending on the primary treatment operation and on the macrophytes growth rate. Reeds and cattails start their life cycle at the beginning of the spring and continue their development during summer. During the autumn season, the plants reach their optimum growth rate, and after that, they enter the dormant phase. The quality of the treated wastewaters was evaluated according to Tunisian standards. The average effluent pH, BOD5, TSS and faecal bacteria were in agreement with the standards, but COD, nitrogen and phosphorus residual loads were still above the values required by the quality criteria.
The research objective was to investigate the ability of marsh–pond–marsh (m–p–m) constructed wetlands to treat wastewater from a confined swine operation over varying nitrogen loads. Swine wastewater was applied to six, m–p–m wetlands in Greensboro, NC, USA, during two experimental periods, summer and winter. The efficiency of each system to remove the following wastewater constituents was determined: total suspended solids (TSS); chemical oxygen demand (COD); nitrogen (N); phosphorus (P). During the study, the wetlands removed an average 35–51% of TSS, 30–50% of COD, 37–51% of total N, and 13–26% of total P from swine wastewater. For wastewater COD and N, treatment efficiency was significantly lower during the winter experimental period compared to the summer. Treatment efficiency for all constituents tended to decrease with decreasing air temperatures and increasing rainfall amounts. While these m–p–m wetlands treated more N than an equal area of farm land they were not superior in their N treatment ability compared to previously studied continuous-marsh systems.
Animal wastewater can be a major contributor to the cultural eutrophication of surface waters. Constructed wetlands are under study as a best management practice to treat animal wastewater from dairy and swine operations. Preliminary results are promising when wetlands are a component of a farm-wide waste management plan, but they are ineffective without pretreatment of the wastewater. The feasibility of constructed wetlands varies with waste characteristics and climate. While the cost of wetland construction is low, the site must be maintained in order for the initial investment in the wetland to be worthwhile. In addition, several design iterations may be necessary before effective treatment is obtained. The design of animal wastewater treatment wetlands is still being researched and a number of the present projects will help provide recommendations for the use of constructed wetlands at animal operations.
The South Nation River Watershed, in eastern Ontario, Canada, is an agricultural watershed impacted by excess nutrient loading primarily from agricultural activities. A constructed wetland for the treatment of agricultural wastewater from a 150-cow dairy operation in this watershed was monitored in its eighth operating season to evaluate the proportion of total nitrogen (TN) (approximated by total Kjeldahl nitrogen (TKN) due to low NO3−) and total phosphorus (TP) removal that could be attributed to storage in Typha latifolia L. and Typha angustifolia L., which dominate this system. Nutrient loading rates were high, with 16.2 kg ha−1 d−1 N and 3.4 kg ha−1 d−1 P entering the wetland and loading the first wetland cell. Plant uptake accounted for 0.7% of TKN removal when the vegetated free water surface cells were considered together. However, separately, in the second wetland cell with lower N and P loading rates, plants accounted for 9% of TKN, 21% of NH4+ and 5% of TP removal. Plant uptake was significant to overall removal given wetland age and nutrient loading. Nutrient storage during the growing season at this constructed wetland helped reduce the nutrient load entering the watershed, already stressed by intensive local agriculture.
Spirodela oligorrhiza, a promising duckweed identified in previous studies, was examined under different cropping conditions for nutrient recovery from swine wastewater and biomass production. To prevent algae bloom during the start-up of a duckweed system, inoculating 60% of the water surface with duckweed fronds was required. In the growing season, the duckweed system was capable of removing 83.7% and 89.4% of total nitrogen (TN) and total phosphorus (TP) respectively from 6% swine lagoon water in eight weeks at a harvest frequency of twice a week. The total biomass harvested was 5.30 times that of the starting amount. In winter, nutrients could still be substantially removed in spite of the limited duckweed growth, which was probably attributed to the improved protein accumulation of duckweed plants and the nutrient uptake by the attached biofilm (algae and bacteria) on duckweed and walls of the system.
The first experiments on the use of wetland plants to treat wastewaters were carried out in the early 1950s by Dr. Käthe Seidel in Germany and the first full-scale systems were put into operation during the late 1960s. Since then, the subsurface systems have been commonly used in Europe while free water surface systems have been more popular in North America and Australia. During the 1970s and 1980s, the information on constructed wetland technology spread slowly. But since the 1990 s the technology has become international, facilitated by exchange among scientists and researchers around the world. Because of the need for more effective removal of ammonia and total nitrogen, during the 1990 s and 2000s vertical and horizontal flow constructed wetlands were combined to complement each other to achieve higher treatment efficiency. Today, constructed wetlands are recognized as a reliable wastewater treatment technology and they represent a suitable solution for the treatment of many types of wastewater.
We re-evaluated PCR primers targeting nirS, nirK and nosZ genes for denaturing gradient gel electrophoresis as a tool to survey denitrifying community composition in environmental samples. New primers for both nirS and nosZ were combined with existing primers, while for nirK the previously published F1aCu:R3Cu set was chosen for denaturing electrophoresis. All three sets yielded amplicons smaller than 500 bp and amplified the correct fragment in all environmental samples. The denaturing gradient gel electrophoresis worked satisfactorily for nirK and nosZ, but not for nirS. This was probably due to the multiple melting domains in this particular nirS fragment. From the excised and sequenced bands, only sequences related to the target genes were detected and tree analysis showed that the selected primers acted as broad range primers for each of the three genes. By use of the new nirS primers it was demonstrated that agricultural soil harbours a substantial diversity of nirS denitrifiers.
Nitrogen (N) processing in constructed wetlands (CWs) is often variable, and the contribution to N loss and retention by various pathways (nitrification/denitrification, plant uptake and sediment storage) remains unclear. We studied the seasonal variation of the effects of artificial aeration and three different macrophyte species (Phragmites australis, Typha angustifolia and Phalaris arundinacea) on N processing (removal rates, transformations and export) using experimental CW mesocosms. Removal of total nitrogen (TN) was higher in summer and in planted and aerated units, with the highest mean removal in units planted with T. angustifolia. Export of ammonium (NH(4)(+)), a proxy for nitrification limitation, was higher in winter, and in unplanted and non-aerated units. Planted and aerated units had the highest export of oxidized nitrogen (NO(y)), a proxy for reduced denitrification. Redox potential, evapotranspiration (ETP) rates and hydraulic retention times (HRT) were all predictors of TN, NH(4)(+) and NO(y) export, and significantly affected by plants. Denitrification was the main N sink in most treatments accounting for 47-62% of TN removal, while sediment storage was dominant in unplanted non-aerated units and units planted with P. arundinacea. Plant uptake accounted for less than 20% of the removal. Uncertainties about the long-term fate of the N stored in sediments suggest that the fraction attributed to denitrification losses could be underestimated in this study.
The naturally occurring genetic heterogeneity of autotrophic ammonia-oxidizing populations belonging to the beta subclass of the Proteobacteria was studied by using a newly developed PCR-based assay targeting a partial stretch of the gene which encodes the active-site polypeptide of ammonia monooxygenase (amoA). The PCR yielded a specific 491-bp fragment with all of the nitrifiers tested, but not with the homologous stretch of the particulate methane monooxygenase, a key enzyme of methane-oxidizing bacteria. The assay also specifically detected amoA in DNA extracted from various aquatic and terrestrial environments. The resulting PCR products retrieved from rice roots, activated sludge, a freshwater sample, and an enrichment culture were used for the generation of amoA gene libraries. No false positives were detected in a set of 47 randomly selected clone sequences that were analyzed further. The majority of the environmental sequences retrieved from rice roots and activated sludge grouped within the phylogenetic radiation defined by cultured strains of the genera Nitrosomonas and Nitrosospira. The comparative analysis identified members of both of these genera in activated sludge; however, only Nitrosospira-like sequences with very similar amino acid patterns were found on rice roots. Further differentiation of these molecular isolates was clearly possible on the nucleic acid level due to the accumulation of synonymous mutations, suggesting that several closely related but distinct Nitrosospira-like populations are the main colonizers of the rhizosphere of rice. Each of the amoA gene libraries obtained from the freshwater sample and the enrichment culture was dominated by a novel lineage that shared a branch with the Nitrosospira cluster but could not be assigned to any of the known pure cultures. Our data suggest that amoA represents a very powerful molecular tool for analyzing indigenous ammonia-oxidizing communities due to (i) its specificity, (ii) its fine-scale resolution of closely related populations, and (iii) the fact that a functional trait rather than a phylogenetic trait is detected.
Denitrification, the reduction of nitrate to nitrous oxide or dinitrogen, is the major biological mechanism by which fixed nitrogen returns to the atmosphere from soil and water. Microorganisms capable of denitrification are widely distributed in the environment but little is known about their abundance since quantification is performed using fastidious and time-consuming MPN-based approaches. We used real-time PCR to quantify the denitrifying nitrite reductase gene (nirK), a key enzyme of the denitrifying pathway catalyzing the reduction of soluble nitrogen oxide to gaseous form. The real-time PCR assay was linear over 7 orders of magnitude and sensitive down to 10(2) copies by assay. Real-time PCR analysis of different soil samples showed nirK densities of 9.7x10(4) to 3.9x10(6) copies per gram of soil. Soil real-time PCR products were cloned and sequenced. Analysis of 56 clone sequences revealed that all cloned real-time PCR products exhibited high similarities to previously described nirK. However, phylogenetic analysis showed that most of environmental sequences are not related to nirK from cultivated denitrifiers.
To study the relationship between the nature of the substratum and the diversity and stability of the ammonia-oxidizing microbial community in a constructed wetland for the treatment of wastewaters.
Samples have been taken the year around from sections of the wetland filled with different substrata. When present, the root zones of the helophyte Phragmites australis were also sampled. The diversity of the ammonia-oxidizing community was established by a coupled PCR-DGGE method based on the 16s rRNA gene. Averaged over the seasons, no large differences in community composition were observed between the different substrata, although the section with zeolite always showed the highest frequencies of bands belonging to ammonia-oxidizing bacteria of the beta-subclass of the Proteobacteria. Only sequences related to the Nitrosospira lineage were detected. Averaged again over the seasons, the section with zeolite was also most constant with respect to the potential ammonia-oxidizing activity.
Although the ammonia-oxidizing communities did not differ significantly between the different sections of the constructed wetland, the characteristics of zeolite were most appropriate to accommodate a stable and active community of ammonia-oxidizing bacteria. The presence of the helophyte had no effect on the diversity and stability of the ammonia-oxidizing community.
It has been shown that substrata used in constructed wetlands made no distinction between ammonia-oxidizing strains in relation to attachment. However, zeolite had the best performance with respect to activity over the seasons.
The diversity and spatio-temporal distribution of ammonia-oxidizing Archaea (AOA) and Bacteria (AOB) were investigated along a salinity gradient in sediments of the Westerschelde estuary. Sediment samples were collected from three sites with different salinities, and at six time points over the year. Denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA and amoA gene fragments was used to identify the AOA and AOB present. Members of the AOA were mainly belonging to the Crenarchaeota Group 1, which were found at all sites, while members of the genus Nitrosomonas, which were abundant at the brackish sites, and of the genus Nitrosospira, which were present in early spring at the marine sites, were found to be the dominant AOB. Statistical analysis indicated that salinity and temperature were the main factors controlling the diversity and distribution of both AOA and AOB. Variability in net primary production rates was also correlated with species composition of both groups, but changes in the nitrite concentration only to the distribution of the AOA.
Combined process of biofilter, constructed wetland and stabilization pond for treatment of rural decentralized sewage
- H F Li
- F Liu
- H J Li
- R L Xiao
- Y He
- D Wang
- J S Wu
Li, H.F., Liu, F., Li, H.J., Xiao, R.L., He, Y., Wang, D., Wu, J.S., 2015. Combined process of
biofilter, constructed wetland and stabilization pond for treatment of rural
decentralized sewage. China Water Wastewater 31, 84e87 (in Chinese).
- F Liu
F. Liu et al. / Journal of Environmental Management 166 (2016) 596e604
- J A Schaafsma
- A H Baldwin
- C A Streb
Schaafsma, J.A., Baldwin, A.H., Streb, C.A., 2000. An evaluation of a constructed
wetland to treat wastewater from a dairy farm in Maryland, USA. Ecol. Eng. 14,
199e206.