Article

A three-stage experimental constructed wetland for treatment of domestic sewage: First 2 years of operation

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Abstract

Hybrid constructed wetland systems have recently been used to treat wastewaters where high demand for removal of ammonia is required. However, these systems have not been used too often for small on-site treatment systems. This is because in many countries ammonia is not limited in the discharge from small systems. Hybrid systems have a great potential to reduce both ammonia and nitrate concentrations at the same time. In our study we employed a three-stage constructed wetland system consisting of saturated vertical-flow (VF) bed (2.5 m2, planted with Phragmites australis), free-drained VF bed (1.5 m2, planted with P. australis) and horizontal-flow (HF) bed (6 m2, planted with Phalaris arundinacea) in series. All wetlands were originally filled with crushed rock (4–8 mm). However, nitrification was achieved only after the crushed rock was replaced with sand (0–4 mm) in the free-drain wetland. Also, original size of crushed rock proved to be too vulnerable to clogging and therefore, in the first wetlands the upper 40 cm was replaced by coarser fraction of crushed rock (16–32 mm) before the second year of operation started. The system was fed with mechanically pretreated municipal wastewater and the total daily flow was divided into two batches 12 h apart. The evaluation of the results from the period 2007 to 2008 indicated that such a system has a great potential for oxidation of ammonia and reduction of nitrate. The ammonia was substantially reduced in the free-drained VF bed and nitrate was effectively reduced in the final HF bed. The inflow mean NH4-N concentration of 29.9 mg/l was reduced to 6.5 mg/l with the average removal efficiency of 78.3%. At the same time the average nitrate-N concentration rose from 0.5 to only 2.7 mg/l at the outflow. Removal of BOD5 and COD amounted to 94.5% and 84.4%, respectively, with respective average outflow concentrations of 10 and 50 mg/l. Phosphorus was removed efficiently despite the fact that the system was not aimed at P removal and therefore no special media were used. Phosphorus removal amounted in 2008 to 65.4%, but the average outflow concentration of 1.8 mg/l is still high. The results of the present study indicate very efficient performance of the hybrid constructed wetlands, but optimal loading parameters still need to be adjusted. The capital cost of the experimental system is comparable to the conventional on-site treatment plant but the operations and maintenance costs are about one third of the conventional plant.

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... It is probably because of the high-strength wastewater and the high wastewater flooding (Dan et al. 2011). Also, the percentage of BOD removal displayed higher than that of other contaminations at the reproductive stage between 65 and 73% (Table 1) due to increased oxygen supply to the rhizosphere (Vymazal and Kröpfelová 2011). Pedescoll et al. (2011) confirmed that P. australis is a good system for removal efficiency of ammonium and COD and high sorption capacity in P. australis is due to excessive iron. ...
... Pedescoll et al. (2011) confirmed that P. australis is a good system for removal efficiency of ammonium and COD and high sorption capacity in P. australis is due to excessive iron. Vymazal and Kröpfelová (2011) displayed that the P. australis in constructed wetlands causes the removal of BOD and COD by 94.5% and 84.4%, respectively. ...
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Article
This study investigates the impact of wastewater irrigation on soil-plant-water system at the vegetative, flowering, and reproductive stages of Phragmites australis for two and four days (in each stage) in the coastal saline area of Urmia Lake. The concentrations of potentially toxic elements were detected in irrigated water, soil, and plant (aboveground and belowground) tissues, and transfer factor and bioaccumulation factor were calculated. The shoot biomass was significantly increased with increasing wastewater exposure, up to four days after the flowering stage. All potentially toxic elements concentrations in belowground (roots and rhizomes) tissues were higher than aboveground (leaves and stems) tissues. Fe showed the maximum concentrations in all organs at different growth stages due to the higher level contents in soil and water. Fe was found to be the least mobile at the reproductive stage and presented in the following order: roots > rhizomes > leaves ≥ stems. By contrast, Zn and Cd metals which are quickly transported in plants exhibited the same trend. Pb was accumulated at the flowering stage as follows: rhizomes > roots > stems > leaves. The toxic threshold was exceeded by Zn, Fe, Cu, and Cd in roots; Fe in rhizomes, and leaves; Cd in rhizomes; and Ni in roots. There was more efficiency in the removal of chemical oxygen demand (61.09%), biochemical oxygen demand (73%), total suspended solids (50%), and ammoniacal nitrogen (59.5%) at the reproductive stage. Therefore, P. australis could be an efficient and valuable tool for the phytoextraction and phytostabilization of metals if harvested at the proper time of growth in high potentially toxic elements polluted coastal ecosystems.
... Similar effects of ammonium nitrogen removal (88-91%) were also obtained earlier in two similar hybrid VF-HF type systems with reed and willow in Poland [20]. On the other hand, much smaller effects of N-NH 4 + removal (84%) were obtained in VF-VF-HF type CWs in Ireland-84% [64], in a HF-VF system in Poland-79% [20] and in a VF-VF-HF system in the Czech Republic-78% [76]. In the HF-VF type object in Nepal the efficiency of ammonium nitrogen removal was only 69% [62]. ...
... In most of the world's hybrid CWs the average efficiency of total phosphorus removal was usually between 70% and 89% [14,59,65,77,86]. There were also some cases where the efficiency of phosphorus removal was low and ranged from 47-65% [11,60,76] or even less than 40% [25,62,64]. It was also shown that the effects of total phosphorus removal in hybrid CWs are usually about 20-40% higher than in one-stage systems [20,38]. ...
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Article
The paper presents the results of a 3-year study on the technological reliability and the efficiency of typical domestic wastewater treatment in two hybrid constructed wetland systems (CWs) located in the area of the Roztocze National Park (Poland). The studied objects consist of an initial settling tank and a system of two beds of the vertical flow (VF) and horizontal flow (HF) (VF–HF) type with reed and willow. The wastewater flow rate in the constructed wetlands systems (CWs) was 0.4 and 1.0 m3/d, respectively. During the study period (2017–2019) 20 series of analyses were performed and 60 wastewater samples were collected. Based on the obtained results the effects of pollutant removal and the technological reliability were determined, which were specified with the Weibull method. The average efficiency of biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) removal was 96–99%. Slightly lower effects were obtained in the case of total phosphorus (TP) removal (90–94%), as well as for total suspended solids (TSS) (80–87%) and total nitrogen (TN) (73–86%) removal. The analysed CWs were characterised by 100% technological reliability for BOD5 and COD, as well as a good reliability for TSS and TP (87–100%) but slightly lower for TN removal (35–89%). Hybrid CWs of VF–HF type should be recommended to use in protected areas for wastewater treatment and water resources quality protection.
... The mean concentrations were 112.8 mg/L for TN and 16.7 mg/L for TP ( Table 2). The values obtained in the present study were similar to those typically measured in wastewater treated in settling tanks [38][39][40][41][42]. Effective removal of pollutants from wastewater in conventional biochemical processes requires the provision of appropriate quantities of nutrients for the optimal growth of the microorganisms participating in the treatment. ...
... The same type of facilities studied by Seo et al. in South Korea [64] and Melián et al. in Spain [56] had COD removal efficiencies of 98% and 80%, respectively. Vymazal and Kröpfelová [41] reported a mean COD reduction efficiency of 84% for a SSVF-SSHF wetland located in the Czech Republic. Lesage et al. [39] obtained a 90% COD removal efficiency for the same kind of two-stage system planted with common reed. ...
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Article
The present paper reports pollutant removal efficiencies and reliability for a four-stage hybrid constructed wetland (HCW) consisting of the following sequence of subsurface (SS), vertical flow (VF) and horizontal flow (HF) beds: SSVF-SSHF-SSHF-SSVF. The experiments were carried out over a period of three years, with sampling done in each season: winter, spring, summer and autumn. Grab samples of wastewater collected from different stages of treatment were tested for total suspended solids (TSS), BOD5, COD, total nitrogen (TN) and total phosphorus (TP). The wetland was found to have a very high efficiency of removal of suspended solids and organics, with relatively little seasonal variability. The three-year average TSS removal efficiency was approximately 92.7%. The effectiveness of elimination of organic compounds was very high throughout the study period at 96.6% BOD5 and 95% COD. The effluent from the four-stage system had significantly lower contents of TN and TP compared to the wastewater discharged from the first two beds of this facility.
... In FTWs, the pollutants are taken up and purified by the roots of vegetated macrophytes (Kadlec and Wallace 2008;Afzal et al. 2014a, b). In FTWs systems, plants perform several functions such as phyto-volatilization, reduce the speed of water and instability, increase the precipitation process, tricking and filtration of suspended particles, and provide a favorable environment for the growth of microbes (Stewart et al. 2008;Vymazal and Kröpfelová 2011). ...
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Article
Globally, water resources contaminated with petroleum hydrocarbons are under much consideration due to their hazardous effects on human beings as well as on plants and animals in the ecosystem. Petroleum hydrocarbons are classified as recalcitrant pollutants in nature. These petroleum products are mostly released in the water resources during the petroleum refining process by oil refineries. The conventional clean-up technologies for hydrocarbons contaminated water have more destructive effects on the aquatic and land ecosystems. Consequently, to develop cost-effective and more environment-friendly techniques that clean up the environment and restore the marine ecosystem to its original forms. Keeping in view, this review article explores the detailed information on fabrication, cost-effectiveness, and an overview of innovation of the floating treatment wetlands (FTWs) using plants and bacterial combined functions to remediate the petroleum hydrocarbons contaminated water. The review also discusses the improvement of microbial efficacy for hydrocarbon degradation using FTWs. The review article shows the various applications of FTWs to remove different organic pollutants in petroleum hydrocarbons contaminated water. The review also describes the prospective benefits of FTWs for their multiple uses for removal of hydrocarbons, chemical oxygen demand (COD), biochemical oxygen demand (BOD), phenol, and solids from hydrocarbons contaminated water. This review widely discusses the role of hydrocarbons in degrading bacteria, and wetland plants and the mechanism involved during the remediation process of hydrocarbons in FTWs. It further demonstrates features disturbing the treatment efficiency of FTWs, and finally, it is concluded by successful applications of FTWs and various suggestions for potential future research prospects. Graphical Abstract
... It was inferred that single stage treatment wetland is less efficient than the hybrid system due to inability to provide both the conditions of aerobic and anaerobic needed for nitrification and denitrification to take place. It was further quoted that vertical flow CW successfully removes ammonia but very little denitrification takes place and on the contrary, the horizontal flow CW provides good condition for denitrification but its ability is limited for nitrification only (Vymazal and Kröpfelová 2011). Wang et al. (2009) found out that, with increasing hydraulic load, the removal efficiency of COD was stable. ...
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Chapter
Ground water is the water that fills the natural open spaces in soil and rock underground. It is stored in the underground geological water system called an aquifer. An aquifer is any geological material that is filled with water and yields useful quantities of ground water to a well or spring. Both consolidated and unconsolidated geological materials are important as aquifers. Sedimentary rocks are the most important consolidated materials (bedrock), because they tend to have the highest porosities and permeability. Although most bedrock aquifers are within sedimentary rock, in some areas igneous or metamorphic rock can be important as aquifers (David et al. 1997). Sand and gravel aquifers are unconsolidated materials.
... The results showed that the nutrients, pathogens, solids, COD and alkalinity decreased after polishing with planted gravel filters (PGFs) ( Table 3). This is because as the effluent moves in PGFs, pathogens are deactivated, nutrients such as P are adsorbed, and others , for example, N are taken up by plants and could be lost through denitrification (Vymazal and Kröpfelová, 2011). Treatment using HFCW improved COD removal, especially in Nepal, from which the values were above the South African NWA standard limits for irrigation using 500 m 3 per day ( Table 3). ...
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Article
Most countries in Sub-Saharan Africa rely on on-site sanitation systems. Integrating on-site sanitation systems with local food systems by recovering nutrients and materials from human excreta, and reuse in agriculture can promote a sustainable circular bioeconomy, which could improve livelihoods and minimize environmental pollution in low-income communities. Although there are several technologies that can valorise human excreta into valuable waste-based agricultural products the scaling up and adoption of these innovations by societies is limited by several institutional challenges. These include an unclear policy and regulatory environment due to inadequate evidence-based information that can inform policy change, stimulate social acceptance, establish economically viable environment and include active participation of women and youth. Based on previous untreated human excreta characterisation studies, meant to inform treatment technological requirements, a scoping review with metanalyses was done to assess the extent to which selected technologies are meeting the requirements of a sustainable sanitation value chain. The selected technologies were shown to comply with the South African and international regulations for the recovery of nutrients from human excreta and reuse in agriculture. The review shows that there is potential to establish circular bio economies, characterised by safe recovery of nutrients and materials from human excreta and subsequent agricultural use, in South Africa and beyond. However minor modifications to the technologies are required to ensure that the products are safe for unrestricted agricultural use, economically viable, socially acceptable and environmentally sustainable.
... Thus, the null hypothesis was rejected and this proved that the synthetic greywater was effectively treated by the experimental HSSFCW. Same statistical difference was also reported by Vyzamal and Kropfelova (2011) and Ragen (2016)). Fig. 3 shows the variation in the BOD removal efficiency of the bed since its start-up. ...
Article
This paper aims at providing design guidelines for a Horizontal sub surface flow constructed wetland treating greywater from single household in Tropical Island. The system was operated using synthetic greywater at variable operating conditions over a period of 41 weeks. The performance was assessed in terms of biological oxygen demand removal efficiency. The biological oxygen demand rate constant was determined using the first order plug flow model by fitting the observed values along the bed. A mean removal efficiency of 84 ± 3.5% (n = 32) was achieved for this system. The biological oxygen demand rate constant values ranging from 0.34–0.50 m/d and averaging to 0.43 ± 0.06 m/d (n = 32) were obtained. Hence rate constants have been developed and can be used for sizing of beds treating greywater in tropical regions.
... Fe 2+ , Zn 2+ , and Ni 2+ ) and effectively removes certain metals such as chromium (Cr 2+ ); -Tolerant to range of pH levels (e.g. used for remediation of acid mine drainage and industrial effluent); -Cosmopolitan species with a widespread distribution (i.e. the ability to growth and survive in a range of environmental conditions) -Extensive root system (Ayyappan et al., 2016;Bonanno and Giudice, 2010;Kumari and Tripathi, 2015;Peruzzi et al., 2009;Vymazal and Kröpfelová, 2011) Typha spp. ...
Article
The composition and concentration of contaminants present in winery wastewater fluctuate through space and time, presenting a challenge for traditional remediation methods. Bio-hydrogeochemical engineered systems, such as treatment wetlands, have been demonstrated to effectively reduce contaminant loads prior to disposal or reuse of the effluent. This review identifies and details the status quo and challenges associated with (i) the characteristics of winery wastewater, and the (ii) functional components, (iii) operational parameters, and (iv) performance of treatment wetlands for remediation of winery effluent. Potential solutions to challenges associated with these aspects are presented, based on the latest literature. A particular emphasis has been placed on the phytoremediation of winery wastewater, and the rationale for selection of plant species for niche bioremediatory roles. This is attributed to previously reported low-to-negative removal percentages of persistent contaminants, such as salts and heavy metals that may be present in winery wastewater. A case for the inclusion of selected terrestrial halophytes in treatment wetlands and in areas irrigated using winery effluent is discussed. These are plant species that have an elevated ability to accumulate, cross-tolerate and potentially remove a range of persistent contaminants from winery effluent via various phytotechnologies (e.g., phytodesalination).
... Constructed wetlands(CWs) comprise of vegetation, substrates, soils, microorganisms and water, will utilize physical, chemical, and biological mechanisms to remove various pollutants or enhance the water quality [1,2,3,4]. According to the method of application of wastewater to the substrate, the constructed wetlands are classified into: free water surface (FWS) CWs and sub-surface flow (SSF) CWs [4]. ...
Article
Since last few years Constructed Wetlands (CWs) are being used to treat secondary or tertiary municipal or domestic wastewater effluents have been recognized as an effective means of “green technology” for wastewater treatment. Constructed wetlands (CWs) provide a natural way for simple, inexpensive, and robust wastewater treatment. The idea of natural management systems is the restoration of disturbed ecosystems and their sustainability for remuneration to nature. The Constructed wetlands (CWs) are designed to copy natural wetland systems, utilizing wetland plants, soil and associated microorganisms using various biological, physicochemical processes to remove unwanted constituents from wastewater effluents. This review paper studies various types of constructed wetlands, i.e., surface or subsurface, vertical or horizontal flow and their type of operation, i.e., continuous, batch or intermittent flow, loading rate, selection of plants and wastewater characteristics that affect the treatment efficiency. The design models with their suitability for various parameters and operational conditions such as Darcy’s equation, Kadlec and Knight Model (K-C* model), Arrhenius equation, and population equivalent calculation have been discussed. Lastly, future research requirements have been considered.
... Most cannas plants are immune to pests and used in constructed wetlands for wastewater treatment in tropical and subtropical weather. They can grow as high as 75-300 cm, with different colors as ivory, yellow, pink, red, creating beautiful landscapes in the city (Vymazal et al., 2008). In this study, the seeding plants ( Fig. 1) had the average height of 20 cm with 2-3 seed leaves. ...
Article
Constructed wetlands have not been commonly used in Vietnam due to the lack of information in the selection of proper types of constructed wetlands, type of reeds, design parameters and performance efficiency, in tropical climates. This paper focuses on Canna generalis, which is a common reed and easy to grow both in water and wet land conditions. Two kinds of hybrid constructed wetlands were employed, including Facultative pond combined with free water sub-surface constructed wetlands system and horizontal subsurface flow combined with Aerobic pond system. It was found that the ponds played an important role in the hybrid system performance and enhanced the performance of constructed wetlands. The pollutant removal efficiencies of the hybrid systems were all higher than the single constructed wetlands. The BOD 5 , TSS, NH 4-N and PO 4-P removal efficiencies averaged 81%, 85%, 93% and 77%, respectively for the hybrid horizontal subsurface flow constructed wetlands system operated at a hydraulic loading rate of 0.075 m/day, while they were 89%, 97%, 97%, and 68%, respectively for the hybrid free water sub-surface constructed wetlands system operated at a hydraulic loading rate of 0.1 m/day. The removal rate constants (k BOD5, k NH4-N, k PO4-P) of the experimental hybrid constructed wetlands were similar to those in previous studies. However, these constants were higher for the hybrid free water subsurface constructed wetlands because of the modified structure flow of the free water subsurface constructed wetlands applied in this study, compared to conventional ones, as well as the additional benefits of the ponds in the hybrid systems.
... The triple synergy of the processes enacted by these systems' physical matrices, plants, and microorganisms achieves the treatment of wastewater (Ilyas and Masih 2018;Hernández-Crespo et al. 2017;Wang et al. 2018a). Plants not only directly absorb pollutants, but also promote the growth and reproduction of microorganisms, and improve the decomposition of pollutants by microorganisms (Hu et al. 2016;Vymazal and Kröpfelová 2011;Wang et al. 2020b). ...
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Article
Water pollution control is the focus of environmental pollution control. Ecological water treatment is widely used because of its low cost and landscape effect, and has no pollution. Aquatic plants have attracted wide attention because of their low cost and high level of resource utilization. In order to study the effects of emergent and submerged plants on the removal of different concentrations of wastewater, and the effect of pollutants on plant growth, two common aquatic plants found in Northeast China (Iris ensata Thunb. and Potamogeton malaianus Miq.) were selected. Under static conditions, the removal efficiency of nitrogen and phosphorus in wastewater with different concentrations by two kinds of plants was studied. The results showed that the removal rate of total nitrogen (TN) in medium-and high-pollutant concentration water samples and total phosphorus (TP) in medium-and low-pollutant concentration water with I. ensata reached more than 75%. The removal rate of TN in the medium-pollutant concentration water with P. malaianus reached 71.4%, while the removal efficiency of TN and TP in the low-pollutant concentration water was higher than 80%. In the Nanhu Park Lake samples, I. ensata had the highest removal rates of TN (80.38%) and TP (85.62%). This study shows that both I. ensata and P. malaianus can be used as aquatic plants to restore the water quality of urban lakes. This research provides an important basis for the phytoremediation and treatment of urban domestic wastewater and urban surface water bodies in Northern China.
... Chemical oxygen demand (COD) is the capacity of water to consume dissolved oxygen during the oxidation of inorganic chemicals, such as nitrites ( NO − 3 ) and ammonia ( NH + 4 ) and the decomposition of organic matter (Xu et al., 2010). Vymazal and Kröpfelová (2011) displayed that the Phragmites australis in constructed wetlands cause to remove of biochemical oxygen demand (BOD) and COD by 94.5% and 84.4%, respectively. Plants may experience oxygen (O 2 ) deficiency conditions if the water becomes hypoxic as a consequence of the high concentration of NO − 3 and NH + 4 , and high organic pollutants (COD and BOD) in the wastewater (Jampeetong & Brix, 2009;Kinidi & Salleh, 2017). ...
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Article
Halophytes are the good candidates in coastal saline areas which could be irrigated with wastewater. The purpose of this study was to evaluate the soil–water–plant system under control and wastewater irrigation (containing toxic elements and organic matter) at three durations (vegetative, flowering, and reproductive stages) and two exposure times (2 and 4 days in each stage). The results obtained in the experimental tests for wastewater irrigation indicated that the Salicornia is efficient for the removal of chemical oxygen demand (61%), biochemical oxygen demand (74%), total suspended solids (47.6%), and ammoniacal nitrogen (64%) at the reproductive stage. At the same time, the average nitrate concentration increased to 51.3 mg L−1 with more solids. Regardless of wastewater irrigation duration, irrigation with wastewater significantly increased organic matter, nitrogen, phosphorus, and potassium of the soil. The Mg2+ and Ca2+ contents in the aboveground biomass of the plants were also high ranged from 0.58 to 1%, and 0.43 to 0.68 mg g−1 DW, respectively. All the exchangeable cations other than Na+ were higher for wastewater irrigation at the flowering stage. Plants maintained noticeably higher Ca2+/Na+ and K+/Na+ ratios in the roots than those in the shoots except for 4 days after the reproductive stage. S. europaea is well adapted to grow in wastewater irrigation and can tolerate hypoxic conditions through improving water and soil quality.
... According to Vymazal's classi cation of hybrid CWs (Vymazal, 2013), the FHSCW-SHSCW-SFCW in this experimental device belongs to the hybrid systems that include the SFCW. Various types of CWs provide different redox conditions that are suitable for enhancing the removal of TN (Vymazal, 2011). It was necessary to compare removal e ciency in terms of removed loadings. ...
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Preprint
Background Single-stage constructed wetlands (CWs) has a single ecological service function and is greatly affected by temperature, which are general in removal of total nitrogen. Multistage hybrid CWs were proven to capable of enhancing removal of nitrogen. Therefore, this study aimed to explore the variation in nitrogen removal in the combined CWs-pond process from summer to winter and the contribution of plant harvesting and the functions of bacteria to nitrogen removal. Methods A pilot-scale multistage constructed wetland-pond system (MCWP) with the process of "the pre-ecological oxidation pond + the two-level horizontal subsurface flow constructed wetland (HSCW) + the surface flow constructed wetland (SFCW) and the submerged plant pond (SPP)" was used to treat actual polluted river water in the field. During the 124 days of operation, the nitrogen concentrations in the units influent and effluent of the system were measured every two days, and the plant height in HSCWs and SFCW was measured once per month. When the system operated stably to the 72nd day, the substrates in the CWs were sampled to analyze the bacterial community structure and composition. Results The concentration of total nitrogen (TN) in the MCWP gradually decreased from 3.46 mg/L to 2.04 mg/L, and the average removal efficiency of TN was approximately 40.74%. The SPP performed the best among all units, and the TN removal efficiency was as high as 16.08%. The TN removal efficiency was significantly positively affected by the daily highest temperature. A formula between the total TN removal efficiency and the highest temperature was obtained by nonlinear fitting. The TN removal load rate in the HSCWs was 2.7–3.7 times that of the SFCW. Furthermore, the TN transformed by Iris pseudacorus L. accounted for 54.53% in the SFCW. Conclusion We found that the significant positive correlation between the daily highest temperature and the total TN removal rate a field MCWP system. The SFCW, as an advanced treatment unit, increased the proportion of nitrogen removed by plant harvesting. The bacteria completed the nitrogen cycle in the SFCW, which had high-density planting, through a variety of nitrogen removal pathways.
... Of all the technologies compared for N removal, constructed wetlands (CWs) are considered an alternative to conventional physicochemical approaches due to the lower economic costs for contaminant removal and less impact on the environment with less input of energy . In recent years, the CW technology has evolved from theory to practice, broadly utilized to treat different water bodies, including rivers, lakes, domestic wastewater, agricultural drainage/run-off and industrial discharge (Vymazal, 2011;Vymazal and Kropfelova, 2011). Among different types of CEs, tidal flow constructed wetlands (TF-CWs) have received increasing attention, due to its fluctuating water tables to provide advantageous habitats for both aerobic and anaerobic organisms. ...
Article
Constructed wetlands are efficient in removing nitrogen from water; however, little is known about nitrogen-cycling pathways for nitrogen loss from tidal flow constructed wetlands. This study conducted molecular and stable isotopic analyses to investigate potential dissimilatory nitrate reduction to ammonium (DNRA), denitrification, nitrification, anaerobic ammonium oxidation (anammox), and their contributions to nitrogen removal by two tidal wetland mesocosms, PA (planted with Phragmites australis) and NP (unplanted), designated to treat Yangtze River Estuary water. Our results show the mesocosms removed ~22.6% of TN from nitrate-dominated river water (1.19 mg·L⁻¹), with better performance obtained in PA than that in NP, which was consistent with the molecular and stable isotopic data. The potential activities of DNRA, anammox, denitrification and nitrification varied between 0.6 and 1.6, 4.6–37.3, 36.4–305.7, and 463.7–945.9 nmol N2 g⁻¹ dry soil d⁻¹, respectively, with higher values obtained in PA than NP. Nitrification accounted for 94.3–99.4% of NH4⁺ oxidation, with the rest through anammox. Denitrification contributed to 77.9–90.3% of NOx⁻ reduction, compared to 9.2–21.6% and 0.5–1.5% via anammox and DNRA, respectively; 78.4–90.9% of N2 was produced through denitrification, with the rest via anammox. Pearson correlation analyses suggest NH4⁺ was the major factor regulating nitrification, while NO3⁻ played an important role in the competition between denitrification and DNRA, and NO2⁻ was a key restrictive factor for anammox. Overall, this study reveals the importance of nitrification, denitrification, anammox and DNRA in nitrogen removal, providing new insight into the nitrogen-cycling mechanisms in natural/artificial tidal wetlands.
... BOD (99.9%), and COD (98.9%) than HSSFCWs. The hybrid systems that consist of various types of wetlands arranged in series and have been mainly used for enhanced removal of nitrogen as these wetland systems could provide different redox conditions suitable for nutrient reduction [151]. When compared to single HSSFCW and SFCW, mostly the hybrid CW systems were known to be more proficient in the removal of total suspended solids, biological and chemical oxygen demand, and nutrients. ...
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Article
Recently, the quickly growing population living in urban location has caused numerous conflicts related to increase in water demand and water pollution. In urban areas, the surface water bodies allow runoffs and storms and in addition act as wastewater drainage pathways. Mostly, the imperfect separation of rainwater and clean wastewater has made large quantities of wastewater discharged into the surface water, resulting in serious pollution. There are many treatment methods for the polluted water bodies such as coagulation, filtration, and ecological floating bed which are related to nutrient removal. The above listed methods are usually capable in reducing pollution load. Wastewaters generated from two sources such as point source (domestic and industries) and non-point source (agricultural and storm water runoff). Finally it reaches nearby water bodies and the abovementioned methods are to be frequently employed in a wastewater treatment plant to remove nutrients. Most of the pollutants in the vastly polluted water are in dissolved forms; hence, an appropriate treatment method relevant to the design and development of the integrated multistage reactor with extended wastewater treatment is reviewed in this paper. Evaluating the accumulation, precipitation, retention, and removal of phosphorus, along with removal of nitrogen, is discussed in brief.
... Where as in China Per M 3 sewage treatment is sewage treatment is 115 US$ and O & M cost 0.116$ using ASP and 28.82 US$ and O&M cost 0.022 $ using phytoremidiation (Li et al. 2009). However (Vymazal and Kröpfelová 2011) showed pre-treated municipal wastewater, the capital cost of the experimental system using hybrid CWs is comparable to the conventional on-site treatment plant but the operations and maintenance costs are about one third of the conventional plant and removal of BOD 5 and COD amounted to 94.5% and 84.4%, achieved using CWs . Hammer 1990 suggested that the cost of phytoremidiation can vary 1/10 to 1/2 of the ASP. ...
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Conference Paper
Nutrients through wastewater reaching the water bodies cause problems of severe eutrophication. Most of the conventional wastewater treatment systems are not designed for nutrient removal. Phytoremediation of nutrients before treated wastewater is finally discharged to water body may be a viable option. This emerging technology offers a cost-effective, non-intrusive, and safe alternative to conventional cleanup techniques by using the ability of certain trees, shrub, and grass species to remove degraded, or immobilize harmful chemicals from the soil and wastewater. In addition to plants, microorganisms that live in the rhizosphere play a major role in degrading organic chemicals, often using these chemicals as carbon source in their metabolism. Various types of constructed wetlands (CWs) use in order to achieve efficient treatment performances. Free water surface wetlands, like most natural wetlands where the water surface is exposed to the atmosphere. Subsurface wetlands, where the water surface is below ground level. The second category, subject of our study, can be categorized according to the flow pattern: Systems with horizontal subsurface flow (HF) Systems with vertical subsurface flow (VF) and Hybrid systems (combination of HF and VF). The main mechanisms of nutrient removal from wastewater in constructed wetlands are microbial processes such as nitrification and denitrification as well as physicochemical processes such as the fixation of phosphate by iron and aluminium in the soil filter. Moreover, plants are able to tolerate high concentrations of nutrients and heavy metals. Plants' involvement in the input of oxygen into the root zone, in the uptake of nutrients and in the direct degradation of pollutants. A review of various studies conducted primarily on nutrient removal by phytoremediation and a catalogue of plants reported to have promising performance is presented. Cost comparison of conventional treatment methods with CWs for removal of contaminants is also summarised.
... Ces RPBs sont utilisés pour augmenter le pH, produire de l'alcalinité et pour enlever les métaux et les sulfates présents dans le DMA en se basant sur l'activité des bactéries anaérobies, y compris les BSR (Neculita et al., 2007). Plusieurs RPBs ont été mis en place avec succès à grande échelle pour traiter les effluents contaminés (Kuyucak et al., 2006;Libéro, 2007;Gusek et al., 2011;Ness et al., 2014) ; 2) les marais artificiels qui sont des zones humides ou des écosystèmes conçus pour imiter les processus naturels associés à la végétation, au sol et aux microorganismes pour traiter le DMA en impliquant différents processus physiques, chimiques et biologiques, notamment l'absorption des nutriments, la dégradation bactérienne (assimilation et transformation microbiologique), la filtration, l'oxydation, la précipitation et l'adsorption (Vymazal et Kröpfelováa, 2011). Les marais artificiels ont été largement utilisés, en particulier dans les sites miniers abandonnés, en raison de leur rapport coût-efficacité ainsi que leurs faibles exigences relatives à la maintenance (USEPA, 2014;Peer et al., 2015) et 3) les barrières réactives perméables (BRPs) qui sont constituées d'une zone de traitement dans laquelle un matériau perméable réactif est placé et à travers lequel les eaux contaminées passent (USEPA, 2014;Shabalala et al., 2017). ...
Thesis
Acid mine drainage (AMD), characterized by low pH and high concentrations of metals and sulfates, is a worldwide problem with significant environmental and ecological impacts. It is generated by oxidation of sulphides (e.g. pyrite and pyrrhotite) in the presence of water and oxygen. At abandoned mine sites, passive treatment systems, which are pseudo-natural attenuation processes, are preferred for AMD treatment, since they offer the possibility to reuse low-cost materials (e.g. industrial waste), consume less energy and improve the quality of the AMD. Nevertheless, like the case of active treatment systems, passive treatment systems generate not negligible quantities of metal-rich residues. Once excavated, these residues exhibited variable chemical stability, which remained difficult to predict, because it depends on the AMD quality to be treated and the treatment technology used. Thus, to ensure a better management of these residues in accordance with the laws and regulations, the case-by-case study is often necessary to prevent the potential mobilization of contaminants. In this context, the main objectives of the thesis are the following: (1) to evaluate the mobility of contaminants from post-treatment residues collected in a laboratory Fe-AMD system; (2) to evaluate the mobility of contaminants from post-treatment residues collected in a field-based Fe-AMD system (Lorraine site); and (3) to evaluate the performance of stabilization/solidification treatment as a sustainable management mode for post-treatment residues from the field system. To achieve these objectives, the methodological approach adopted consisted firstly of post-treatment residues sampling from the two treatment systems. Then, the sampled residues were characterized for physicochemical parameters and mineralogy. Afterwards, leaching and kinetic tests were conducted to evaluate the mobility of contaminants from residues. Finally, the post-treatment residues from the field system were subjected to a stabilization/solidification treatment. To evaluate the performance of this management, the treated residues were mineralogically characterized and were subjected to static and semi-dynamic leaching tests to assess their environmental behavior.
... For decades, constructed wetlands have been widely used for water purification (Fountoulakis et al. 2017;Pelissari et al. 2017), specifically for removing nitrogen (N) and phosphorus (P) contaminants from domestic sewage (Vymazal and Kröpfelová 2011;Almeida et al. 2017). A number of wetland plant species have been evaluated by their purification efficiency Button et al. 2016), such as Phragmites australis and Typha orientalis (Liu et al. 2012;Vymazal and Březinová 2018). ...
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Article
Secondary pollution resulting from shoot death is a difficult problem that complicated the application of wetland plants for water purification in northern wetlands. Phalaris arundinacea, a perennial herb with an obviously declining stage, or senescence, is a species that is often selected for water purification in Northern China; however, whether it reduces the secondary pollution risk via nitrogen (N) and phosphorus (P) accumulation during senescence or not remains unclear. To investigate this question, an experiment was conducted with containerized plants during the winter of 2016, after roughly half the leaves on the plants had withered. The experimental observations and analyses were conducted within 0, 2, 4, 6, and 8 weeks of the initiation of senescence. Results revealed that leaves continued to wither and shoot death occurred during weeks 4 to 6 and 8 to 10, respectively. However, no significant differences occurred in fresh biomass or in N and P accumulations of a single plant during senescence. The root biomass, root weight per volume, and total N content increased significantly, while total P content remained stable when leaves withered, respectively. H+-ATPase, a key enzyme for ion transportation, decreased after the leaves withered. However, root activity, evaluated by absorption surface per root volume, remained stable, and percentage of fine root length (diameter < 1 mm) increased significantly during senescence. In conclusion, the root activity and morphology enables P. arundinacea to accumulate N and P during senescence, which makes it a good choice for water purification in northern wetlands.
... Some researchers reported the potential of plant species such as bulrush (Scirpus spp.), cattail (Typha angustifolia L.), and vetiver grass (Vetiveria zizanioides L.) for piggery wastewater treatment [3]. Among wetland plants, Phragmites australis has been widely used in CWs [4] and this species had an appropriate efficiency in the treatment of municipal wastewater [5 -7], domestic wastewaters [8] and swine wastewater [9,10]. In a prior study evaluating chemical oxygen demand (COD) removal efficiency from swine wastewater by free water surface flow constructed wetland (FWS CW), it has showed that plants and microorganisms have important role in this process [11]. ...
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Article
Constructed wetlands (CWs) have been used to treat various types of wastewaters such as urban runoff, acid mine drainage, municipal, industrial, and livestock wastewaters. This study was conducted to evaluate the effectiveness of two constructed wetlands (surface and horizontal subsurface flows) for piggery wastewater treatment after biogas process. The wetland plant Phragmites australis Cav. was used in two CWs. The flow rate of the CWs was 100 liters/day with the hydraulic retention time (HRT) of 3 days. Parameters including pH, chemical oxygen demand (COD), total suspended solids (TSS), NH 4 +-N, total nitrogen (TN) and total phosphorus (TP) were measured. After 45 days experiments, the results showed that the horizontal subsurface flow CWs had better treatment performance compared to the surface flow system. The pH of the wastewater after CWs treatment was in the range of 6.7 to 7.3. The removal efficiency of TP, TSS, COD, TN and NH 4 +-N by surface flow CWs was 80, 60, 66, 60 and 65 %, respectively while those by horizontal subsurface flow system was 86, 78, 74.6, 67.1 and 74.2 %, respectively. The water quality of the effluents of both two CWs met the Vietnamese standards for livestock wastewater (QCVN62-MT:2016/BTNMT, column B).
... De modo semejante, el P puede ser eliminado mediante la asimilación por las plantas. La mayor par te del fósforo procedente de las aguas servidas es asimilado por las raíces, hojas y brotes de las plantas, pero esta cantidad es generalmente muy baja (2,3-9%) (vohla et al., 2005;Kröpfelová, 2011;López et al., 2015). Se han repor tado para HFSS acumulación de fósforo en el rango de 0,7-5,5 g P/m 2 (vymazal & Kröpfelová, 2011). ...
Book
No es fácil hacer investigación en América Latina, principalmente investigación de calidad, la que necesita un monitoreo amplio, trabajos de campo, análisis de laboratorio, equipos sofisticados y bien mantenidos, material de consumo siempre disponible y un equipo de trabajo capacitado, concentrado y dedicado; en resumen, recursos financieros y humanos. Los últimos, los tenemos con facilidad, y los primeros, hay que siempre estar buscándolos y venciendo las dificultades. Por ese motivo, cuando uno ve resultados de una investigación bien desarrollada, bien sucedida y con resultados impor tantes para su país, el hecho debe ser muy bien valorado. Después de obtenidos los resultados de la investigación, hay que tornarlos públicos, o sea, publicarlos. La ruta más común es la publicación en periódicos científicos y anales de congresos. Eso permite que la información llegue a científicos y estudiantes que trabajan en el tema, y así la ciencia y la tecnología siguen sus avances. También es común la publicación de reportes técnicos meramente burocráticos para las agencias que fomentan la investigación. Sin embargo, en un gran número de veces, la información digerida y palpable no llega a la población interesada y no genera resultados que sean directamente aplicables. Por todos esos motivos se debe celebrar mucho cuando se ve los resultados de una investigación exitosa ser presentados a un público más amplio en la forma de un libro. Un libro que trae los aspectos generales de la práctica y el sopor te de la base teórica. Un libro que presenta las informaciones de forma clara y didáctica, con ilustraciones preciosas, tablas con resumen de datos importantes y un texto fluido y claro. Un libro que enseña como concebir, diseñar, construir y operar, o sea, que cubre toda la secuencia de implementación de un sistema, garantizando que éste tenga condiciones de cumplir con eficacia sus objetivos a lo largo del tiempo. Esta es exactamente la sensación que uno tiene al estudiar el excelente libro “Humedales construidos. Diseño y operación”, escrito y editado por las colegas Gladys Vidal y Sujey Hormazábal, de la Universidad de Concepción, Chile, y que también contó con la colaboración de otros autores. El tema es de gran relevancia para nuestra realidad en América Latina, con todo su déficit en cobertura de saneamiento. La tecnología descrita es de enorme importancia para comunidades rurales, que son el foco principal de la investigación. Sabemos que una solución exitosa para comunidades rurales no es simplemente tecnológica, y por eso el libro abre su visión para alcances más amplios, que tornen posible la apropiación de la técnica por las comunidades rurales. Los humedales representan un proceso de tratamiento de aguas residuales que tienen la simplicidad como una de sus principales fuerzas, y dar valor a esta simplicidad, sin mezclarla con conceptos muy avanzados y de comprensión más difícil es una de las vir tudes del libro. O qué son los humedales, su historia, el rol de las plantas, y cómo diseñarlos, construirlos y operarlos, todo está muy bien explicado en la parte general del libro, que establece las bases teóricas y prácticas de los sistemas de humedales. A seguir, los resultados de la investigación están presentados de forma clara. Uno de los capítulos cubre la evaluación detallada de un sistema de flujo horizontal implementado en Chile, y otro capítulo cubre un análisis estadístico de la calidad de los efluentes generados por distintos sistemas de humedales en España. Todos los autores involucrados en el proceso de desarrollo y escritura del libro deben ser felicitados por el éxito alcanzado, en especial Gladys y Sujey. Las felicitaciones son extendidas también a la Universidad de Concepción y a los organismos que dieron apoyo a la investigación. ¡Que sigan los humedales cada vez tratando más nuestras aguas residuales y contribuyendo para la preservación del ambiente y la salud pública!. Marcos von Sperling
... The wastewater treatment processed mainly includes filtration, adsorption, precipitation, ion exchange, plant absorption, microbial degradation, etc. [11]. There are many types of research on the removal of chemical oxygen demand (COD), nitrogen and phosphorus by constructed wetland systems [12][13][14], but there are relatively few studies on the purifying petroleumcontaining wastewater. Therefore, constructed wetland could be used as a supplement of conventional biological treatment process for petroleum-containing wastewater. ...
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Article
A constructed wetland system with Acorus calamus (A. calamus) was developed to investigate the purification efficiency of petroleum-containing wastewater. High-throughput sequencing was employed to investigate bacterial richness and diversity, bacterial community structure variation between spring and summer, and the effect of bacteria on petroleum-containing wastewater purification in the system. The results showed that the constructed wetland systems with A. calamus purified the petroleum-containing wastewater well. The average removal rates of petroleum pollutants, chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were 97%, 80%, 67%, and 54%, respectively. A total of 22 strains were identified by 16SrDNA clone library gene sequencing. The bacteria mainly contained Acinetobacter, Rhizobium, and Rhodobacter. These bacteria had significant effects on organic matter decomposition and nitrogen removal, and played a major role in the removal of petroleum pollutants, COD, and TN in the constructed wetland. The bacterial richness and community diversity were higher in the summer sample than that in the spring sample. The treatment effect on petroleum pollutants was better in summer. Petroleum pollutant removal rate by the A. calamus system has a significant positive correlation with the Chao1 and Ace diversity indices (p < 0.05).
... Therefore, the ability to remove antibiotics is limited. The traditional sewage treatment plant includes pre-treatment, primary stage treatment, two stages treatment system [8][9] and a conditional sewage treatment plant will also start a three stages treatment program, such as chemical oxidation, activated carbon adsorption or ultraviolet oxidation [10][11][12]. The pre-treatment and primary stage treatment processes are aimed at removing organic suspension which is large and easy to settle. ...
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Article
In this study, biochars derived from bagasse were prepared and their ability for the adsorption of four kinds of sulfonamide antibiotics (sulfamethoxazol, thiazole, methylpyrimidine, dimethylpyrimidine) was investigated. Results showed that the modified biochar can efficiently adsorb sulfonamides in water. The biochar obtained at 500 o C and modified with 30% hydrogen peroxide was chosen as the adsorbent. Under optimum conditions, pH 4 and 35°C, great adsorption performance was exhibited in the adsorption process of the four sulfonamide antibiotics. The productivity of the modified biochar was ~ 89% compared to un-modified biochar which is ~31%. The successful preparation of biochar from bagasse indicates that it is a good way to reuse the resources. Besides the adsorption of antibiotics, the obtained material also has a great prospect in the removal of other pollutants.
... Furthermore, studies have shown that multi-stage SFCWs remove N and P more effectively than single-stage SFCWs (Canepel and Romagnolli, 2010;Wu et al., 2015). This may be due to the ability of multi-stage SFCWs to provide more redox condition opportunities, thereby improving the rate of nitrification and denitrification (Vymazal and Kröpfelová, 2011). ...
Article
A multi-stage surface flow constructed wetland (SFCW) is used to treat decentralized rural domestic sewage. The performance of a multi-stage SFCW located in Hunan, China, and the associated microbial community structures were investigated. The average removal rates of the multi-stage SFCW planted with Myriophyllum elatinoides were 1.0 g m-2 d-1, 0.84 g m-2 d-1, 61.3 mg m-2 d-1, and 85.3 mg m-2 d-1 for total nitrogen (TN), ammonia (NH4+), nitrate (NO3-), and total phosphorus (TP), respectively. Furthermore, the sediment and presence of plants were found to be important for the removal N and P. The average removal rates by sediment and plants were 196.6 mg N m-2 d-1 and 49.9 mg P m-2 d-1, 17.6 mg N m-2 d-1 and 8.1 mg P m-2 d-1, respectively. The microbial community profiles demonstrated that Proteobacteria, Chloroflexi, Bacteroidetes, Firmicutes and Euryarchaeota were the predominant phyla in each stage and at different sampling times. The concentrations of NO3-, TP, TN, and NH4+, and the pH of the sediment and water had a significant effect on the presence of denitrifying bacteria in the anaerobic environment. Whereas, dissolved oxygen (DO) and redox potential (Eh) had a significant effect on the presence of nitrifying bacteria in the aerobic environment. This research strongly supports that the use of the multi-stage SFCW promotes bacterial diversity and changes bacterial community in the sediment.
Article
Multi-stage constructed wetlands (CWs) are widely used for water quality improvement, especially in the treatment of wastewater. Many studies focus on their treatment efficiency under steady loading, but fewer studies consider their sustainability under variable conditions. This study examines the multi-stage CWs in the Hong Kong Wetland Park for their long-term performance and sustainability in terms of water quality under seasonal changes, storm events, and shock loadings of pollutants. The results show that the multistage design performs well and is stable under these changing conditions. In such multistage CWs, the type of units and some changing conditions (e.g., inflow concentrations, seasonal changes of vegetation, and water levels) also affect the performance of the whole system. Compared to individual CW, a multi-stage CW system could recover more quickly on dissolved oxygen (DO), and ammonia nitrogen (NH4), but slowly on biochemical oxygen demand (BOD) and total phosphorus (TP). A pre-processing and buffering area is necessary to handle the shock loadings of BOD and TP in such a multistage CW system. Although water levels recover quickly in both, it is difficult to return to original water levels in multi-stage CWs compared to single ones. Besides, for sustainable operation, attention should be paid to the DO of the inlet, and aeration measures might be taken.
Chapter
The issue of water pollution and demand for clean water access has become an increasing concern. Wastewater treatment technologies are of high importance to improve water quality and protect human health and ecosystems. Among biological technologies, constructed wetlands (CWs) and oxidation ponds (OPs) have been successfully applied in the treatment of various wastewater types such as domestic wastewater, landfill leachate, agricultural, and industrial effluents. This chapter aims to review advances in CWs and OPs in wastewater treatment. Advances in CWs including aerated wetlands, CWs coupled with microbial fuel cells, tidal flow CWs, and bacterial endophytes–augmented CWs are analyzed in the chapter. The chapter also summarizes advances in OPs, that is, aerated ponds, rock filters–based ponds, and advanced integrated wastewater pond systems. Moreover, applications of integrated wetland–pond systems for wastewater treatment are presented in the chapter. Finally, the challenges and prospects of CWs and OPs are also evaluated.
Chapter
Pollution of the surface by harmful chemicals discharged from municipal, home, hospital, and industrial wastewater has become a global environmental issue due to its adverse effects on human health, agriculture crop productivity, and the freshwater environment. Treatment and reuse of wastewater in constructed wetlands (CWs) is a low-cost, environmentally friendly alternative to traditional technological solutions for a pollution-free environment. Toxic and pollutant phytoremediation has almost amazing potential with CWs. Their unique advantage is the complete low-cost treatment of large volumes of water. Because of the diverse conditions of hydrological, soil, and sediment types, plant species richness, growth season, and water chemistry, the CWs are complex ecosystems. CWs differ from terrestrial phytoremediation and traditional physical-chemical methods in that they deal with large volumes of contaminated soils or groundwater, whereas terrestrial phytoremediation and conventional physical-chemical methods deal with small volumes of contaminated soils or groundwater. CWs are one of the most widely used nature-based wastewater management solutions. Due to its excellent wastewater treatment, this ecotechnology is widely accepted. This chapter focuses on the operational scale, proposing metals’ phytoremediation of green desalination in CWs for safe ecosystems.
Article
The requirement of artificial aeration for increasing nitrogen removal in vertical flow constructed wetlands (VFCWs) brings extra energy consumption and complex maintenance. The feasibility of a modular design to replace artificial aeration for partially saturated VFCWs with palm bark as a carbon source (PSVFCW-pb) to achieve water quality control, especially nitrogen removal was evaluated. The PSVFCW-pb with a spatially separate structure and perforated peripheries for better oxygen diffusion had a promising total nitrogen removal (e.g., 66.4% at a dosage of 1.435 g/L of palm bark pretreated at 120 °C for 40 min) without additional aeration, while organic carbon removal was nearly unaffected. An appropriate increase of the palm bark dosage (≤1.435 g/L) resulted in higher nitrogen removal; however, a more palm bark (1.875 g/L) could not further increase nitrogen removal but caused color pollution. In addition, the removal of nitrogen by the modularized PSVFCW-pb was more sensitive to the ambient temperature than the removal of organic carbon and phosphorus, and the higher temperature was preferable. Notably, the more attractive property of the modular design is its great potential to improve nitrogen removal by conveniently altering the number and/or scale of oxic and oxygen-free modules. Finally, the relationships between the hydraulic load and inflow concentration were explored, by which the suitable hydraulic load could be flexibly adjusted based on real-time water quality to meet the specified surface water quality criteria in different seasons. This study provides a reliable CW design for controlling nutrient pollution in surface waters.
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Preprint
In the last few decades, nutrient-rich wastewater has become a worldwide problem due to exponentially increased anthropogenic activities causing eutrophication or algal blooms in waters and affect the water bodies with their biological and chemical activities. Physico-chemical techniques have shown promising results, while operational cost, hefty sludge generation, and energy requirement are the major drawbacks. On the other hand, biological processes are cost-effective and efficient, although they are associated with design complexity and extensive monitoring. Among biological techniques, constructed wetland (CW) is an economical, efficient, and green technique for nutrient removal comprising of inherent mechanisms, such as microbial degradation, rhizofiltration, phytodegradation, sorption, etc. This major highlight of the present study is to apprise and critically analyze the ideal conditions and system insights to enhance the nutrient removal efficiency of CW. Macrophytes play a vital role in CW and its planting practices, namely monoculture and polyculture, also influence the removal efficiency of the CW. In the present study, an in-depth analysis reflected that polyculture exhibits better treatment for TN and TP compared to monoculture practices. The observed optimum conditions for nutrient removal in CW were polyculture in combination with higher temperature (23ºC-29 º C), artificial aeration, advanced substrate, and bioaugmentation. The review emphasized the process and design criticality of CWs in removing nutrients from various types of wastewater, which may be instrumental for water research and field applications.
Chapter
The world we are living in is slowly getting urbanized. The world’s urban population which accounts for 55% today will rise to 66% by 2050 (World Urbanization Prospects: the 2014 Revision UN) (United Nations 2014). This increasing influx of the population into the cities has increased the stress in the water demand, as most of the cities are already facing severe water crisis (Hanjra and Qureshi 2010; Jury and Vaux 2007). Even if the water demand is met, it will create an additional challenge to treat wastewater generated, which accounts for almost 80% of water supplied. The latest report by United Nations World Water Assessment Programme (WWAP) (2017) highlighted that the 80% of the wastewater generated in the entire world is disposed without treatment, directly into the water bodies or open drainage and this figure is 95% in some poor countries. Disposal of this untreated wastewater in the lake, river, and stream will lead to unprecedented deterioration of health of these water bodies (Edokpayi et al. 2017; Lee et al. 2016; Khan and Ansari 2005). Untreated wastewaters have a very high concentration of nutrients, possibly heavy metals, emerging contaminants, suspended solids and pathogens, which alter the physical, chemical and biological properties of water, and thereby affect natural properties of water bodies, and biological life that thrive in it (Khan and Ansari 2005). Eutrophication, also known as an algal bloom, is one of the worst ramifications of excessive nutrient loading in water bodies due to discharge of nutrient-rich (nitrogen and phosphorus) wastewater in it (US EPA 1999; Khan and Ansari 2005).
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Article
There are currently more than 176 high schools in DKI Jakarta with no wastewater treatment plant in the canteens. Canteens wastewater contains high organic compounds which must be treated before discharging into the body of the water. A subsurface constructed wetland (SCW) multilayer filtration (MLF) system with vertical flow (VF) field plants was planned, implemented and operated at the High School in South Jakarta. The field-scale of the SCW-MLF was planted with Vetiveria zizanioides and the other plants free (MLF). These were operated at a hydraulic load of 6.9 m3/day, and the organic loading rate was between 1.43 and 8.3 kg BOD/day. Research has shown that the removal efficiencies in SCW-MLF for COD, BOD, TKN, and TP were 70.5%, 75%, 62.6%, and 54.3%, respectively. Also, the COD and BOD organic loading at SCW-MLF were between 917.08-4,126.84 kg COD/Ha/day and 309.78-850.73 kg BOD/Ha/day, respectively. Based on the results, the SCW-MLF unit was more efficient compared with MLF in COD, BOD, oil and grease removals, TKN, and TP parameters. Besides, a two-sided t-test was used to identify any significant differences in the mean efficiencies of the two units, with p < 0.05. In conclusion, SCW-MLF has proven to be more effective in the treatment of wastewater from canteens which complies with the Ministry of the Environment and Forestry's Standard for wastewater Nr. P.68/2016 for COD, BOD, and TKN.
Chapter
Wastewater is degraded and discarded water inevitably and ubiquitously generated from human facilities and anthropogenic activities, and discharged into the environment. It is a cocktail of countless chemicals, both beneficial and harmful ones ranging from organic matter to toxic metals, nutrients to persistent organic pollutants and pathogens, and is therefore, rightly regarded as a blessing in disguise. United Nations Sustainable Development Goals (SDG) 6.3 urges humanity reducing pollution, discharge of hazardous contaminants mixed in wastewaters into the waterbodies, halving the proportion of untreated wastewater and substantially increasing safe reuse, recycling and resource recovery globally by 2030. It calls for a paradigm shift in the approach of wastewater treatment and its reclamation from capital and energy intensive conventional technology to low-cost, environment friendly, sustainable ecotechnology. Ecotechnology is the design of sustainable systems in sync with natural systems following ecological principles, which integrate human society with its natural environment for mutual benefits. It uses Nature as model, measure, and mentor, attempts to design with Nature, and follows the ecological principles of reliance on solar energy, species cooperation, and material cycling and regeneration. The basic idea is that our treatment system can be modeled on natural ecosystems. The working and architecture of natural systems offer a blueprint for such technological design. The design philosophy, in essence, takes advantage of the wealth of information available from Mother Nature's living library—its biodiversity. The present book chapter attempts to present a comprehensive picture of nature-inspired ecological treatment, regenerative reclamation and valorization of wastewater through closing the loop. It shows how ecosystem mimics portray structural diversity yet functional unity in different ecotechnologies such as living machines, floating treatment wetlands, waste stabilization ponds train, constructed wetlands, hydroponics, and wastewater-fed aquaculture, all employing a range of functional organisms from Mother Nature's living library, comprising microbes, macrophytes, mollusks, fish, and other species, as a collaborative enterprise.
Chapter
Wastewater treatment, recycle, and reuse cannot be underestimated in the present context. Microbial units containing bacterial and/or algal biomass are often overrated as treatment techniques providing cheap and effective alternatives. Nonetheless, they come with a setback of limitedly understood systems especially with respect to mechanisms involving pollutant degradation and relationships among diverse environmental factors. Although different modeling techniques have been in use for predicting biodegradation, data mining based soft computing tools such as artificial neural networks (ANNs) and genetic programming (GP) offer substantial control over process operation in terms of specific understanding between experimental inputs and output. ANN and GP are also used in performance prediction over wider influent fluctuations with respect to variations in pH, single- or multipollutants, biomass, and/or e⁻donor/acceptor concentrations. Although these tools have found applications in the domain of wastewater treatment, the current practice is mostly on treatment plant performance while limited or no emphasis on relationships between diverse environmental factors and pollutant removal. When compared to models based on kinetic equations and the following cumbersome solving of these equations, soft computing methods decipher the information concealed in the data obtained from many experimental and real-time biological experiments. This chapter provides its readers an insight into biological system aimed at pollutant degradation and use of soft computing tools to precisely identify influential parameters among several factors involved in biodegradation of a certain pollutant. A comprehensive approach of ascertaining and optimizing influential parameters in the removal of specific pollutants from aerobic, anaerobic bioreactors and constructed wetlands (CWs) has been given herewith. It is shown that biochemical oxygen demand removal from the biological systems depended on crucial parameters such as the differential temperature (Ta–Tw; the difference between apparent temperature and wastewater temperature) in CWs and detention times in bioreactors. Root mean square error (RMSE) was used to compute the model performance, for cyanide and phenol removal using GP, and the RMSEs of 1.69 and 2.71 were obtained, respectively, while an RMSE of 5.03 was obtained for modeling CW using ANN. The case studies and modeling approaches discussed here shall direct its readers in selecting and programming data-driven models to better predict and understand the roles of influencing parameters in the removal of complex contaminants treated in biological units.
Chapter
The Mediterranean region is one of the most vulnerable areas to climate change. This area is affected by severe water scarcity, which is expected to prevail by the upcoming years. The use of reclaimed water (RW) in agriculture is a way to reduce water scarcity, alleviate pressures on groundwater and other freshwater resources, and improve irrigated crop productivity and environmental sustainability. RW is already being used, directly or indirectly, in many semi-arid areas of the world (e.g. Africa, Central America, Southern Europe, and Southern Asia).
Chapter
Water resources throughout the world are severely threatened from different pollutants released into water bodies, thereby causing water pollution. Sewage is wastewater released by household drains, residential apartments, communities living in urban agglomerations, and contains of human fecal matter and large volume of water. Chemically, it contains suspended and dissolved solids (TSS and TDS), dissolved organics, nutrients (nitrate, ammonia, and phosphorus), minerals, and pathogens (bacteria, protozoans, viruses, helminth eggs), gases like H2S, CO2, CH4, and NH3, etc. Almost all the sewage ultimately finds its way to the aquatic ecosystems and is a major source of water pollution. There are several wastewater treatment technologies; however, Constructed Wetlands (CW) have emerged as an eco-friendly, economically viable option for sustainable treatment of sewage. CWs are manmade or engineered wetlands that are designed built and operated to harness the functions of natural wetlands for the treatment of various pollutants from wastewater. Constructed wetland is a well-known technology in the different parts of the world especially in European countries for the treatment of domestic sewage. But, in Indian context such studies are very limited and this technology can be applied to even the remote areas of the country where capital and energy inputs are the major issues related to sewage treatment. Under present chapter, we have reviewed some important studies conducted worldwide dealing with application of CWs for the treatment of the sewage. We have also reviewed such studies conducted in Indian context. Our study suggests that the CWs are a natural technology of wastewater treatment and it had been a successful technology in the Europe; however, its use has been very limited in India context and more studies can establish this technology as a viable option for sewage treatment in Indian context.
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Article
The migration of nitrogen (N) from farmland to lake aggravates eutrophication. Riparian buffer strips (RBSs) are crucial in alleviating nitrogen into water bodies. This study examined the impacts of different RBS patterns on nitrogen removal. The effects of different RBSs of various widths (5, 15, 30, and 40 m), with different vegetation types (Taxodium hybrid ‘Zhongshanshan’, poplar (Nanlin-95), and a mixed forest of T. hybrid ‘Zhongshanshan’ and poplar) and at different densities (400, 1,000, and 1,600 plants·hm−2) on the TN, NH4+-N and NO3−-N removal rates in different depths of runoff water were studied. The results showed that the 15 m-wide RBS removed nitrogen the most effectively, with average removal rates of NH4+-N, NO3−-N and TN reaching 67.79%, 65.93% and 65.08%, respectively. Among the RBSs with different vegetation types, the poplar forest RBS removed the most NH4+-N (74.28%) and NO3−-N (61.71%). The mixed-forest RBS removed the most TN (65.57%). The RBS with 1,000 plants·hm−2 was more suitable in terms of the removal of NH4+-N (74.25%), NO3−-N (71.08%) and TN (62.67%). The conclusion can provide the basis of vegetation and width optimization for the design and construction of an RBS for maximum eutrophication nutrient removal. HIGHLIGHTS Construction and stability of different RBS patterns were operated for around three years.; Removal capacity of N pollutants from runoff by different patterns was compared quantitatively.; The 15 m-wide RBS with 1,000 stem·hm−2 poplar plantation removed nitrogen the most effectively.;
Article
In the last two decades, several process-based models had been developed to describe the transport and fate of contaminants in subsurface flow constructed wetlands (SSF CWs) under a variety of conditions. These models have become valuable tools to better design, control and optimize the SSF CW system. Moreover, they can aid investigations on the effects of variables of interest on the system. While excellent review papers on these models have been published, the ability of the existing process-based models in simulating the nitrogen transformations in the SSF CWs have not been highlighted. Consequently, a critical review of the simulation of nitrogen transformation processes is desirable. This paper presents an overview of the available models which are capable of modelling the nitrogen dynamics in the SSF CWs. The existing process-based models can be mainly categorized as the process-dedicated models and Gujer matrix models. A process-dedicated model is a feasible tool for design purposes. Meanwhile, the Gujer matrix model delivers valuable insights into scientific studies. In this paper, the existing models are summarized and critically discussed with regards to their capability and practicality in simulating the nitrogen dynamics in SSF CWs. Organic nitrogen, ammonium, and nitrate are the common nitrogen compounds considered in the process-based models of SSF CWs. Meanwhile, nitrite was frequently considered together with nitrate due to its low concentration in the effluent of SSF CWs. On the other hand, ammonification, nitrification, denitrification, plant uptake and ammonium adsorption are the typical nitrogen transformation and degradation processes found in the existing models, whilst ammonia volatilization was rarely found in the literature. Oxygen and organic matter are the major limiting reactants of nitrogen transformation and degradation processes in the modelling, and other factors such as microbial population, temperature and pH are also considered. The recommendations and future research directions on the influence of microorganism distribution, resting period, oxygen release, ammonium adsorption and plants are outlined.
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Aquatic plants have attracted wide attention because of their low cost and high level of resource utilization. In order to study the effects of emergent and submerged plants on the purification of different concentrations of wastewater, two common aquatic plants found in Northeast China, Iris ensata Thunb. and Potamogeton malaianus Miq., were selected Under static conditions, nitrogen and phosphorus removal from simulated wastewater with different concentrations (high, medium and low) and lake samples of Nanhu Park, Changchun, Jilin Province, China, were studied. The results showed that the removal rate of total nitrogen (TN) in medium- and high-pollutant concentration water samples and total phosphorus (TP) in medium- and low-pollutant concentration water with I. ensata reached more than 75%. The removal rate of TN in the medium-pollutant concentration water with P. malaianus reached 71.4%, while the removal efficiency of TN and TP in the low-pollutant concentration water was higher than 80%. It is more advantageous to use plants to purify high-pollutant concentration water after further purification. The purification plants suitable for medium-pollutant concentration water are limited, but under low-pollutant concentration water conditions, there are more diverse options regarding the choice of wastewater purification plants. In the Nanhu lake samples, I. ensata had the highest removal rates of TN (80.38%), and TP (85.62%). This study shows that both I. ensata and P. malaianus can be used as aquatic plants to restore the water quality of urban lakes. A reasonable combination of different plants for addressing different pollutants is more beneficial to improve the purification effect. This research provides an important basis for the phytoremediation and treatment of urban domestic wastewater and urban surface water bodies in northern China.
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En la actualidad, uno de los principales retos en torno al tratamiento de aguas residuales es su sostenibilidad basado en requerimientos energéticos. En el caso de sistemas aerobios, las plantas de tratamiento de aguas residuales convencional poseen un sistema de suministro de oxígeno a los microorganismos heterótrofos a través de aireadores mecánicos, con el fin de eliminar la materia orgánica presente en el agua (Hwang et al., 2016). Este sistema requiere aproximadamente 1 kW/h de electricidad para suministrar el aire necesario para la remoción de 1 kg de DBO demanda bioquímica de oxígeno (Abdel-Raouf et al., 2012), lo que equivale alrededor del 40 % del costo total de la electricidad en las plantas de tratamiento de aguas residuales, presentando una desventaja debido al aumento de los costos operativos. Estos procesos de tratamiento aeróbico de aguas residuales, conocidos usualmente como lodos activados, además de presentar altos costos en insumos de energía asociados con el suministro de O2, generan una gran cantidad de lodos que deben eliminarse y un impacto ambiental resultante de la emisión de gases de efecto invernadero como el CO2.
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The sewage waters are used as potential source of irrigation for raising vegetables and fodder crops around the sewage disposal sites. Soil contamination by sewage and industrial effluents has affected adversely both soil health and crop productivity. A study was conducted to evaluate the pollutant removal efficiency of lab scale hybrid constructed wetland system (HCWS) for recycling the sewage water for agriculture. Native aquatic plants viz., Brachiaria humidicola and Typha angustifolia were selected and utilized for the lab scale study. The results of this HCWS showed that removal efficiencies of BOD, COD was higher with the hydraulic retention time (HRT) of 5 days due to the combined effect of HF and VF by using the native aquatic plants like Brachiaria humidicola and Typha angustifolia.
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Constructed wetland is one of the well-knowncost-effective technologies for treating domestic sewage. This work is mainly focuses to study the performance of constructed wetland at initial stage of wetland. Three types of constructed wetland namely Vertical Flow Constructed Wetland (VFCW), Horizontal zigzag flow Constructed wetland (HFCW) and Upflow Constructed Wetland (UFCW) were made based upon the direction of water flow through porous medium. The primary treated sewage is passed through three wetlands and the water quality was tested before and after treatment. Wetland performance was analyzed continuously for one month after sapling stage. Water quality parameters such as pH, Temperature Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Chemical Oxygen Demand (COD), Nitrates (NO 3 ⁻ ) and Phosphate (PO 4 ⁻ ) were tested. Removal of COD and Phosphates are uniformly increasing for this duration. The maximum removal of COD, TSS and Phosphates are 40%, 30%, 87% and 45% respectively. Nitrification is good from initial stage of constructed wetland. In one month experimental period, removal of solids is not stable. It was observed that, heavy fluctuation was occurred during experimental period. But increasing trend is observed in the removal of solids. Also it is recommended that more sampling is needed at initial stage of constructed wetlands.
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In this study an attempt is made to study the comparison of effectiveness of single constructed wetland and hybrid constructed wetland for treating wastewater. Single constructed wetland is made with Phragmites Australis . The flow of water is vertical. Hybrid constructed wetland is made with vertical flow constructed wetland allied with water hyacinth based free floating wetland system. Primary treated sewage is allowed to the wetland. Water quality parameters namely Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS) are measured before and after treatment. Two case studies have been in this study. In first study the water is allowed for one day contact time in single constructed wetland. In second case study, the treated water from one wetland is immediately transferred to other wetland. It is evident that, a hybrid constructed wetland gives better result in removing BOD and COD in wastewater. It is observed that there is no significant difference is observed in removing TSS removal. The water is allowed to different type of plants may increase the removal efficiency. The maximum BOD removal is obtained for hybrid wetland is 86% at one day detention time. The COD removal is obtained at one day is 48%.
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Constructed wetland (CW) has been proved to be a reliable wastewater treatment technology for removal of various contaminants. However, the removal of specific contaminants such as steroid hormones by wetlands without optimized design parameters would be unstable. Here we investigated the removal mechanism of steroid hormones by constructed wetlands, and optimized various design parameters for the removal of these contaminants in wastewater. Four CW systems with different designs (artificial aeration or series wetland unit) were constructed outdoors to treat raw domestic sewage. The results showed that 9 steroid hormones were detected at concentrations from 7.13 ± 0.28 ng/L to 3040 ± 199 ng/L, with their removal rates ranged from 14.7 ± 3.04% to 100% by these CWs. It was also found that enhanced designs including aeration and series wetland unit can effectively improve the removal of steroid hormones. Combined with ecological risk assessment, CW4 (aerated VSSF CW and aerated HSSF CW combination) was the best design for removal of steroid hormones, but CW2 (VSSF CW with artificial aeration) may be better for urban areas with limited space. Based on mass balance calculation, biodegradation played a dominant role in removing steroid hormones by CWs, while substrate adsorption and plant uptake also played a limited role. The findings from this study suggest that CWs can be optimized to better remove steroid hormones in sewage before discharge into receiving environments.
Chapter
Water is an important resource that supports life on the earth. Contamination with diverse categories of pollutants (toxic metals, agrochemicals, synthetic pesticides, and organic substances) has drastically altered the quality of aquatic ecosystems. Undoubtedly, there are numerous technologies and approaches to deal with menace of contamination in aquatic environs. Nowadays, application of aquatic plants (macrophytes) has been proven to be a safe and viable technology for degradation and cleaning of harmful and toxic substances from aquatic environs both naturally as well as experimentally. Macrophytes are important in reducing the pollution level of aquatic ecosystems. They have the capacity to improve the water quality by removing nutrients, heavy metals, toxic organics, suspended solids, and other pollutants from contaminated wastewaters, thus plays an important role in purification of wastewater. Furthermore, macrophyte component of aquatic environment helps indirectly in metal retention by slowing the water current to sediment and suspend heavy metals. These aquatic plants could be applied as an effective, efficient, and choice to clean the wastewaters contaminated with metals, nutrients, and pesticides.
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A novel tidal flow constructed wetland coupled with a microbial fuel cell system (TFCW-MFC), using the influent chemical oxygen demand (COD)/total nitrogen (TN) ratio of 10:1 (Device A) and 5:1 (Device B), systematically assessed nitrogen attenuation and power production performance; the spatiotemporal distribution characteristics of denitrifying functional genes and their relationship with nitrogen removal were also determined. The results showed that the TFCW-MFC achieved high removal efficiencies for COD and TN, with both devices above 95% and 83%, respectively. The maximum power density showed a notable increase from 16.97 in Device B to 25.78 mW/m³ in Device A. The distribution of the Shannon index indicated that the diversity of napA, nirK, and nirS were higher at the cathode layers in two devices. The high COD/TN ratio obviously increased the nirK diversity in anode on the 30th day, while a low COD/TN ratio apparently promoted the diversities increase of narG, nirK, and nirS in upper or bottom layers. Proteobacteria was the dominant phylum in both devices, and the composition differentiation of the dominant denitrifying genera was mainly affected by the space variation, specifically the nitrogen concentration, pH, dissolved oxygen, and their collaborative roles, rather than the COD/TN ratio. Furthermore, TN removal was very significantly positively correlated with voltage and the relative abundance of Rhodanobacter. In summary, this study provided an insight for the key functional genes shaping the enhanced nitrogen removal by the newly designed TFCW-MFC system.
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In this study, a comparative investigation of palm bark and corncob (a well-investigated material) for enhancing nitrogen removal efficiency in partially saturated vertical constructed wetland (PSVCW) was performed to evaluate an effective and cost-effective supplementary carbon source. The characteristics of the released organic matter and the release processes were analyzed through optical property characterization and a first-order release-adsorption model, respectively, and the nitrogen removal performance was evaluated in a series of pilot-scale PSVCWs. Results showed that the amount of organic matter released per unit mass of corncob was larger than that released per unit mass of palm bark under the same pretreatment conditions (control, heat, and alkaline pretreatment). The organic matter released from corncob has a higher apparent molecular weight and a higher degree of aromatic condensation than those of the organic matter released from palm bark, whereas the organic matter released from palm bark has higher and more stable bioavailability. Moreover, palm bark showed a more significant improvement of release capacity with the heat and alkaline pretreatment methods. Pilot-scale studies revealed that PSVCW using palm bark as the supplementary carbon source has a longer replacement cycle and higher total nitrogen (TN) removal efficiency than that using corncob, indicating that palm bark can be considered an effective and inexpensive supplementary carbon source. This study provides initial guidance for the ongoing research on supplementary carbon sources for improving nitrogen removal efficiency in constructed wetlands.
Article
In developing countries, high cost of conventional wastewater treatment is a major hindrance in its application. Constructed wetlands (CWs) offer low-cost and effective solution to this issue. The current study aimed to evaluate an innovative maneuver of CWs i.e. hybrid flow constructed wetlands (HCWs) for municipal wastewater (MWW). The HCWs included two lab scale CWs; one horizontal and one vertical, in series. Local plant species were used. HCWs were operated in both, batch and continuous mode. Batch mode was used to (1) optimize detention time and (2) find pollutants removal efficiency. Continuous operation (at batch optimized retention time) was carried out for the evaluation of mass removal rate, r (g/m²/d), volumetric rate constant, Kv (per day) and areal rate constant, Ka (m/day). Among two local plants tested, Pistia Stratiotes gave better removal efficiency than Typha. Optimum detention time in HCWs was found to be 8 days (4 + 4 each). The optimum COD, BOD, TSS, TKN and P removal observed for Pistia Stratiotes planted HCWs was 80%, 84%, 82%, 71% and 88% respectively. Effluent standards for COD, BOD and TSS were met at optimum conditions. The values of Ka and Kv demonstrated that more removal occurred in vertical flow as compared to horizontal flow CW.
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Abstract: Water issues are still here, urbanization and industries generate different types of wastes which then affect water. Many technologies have been introduced for water treatment and efforts are being made to improve and maintain water quality, while also providing easily available and low-cost technologies. Several methods which are easily available but due to high cost, they cannot be introduced everywhere, especially rural areas. Recently, constructed wetlands have been proven to be an efficient technology to treat water. With its biological, physical and chemical treatment, constructed wetland technology becomes the best choice by many countries around the world. Existing research shows that COD (Chemical Oxygen Demand), BOD5 (Biological Oxygen Demand), TKN (Total Kjeldahl Nitrogen), TSS (Total suspended solids) etc. have been removed to a significant degree by using constructed wetlands. This technology is a system of different materials, such as gravel, vegetation and recently introduced tool knows as biochar. The combination of these makes the system efficient for water treatment but some factors such as area, weather conditions, type of wastes do matter. Selection of constructed wetland type and suitable plants is very important. In this paper, efficiency of constructed wetland system, its mechanism, the types of plants used in the system and role of plants to enhance the efficiency of the wetland system from all over the world are widely reviewed and discussed.
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The pollutant removal performance of traditional horizontal subsurface flow (HSSF) constructed wetlands (CWs) is limited because of the dissolved oxygen (DO) supply is insufficient. The aeration of HSSF CWs usually improves their pollutant removal performance, but a high DO induces the accumulation of nitrate-nitrogen (NO3--N) and suppresses the improvement of total nitrogen (TN) removal. In this study, an integrated solution that involved in-tank front aeration and internal recirculation (FAIR) was used to improve the pollutant removal performance of HSSF CWs. Based on the experimental results, the FAIR system significantly increased the removal efficiencies of biochemical oxygen demand (BOD) from 53.8-76.0% to 82.0-91.7% and reduced the BOD concentration in the effluent to below 10 mg L-1. The removal efficiency of ammonia-nitrogen (NH3-N) increased from 15.1-78.3% to 98.5-98.6% while the removal efficiencies of the total Kjeldahl nitrogen (TKN) of the control and FAIR HSSF CWs were 18.2-77.1% and 93.5-94.3%, respectively. HSSF CWs with FAIR outperformed aerated HSSF CWs in the removal of NH3-N and TKN. The effects of two recirculation flow ratios (Rr = recirculation flow rate/influent flow rate), 14.3 and 3.0, on the improvement of pollutant removal performance were investigated. The lower Rr did not significantly affect the improvement of BOD, NH3-N, and TKN, but a higher Rr resulted in more severe accumulation of NO3--N. The removal efficiency of TN in control HSSF CWs ranged from 20.4% to 75.5%, and in the FAIR HSSF CW was 71.6% for Rr = 14.3 and 81.3% for Rr = 3.0. However, the FAIR system did not enhance the removal performance of total phosphorus, suggesting that the DO level and internal recirculation were not dominant mechanisms for the removal of phosphorous. The easy maintenance of the FAIR system made it a superior modification for improving the pollutant removal performance of HSSF CWs.
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CEMAGREF has been studying Emergent Hydrophyte Treatment Systems (EHTS) since 1983 on three experimental sites. Two of them can be considered as typical for the Max-Planck-Institute Process (MPIP) as developed by Dr. Seidel, regarding their general layout with the succession of five treatment stages in cascade planted with different Emergent Hydrophyte species. The performance of one of these two plants (Saint Bohaire), designed by Dr. Seidel herself, proved that it is possible to feed the drained beds (1st and 2nd stages), planted with reeds and alternately fed, with raw sewage at high loading rates without the occurence of clogging. However, it also showed that the last three stages, continuously fed, were not sufficiently oxygenated and clogged rapidly. This failure was also confirmed in Pont-Rémy although this plant is underloaded. The performance of the first stage beds could be improved further by the use of batch feeding (intermittent feeding), by increasing the height of the filter media and by choosing a more adequate granulometry. Alternately fed percolation flow beds can also be used as a first stage of treatment followed by wastewater stabilization ponds. The example of Gensac la Pallue shows that they can remove 85 % of the suspended solids and 70 % of the organic load, at a loading rate of 30 to 35 g of BOD = per square metre. Such a combined system can thus provide an efficient and reliable treatment requiring a specific surface reduced by 40 % as compared to wastewater stabilization ponds only.
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For several years, the CEMAGREF has been interested in the study of treatment plants adapted to rural areas. In this field, “macrophyte beds”, as a new procedure in water treatment, has been closely followed. This treatment plant is made up of a series of watertight tubes filled with gravel and rooted with aquatic plants. Since autumn of 1982, this plant has been treating the wastewater of a rehabilitation center which functions according to a scholastic calendar. Receiving loading of 28 population equivalents, the plant must be able to cope with loading variations reaching a factor of 6. The total planted surface is 63 m2, thus 2.5 m2 per population equivalent. The different series of measurements taken during an annual plant cycle show that:–the abatement of the organic loading (COD, BOD5) reaches 85% to 90%;–the elimination rate of total nitrogen is near 50%;–the phosphorus is mineralised but is not retained by the treatment. The samplings of effluent discharge, taken several times over a three year study period, showed that the once satisfactory discharge had degraded. The origin of this degradation should be looked into. The first results (as described above) will be completed by those obtained during a study which is being conducted on a larger scale (500 population equivalent). This plant was put into use in September 1985 and receives a loading of domestic wastewater from an urban neighborhood. The research project has as its aim to optimize both the economic and operational aspects of the treatment plant to answer the real needs of small rural communities.
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Conference Paper
We constructed hybrid reed bed system to purify milking parlor wastewater in eastern part of Hokkaido, Japan in November 2005. The system was composed of first 250m 2 VF gravel bed, second 250m 2 VF sand and gravel bed and third 500m 2 HF gravel and soil bed. Mainly volcanic material was used for the beds. About 1,400 reed (phragmites australis) pots were planted on the bed in October. The main characters of the system were the combination of aerobic and anaerobic beds, self-priming siphon for intermittent flow, first gravel bed to decrease SS and a larch wood chip layer to prevent from icing in the cold climate. They are basically following French and northern European systems. The size of each bed was calculated with reference to the estimated ability of nitrification, COD and SS removal and denitrification. The amount and temperature of water were measured and water samples were collected at every inlet and outlet of each bed. TN, TP, SS, COD, NH 4 -N and NO 3 -N in the samples were analyzed. The mean temperature of the influent and effluent were about 15 and 3 to 4 centigrade on February and March. The mean amount of treated wastewater was about 16.3 m 3 d -1 and removal rates of TN, TP, SS, COD were 76.4, 84.0, 97.9 and 86.9 % in the first six month. The main purification factor is considered to be a physicochemical mechanism such as filtration and adsorption at the beginning. It is important to monitor biological decomposition, nitrification and denitrification through the year. KEYWORDS Hybrid reed bed system, subsurface flow constructed wetland, dairy milking parlor wastewater, cold climate
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Several European countries have produced guidelines for the construction of subsurface flow constructed wetland systems. No consensus has however been reached because the discharge requirements vary from country to country. The guidelines cannot be directly transferred to Denmark because of very stringent outlet requirements. In order to improve the knowledge on nitrification capacity of vertical flow systems and the potential to remove phosphorus in constructed wetlands, a number of studies were conducted in a five-year old constructed wetland system with a horizontal subsurface flow bed and a vertical flow bed, serving two small communities in Denmark. The experiments evaluated the nitrification activity in vertical flow systems as a function of area mass loading rate, loading frequency and temperature of treated, but not nitrified, effluent. The constructed wetland system used as basis for the experiments was, however, poorly suited for these experiments because of the restricted bed depth and other on-site problems with system design and wastewater composition. It was therefore not possible to establish the relationship between area loading rate and nitrification activity. However, the studies do indicate that frequent pulse loadings increase the nitrification rate. Furthermore, nitrification occurred even at 2degreesC. Thus, a pulse loaded vertical bed can sustain some nitrification activity even at very low water temperatures. The studies also documented that recycling of nitrified effluent water to the sedimentation tank increases the removal of total-nitrogen because of denitrification. It is concluded that constructed wetland systems with vertical non-saturated flow will be able to fulfil the most stringent treatment requirements imposed for on-site treatment of domestic sewage in rural areas. However, design and area demand is not yet fully established, and more work is needed to refine the removal process for phosphorus. A set of provisional guidelines for the design and construction of vertical flow systems is presented.
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This paper outlines the influence of temperature, flow rate and input concentrations on the treatment efficiency of organic matter and nutrients in constructed wetlands (CWs). Three integrated 10 PE systems with horizontal subsurface flow (HSF) treating domestic wastewater are described. Particular attention is devoted to: (1) aerobic pre-treatment in vertical-flow filters, (2) filter media with high phosphorus (P) sorption capacity, and (3) the treatment efficiency during winters. Aerobic pre-treatment followed by CW units including P sorption media removed most organic matter (BOD> 75%), P (> 90%) and total and ammonia N (40–80%). P retention was relatively stable in wetland filters, both with lightweight aggregates and ferruginous sand during 3–6 years of monitoring. Iron-rich sand from Bsh and Bs, horizons of ferro-humic podzols was efficient for P sorption, but removal efficiencies of COD, TOC and SS were negative. The differences in efficiency between cold and warm periods were less than 10 percentage points for all parameters. It is anticipated that temperature effects are partially compensated by the large hydraulic retention time. The findings suggest that HSF systems do not require vegetation.
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There is severe degradation of the water quality of the Texcoco River in central Mexico as a result of discharges of raw sewage from communities into thewatershed. Constructed wetlands may be appropriate technologies for treating the domesticwastewater generated by small communities in central Mexico. To assess the removal of pollutants from wastewater, we constructed a pilotscale treatment wetland in the small community of Santa Mar´ıa Nativitas in the Rio Texcoco watershed. The system, consisting of sedimentation terraces, stabilization pond, subsurface flow wetland (SSFW) and vertical flow wetland (VFW), removed >80% of TSS, COD and nitrate from domestic sewage. Removal of ammonium was less efficient at about 50%. This study also showed that ornamental flowers with high economic value planted in the SSFW performed as well as cattail (Typha angustifolia) in removing TSS and nitrogen. The treated water was suitable for irrigation, which could help to alleviate the scarcity of water in the Rio Texcoco watershed. Modeling exercises indicated that the pilot-scale wetland could be readily adapted to treat sewage from six families.
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Article
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.
Article
Constructed wetlands proved to be an effective and low-cost technology to control environmental pollution. The introduction of such low-tech systems is supported by the Slovenian Government. The aim of our research project was to intensify the reduction of nutrients (nitrogen compounds mainly) prior to discharging the effluents into the rivers, a contribution to the common target of the global environmental policy. The construction of the integrated system was completed in Autumn 1993 to treat domestic sewage for 10 PE. The system consists of three interconnected beds with vertical and horizontal flows. The vertical flow at the first stage is intermittent, while the horizontal one is continuous. The system is flexible due to mode of operation and the quality of the influent. Ten analyses were made during the initial months of operation. In bed B nitrification was taking place and the reduction of all other parameters but NO3-N was documented. In bed A denitrification was on in spite of intermittent vertical flow. Since the reed stand was scarce, recultivation was needed. The system showed its characteristics more clearly when more concentrated domestic wastewater was led in. Further investigation should reveal further details on proper media, surface area, and flow sequence selection. Reduction of some parameters was as follows: NH3-N 97.5%, NO3-N 74.5%, org-N 84.8%, P-tot 97.1% and COD 94.4%.
Chapter
The success of the two sewage treatment systems based on aquatic plants at Oaklands Park in Gloucestershire has attracted the attention of the industry and the media. The industry has been impressed by the performance of the two systems; the media and the public are drawn to the concept of a sewage treatment system being an attractive community amenity. The incorporation of FLOWFORMS to impart rhythmical, pulsating movement into the heart of the treatment “organisms” also creates further interest. The philosophy of these two systems - that the responsibility for cleansing wastewater rests with the community - has inspired a number of other (dedicated) communities to work with similar landscaped sewage treatment systems.
Thesis
Aangelegde moerassen kunnen toegepast worden voor de zuivering van huishoudelijk, agrarisch en industrieel afvalwater, effluenten van mijn- en stortactiviteiten, en overstort- en stormwater. De verwijdering van zware metalen in aangelegde zuiveringsmoerassen wordt gewaarborgd door een complex samenspel van fysico-chemische en biologische processen. Een eerste deel van dit werk handelt over het gedrag van zware metalen in aangelegde moerassen voor de zuivering van huishoudelijk afvalwater in Vlaanderen. Concentraties van zware metalen in de influenten van verschillende types zuiveringsmoerassen het afvalwater werden gekenmerkt door een grotere variabiliteit dan deze in het effluent. Dit wijst op de bufferende werking van deze zuiveringsmoerassen. Metaalconcentraties in de effluenten waren meestal beduidend lager dan de basismilieukwaliteitsnormen voor oppervlaktewater. De wortelzonerietvelden voor secundaire waterzuivering vertoonden algemeen de hoogste verwijderingsefficiënties. In tegenstelling tot de uniforme distributie van metalen in het sediment van het vloeirietveld, werden metalen voornamelijk geconcentreerd in het sediment van de inlaatzone van het wortelzonerietveld. Een tweede deel van dit werk gaat dieper in op de rol van helofyten in aangelegde zuiveringsmoerassen. In zowel veldstudies als experimenteel onderzoek werd duidelijk aangetoond dat helofyten geen sterk verhoogde concentraties van zware metalen accumuleren in hun bovengrondse biomassa. Helofyten kunnen echter eveneens op indirecte manier een invloed uitoefenen op metaalverwijdering, bijvoorbeeld door zuurstofafgifte van de wortels. De selectie van helofytensoorten wordt best voornamelijk afgestemd op het te behandelen afvalwater en het beoogde verwijderingmechanisme. In een derde deel van dit werk werd de mogelijke toepassing van twee verschillende types zuiveringsmoerassen voor een industrieel afvalwater gecontamineerd met Co, Ni, Cu, Zn en sulfaten onderzocht. De zware metalen werden efficiënt geïmmobiliseerd in het substraat van een met riet beplante grindfilter. Verwijdering op korte termijn werd gewaarborgd door sorptie, verwijdering op lange termijn door neerslag met sulfiden. Beide types aangelegde moerassen hebben toepassingsmogelijkheden voor de tertiaire zuivering van industrieel afvalwater, in het bijzonder in ontwikkelingslanden.
Article
The paper reviews the different options for the combination of vertical- and horizontal-flow beds used in hybrid reed bed/wetland systems. The design and performance of these systems are briefly described. The importance of the oxygen transfer capacity of the different arrangements to their performance and their size is discussed. Alternative methods for denitrification are briefly described.
Article
The paper reviews the different options for the combination of vertical- and horizontal-flow beds used in hybrid reed bed/wetland systems. The design and performance of these systems are briefly described. The importance of the oxygen transfer capacity of the different arrangements to their performance and their size is discussed. Alternative methods for denitrification are briefly described.
Book
The Authors.- Preface.- Introduction.- Transformation Mechanisms Of Major Nutrients And Metals In Wetlands.- Wetland Plants.- Types Of Constructed Wetlands For Wastewater Treatment.- Horizontal Flow Constructed Wetlands. Types Of Wastewater Treated In HF Constructed Wetlands.- The Use Of HF Constructed Wetlands In The World.- References.-Suggested Reading.- Subject Index.
Article
Constructed wetlands proved to be an effective and low-cost technology to control environmental pollution. The introduction of such low-tech systems is supported by the Slovenian Government. The aim of our research project was to intensify the reduction of nutrients (nitrogen compounds mainly) prior to discharging the effluents into the rivers, a contribution to the common target of the global environmental policy. The construction of the integrated system was completed in Autumn 1993 to treat domestic sewage for 10 PE. The system consists of three interconnected beds with vertical and horizontal flows. The vertical flow at the first stage is intermittent, while the horizontal one is continuous. The system is flexible due to mode of operation and the quality of the influent. Ten analyses were made during the initial months of operation. In bed B nitrification was taking place and the reduction of all other parameters but NO3−N was documented. In bed A denitrification was on in spite of intermittent vertical flow. Since the reed stand was scarce, recultivation was needed. The system showed its characteristics more clearly when more concentrated domestic wastewater was led in. Further investigation should reveal further details on proper media, surface area, and flow sequence selection. Reduction of some parameters was as follows: NH3−N 97.5%, NO3−N 74.5%, org-N 84.8%, P-tot 97.1% and COD 94.4%.
Chapter
A two-stage constructed wetland (CW) system consisting of two vertical flow beds with intermittent loading operated in series has been investigated. The first stage uses a grain size of 1–4 mm for the main layer and has a drainage layer that is operated under saturated conditions; the second stage uses a grain size of 0.06–4 mm and a drainage layer with free drainage. The two-stage system was operated with an organic load of 80 g COD m–2 day–1 for the first stage (1 m2 per person equivalent), i.e. 40 g COD m–2 day–1 for the whole system (2 m2 per person equivalent). The system has been investigated using indoor pilot-scale CWs. The results of the indoor experiments are currently verified outdoor. Organic matter and ammonia nitrogen (NH4-N) removal has been very high and has been shown to be the same as for a single-stage CW system (grain size for main layer 0.06–4 mm, free drainage, organic load 20 g COD m–2 day–1, i.e. 4 m2 per person). A total nitrogen elimination rate of 58% could be reached for the two-stage indoor system compared to almost no nitrogen elimination for a single-stage system. The first results of the outdoor experiments are similar compared to the indoor experiments regarding organic matter, nitrogen, and microbial parameters. The nitrogen elimination reached in the first 3 months of operation was 63%. By using the two-stage CW system it is possible to obtain a higher effluent quality compared to a standard single-stage CW system with only half of the specific surface area requirement. Nitrogen removal efficiencies of about 60% and nitrogen elimination rates of more than 1,400 g N m–2 year–1 can be reached without recirculation.
Article
To treat the wastewater of a hospital at Dhulikhel/Nepal, a two-stage constructed wetland was built with a settlement tank, a horizontal flow bed as first stage and a vertical flow bed as second stage. The plant is operated without electric power. The aim was the elimination of organic compounds, nitrification and a significant reduction of indicator bacteria. Different phases of operation (high and low water level within the soil profile, serial operation, one stage operation) were investigated, of which the serial operation with high water level in the horizontal flow bed and low water level in the vertical flow bed showed the best elimination performance. The areal removal rate constants (k-values) turned out to be very high (especially of the vertical flow bed) compared with literature values of other subsurface flow constructed wetlands. For the vertical flow bed kCOD was 0.22 m/d and kNH4-N was 0.85 nVd during serial operation. For kNH4-N a strong correlation with the hydraulic loading rate and the COD inlet concentration was found.
Article
To improve total nitrogen removal, a full-scale experimental study was conducted on a hybrid constructed wetlands plant designed for 100 person equivalents. The plant was composed of a first stage of vertical filters (fed with raw wastewater), followed by a second stage of horizontal filters. It was monitored over one year, measuring hydraulic conditions, physico-chemical conditions, gas emission, oxygen levels in the gas phase as well as regular treatment performance by 24-h composite samples. Different vertical filter configurations (media depth, intermediate and passive aeration system) were tested as well as two horizontal filter designs. Nitrogen removal is discussed in terms of the efficiency of each stage in relation to the season and the load applied. This study indicates limits for systems configuration and suggests some design avenues for hybrid systems to reach high and regular levels of nitrogen removal with reasonable surface area per person.
Article
This paper analyses the purification efficiency and mass removal of organic material, suspended solids, nitrogen and phosphorus in a hybrid constructed wetland (CW) system treating wastewater from a basic school in Paistu, Estonia. The CW consists of two subsurface flow filter beds using lightweight aggregates (LWA): a two-chamber vertical subsurface flow (VSSF) filter bed followed by a horizontal subsurface flow (HSSF) filter bed, with a total area of 432 m2. This CW was constructed in summer 2002 by the Centre for Ecological Engineering in Tartu (CEET). Eighteen series of water samples (from 30.10.2003 to 15.10.2005) were undertaken. The analyses show the outstanding purification effect of the system: for BOD7 the average purification efficiency is 91%; for total suspended solids (TSS)—78%, for total P—89%, for total N—63%, and for NH4N—77%. The average outlet values for the above-listed parameters were 5.5, 7.0, 0.4, 19.2 and 9.1 mg L−1, respectively. According to our results, the purification parameters meet the standards set by the Water Act of Estonia for wastewater treatment plants of 2000–9999 PE: 15, 25, and 1.5 mg L−1 for BOD7, TSS and total P, respectively. The results show that hybrid CW systems consisting of subsurface flow filter beds can work efficiently in conditions of changing hydraulic loading and relatively cold climate. We did not find significant differences between the removal efficiency, mass removal, and values of the first-order rate-constant k for most water quality indicators during the warm (May–October) and cold (November–April) periods. Locally produced LWA as a filter material in CWs has shown good hydraulic conductivity and phosphorus sorption capacity (k = 17.1 ± 12.4 m yr−1). The Paistu CW, with its proper design and outstanding purification results, can be considered one of the best systems in Estonia.
Article
The first experiments using wetland macrophytes for wastewater treatment were carried by out by Käthe Seidel in Germany in early 1950s. The horizontal sub-surface flow constructed wetlands (HF CWs) were initiated by Seidel in the early 1960s and improved by Reinhold Kickuth under the name Root Zone Method in late 1960s and early 1970s and spread throughout Europe in 1980s and 1990s. However, cohesive soils proposed by Kickuth got clogged very quickly because of low hydraulic permeability and were replaced by more porous media such as gravel in late 1980s in the United Kingdom and this design feature is still used. In fact, the use of porous media with high hydraulic conductivity was originally proposed by Seidel. HF CWs provide high removal of organics and suspended solids but removal of nutrients is low. Removal of nitrogen is limited by anoxic/anaerobic conditions in filtration beds which do not allow for ammonia nitrification. Phosphorus removal is restricted by the use of filter materials (pea gravel, crushed rock) with low sorption capacity. Various types of constructed wetlands may be combined in order to achieve higher treatment effect, especially for nitrogen. However, hybrid systems are comprised most frequently of vertical flow (VF) and HF systems arranged in a staged manner. HF systems cannot provide nitrification because of their limited oxygen transfer capacity. VF systems, on the other hand, do provide a good conditions for nitrification but no denitrification occurs in these systems. In hybrid systems (also sometimes called combined systems) the advantages of the HF and VF systems can be combined to complement processes in each system to produce an effluent low in BOD, which is fully nitrified and partly denitrified and hence has a much lower total-N outflow concentrations.
Article
Nitrate reduction to NH4+ and incorporation into organic matter was investigated in sediment-water systems composed of a 2.4-cm layer of estuarine sediment covered by 2 cm of water. Between 15 and 28% of the 15N-labelled NO3− added to the sediment or floodwater of the systems was recovered as NH4+ and organic N. The results indicated that NO3− was reduced to NH4+ by a dissimilatory mechanism. A separate experiment examined the influence of redox potential (+300, 0 and −200 mV) on NO3− reduction in sediment suspensions maintained at pH 7.5. Conversion of NO3− to NH4+ and organic N increased markedly with decreasing redox potential. The results suggested that although the reaction accounted for 35–42% of the NO3− reduced under intensely-reduced conditions (−200 mV), the significance of the reaction in nature was dependent upon NO3− movement into zones sufficiently reduced for reduction of NO3− to NH4+ instead of denitrification. Under conditions in which NO3− moved downward through a sediment-water column into a reduced sediment zone approximately 15% of the NO3− was reduced to NH4+ and recycled in the sediment.
Article
Wetlands have been intensively studied in the Czech Republic for more than 30 years, but the first full-scale constructed wetland (CW) for wastewater treatment was built in the Czech Republic in 1989. By the end of 1999, about 100 CWs were put in operation. The majority of the systems are horizontal subsurface flow (HSF) CWs and are designed for the secondary treatment of domestic or municipal wastewater. The size of CWs ranges between 18 and 4500 m2 and between 4 and 1100 population equivalent (PE). Most frequently used filtration media are gravel and crushed rock with size fractions of 4/8 and 8/16 mm and Phragmites australis is the most commonly used plant. The treatment efficiency is high in terms of BOD5 (88.0% for vegetated beds) and suspended solids (84.3% for vegetated beds). The removal of nutrients is lower for vegetated beds, and averages 51 and 41.6% for total phosphorus and total nitrogen, respectively.
Article
The constructed wetland (CW) was developed as a pilot integrated system for the capital city's old sanitary landfill site. It consisted of three interconnected beds, two of vertical flow and one of horizontal flow stage. The CW covered 311 m2 with an intermittent hydraulic load of 0.5 cm d−1, filled with sand media and planted with reeds and cattails. The performance efficiency of the CW systems was evaluated for 7 years through physical and chemical parameters. Some monitored parameters varied noticeable. The efficiency for COD was 50%, BOD5 (59%), ammonia nitrogen (51%), nitrate (negative), total phosphorus (P) (53%), sulfates (negative), sulfides (49%), chlorides (35%), and Fe (84%). The average concentrations of suspended solids, COD, BOD5, nitrate, total P, sulfates, sulfides, and Fe were below limits after treatment. The ratio between N and P showed a limited level of P for biological processes. The performance of the system did not vary significantly with regard to temperature, however, it varied with precipitation. The results showed that the CW system, as a tertiary system or as an independent system, could be a low-cost alternative for the treatment of leachate from old landfill sites.
Article
The first constructed wetland (CW) for wastewater treatment was built in the Czech Republic in 1989. This recent survey shows that at the end of 1999 101 systems are in operation and several more are under construction. 95 CWs are designed with sub-surface horizontal flow, 6 systems are hybrid with a combination of vertical and horizontal flow beds. Most systems (56) were designed for the treatment of municipal and domestic sewage while 38 CWs were designed for the treatment of wastewater from combined sewer systems. The most commonly used size of vegetated beds is 1,001-2,500 m2 (31 systems) followed by the area between 51-250 m2 (19%). The area of vegetated bed of the largest system is 4,493 m2. Size distribution is quite evenly spread from very small systems (PE = 3 or 4) up to 1,000 PE. However, most systems (44) were sized to treat wastewater from sources between 101 and 500 PE. The most commonly used macrophyte is Common reed (Phragmites australis) which is used in 34 systems as a monotypic stand and in 44 systems in combination with other macrophytes, most frequently with Reed canarygrass (Phalaris arundinacea) (31 systems) and cattails (Typha spp.) (8 systems).
Article
Pig farm wastewater creates various problems in many areas throughout Thailand. Constructed wetland systems are an appropriate, low cost treatment option for tropical countries such as Thailand. In this study, a combined system (a vertical flow bed planted with Cyperus flabelliformis over a horizontal flow sand bed without plants) was used to treat settled pig farm wastewater . This system is suitable for using in farms where land is limited. The average COD and nitrogen loading rate of the vegetated vertical flow bed were 105 g/m2.d and 11 g/m2.d respectively. The wastewater was fed intermittently at intervals of 4 hours with a hydraulic loading rate of 3.7 cm/d. The recirculation of the effluent increased total nitrogen (TN) removal efficiency from 71% to 85%. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal efficiencies were 95% and 98%. Nitrification was significant in vertical flow Cyperus bed, and the concentration of nitrate increased by a factor of 140. The horizontal flow sand bed enhanced COD removal and nitrate reduction was 60%. Plant uptake of nitrogen was 1.1 g N/m2.d or dry biomass production was 2.8 kg/m2 over 100 days.
Article
The first Irish municipal application of a hybrid reed bed treatment system (RBTS) was designed and constructed at Colecott, County Dublin. The hybrid design for Colecott RBTS was based on modifications to the Max Planck Institute Process (MPIP). The constituent parts of the design were a septic tank, a pump sump, two stage vertical flow beds, a secondary settlement tank, a horizontal reed bed, an outlet chamber and outfall pipe. The population at the time of design was 48, but with future development in mind 60 was used as the population equivalent (pe). Construction and operational characteristics are outlined. Results of a two year monitoring study are presented, showing good performance and producing a final effluent with 88% BOD removal, 89% COD removal and 99% SS removal. Percentile compliance with EU discharge standards were BOD 60%, COD 100%, SS 100% with 50% for nitrogen and 0% for PO4. Surface water input increased flows to twice the average, resulting in increased maintenance visits without affecting results. The ability to deal with the excess inflow is demonstrated by the system. The method of distribution to the primary vertical beds was satisfactory while that on the secondary vertical beds was not.
Article
Simultaneous determinations of nitrogen gas production, ammonia, and particulate organic nitrogen formation in the coastal sediments of Mangoku-Ura, Simoda Bay, and Tokyo Bay were made by using the N-label tracer method. The rate of nitrogen gas production in the sediment surface layer was about 10 mug atom of N per g per h, irrespective of the location of the sediments examined. [N]ammonia and -particulate organic nitrogen accounted for 20 to 70% of the three products, and after several hours of incubation, the major fraction of nondenitrified N in Mangoku-Ura and Simoda Bay sediments was recovered as ammonia. In Tokyo Bay sediments, particulate organic nitrogen was produced at a greater rate than was ammonia. The reduction rate data suggest that the pathway of nitrate reduction to ammonia is important in coastal sediments.
Nitrification and denitrification in hybrid constructed wetlands systems
  • Cooper
Cooper, P.F., 2001. Nitrification and denitrification in hybrid constructed wetlands systems. In: Vymazal, J. (Ed.), Transformations of Nutrients in Natural and Constructed Wetlands. Backhuys Publishers, Leiden, The Netherlands, pp. 257-270.
Data evaluation of constructed wetlands for treatment of domestic sewage
  • Mitterer-Reichmann
Mitterer-Reichmann, G.M., 2002. Data evaluation of constructed wetlands for treatment of domestic sewage. In: Proc. 8th Internat. Conf. Wetland Systems for Water Pollution Control, University of Dares Salaam, Tanzania, pp. 40-46.
Vertical flow–horizontal flow constructed wetlands combined treatment system design and performance
  • House
House, C.H., Broome, S.W., 2000. Vertical flow-horizontal flow constructed wetlands combined treatment system design and performance. In: Proc. 7th Internat. Conf. Wetland Systems for Water Pollution Control, University of Florida, Gainesville and International Water Association, London, pp. 1025-1033.
Economics of on-site treatment of wastewaters
  • Slavíček
Slavíček, M., 2008. Economics of on-site treatment of wastewaters. In: Proc. Conf. Decentralized Wastewater Treatment, ARDEC, s.r.o., Brno, Czech Republic, pp. 53-59 (in Czech).
Macrophytes and water purification Biological Control of Water Pollution
  • K Seidel
Seidel, K., 1976. Macrophytes and water purification. In: Tourbier, J., Pierson, R.W. (Eds.), Biological Control of Water Pollution. Pennsylvania University Press, Philadelphia, USA, pp. 109-122.
Neue Wege zur Grundwasseranreicherung in Krefeld, Vol. II. Hydrobotanische Reinigungsmethode
  • Seidel