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High-efficient nitrogen removal by coupling enriched autotrophic-nitrification and aerobic-denitrification consortiums at cold temperature

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... It is easier to obtain a bacterial consortium than a pure strain. Many studies have reported the enrichment of AOB by nitrifying activated sludge systems, such as sequencing batch reactors (SBRs) (Vadivelu et al., 2007;Zou et al., 2014;Zhang et al., 2015;Yuan et al., 2016); however, they have mainly focused on the susceptibility of AOB to the environment and changes in population structure, and the isolation and application of these populations were ignored. ...
... Metabolites, signalling molecules, genetic material and defensive compounds are interchanged by short diffusion pathways, which achieves the maximization of substrate use (Flemming et al., 2016). For instance, Zou et al. (2014) demonstrated that the coupling of an enriched autotrophic nitrifying consortium and a heterotrophic denitrifying consortium in SBRs greatly enhanced nitrogen removal and reduced carbon supply. The prolonged purification effect and minor impact on the bacterial community have been observed in wastewater treatment by inoculating with a bacterial consortium (Festa et al., 2016). ...
... Such a result was not affected by FNA, indicating that the heterotrophic and autotrophic bacteria in the ammonia-oxidizing bacterium consortium cooperated with each other for nitrogen removal, probably the reason for the exchange of substrates between AOB and heterotrophs. The cooperation was also observed in previous studies (Zou et al., 2014;Yong et al., 2015;Jin et al., 2017). ...
... Most denitrifiers work efficiently at 25 • C − 35 • C and neutral pH condition, which are strict to the external environment [4,5]. Normally, there is persistent nitrite accumulation during denitrification process [6]. Shi et al. [7] and Si et al. [8] reported that high pH (pH = 9) value could induce significant nitrite accumulation in denitrification, reducing TN removal efficiency with nitrite as the end-product. ...
... The C/N ratios were adjusted to 2, 4, 6, 8, 10, and 12 by different trisodium citrate feeding. The pH, DO and temperature conditions were controlled as follows: adjusting the initial pH to 5,6,7,8,9,10, and 11 by adding 1 mol/L HCl or 1 mol/L NaOH; adjusting the shaking speed to 0, 50, 100, 150, and 200 rpm; setting the temperature of the shaker to 15,20,25,30,35,40, and 45 • C. All the above experiments were conducted in triplicate in 250 mL Erlenmeyer flasks with 200 mL of sterile DM-1 medium with the inoculation size of 5% (v/v), and non-seeded samples served as controls. Unless the single-factor was adjusted as experimental design, the medium with a constant NO 3 --N concentration (100 mg/L) was incubated at 30 • C, pH 7, and 100 rpm for 3 days. ...
Article
A new facultative anaerobic denitrifier was isolated from anoxic activated sludge and identified as Pseudomonas stutzeri strain HK13. Single-factor experiments indicated that the optimal conditions for nitrate removal were a C/N ratio of 8, an initial pH of 7 - 10, a shaking speed of 100 rpm, and a temperature of 30 °C - 40 °C. When 100 mg/L NO3--N and NO2--N were used separately as sole nitrogen sources, the strain exhibited efficient denitrification ability with total nitrogen (TN) removal efficiencies of 98.22% and 98.58%, respectively, in 15 h with the corresponding maximum removal rates of 20.03 and 21.77 mg/L/h. And there was no nitrite accumulation finally in the nitrate denitrification system. In addition, 97.42% total oxidized nitrogen (TON) was removed at 20 °C and 93.46% NO3--N was reduced at 45 °C, suggesting that strain HK13 had a wide range of temperature and pH to adapt to the environment. Moreover, strain HK13 exhibited a notable ability to tolerate high nitrate loading (initial NO3--N >450 mg/L) with a TON removal amount of over 200 mg/L/day. These findings demonstrate that strain HK13 is effective for nitrogen removal in wastewaters containing high concentrations of nitrate and nitrite.
... The general trend of biomass contents in the upper layers of the three biofilters was reduced with height due to nutrient substances depleting. However, iron scrap containing biofilters had higher biomass contents, which was probably induced by the fact that iron ions existing in the biomass promote the microbial growth (Zou et al., 2014). Furthermore, the GAC layer with larger specific surface area accumulated more biomass. ...
... This made the anaerobic zone exist more easily, and the organic matters were consumed more slowly inside the biofilm of Fe-CE and Fe-AC than those in biofilter CE, which agreed the local anaerobic denitrification to occur. Moreover, it was reported that denitrification process could be promoted by the Fe 3þ Zou et al., 2014), thus the denitrification occurring in these biofilters might be enhanced by the retained iron ions in biofilm. Previous study found that the iron scrap would even stimulate aerobic denitrification, making SND happen under the aerobic condition (Chen et al., 2018). ...
Article
Textile dyeing wastewater is characterized by low biodegradability and high nitrogen strength, which is difficult to meet the increasingly stringent discharge requirements. Therefore, the tertiary nutrient and refractory organics removal is considered and aerated biofilter is often adopted. However, the aerobic condition and carbon source shortage restrict tertiary biological nitrogen removal. In this study, iron scrap was introduced as the filter medium to enhance the pollutant removal capacity, and three aerobic biofilters were constructed. Biofilter Fe-CE was filled with iron scrap and ceramisite; biofilter Fe-AC was added with iron scrap and granular activated carbon, and biofilter CE only had ceramisite to pad as control system. After the biofilters were acclimatized by synthetic wastewater and actual dyeing wastewater, the optimal operation parameters based on nitrogen removal were determined as pH 7, gas-water ratio 5:1, hydraulic retention time 8 h and C/N ratio 8.5:1. The iron scraps improved total nitrogen (TN) removal significantly, with TN removal efficiency of 68.7% and 57.3% in biofilter Fe-AC and biofilter Fe-CE, comparing with biofilter CE of 29.9%. Additionally, phosphorus and COD had better removal performance as well when iron scrap existed. Further investigation interpreted the reason for iron's facilitating effect on tertiary nutrient and refractory organics removal. The introduction of iron scrap made the habitat conditions such as pH values, DO concentrations and biomass contents inside the biofilters change towards the direction beneficial for pollutant elimination especially for nitrogen removal. In iron containing biofilters, the majority of nitrogen, phosphorus and organic pollutants were removed in the iron scrap layers, and more pollutants types appeared, implying that iron triggered pollutants to go through more diverse degradation or transformation pathways. Moreover, the phylum Proteoabcteria dominated in samples of ceramisite-containing biofilters, with abundances more than 40%. The iron scrap existence increased the abundances of phyla Bacteroidetes and Firmicutes, and triggered higher abundance of denitrification bacteria.
... The enriched microbial inoculum used in this study was mixed by three groups of microorganisms, including (1) heterotrophic nitrifying bacterium, (2) autotrophic nitrifying bacteria and (3) a commercially available complex agent BZT Ò . The purpose of mixing (3) into (1) and (2) is to obtain a mixed culture with high biodiversity, which has been proven to benefit an overall nitrifying and denitrifying functionality of microbial consortia (Zou et al., 2014). ...
... Some recent studies have reported that several lineages, such as Acinetobacter (Zhao et al., 2010), Aeromonas (Carter et al., 1995), Enterobacter (Feng et al., 2012), Bacillus , and Flavobacterium (Zou et al., 2014) were aerobic heterotrophs capable of nitrification and denitrification. These genera accounted for more than half in relative abundance in the community of BS. ...
Article
Compound microbial inocula were enriched and applied to a pilot-scale constructed wetland system to investigate their bioaugmentation effect on nitrogen removal under cold temperature (10 oC). The results showed a 10% higher removal efficiency of ammonia and total nitrogen compared to a control (unbioaugmented) group. The microbial community structures before and after the bioaugmentation were analyzed through high throughput sequencing using Miseq Illumina platform. A variation of species richness and community equitability was observed in both systems. It is demonstrated that, based on the response of both the performance and microbial community, bioaugmentation using compound microbial inocula can fine tune the bacterial population and enhance the nitrogen removal efficiency of a constructed wetland system.
... Ammonia oxidizing bacteria and the nitrate oxidizing bacteria functions in the removal of nitrogen from the municipal wastewater system with partial nitrification under the anoxic condition in the continuous plug flow processes [114]. Coupling aerobic consortiums like enriched autotrophic nitrifying and heterotrophic denitrifying consortiums implied a huge potential in the removal of heavy nitrogen from lowstrength domestic wastewater [115,116]. Performance of the nitrifying bacteria revealed the increase in nitrification potential concerning granulation of the nitrifying sludge in a continuous flow airlift reactor (ALR) [117]. The hydrodynamic parameter in continuous flow airlift bioreactor is the main aspect in the improvement of nitrification potential for the granulation of the nitrifying bacterial groups in ALR [118]. ...
Article
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To deal with the increasing risk of pollutants from the aquaculture practice, wastewater treatment systems are considered to be an ideal strategy, for reducing the impact on the natural ecosystem. Biological treatment systems per se bioreactors involving microorganisms are efficient in the bioremediation process is determined by the reactor design, operational module i.e., structure of the bacterial community, and their diversity which in turn reveals the essential relationship between its ecosystem and the environmental factors. Microbial diversity and the dynamics of the microbial populations illustrate the principal background of different bacterial communal development performing bioremediation. Progression in genome exploration led to multifaceted technical ease in recent with the emergence of different generation sequencing technologies e.g., Sanger sequencing, 454 sequencing, Illumina/Solexa sequencing, Single-molecule real-time sequencing, and Oxford nanopore sequencing. Though the recent advancements provide a greater profile of information for research, using high throughput sequencing could not be a suitable option in all aspects, especially in consideration of the initial research requirement, the low number of targets, minimal samples, and also the diversity scaling methodologies. In this review, we have discussed the PCR-based molecular fingerprinting techniques which go accessible with sanger sequencing methodologies as well as by combining different statistical and bioinformatic algorithms. The systematic analysis with the elementary molecular techniques combining sequence technologies and bioinformatics tools would enable us to understand the overview and diversity structure of the biofilm and further in-depth research by selecting appropriate sequencing platforms results in the dynamics of the microbial community.
... Subsequently, the simultaneous decline in ammonium and nitrate confirmed that heterotrophic nitrification-aerobic denitrification occurred. Notably, no detection of nitrite was observed throughout the process, overcoming the shortcoming of nitrite accumulation during aerobic denitrification mediated by other aerobic denitrification bacteria [17,19,20]. High accumulation of nitrite would inhibit the respiration and proliferation of nitrifiers and denitrifying bacteria. ...
Article
Full-text available
Discharge of wastewater contained high amount of nitrogen would cause eutrophication to water bodies. Simultaneous nitrification and denitrification (SND) has been confirmed as an effective process, the isolation of SND bacteria is crucial for its successful operation. In this study, an SND strain was isolated and identified as Pseudomona aeruginosa LS82, which exhibited a rapid growth rate (0.385 h−1) and good nitrogen removal performance (4.96 mg N·L−1·h−1). Response surface methodology was applied to optimize the TN removal conditions, at which nearly complete nitrogen (99.8 ± 0.9%) removal were obtained within 18 h at the condition: pH 8.47, 100 rpm and the C/N ratio of 19.7. The saddle-shaped contours confirmed that the interaction of pH and inoculum size would influence the removal of total nitrogen significantly. Kinetic analyses indicated that the reduction of nitrite was the rate-limiting step in the SND process. Our research suggested strain LS82 can serve as a promising candidate for the treatment of ammonium rich wastewater, and expended our understanding the nitrogen removal mechanism in the SND process.
... Meanwhile, NO 2 − -N accumulation was hardly detected during NO 3 − -N removal, which contradicted the theory that Frontiers in Environmental Science | www.frontiersin.org January 2022 | Volume 9 | Article 818316 NO 2 − -N accumulation is inevitable during biological treatment of wastewater (Zou et al., 2014;Zhao et al., 2018;Lang et al., 2020). Overall, these results showed that strain EM-A1 is a heterotrophic nitrifying-aerobic denitrifying bacterium that can efficiently remove low concentrations of NH 4 + -N, NO 2 − -N, and NO 3 − -N within 48 h. ...
Article
Full-text available
Removal of nitrogen from hydroxylamine could effectively improve the wastewater treatment efficiency. In this work, Bacillus thuringiensis EM-A1 was obtained from a biogas digester with hydroxylamine as the only nitrogen source. Hydroxylamine (100%) and total nitrogen (71.86%) were efficiently removed under the following conditions: 30°C, sucrose as carbon source, carbon to nitrogen ratio 40, rotation speed 0 rpm, pH 9.58, and inoculant concentration of 0.58×108 colony-forming units. Ammonium was completely consumed by strain EM-A1, and 8.32 ± 0.08 mg/L of nitrate was produced during the ammonium removal process. During aerobic denitrification, the removal efficiencies of NO2 −-N and NO3 −-N by strain EM-A1 were 100 and 76.67%, respectively. There were about 29.34 ± 0.18%, 26.71 ± 0.36%, and 23.72 ± 0.88% initial total nitrogen lost as nitrogenous gas when NH4 +, NO3 −, and NO2 − were separately used as the sole nitrogen source. The specific activities of ammonia monooxygenase, hydroxylamine oxidoreductase, nitrate reductase, and nitrite oxidoreductase were successfully detected as 0.37, 0.88, 0.45, and 0.70 U/mg protein, respectively. These results indicated that B. thuringiensis EM-A1 is a promising candidate for bioremediation of inorganic nitrogen from wastewater.
... Moreover, the accumulation of nitrite in the experimental groups of these three phases (phases 1.1, 1.2, and 1.3) were very low with a peak value of 0.38 mg L -1 (Fig. 1b), which showed that the denitrification process in the reactor was relatively exhaustive. Previous studies have shown that the accumulation of nitrite during denitrification processes is inevitable [11]. -1) List of symbols at the end of the paper. ...
Article
This study developed a bio-aggregate reactor by Pseudomonas strain GF2. The response surface method (RSM) indicated that the optimal parameters were pH of 7, HRT of 6 h, initial nitrate concentration of 25 mg L–1. The maximum nitrate removal reached 99.19% during the carbon to nitrogen (C/N) ratio of 2. Gas detection revealed that nitrogen gas was the main product (98.46%). 3D fluorescence spectrum (3D-EEM) analysis showed that with increasing HRT, the fulvic acid-like, tryptophan, and protein-like substances increased, which were consistent with the change in microbial community. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the existence of O–H, C–H, C=O, and C=C. High-throughput sequencing result manifested that Pseudomonas and Azospira were the dominant genera.
... The results showed that the strain GZWN4 gave priority to the utilization of NH 4 + -N under the condition of coexistence of three nitrogen sources, which may be because the activity of ammonia monooxygenase was higher than that of nitrite reductase and nitrate reductase, which was similar to that of Pseudomonas bauzanensis DN13-1 [11]. In addition, it has been reported that some strains [37] could accumulate NO 2 − -N or cannot completely remove NO 2 − -N, and the presence of NO 2 − -N may inhibit the progress of denitrification and cause toxicity to certain strains [38], thus limit the practical application effect of the strain. During the nitrogen removal process of strain GZWN4 under different nitrogen sources, NH 4 + -N and NO 2 − -N almost did not accumulate, which can effectively avoid the inhibition of intermediate product on nitrogen removal process and toxicity to other strains. ...
Article
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A novel Pseudomonas sp. GZWN4 with the aerobic nitrogen removal ability was isolated from aquaculture water, whose removal efficiency of NO2⁻–N, NO3⁻–N and NH4⁺–N was 99.72%, 82.54% and 98.62%, respectively. The key genes involved in nitrogen removal, nxr, napA, narI, nirS, norB and nosZ, were successfully amplified and by combination with the results of nitrogen balance analysis, it was inferred that the denitrification pathway of strain GZWN4 was NO3⁻–N → NO2⁻–N → NO → N2O → N2. The strain GZWN4 had excellent nitrite removal performance at pH 7.0–8.5, temperature 25–30 ℃, C/N ratio 5–20, salinity 8–32‰ and dissolved oxygen concentration 2.52–5.73 mg L⁻¹. The receivable linear correlation (R² = 0.9809) was obtained with the range of quantification between l0³ and 10⁸ CFU mL⁻¹ of the strain by enzyme-linked immunosorbent assay. Strain GZWN4 could maintain high abundance in the actual water and wastewater of mariculture and the removal efficiency of TN were 52.57% and 63.64%, respectively. The safety evaluation experiment showed that the strain GZWN4 had no hemolysis and high biosecurity toward shrimp Litopenaeus vannamei. The excellent nitrogen removal ability and adaptability to aquaculture environment made strain GZWN4 a promising candidate for treatment of water and wastewater in aquaculture.
... The enriched microbial inoculum used in this study was a mixture of a heterotrophic nitrifying bacterium, autotrophic nitrifying bacteria, and a commercially available complex agent BZT. The mixture has proven to benefit the nitrification and denitrification capability of microbial consortia (Zou et al., 2014). Due to the bioaugmentation the average removal efficiency of COD, NH 4 -N, and TN removal efficiencies of the inoculated system increased by 5.6%, 13.3%, and 8.8%, respectively (Zhao et al., 2016). ...
Article
Constructed wetlands (CWs) are one of the most promising and sustainable alternatives for wastewater treatment that are being successfully implemented in several countries, especially in tropical and sub-tropical regions. The predominant mechanisms of removal of contaminants in CWs are microbial degradation, phytodegradation, phytoextraction, filtration, sedimentation, and adsorption, etc. Vertical flow subsurface CWs and hybrid CWs demonstrated promising results in terms of TN, BOD, and COD removal, while horizontal flow subsurface CWs were proficient in removal of TP. The performance of the CWs depends upon a various factors, such as hydraulic loading rate, pH, dissolved oxygen, temperature, etc. Among these, low temperature had the most antagonistic effect on the performance of the CWs because freezing ambient temperature lead to ice formation, hydraulic imperfections, malfunctioning of biotic and abiotic components, etc. Over the past three decades, thousands of studies have been conducted involving treatment of wastewater using CWs, among which only few have addressed the issues and concerns of cold climate representing a significant research gap in this field. Furthermore, the performance of CWs in terms of TN, TP, and COD removal was significantly lower in cold climates than that in tropical and sub-tropical climates. In order to find suitable remedies to overcome the challenges faced in cold climate various modifications, such as incorporating greenhouse structure, providing insulating materials, bio-augmentation, identification of suitable macrophytes, etc., in around 20 different scenarios have been studied. Greenhouse construction led to 20% increase in removal of TN and COD, while plant collocation accounted for up to 18% increase in the removal of COD. Artificial aeration, insulation and bio-augmentation also enhanced the performance of the CWs in low temperatures.
... Nevertheless, there was a minor level of nitrite accumulation observed as shown in Fig. 2(b), with peak concentrations reaching 1.21 mg·L -1 in Y1 and 1.26 mg·L -1 in Y2. Previous studies have shown that the accumulation of nitrite is inevitable in the initial denitrification stage [26]. In addition, the removal of phosphorus at this stage was not considerable and requires further strengthening. ...
Article
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Single denitrification using bacteria has been widely investigated, but few studies have focused on the simultaneous removal of nitrate, phosphorus. and tetracycline. Strain L2, an iron-reducing bacteria, was immobilized using chitosan/polyvinyl alcohol to simultaneously remove nitrate and phosphorus. The effects of carbon/nitrogen ratio (1:1, 1.5:1, and 2:1), initial Fe²⁺ concentration (0, 15, and 30 mg·L⁻¹), and HRT (2, 4, and 6 h) were assessed in bioreactors and optimum conditions were established. Results showed that the nitrate and phosphorus removal efficiency reached 100.00% (2.697 mg·L–1·h–1) and 81.93% (1.533 mg·L–1·h–1) under the conditions of carbon/nitrogen of 2:1, Fe²⁺ concentration of 30 mg·L⁻¹ and HRT of 6 h. The precipitation of bioreactor, which identified as FeOOH by XRD, had significant adsorption on tetracycline. The results of high-throughput sequencing indicated that strain L2 played a significant role in denitrification. This bioreactor provided effective method for the treatment of polluted water contaminated by nitrate, phosphorus, and tetracycline. Graphic abstract
... It was found that hydroxylamine oxidase (HAO) played a key role. Higher nitrite accumulation was observed during ammonium oxidization by a pure strain of ammonia-oxidizing bacteria (AOB) or a population of AOB in an activated sludge system (Fumasoli et al., 2017;Miao et al., 2017;Zou, Yao, & Ni, 2014). We can suspect the possibility that isolated bacteria SMFC-7 and SMFC-17 also oxidize ammonia by HAO. ...
Article
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Purpose Sediment microbial fuel cell (SMFC) is a promising bioremediation technology in which microbes play an important role. Electricigens as the bio-catalysts have effect on pollution control and electricity generation. It is of great significance to screen the microorganisms with the ability of generating electricity. Methods The SMFC anode biofilm was used as microbiological source to study the feasibility of electricigens with iron-reducing property for eutrophication water treatment. Preliminarily, we isolated 20 facultative anaerobic pure bacteria and evaluated their cyclic voltammogram (CV) through the three-electrode system and electrochemical workstation. The power generation performance of strains was verified by air-cathode microbial fuel cells (AC-MFCs) under different single carbon sources. Result According to its morphological, physiological, and biochemical characteristics, along with phylogenetic analysis, the two strains (SMFC-7 and SMFC-17) with electrical characteristics were identified as Bacillus cereus . Compared with SMFC-7, SMFC-17 exhibited efficient NH 4 ⁺ -N and NO 3 ⁻ -N removal and PO 4 ³⁻ -P accumulation from eutrophic solution with a removal rate of 79.91 ± 6.34% and 81.26 ± 1.11% and accumulation rate of 57.68 ± 4.36%, respectively. Conclusion The isolated bacteria SMFC-17 showed a good performance in eutrophic solution, and it might be a useful biocatalyst to enable the industrialized application of SMFC in eutrophic water treatment.
... The most dominant genus was Flavobacterium (12.0%) in OTS while Nitrospira (5.8%) in OTM. Flavobacterium have been reported to participate in nutrient removal and enhance biological phosphate removal (Zou et al., 2014). Therefore, the dominant genus could shift between two various carrier in this EABF system. ...
Article
An enriched aerobic/anoxic biological filter (EABF) filled with iron-based microbial coupling carrier (IBMC) was used for highly efficient biodegradation of nitrogen pollutants in low C/N ratio domestic wastewater. The nitrogen removal efficiency, functional microbiological community of nitrogen cycle, and iron cycle in the EABF based on IBMC, were investigated. The NH4⁺-N, TN and COD removal efficiency were 97.6%, 86.9% and 85.3%, respectively, in the EABF-filled IBMC with DO of 3.5 mg L⁻¹, HRT of 12 h and reflux ratio of 5.5:1. Furthermore, differences were observed in the microbial communities, and Thiobacillus, Denitratisoma and Saprospiraceae were the dominant genera. Nitrosomonadaceae, Nitrospira, Ferritrophicum and Acidovorax were dominant in the nitrogen and iron-cycle communities. Besides, IBMC significantly affected the microbial compositions. Thus, the developed EABF achieved efficient nutrients removal from low C/N ratio domestic sewage, which is suitable for practical application.
... Thauera, Citrobacter, Azospira and Comamonas were the dominant genus in anoxic zones. While in oxic zones, Azospira, Hyphomicrobium, Dechloromonas, Pseudomonas and Thiothrix were more abundant, among which were mostly recognized as aerobic denitrifiers (Horn et al., 2005;Nam et al., 2016;Zou et al., 2014). These microbial discoveries were consistent with the nitrogen removal performance in Fig. 4a and b. ...
... To date, many HN-AD bacteria have been isolated and investigated, such as Thiosphaera pantotroph (Paracoccus denitrificans) (Robertson et al., 1988), Pseudmonas stutzeri (Su et al., 2001), Alcaligenes faecalis (Joo et al., 2005), Bacillus subtilis (Yang et al., 2011), etc. However, many researches documented that nitrite accumulation by these HN-AD bacteria was inevitable during the SND process, when nitrate and ammonia were served simultaneously as nitrogen source, which was caused by the rapid nitrate conversion (Medhi et al., 2017;Zhang et al., 2015) and resulted in high level of total inorganic nitrogen (TIN) remained (Zhao et al., 2010a, Liang et al., 2013, Zou et al., 2014He et al., 2017). Moreover, the existence of nitrite could be harmful to the nitrogen removal bio-system. ...
Article
Nitrogen contaminants are widespread presence in municipal wastewater, heterotrophic nitrification and aerobic denitrification (HN-AD) bacteria have advantages of dealing with multiple nitrogen. Strain LJ81 was isolated from domestic sludge, identified as Ochrobactrum anthropic, which was oxygen-dependent and could survive in a wide range of pH values. Results showed that strain LJ81 could achieve simultaneous nitrification and denitrification (SND) under aerobic condition, whilst more than 80% of initial nitrogen was converted into gaseous nitrogen. The removal rates of ammonia increased from 3.75 to 3.85 and 5.70 mg-N L⁻¹ h⁻¹ by adding nitrite and nitrate, respectively, while the nitrate denitrification was the rate-limiting step of SND process. Moreover, adding chlorate could inhibit not only the cell growth slightly but also denitrification of nitrate. All results indicated that O. anthropic strain LJ81 exhibited excellent performance on nitrogen removal without nitrite accumulation under aerobic condition.
... Ammonia, one of the major environmental pollutants in water, exists in two chemical forms, ionized ammonia (NH 4 + ) and unionized ammonium (NH 3 ) [1], with different percentage depending on pH and temperature. Excess ammonia in the natural receiving water bodies, usually originating insufficient treatment of discharging water in wastewater treatment plants [2], is not only one of the factors leading to eutrophication, but also toxic to aquatic organisms and human beings. Experiments have shown that the lethal concentration for a variety of fish species ranges from 0.2 to 2.0 mg L −1 [3]. ...
Article
The effects of low temperature on enhanced coagulation were studied. A new composite coagulant called SynthA was synthesized. The effects of enhanced coagulation on the removals of dissolved organic matter, dissolved organic nitrogen, and so on under room temperature or low temperature (2-5℃) were determined, and their influences on biological treatments were investigated by using membrane fractionation distribution, three-dimensional fluorescence spectrum (3DEEM), and differential ultraviolent absorbance. The results showed that, under room temperature, the removals of particulate COD, particulate nitrogen, colloidal COD, and colloidal nitrogen were highly correlated with turbidity reduction by coagulation using aluminum chloride (AlCl3), poly aluminum chloride (PACl), and SynthA as coagulants separately, while the relationship was not clear between the dissolved parameters and turbidity reduction. The reduction of fluorescence value of dissolved organic matter after coagulation was much higher than that of dissolved COD. Dissolved organic nitrogen (DON) is removed to the greatest extent by preset coagulation along with particulate nitrogen (PN) and colloidal nitrogen (CN). Low temperature affected enhanced coagulation in many aspects. It inhibited turbidity reduction and COD removal by the three coagulants with the order being AlCl3 > PACl > SynthA. It exhibited differential influences on the removals of particulate, colloidal and dissolved COD, and nitrogen, and it showed greater adverse effects on particulate and colloidal COD and nitrogen. The fluorescence value of dissolved organic matter in low temperature water showed a significant increase, and its reduction by coagulation was high, compared with that in room temperature water. Low temperature coagulation exerted greater impacts on ultraviolet differential absorbance than did room temperature. Under low temperatures, slight increases of total nitrogen (TN) removal, DN, and DON removals were achieved by using SynthA as coagulant, and removals of PN and CN were maintained, compared with room temperature. As an example, when SynthA dosage was above 30 mg ·L-1, DON removal reached 28.5%-41.7% at low temperature, while the removal was only 17%-31.4% at room temperature. A large portion of the COD and some TN were removed by coagulation as a pretreatment, indicating that a large amount of the time in an aeration pond could be reduced, and the removal efficiency of TN would be stabilized. Therefore, in winter, the decrease of biological treatment efficiency could be alleviated to some extent by using enhanced coagulation with an adaptable coagulant, such as SynthA as a pretreatment, which would relieve the stress of denitrogen and stabilize treatment efficiency.
... 9,14,15 When using Paracoccus versutus LYM to simultaneously remove NH 4 + -N and NO 3 − -N, some NO 2 − -N was left during the SND process, and Fe 2+ adding benefited bacterial growth and NO 2 − -N reduction. 16 After growing Paracoccus pantotrophus P16 in medium supplemented with 1.5 uM Fe 3+ , the enzymatic activity of nitrate and nitrite reductase showed a 2.6-and 1.7-fold increase. 17 In addition, adding Fe 3+ of 50 mg/L obtained a considerable increasing in TN and NH 4 + -N removal during the nitrification-denitrification process in a submerged membrane bioreactor. ...
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Simultaneous nitrification and denitrification (SND) is a promising single-reactor biological nitrogen-removal method. Activated sludge with and without iron scrap supplementation (Sludge-Fe and Sludge-C, respectively) was acclimated under aerobic condition. The total nitrogen (TN) content of Sludge-Fe substantially decreased from 25.0±1.0 to 11.2±0.4 mg/L, but Sludge-C did not show the TN-removal capacity. Further investigations excluded a chemical reduction of NO3--N by iron and a decrease of NH4+-N by microbial assimilation, and the contribution of SND was verified. Moreover, the amount of aerobic denitrifiers, such as bacteria belonging to the genera Thauera, Thermomonas, Rhodobacter and Hyphomicrobium, was considerably enhanced, as observed through Miseq Illumina sequencing method. The activities of the key enzymes ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR), which are associated with nitrification, and periplasmic nitrate reductase (NAP) and nitrite reductase (NIR), which are related to denitrification, in Sludge-Fe were 1.23-, 1.53-, 3.60- and 1.55-fold higher than those in Sludge-C, respectively. In Sludge-Fe, the quantity of the functional gene NapA encoding enzyme NAP, which is essential for aerobic denitrification, was significantly promoted. The findings indicate that SND is the primary mechanism underlying the removal of TN and that iron scrap can robustly stimulate SND under aerobic environment.
... Cytoplasmic components including cellular ATP level, intracellular enzyme degradation, and DNA extraction were determined commercial kits referring to previous study [16]. PCR was performed using universal primers, F27 (5′-AGAGTTTGAT-CMTGGCTCAG-3′) and reverse primer R1492 (5′-TTGGYTACCTTGTT-ACGACT-3′) [32]. Nearly full length 16S rRNA gene (∼1500 bp), instead of a specific target gene, was amplified [33]. ...
... Polyphosphate-accumulating organisms (PAO) and denitrifying bacteria are both heterotrophic [9,10], and thus able to take up organic carbon under anaerobic conditions and store it for growth once a suitable electron acceptor is available [14,[16][17][18]. In combined denitrification and EBPR systems, organic carbon availability is usually the limiting parameter [19,20], denitrifers and PAOs directly compete for the available organic carbon [11,21]. Both processes are inhibited by this competition [13,22]. ...
Article
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The discharge of nitrate-rich effluent has adverse effect on the receiving environment and the public health of the polluted water users. The nitrates are eliminated in a denitrification step that requires reducing power in form of organic carbon. The objective of this study was to evaluate the potential of utilizing organic carbon in effluent from the anaerobic SBR as a carbon source for denitrification. Reactors were operated for one year using meat processing wastewater. Anaerobically treated abattoir wastewater equivalent to 5, 10 and 15% of aerobic SBR hydraulic volume were added to three separate reactors. A 12 h operating cycle consisted of the following periods: (a) filling, 0.30 h; (b) settling, 11 h and (d) decanting, 0.30 h for the anoxic reactor. A comparison between different carbon loads was performed based on biological carbon, nitrogen and phosphorus removal. Sufficient denitrification was achieved with 10% (aerobic SBR hydraulic volume) of anaerobically-treated abattoir wastewater. TCOD, BOD5, TKN, N02 -N, NO3 -N, PO4 3-, TS, EC and temperature and turbidity were reduced by 78, 70, 91, 100, 98, 62, 39, 65, 71, 5 and 39% respectively, with effluent mean concentrations of 80 ± 5 mg/L, 54 ± 12 mg/L, 35 ± 4, 00 ± 0, 2 ± 1, 18 ± 1, 254 ± 12, 1.64 ± 0.01, 22.04 ± 0.02 and 738 ± 9 FAU. Organic carbon in effluent from the anaerobic SBR can be used as a carbon source for anoxic denitrification. However, the denitrification rate is affected by the organic carbon load used. Except TKN and o-PO43- mg/L, all other parameters in the denitrified effluent met discharge standards
... All rights reserved. Zumft, 1989;Li et al., 2012;Sparacino-Watkins et al., 2014), and potential applications (Joo et al., 2006;Shoda and Ishikawa, 2014;Zou et al., 2014). ...
Article
The present study investigated effect of ammonium utilization on aerobic denitrification by Pseudomonas stutzeri T13. Per nitrogen balance calculation, all consumed ammonium was utilized as nitrogen source for cell propagation by assimilation rather than heterotrophic nitrification. Total organic carbon (TOC) and ammonium were necessary substrates to sustain heterotrophic propagation of P. stutzeri T13 at optimum proportion equal to seven. Under aerobic condition, nitrate was utilized as substitute nitrogen source when ammonium was completely exhausted. Biomass production effectively increased with increasing initial ammonium from 0 mg/L to 100 mg/L. Owing to enlarged biomass, average nitrate reduction rate increased from 7.36 mg L⁻¹ h⁻¹ to 11.95 mg L⁻¹ h⁻¹. Such process also successfully reduced nitrite accumulation from 121.8 mg/L to 66.16 mg/L during aerobic denitrification. As important accessory during aerobic denitrification, ammonium assimilation efficiently doubled total nitrogen (TN) removal from 54.97 mg/L (no ammonium provided) to 113.1mg/L (100 mg/L ammonium involved).
... However, some runs (5, 13, 15, and 20) showed extremely low cyanide degradation, an indication of slow and/or minimal microbial growth resulting from low temperature and/or pH which is known to facilitate cyanide efficacy as a metabolic inhibitor [10,24]. The residual ammonium-nitrogen and nitratenitrogen observed were considerably low especially at low pH and/or low temperatures. ...
Conference Paper
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This work reports the use of a cyanide resistant fungus Fusarium oxysporum for the bioremediation of wastewater containing free cyanide, its preference for beetroot agro-waste as the primary carbon source, and the optimization of the free cyanide (CN-) bioremediation conditions using statistical modelling of response surface methodology (RSM). Higher growth rate of F. oxysporum was observed on beetroot waste (OD = 3.430) compared to glucose (OD = 1.953). The cultures highest free cyanide biodegraded was 180.9 mg CN-/L from an initial 300 mg CN-/L after 72 h at 25°C, pH of 12.70, and substrate concentration of 300 mg/L. The ANOVA of the quadratic model indicated the model obtained is highly significant (R2 = 0.9240). The response from the central composite design (CCD) indicated that temperature and substrate concentration are significant factors affecting the CN- biodegradation. The fungus growth on cheap agro-waste would ensure economic sustainability of free cyanide biodegradation system in environmental engineering applications. This study provides a platform for further research on the thermodynamics of CN- biodegradation.
... However, if these external sources were over supplied, the effluent after denitrification may contain a great amount of OC which could lead to secondary pollution, and may also increase system operation cost (Sun and Nemati 2012). In order to address such problems, the coupled heterotrophic and autotrophic denitrification has received increasing attention in recent years (Zhao et al. 2012;Zou et al. 2014;. ...
Article
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A three-dimensional biofilm-electrode reactor (3DBER) was integrated with sulfur autotrophic denitrification (SAD) to improve nitrogen removal performance for wastewater reclamation. The impacts of influent carbon/nitrogen (C/N) ratio, electric current, and hydraulic retention time (HRT) were evaluated. The new process, abbreviated as 3DBER-SAD, achieved a more stable denitrification compared to the recently studied 3DBER in literature. Its nitrogen removal improved by about 45 % as compared to 3DBER, especially under low C/N ratio conditions. The results also revealed that the biofilm bacteria community of 3DBER-SAD contained 21.1 % of the genus Thauera, 19.3 % of the genus Thiobacillus and Sulfuricella, as well as 5.3 % of the genus Alicycliphilus, Pseudomonas, and Paracoccus. The synergy between these heterotrophic, sulfur autotrophic, and hydrogenotrophic denitrification bacteria was believed to cause the high and stable nitrogen removal performance under various operating conditions.
... It should be noted that, in a typical FO system, additional energy will be required for further treatment of concentrated feed solution. Because of reverse salt flux, concentrating effect and high membrane rejection, salinity build-up (or salt accumulation) at the feed side is inevitable and will need to be properly controlled, and a number of methods have been investigated including electrodialysis (ED), integrated biological degradation, filtration (microfiltration for instance) and/or bioelectrochemical systems (BES) with recoverable draw solutes Luo et al., 2015;Qin and He, 2014;Zou et al., 2014). Energy-efficient strategies of salinity mitigation warrant further investigation to proper evaluation of the viability of FO system. ...
Article
Using fertilizers as draw solutes in forward osmosis (FO) can accomplish wastewater reuse with elimination of recycling draw solute. In this study, three commercial fast-release all-purpose solid fertilizers (F1, F2 and F3) were examined as draw solutes in a submerged FO system for water extraction from either deionized (DI) water or the treated wastewater. Systematic optimizations were conducted to enhance water extraction performance, including operation modes, initial draw concentrations and in-situ chemical fouling control. In the mode of the active layer facing the feed (AL-F or FO), a maximum of 324 mL water was harvested using 1-M F1, which provided 41% of the water need for fertilizer dilution for irrigation. Among the three fertilizers, F1 containing a lower urea content was the most favored because of a higher water extraction and a lower reverse solute flux (RSF) of major nutrients. Using the treated wastewater as a feed solution resulted in a comparable water extraction performance (317 mL) to that of DI water in 72 h and a maximum water flux of 4.2 LMH. Phosphorus accumulation on the feed side was mainly due to the FO membrane solute rejection while total nitrogen and potassium accumulation was mainly due to RSF from the draw solute. Reducing recirculation intensity from 100 to 10 mL min−1 did not obviously decrease water flux but significantly reduced the energy consumption from 1.86 to 0.02 kWh m−3. These results have demonstrated the feasibility of using commercial solid fertilizers as draw solutes for extracting reusable water from wastewater, and challenges such as reverse solute flux will need to be further addressed.
... The simulated winter conditions affected the activity of the microorganism. Previous research has recognised that a temperature drop in winter is a key inhibitor to microbial activity, thus resulting in low removal of contaminants (Zilouei et al. 2006;Zou et al. 2014). The high amount of residual ammonium-nitrogen (up to 50 mg NH4 + -N/L) and nitrate-nitrogen (up to 140 mg NO3 --N/L) showed the impact of the temperature on cyanide biodegradation efficiency. ...
Article
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The kinetics of free cyanide biodegradation were investigated under simulated winter (5 °C) and optimum conditions (22 °C and pH of 11) using a Fusarium oxysporum isolate grown on Beta vulgaris waste as a sole carbon source in the presence of heavy metals, i.e. As, Fe, Cu, Pb, and Zn. The highest free cyanide degradation efficiency was 77% and 51% at 22 °C and 5 °C respectively, in cultures containing free cyanide concentration of 100 mg F-CN/L. When compared with the simulated winter conditions (5 °C), the specific population growth rate increased 4-fold, 5-fold, and 6-fold in 100, 200 and 300 mg F-CN/L, respectively, for cultures incubated at 22 °C in comparison to cultures at 5 °C; an indication that the Fusarium oxysporum cyanide degrading isolate prefers a higher temperature for growth and cyanide biodegradation purposes. The estimated energy of activation for cellular respiration during cyanide degradation was 44.9, 54, and 63.5 kJ/mol for 100, 200, and 300 mg F-CN/L cultures, respectively, for the change in temperature from 5 to 22 °C.
... The simulated winter conditions affected the activity of the microorganism. Previous research has recognised that a temperature drop in winter is a key inhibitor to microbial activity, thus resulting in low removal of contaminants (Zilouei et al. 2006;Zou et al. 2014). The high amount of residual ammonium-nitrogen (up to 50 mg NH4 + -N/L) and nitrate-nitrogen (up to 140 mg NO3 --N/L) showed the impact of the temperature on cyanide biodegradation efficiency. ...
Article
The kinetics of free cyanide biodegradation were investigated under simulated winter (5 °C) and optimum conditions (22 °C and pH of 11) using a Fusarium oxysporum isolate grown on Beta vulgaris waste as a sole carbon source in the presence of heavy metals, i.e. As, Fe, Cu, Pb, and Zn. The highest free cyanide degradation efficiency was 77% and 51% at 22 °C and 5 °C, respectively, in cultures containing free cyanide concentration of 100 mg F-CN/L. When compared with the simulated winter conditions (5 °C), the specific population growth rate increased 4-fold, 5-fold, and 6-fold in 100, 200, and 300 mg F-CN/L, respectively, for cultures incubated at 22 °C in comparison to cultures at 5 °C; an indication that the Fusarium oxysporum cyanide degrading isolate prefers a higher temperature for growth and cyanide biodegradation purposes. The estimated energy of activation for cellular respiration during cyanide degradation was 44.9, 54, and 63.5 kJ/mol for 100, 200, and 300 mg F-CN/L cultures, respectively, for the change in temperature from 5 °C to 22 °C.
... Autotrophic denitrification is an attractive process for wastewater treatment because several studies have reported nutrient removal efficiencies above 90% (Ramanathan et al., 2014;Zou et al., 2014). This process can also be considered suitable for removing sulfides from wastewater and groundwater (Sierra-Alvarez et al., 2007;Tanaka et al., 2007) or even to remove H 2 S from biogas generated during anaerobic digestion of effluents containing sulfate (canneries, petrochemical industries, tanneries, among other) or flue gas (Baspinar et al., 2011;Qian et al., 2015). ...
... Up to date, limited reports are available on a bacterium which could conduct nitrification and denitrification aerobically at low temperature. Additionally, most studies indicate that nitrite accumulation is inevitable during biological treatment of wastewater (Zhao et al., 2010;Liang et al., 2013;Zou et al., 2014), which would reduce the removal efficiency of total nitrogen because the nitrite nitrogen is the end-product instead of gaseous nitrogen. Some researches indicate that membrane-bound nitrate reductase (NAR) and nitrite reductase (NIR) are sensitive to dissolved oxygen inhibition (Bell et al., 1990;Körner and Zumft, 1989), which would decrease the nitrogen removal efficiency also. ...
Article
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A hypothermia aerobic nitrite-denitrifying bacterium, Pseudomonas tolaasii strain Y-11, was found to display high removal capabilities for heterotrophic nitrification with ammonium and for aerobic denitrification with nitrate or nitrite nitrogen. When strain Y-11 was cultivated for 4days at 15°C with the initial ammonium, nitrate and nitrite nitrogen concentrations of 209.62, 204.61 and 204.33mg/L (pH 7.2), the ammonium, nitrate and nitrite removal efficiencies were 93.6%, 93.5% and 81.9% without nitrite accumulation, and the corresponding removal rates reached as high as 2.04, 1.99 and 1.74mg/L/h, respectively. Additionally, ammonium was removed mainly during the simultaneous nitrification and denitrification process. All results demonstrate that P. tolaasii strain Y-11 has the particularity to remove ammonium, nitrate and nitrite nitrogen at low temperatures, which guarantees it for future application in winter wastewater treatment.
... Differences in NH þ 4 -N were statistically nonsignificant between 15 and 10˚C; however, between the pairs 15 and 5˚C and 10 and 5˚C, such differences were statistically significant confirmed with p-values < 0.05. This confirmed that nitrogen removal, including both nitrification and denitrification, was sensitive to lower temperatures (26% removal at 5˚C compared to 31% at 15˚C), which is in agreement with previous findings [20,21]. In general, the differences of NH þ 4 -N concentrations between influent and effluent were low, with removal efficiencies in the range of 22-32% (Table 1). ...
Article
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The influence of temperature in a range of 15–5°C, fluctuations in soluble chemical oxygen demand (sCOD) and suspended solids (SS) of the influent and also long hydraulic retention times (HRT) of 36 or 50 d on the performance of a laboratory septic tank were studied. A laboratory-scale septic tank with a volume of 20 L, started up at 15°C was fed with domestic wastewater from two settlements with sCOD up to 450 and up to 2,000 mg/L, respectively. The efficiency of the septic tank was assessed based on pollutant removal and biogas production. A stepwise decrease in temperature by 5°C in the range of 15–5°C halved the daily emission of biogas. Removal efficiencies for sCOD and SS were in the range of 74–86 and 86–88%, respectively. An increase in sCOD of influent from 450 to 4,000 mg/L resulted in a decreased performance of the septic tank (to ~25% less). The highest biogas emission was observed at 10°C and at retention time (36 d), owing to increased consumption of CO2 and CH4 by autotrophic microorganisms over the longer retention time (50 d). At the 15°C, biogas emission was lower than in case of lower temperatures applied. In the range of 15–5°C, operational temperature did not correlate significantly (p > 0.05) with the removal efficiency of sCOD or SS, assuming as a consequence of the long HRT.
... This was shown by a rise in temperature, enhanced bacterial species richness 47 and competition between denitrifiers and other heterotrophic microbes. 48 Nitrogen Transformation Pathway. Path analysis was employed to assess the contribution of functional gene groups to nitrogen removal in T1, T2, and T3. ...
Article
The newly isolated aerobic denitrifying bacterium Bacillus simplex H-b removed various forms of inorganic nitrogen (nitrate, nitrite, and ammonium) from wastewater, even when the temperature was as low as 5°C. Although this environmentally functional bacterium has been suggested as a promising candidate for nitrogen-contaminated water treatment at low temperatures, understanding its cold adaptation mechanism during aerobic denitrification is limited.
Article
Climate affects the natural landscape, the economic productivity of societies, and the lifestyles of its inhabitants. It also influences municipal wastewater treatment. Biological processes are widely employed in municipal wastewater treatment plants (WWTPs), and the prolonged cold conditions brought by the winter months each year pose obstacles to meeting the national standards in relatively cold regions. Therefore, both a systematic analysis of existing technical bottlenecks as well as promising novel technologies are urgently needed for these cold regions. Taking North-east China as a case, this review studied and analyzed the main challenges affecting 20 municipal WWTPs. Moreover, we outlined the currently employed strategies and research issues pertaining to low temperature conditions. Low temperatures have been found to reduce the metabolism of microbes by 58% or more, thereby leading to chemical oxygen demand (COD) and NH +4 -N levels that have frequently exceeded the national standard during the winter months. Furthermore, the extracellular matrix tends to lead to activated sludge bulking issues. Widely employed strategies to combat these issues include increasing the aeration intensity, reflux volume, and flocculant addition; however, these strategies increase electricity consumption by > 42% in the winter months. Internationally, the processes of anaerobic ammonium oxidation (anammox), granular sludge, and aerobic denitrification have become the focus of research for overcoming low temperature. These have inspired us to review and propose directions for the further development of novel technologies suitable for cold regions, thereby overcoming the issues inherent in traditional processes that have failed to meet the presently reformed WWTP requirements.
Article
To determine the effect of microbial inoculants on the removal of ammonia nitrogen (NH4+‐N), six different complex microbial inoculants were studied. In this study, their effectiveness on NH4+‐N removal was compared and their microbial community composition was determined. High‐throughput sequencing results showed that Proteobacteria or Firmicutes were the dominant phyla in six samples. Before the reaction, Bacillus, Cyanobacteria and Mitochondria genera were the dominant genera. The dominant genera were significantly different after the reaction with the addition of bacterial agents. The six water samples were Massilia, Escherichia‐Shigella, Brevibacillus, Mitsuaria, Bacillus, and Ralstonia. Among the six complex microbial inoculants, “Gandu nitrifying bacteria (NR4)” has the best removal effect on NH4+‐N. In addition, the removal effect of six different bacterial agents on Chemical Oxygen Demand (COD) was compared. The results showed that “Bilaiqing ammonia nitrogen removal bacteria agent (NR5)” has the best removal effect on COD. Single factor experiments suggested that the optimal conditions for NR4 bacteria were pH 7, 30 °C, 1.0 g/L of bacterial agent dosage and a wide range of NH4+‐N from 30 to 300 mg/L.
Article
The disposal of wastewater containing tetramethylammonium chloride (TMAC) generated from the semiconductor and photoelectric industries is a challenging problem due to the limited information is available regarding its treatability. This study aims to investigate the feasibility of using biological processes to treat TMAC. An activated sludge collected from a lake near the Southern Taiwan Science Park was used. Various operational parameters, including operating temperature, pH conditions and TMAC dosages were evaluated for the optimal condition. Results showed that the activated sludge could successfully degrade TMAC, and subsequently achieve simultaneous nitrification and denitrification (SND) of the nitrogen-containing intermediates under mild conditions (pH at a range of 3-7 and temperature at a range of 20- 40 oC). Besides, more than 60% of the nitrogen-containing intermediates were converted into gaseous nitrogen (N2). TMAC biodegradation was found to follow first-order kinetics. The observed rate constant of TMAC biodegradation increased from 0.64 ╳ 10⁻⁴ to 9.57 ╳ 10⁻⁴ 1/min as the concentration of TMAC decreased. In addition, TMAC demethylation was identified as the rate-limiting step of the entire reaction. Major functional organisms of the activated sludge were identified as Mycobacterium, Ochrobactrum and Arthrobacter species which are aerobic and acidophilic strains. This study can be an important reference for future researches attempting to treatment TMAC wastewater by biological processes.
Article
Bio-enhanced activated carbon (BEAC) filters have shown potential in source water purification. The key drawback of this system is the difficulty of the set-up at low temperature. Here, glucose was applied to help immobilize more functional heterotrophic nitrifiers and further improve NH4⁺-N removal by BEAC. Results showed that pre-loading glucose on granular activated carbon could achieve better immobilization efficiency with 5.12×10⁸ CFU/g-DW C biomass and 3.77 mg TF/L/g-DW C dehydrogenase activity after artificial immobilization, which were separately 12.5 and 4.2 times of the control. 95-d running data at different conditions showed the superiority of both immobilization and NH4⁺-N removal could last and defend environment changes during relatively long period. Even at the end of operating, the abundance of targeting genus (Acinetobacter) still occupied 9.59% of microbial communities on BEAC, while this value was only 1.24% without pre-loading glucose. Biolog-ECO plate analysis found pre-loading glucose improved organic nitrogen metabolism effectively, along with carbohydrate, amino, alcohol, amine and carboxylic acid metabolism on BEAC.
Article
Six bacterial strains with simultaneous nitrification-denitrification abilities were isolated from a Beijing sewage treatment plant to improve nitrogen biodegradation efficiency. One of these strains, X49, was identified as Pseudomonas mendocina, and was characterized as the best strain with which to rapidly degrade a high concentration of inorganic nitrogen. X49 completely converted 5-100 mg.L-1 of ammonia in 12 h, with no nitrite accumulation; the maximum removal rate of 26.39 mg (N).L-1.h-1 was achieved between 4 h and 6 h. In 16 h, the strain removed 100 mg.L-1 nitrite and 72.61 mg.L-1 nitrate under aerobic conditions, at degredation rates which reached 4.54 and 6.25 mg (N).L-1.h-1, respectively. Our results suggest that P. mendocina X49 achieved efficient and simultaneous nitrification and denitrification ability under heterotrophic aerobic conditions.
Article
Bacteria capable of simultaneous nitrification and denitrification (SND) and phosphate removal could eliminate the need for separate reactors to remove nutrients from wastewater and alleviate competition for carbon sources between different heterotrophs in wastewater treatment plants (WWTPs). Here we report a newly isolated Thauera sp. strain SND5, that removes nitrogen and phosphorus from wastewater via SND and denitrifying-phosphate accumulation, respectively, without accumulation of metabolic intermediates. Strain SND5 simultaneously removes ammonium, nitrite, and nitrate at an average rate of 2.85, 1.98, and 2.42 mg-N/L/h, respectively. Batch testing, detection of functional genes, nitrogenous gas detection and thermodynamic analysis suggested that nitrogen gas, with hydroxylamine produced as an intermediate, was the most likely end products of heterotrophic ammonium oxidation by strain SND5. The generated end products and intermediates suggest a novel nitrogen removal mechanism for heterotrophic ammonium oxidation in strain SND5 (NH4+→NH2OH→N2). Strain SND5 was also found to be a denitrifying phosphate-accumulating organism, capable of accumulating phosphate, producing and storing polyhydroxybutyrate (PHB) as an intracellular source of carbon while using nitrate/nitrite or oxygen as an electron acceptor during PHB catabolism. This study identifies a novel pathway by which simultaneous nitrogen and phosphorus removal occurs in WWTPs via a single microbe.
Article
Heterotrophic nitrification–aerobic denitrification (HN-AD) has advantages over the traditional nitrogen removal process when removing multiple types of nitrogen in wastewater treatment. Acinetobacter tandoii MZ-5, which is capable of HN-AD, was isolated from the sediment of a polluted river for the first time. It used NH4⁺-N, NO2⁻-N and NO3⁻-N as sole nitrogen sources with maximum removal rates of 2.28, 1.18 and 1.04 mg L⁻¹ h⁻¹, respectively. Simultaneous nitrification and denitrification were observed when using mixed N sources and NH4⁺-N was preferentially utilized. High nitrogen removal efficiencies (>90%) were achieved under the following conditions: C/N ratio 11–18, pH 6–8, 25–30 °C and dissolved oxygen 7.35–7.66 mg L⁻¹. Strain MZ-5 was effective at treating wastewater from landfill leachate treatment plants, with NH4⁺-N, NO3⁻-N and total nitrogen removal efficiencies of 99.28%, 44.85% and 45.31%, respectively. Thus, strain MZ-5 may be a good candidate for wastewater treatment.
Article
The effect of change of hydraulic characteristic and microbial community on pollution removal efficiency of the infiltration systems in the bioclogging development process remain poorly understood. In this study, therefore, the pollutant removal as a response to hydraulic conductivity reduction and the change of diversity and structure of microbial communities in vertical flow constructed wetlands (VFCWs) was investigated. The results indicated that the richness and diversity of the bacterial communities in the columns at different depths were decreased, and the microbial communities of genus level were changed in the process of bioclogging. However, the variation of microbial communities has a low impact on the purification performance of VFCWs because the abundance of function groups, respiratory activity and degradation potentiality of microorganisms remain steady or even get improved in the columns after bioclogging. On the contrary, the hydraulic efficiency of VFCWs decreased greatly by 16.9%, 9.9%, and 57.1% for VFCWs filled with zeolite (Column I), gravel (Column II), and ceramsite (Column III) respectively. The existence of short-circuit and dead zones in the filter media cause the poor pollution removal efficiency of VFCWs due to the short contact time, decrease of oxygenation renewal as well as low activity in the dead zone.
Article
For solving the nutrient removal from urban domestic sewage at low temperature and low C/N ratio, the full-scale Bi-Bio-Selector for Nitrogen and Phosphorus removal (BBSNP) process was set in Shanghai, China and run continuously at C/N about 3.6. It was run for 133 days along with the temperature dropping from 22 ± 2℃ to 10 ± 2℃. After 27 days’ operation, the performance of BBSNP process reached to stable. Chemical oxygen demand (COD), NH4⁺-N, total nitrogen (TN) and total phosphorus (TP) in effluent were lower than 40, 0.5, 8 and 0.1 mg/L, respectively. The NH4⁺-N and TN removal efficiency were influenced and decreased at low temperature (10 ± 2℃). After improving mixed liquor suspended solids (MLSS) from 4000 mg/L to 6000 mg/L, the nitrogen removal efficiency lifted to previous level because of the increasing NH4⁺-N and NO2--N oxidation rate of suspended sludge. Denitrifying phosphorus accumulating organisms (DPAOs) were the dominant bacteria responsible for phosphorous removal in this study. The Denitrifying phosphorus removal (DPR) efficiency was as high as 74.16 ± 4.40%. Dechloromonas was in higher amount than other DPAOs in the BBSNP process. The results of this study provided a convincing evident that BBSNP could be a practical and cost-effective process for removing nutrient from urban domestic sewage.
Article
A novel strain was isolated from municipal activated sludge and identified as Acinetobacter sp. ND7 based on its phenotypic and phylogenetic characteristics, which had efficient capability for heterotrophic nitrification and aerobic denitrification. Strain ND7 could remove approximately 99.8% of ammonium-N (51.0 mg/L), 96.2% of nitrite-N (51.8 mg/L) and 97.18% of nitrate-N (52.1 mg/L), with the maximum specific removal rate of 5.74, 4.17 and 3.63 mg/(L h), respectively. Ammonium was manifested to be utilized preferentially during simultaneous nitrification and denitrification. The functional genes hao, napA and nirS were successfully amplified by PCR, further evidencing the heterotrophic nitrification and aerobic denitrification capability of Acinetobacter sp. ND7. The optimal conditions for nitrogen removal were temperature of 35 °C, C/N ratio of 8. Acinetobacter sp. ND7 displays superior performance for nitrogen removal, with no nitrite accumulation under aerobic condition, and thus has significant potential for practical application for nitrogen removal from wastewater.
Article
Alkaline fermentation has been considered as one of the efficient methods for waste activated sludge (WAS) treatment, but usually limited by microbial fermentation activities under extreme pH condition. One newly isolated alkali-tolerant strain Corynebacterium pollutisoli SPH6 was used to assess its potential role and effect on WAS alkaline fermentation process. Results from response surface method showed that the optimal organic nitrogen degradation rate by SPH6 was obtained under temperature of 35 °C, initial pH of 10, shaking speed of 80 rpm, inoculation ratio of 6.5%. Batch-scale experiments demonstrated that, compared with the control group, the inoculation of SPH6 finally achieved higher productions with 13.4% of carbohydrates, 27.1% of protein and 25.4% of total volatile fatty acids (VFAs), and more predominant functional bacteria characterized by high-throughput sequencing, such as genera Acinetobacter in phylum Proteobacteria, Tissierella and Acetoanaerobium in phylum Firmicutes. The strain SPH6 might play a vital role in maintaining and facilitating the growth and diversity of functional bacteria in WAS alkaline fermentation process. It has implied promising practical application of the present strain in enhancing WAS reduction and utilization.
Article
Ozone oxidation and ozonation catalyzed with MgO were applied to remove ammonia in water at low temperature (10℃). Results show that pH played a critical role in both ozonation and catalytic ozonation for ammonia removal, especially in the ozonation rate of ammonia and the types of oxidation products. For single ozonation, both O 3 and [rad] OH contributed to ammonia degradation. Lower pH is beneficial to high selectivity of gaseous products (N 2 or N 2 O)in the presence of Cl ⁻ . Significantly enhanced efficiency of ammonia removal was obtained under the catalysis of MgO, which worked as a solid alkali as well as a catalyst, facilitating ammonia oxidation both in the solution and on the MgO surface. Molecular O 3 dominated ammonia removal in the heterogeneous catalytic ozonation system, while the contribution of [rad] OH was not significant in quantity and a small part of ammonia was degraded by the reaction of ClO x⁻ with NH 4⁺ . A relatively high removal efficiency (77.53%˜80.17%)of ammonia could also be achieved in the temperature range of 0℃˜10℃, which indicates that catalytic ozonation over catalysts like MgO may be a potential method to control ammonia pollution during cold weather or under other conditions difficult for biological treatment.
Article
Simultaneous nitrogen and phosphorus removal in winter is one of the great challenges in wastewater treatment processes due to the poor bioactivity of microbial communities. In this study, excellent performance of simultaneous nitrification, denitrification and phosphorus removal (SNDPR)was achieved at low temperature of 10 ° C and COD/N ratio of 6 in a lab-scale sequencing batch reactor. Total nitrogen (TN)and phosphorus (TP)removal efficiency reached 89.6% and 97.5%, respectively, accompanied with N 2 O emission of 7.46% TN due to the primary contribution (70%)of nitrifier denitrification. It was further confirmed that polyphosphate accumulating organisms (PAOs)were dominant in microbial communities revealed by fluorescence in situ hybridization and 16S rRNA amplicon sequencing. Moreover, denitrifying phosphorus removal by PAOs through nitrite pathway was found to be the main reason for the high efficiency of this SNDPR process. Denitrifying PAOs, especially the subgroup PAOII capable of utilizing nitrite to take up phosphorus, played a significant role in highly efficient TN and TP removal at low temperature. Furthermore, genus Propionivibrio was enriched (48.9%)in the bacterial community based on the 16S rRNA analysis, which was proposed to be a crucial member involved in the nitrogen and phosphorus removal simultaneously at low temperature in this system.
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Biological nitrogen removal from industrial wastewater (pharmaceutical synthetic wastewater) was studied. Sequencing batch reactor (SBR) and sequencing batch biofilm reactor (SBBR) were utilized to treat ammonium-rich wastewater. No external carbon source was added to the reactors. At nitrogen loading rate (NLR) of 2.5 kg N/(m 3 ·day), the efficiency of ammonium removal from synthetic wastewater in SBR was 86.9%. SBBR ammonium removal efficiency under fixed dissolved oxygen (DO) concentration of 0.3 mg O2/dm 3 was 98.4%. Specific nitrification rate (SNR) and specific deni-trification rate (SDNR) in SBR were 9.24 mg NH4 +-N/(g MLVSS·h) and 18.56 mg NO3-N/(g MLVSS·h), respectively. Nitrite accumulation rate (NAR) showed high correlation with DO decrement (R² = 0.983), NAR and simultaneous nitrification and denitrification (SND) had high correlation, too (R² = 0.976). SND efficiency in SBBR reached 94.1% while ammonium oxidizing bacteria (AOB) were dominant and NAR in SBBR process at the DO level of 0.3 mg O2/dm 3 was 90.3%. ABBREVIATIONS USED IN THE TEXT AOB-ammonium oxidizing bacteria BOD-biological oxygen demand COD-chemical oxygen demand DO-dissolved oxygen DR-denitrification ratio HRT-hydraulic retention time _________________________
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Biofilm processes have a better nitrogen removal ability than traditional activated sludge at low temperatures (< 15 °C). Many biofilm processes, as well as integrated biofilm and activated sludge processes, are potential and realizable nitrogen removal upgrading methods for domestic wastewater treatment plants (WWTPs). Therefore, biofilm packing material is attractive for domestic WWTP upgrading and reconstruction in winter. For a half decade, researchers have successfully applied activated carbon to biochar as biofilm carrier in the wastewater treatment field. Biochar, as a biostable soil amendment with pores and crevices on its surface, has been applied in the soil–plant system, which promoted the adsorption of NH4⁺ and NO3⁻, decreased N2O emission, transcriptional level of narG, nxrA, and nirS, and changed the microbial community composition for better nitrogen removal. However, in the field of wastewater treatment, the study of biochar-packed process is merely in the laboratory stage of simulated wastewater, which deserves further research in the future. In this mini review, we will discuss the performances of different processes at low temperatures, the related mechanism of the biochar-packed process for nitrogen removal, and other potential applications of biochar carriers.
Article
Poor nitrogen removal efficiency (mainly nitrate, NO3--N) at low temperatures strongly limits application of subsurface wastewater infiltration systems (SWISs). Seven psychrophilic strains (heterotrophic nitrifying bacteria and aerobic denitrifying bacteria) were isolated and added to SWISs to investigate the effect of embedding and direct-dosing bioaugmentation strategies on sewage treatment performance at low temperature. Both bioaugmentation strategies improved ammonium (NH4+-N) removal efficiencies, and the embedding strategy also exhibited satisfactory NO3--N and total nitrogen (TN) removal efficiencies. Pyrosequencing results of the bacterial 16S rRNA gene indicated that the embedding strategy significantly decreased the indigenous soil microbial diversity (p < .05) and altered the bacterial community structure, significantly increasing the relative abundance of Clostridia, which have good nitrate-reducing activity.
Article
This study aimed to present an anaerobic- multistage anaerobic/oxic (A-MAO) process to treat municipal wastewater. The average COD, NH4⁺-N, TN, and TP removal efficiency were 91.81%, 96.26%, 83.73% and 94.49%, respectively. Temperature plunge and C/N decrease have a certain impact on the modified process. Characteristics of microbial community, function microorganism, and correlation of microbial community with environmental variables in five compartments were carried out by Illumina Miseq high-throughput sequencing. The differences of microbial community were observed and Blastocatella, Flavobacterium and Pseudomonas were the dominant genus. Nitrosomonas and Nitrospira occupied a dominant position in AOB and NOB, respectively. Rhodospirillaceae and Rhodocyclaceae owned a considerable proportion in phosphorus removal bacteria. DO and COD played significant roles on affecting the microbial components. The A-MAO process in this study demonstrated a high potential for nutrient removal from municipal wastewater.
Article
The removal of total nitrogen in wastewater treatment plants (WWTPs) is often unsatisfactory for a variety of reasons. One possible measure to improve nitrogen removal is the addition of external carbon. However, the amount of carbon addition is directly related to WWTP operation costs, highlighting the importance of accurately determining the amount of external carbon required. The objective of this study was to obtain a low nitrate concentration in the anoxic zone of WWTPs efficiently and economically by optimizing the external carbon source dosage. Experiments were conducted using a pilot-scale pre-denitrification reactor at a Nanjing WWTP in China. External carbon source addition based on online monitoring of influent wastewater quality and a developed nitrification-denitrification numerical model was investigated. Results showed that carbon addition was reduced by 47.7% and aeration costs were reduced by 8.0% compared with those using a fixed-dose addition mode in the pilot reactor. The obtained technology was applied to the full-scale Jiangxinzhou WWTP in Nanjing with promising results.
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This review focuses on the research literatures published in 2014 relating to topics of thermal effects in water pollution control. This review is divided into the following sections: anaerobic wastewater and sludge treatment, biological nitrogen and phosphorus removal, membrane biological treatment, sewage sludge pyrolysis, natural treatment, resource recovery, electrolysis, oxidation and adsorption treatment.
Article
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The distribution and role of autotrophic nitrifying bacterial populations in nitrogen removal in aquatic macrophyte-based aquatic treatment systems (ATSs) was assessed. Pilot-scale systems using the macrophytesElodea nuttallii, Myriophyllum heterophyllum andLemna minor were used to evaluate macrophyte type and seasonal effects on nitrifier distributions. Distributions of pelagic, epiphytic and sedimentary nitrifiers were determined using a most probable number (MPN) microtechnique. Nitrifying populations are present in the reactors year-round. Season has no apparent effect on distribution. Relative abundances between pelagic, epiphytic and sedimentary populations are similar. Ammonium oxidizers are more abundant than nitrite oxidizers. Seasonal net ammonium removal rates, net nitrification rates and nitrogen budgets were also conducted onElodea nuttallii reactors. Rates of net ammonium removal and net nitrate production are very much affected by macrophyte productivity. The data suggest that nitrification is relatively constant but that reactor nitrate levels are governed both by macrophyte utilization of ammonium or nitrate and by denitrification. Mass balances on total nitrogen (TN) support these observations. WhenElodea nuttallii productivity is low, detrital sedimentation is the predominant nitrogen removal mechanism. When productivity is high, macrophyte uptake of ammonium or nitrate and dentrification are the predominant nitrogen removal mechanisms; thus indicating that nitrifiers play a significant role in nitrogen removal in ATSs. In terms of using ATSs for nitrogen control for sewered small communities, consideration of macrophyte type, harvesting strategy and detrital sediment collection and removal should be given to control effluent TN, ammonium and nitrate.
Article
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The temperature effect on denitrification rate of a two-sludge system has been studied. An industrial high-strength wastewater and an industrial by product containing mainly methanol, as external carbon source, were used in this study. The maximum denitrification rate (MDR) was determined at six different temperatures 6, 8, 10, 15, 20 and 25degreesC in batch mode. The temperature coefficient was found to be 1.10 +/- 0.01 at temperatures between 10 to 25degreesC and 1.37 +/- 0.01 at temperatures between 6 to 10degreesC. The MDR obtained in the two sludge system (0.28 mg N mg VSS-1 d(-1) at 25degreesC) was higher than the one obtained in a single sludge system with a similar external carbon source. The COD/N ratio required for complete denitrification in the two-sludge system was approximately stoichiometric, which is 3.7 +/- 0.09 mg COD mg N-1.
Article
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Although many studies regarding nitrogen removal via nitrite have been carried out, very limited research has been undertaken on nitrogen removal via nitrite at low temperatures. In this study, to improve the nitrogen removal efficiency from municipal wastewater, a pilot-plant of sequencing batch reactor with a working volume of 54 m3 was used to investigate nitrogen removal via nitrite from municipal wastewater at normal and low water temperature. The obtained results showed that high nitrogen removal efficiency with effluent total nitrogen below 3 mg/L could be achieved. Using real-time control with temperature ranging from 11.9 to 26.5 degrees C under normal dissolved oxygen condition (> or =2.5 mg/L), nitrogen removal via nitrite was successfully and stably achieved for a long period (180 days) with average nitrite accumulation rate above 95%. Fluorescence in situ hybridization was carried out to investigate the quantitative changes of nitrifying microbial community in the activated sludge. Fluorescence in situ hybridization results approved that the nitrifying microbial communities were optimized; ammonia oxidizing bacteria became the dominant nitrifying bacteria and nitrite oxidizing bacteria had been washed out of the activated sludge.
Conference Paper
A sequencing batch biofilm reactor (SBBR) treating domestic wastewater in low temperature (T T<10.0) was studied. The results showed: the average removal rates for COD Cr, NH 4+-N, TN and turbidity were 93%, 98%, 71% and 97%, respectively. The operation mode of sequencing batch made a gradient of substrate with time as plug-flow and the biofilm distributed equally. High biomass concentration, long aeration time and bio-filtration could increase the removal efficiency of COD, NH 4+-N and turbidity in low temperature. Simultaneous nitrification and denitrification in biofilm could enhance the removal of TN.
Article
Fill-and-draw completely mixed activated sludge reactors were used to determine the effects of MLVSS concentration, pH, and temperature on nitrification rate. Forty-five experiments were divided into three series of MLVSS concentrations. Each series of 15 experiments were distributed among three different pH groups. In each group, five experiments were conducted at 4°, 10°, 17°, 25°, and 33°C. The best nitrification performance was obtained at pH 8.3, between 25° and 33°C. There was no interaction between the effects of temperature and pH. However, a change in biomass concentration altered both the pH and temperature dependence of the process. The temperature coefficient is expressed as a function of MLVSS concentration.
Article
Nitrogen pollution has been serious problem in environmental water particularly in freshwater ecosystems. A heterotrophic nitrifier and aerobic denitrifier was isolated and characterised from domestic wastewater. Based on phenotypic and phylogenetic characteristics, the isolate was identified as Klebsiella pneumonia. The strain had the capability to utilise ammonia, nitrate and nitrite as a sole nitrogen source. The maximum growth rate (μmax) of isolate was 0.55 h−1 when ammonia used as nitrogen source. The isolate could express hydroxylamine oxidase (hao), periplasmic nitrate reductase (nap) and nitrite reductase (nir) which are essential for heterotrophic nitrification and aerobic denitrification. Both hao and napA genes were amplified in isolated strain by PCR. Furthermore, the isolate showed capacities of extracellular polymeric substances (EPS) secretion and auto-aggregation. Results demonstrated that the isolation of heterotrophic nitrifier and aerobic denitrifier favoured the bioremediation of nitrogenous compounds from domestic wastewater.
Article
The nitrification and nitrite accumulation were studied in various free ammonia (FA) concentration and temperature combinations. Both ammonia oxidation rate and nitrite oxidation rate increased significantly with the increase in temperature from 10 to 30°C. The increase in the substrate oxidation rate with temperature was relatively faster for ammonia than nitrite. Nitrite accumulation started to occur at 20°C when the specific oxidation rate of ammonia showed a higher value than that of nitrite. Subsequently, the nitrite accumulation continuously increased with the increasing temperature from 20 to 30°C. The broad range in FA concentration exhibited negligible effect on the specific substrate utilization rate as well as the relative nitrite accumulation. On the basis of Arrhenius equation, the activation energies of ammonia oxidation were 87.1 and 38.6kJmol−1 in the temperature ranges 10–20°C and 20–30°C, respectively. However for the nitrite oxidation, the activation energy was obtained as a constant value of 34.2kJmol−1 in the temperature range of 10–30°C.
Article
A psychrotrophic heterotrophic nitrifying-aerobic denitrifying bacterium was newly isolated and identified as Acinetobacter sp. with phenotypic and phylogenetic analysis. The strain possessed excellent tolerance to low temperature with 20°C as its optimum and 4°C as viable. Moreover, ammonium, nitrite and nitrate could be removed efficiently under low-temperature, solely aerobic conditions with little accumulation of intermediates. The average removal rate at 10°C reached as high as 3.03, 2.51 and 1.88mgNL(-1)h(-1) for ammonium, nitrite and nitrate respectively. N2 was produced through heterotrophic nitrification and aerobic denitrification via nitrite but N2O was never detected in the whole process. Nitrogen balance analysis indicated that N2 and intracellular nitrogen were two major fates of the initial ammonium, accounting for 32.4 and 49.2%, respectively. Further aerated batch test demonstrated efficient removal of COD and TN from synthetic wastewater, which implied promising practical application of the present strain.
Article
This study attempts to elucidate the emission sources and mechanisms of nitrous oxide (N2O) during simultaneous nitrification and denitrification (SND) process under oxygen-limiting condition. The results indicated that N2O emitted during low-oxygen SND process was 0.8±0.1mgN/gMLSS, accounting for 7.7% of the nitrogen input. This was much higher than the reported results from conventional nitrification and denitrification processes. Batch experiments revealed that nitrifier denitrification was attributed as the dominant source of N2O production. This could be well explained by the change of ammonia-oxidizing bacteria (AOB) community caused by the low-oxygen condition. It was observed that during the low-oxygen SND process, AOB species capable of denitrification, i.e., Nitrosomonas europaea and Nitrosomonas-like, were enriched whilst the composition of denitrifiers was only slightly affected. N2O emission by heterotrophic denitrification was considered to be limited by the presence of oxygen and unavailability of carbon source.
Article
Nitrogen removal in wastewater treatment plants is usually severely inhibited under cold temperature. The present study proposes bioaugmentation using psychrotolerant heterotrophic nitrification-aerobic denitrification consortium to enhance nitrogen removal at low temperature. A functional consortium has been successfully enriched by stepped increase in DO concentration. Using this consortium, the specific removal rates of ammonia and nitrate at 10°C reached as high as 3.1mgN/(gSSh) and 9.6mgN/(gSSh), respectively. PCR-DGGE and clone library analysis both indicated a significant reduction in bacterial diversity during enrichment. Phylogenetic analysis based on nearly full-length 16S rRNA genes showed that Alphaproteobacteria, Deltaproteobacteria and particularly Bacteroidetes declined while Gammaproteobacteria (all clustered into Pseudomonas sp.) and Betaproteobacteria (mainly Rhodoferax ferrireducens) became dominant in the enriched consortium. It is likely that Pseudomonas spp. played a major role in nitrification and denitrification, while R. ferrireducens and its relatives utilized nitrate as both electron acceptor and nitrogen source.
Article
The effects of the dissolved oxygen concentration on biological nitrification in suspended biomass processes are investigated. A model of nitrification, in which the kinetics is expressed by considering both the intrinsic rate of ammonia oxidation and the diffusion rate of substrates inside the biological floc, is presented. The model is calibrated and validated utilizing experimental data of tests performed in conditions of oxygen limiting kinetics. Excellent agreement is found between experimental results and model predictions. Finally, the model is applied to evaluate the effectiveness factor, η, i.e. the ratio between the actual substrate removal rate and the intrinsic rate, as a function of the biofloc's diameter at different levels of dissolved oxygen concentration. The results obtained show that in nitrification processes, the effects related to oxygen internal diffusion resistances cannot be neglected in evaluating the overall kinetics. A marked decrease in the η value is found at a biofloc diameter greater than 100 μm, particularly when the dissolved oxygen concentration is ⩽ 2 mg l−1.
Article
The effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater was investigated. Experiments were conducted in a modified Ludzack–Ettinger pilot-plant configuration for 365 days. Total nitrification of an influent concentration of 1200 mg NH4+–N l−1 was obtained in this period. Influent COD/N ratios between 0.71 and 3.4 g COD g N−1 were tested by varying the nitrogen loading rate (NLR) supplied to the pilot plant. An exponential decrease of nitrification rate was observed when the influent COD/N ratio increased.The experimental COD/N ratio for denitrification was 7.1±0.8 g COD g N−1 while the stoichiometric ratio was 4.2 g COD g N−1. This difference is attributable to the oxidation of organic matter in the anoxic reactor with the oxygen of the internal recycle. The influence of influent COD/N ratio on the treatment of high-strength ammonium industrial wastewater can be quantified with these results. The influence of COD/N ratio should be one of the main parameters in the design of biological nitrogen removal processes in industrial wastewater treatment.
Article
In this study, the performance of partial nitrification via nitrite at low temperature was investigated in a pilot-scale sequencing batch reactor (SBR) with a working volume of 7.0m(3). A novel real-time control strategy, based on blower frequency (BF) and pH, was designed and evaluated. The nitrogen break point (NBP) in the BF curve and the nitrate/nitrite apex point (NAP) in the pH curve were used to identify the endpoint of the aerobic and anoxic phases, respectively. The nitrite accumulation rate (NAR) rapidly increased from 19.8% to 90%. Partial nitrification was achieved at low temperature (11-16°C) in 40 days and was stably maintained for as long as 140 days by applying a real-time control strategy based on pH and BF. Fluorescence in situ hybirdization (FISH) results demonstrated that ammonia oxidation bacteria (AOB) had developed into the dominant nitrifying bacteria compared to nitrite oxidation bacteria (NOB) in the system.
Article
Direct anaerobic treatment of municipal waste waters allows for energy recovery in the form of biogas. A further decrease in the energy requirement for waste water treatment can be achieved by removing the ammonium in the anaerobic effluent with an autotrophic process, such as anammox. Until now, anammox has mainly been used for treating warm (>30 °C) and concentrated (>500 mg N/L) waste streams. Application in the water line of municipal waste water treatment poses the challenges of a lower nitrogen concentration (<100 mg N/L) and a lower temperature (≤ 20 °C). Good biomass retention and a short HRT are required to achieve a sufficiently high nitrogen loading rate. For this purpose a 4.5 L gaslift reactor was inoculated with a small amount of anammox granules and operated for 253 days at 20 °C. The synthetic influent contained (69 ± 5) mg (NH(4)(+) + NO(2)(-))/L and 20 vol.% of anaerobically stabilised effluent. Results showed a clear increase in nitrogen loading rate (NLR) up to 0.31 g (NH(4) + NO(2))-N/(L × d) at a hydraulic retention time (HRT) of 5.3 h. A low effluent concentration of 0.03-0.17 mg (NH(4)(+)+NO(2)(-))-N/L could be achieved. Anammox biomass was retained as granules and as a biofilm on the reactor walls, which contributed 54 and 46%, respectively, towards total activity. The biomass was further characterised by an estimated net growth rate of 0.040 d(-1) and an apparent activation energy of 72 kJ/mol. The results presented in this paper showed that anammox bacteria can be applied for autotrophic nitrogen removal from the water line at a municipal waste water treatment plant. Combining direct anaerobic treatment with autotrophic nitrogen removal opens opportunities for energy-efficient treatment of municipal waste waters.
Article
Nitrification can be difficult to maintain at wastewater treatment plants (WWTPs) during cold periods resulting in disrupted nitrogen removal. The aim of this study was to relate nitrification process performance to abundance and composition of the ammonia oxidizer communities in two closely located municipal WWTPs in Sweden during an eight month period covering seasonal changes and low temperature conditions. Both facilities showed lower NH(4)(+)-N removal efficiency and nitrification rates as temperature decreased. However, one of the plants had a more stable nitrification rate and higher ammonia removal efficiency throughout the entire period. The differences in performance was related to a shift in the composition of the bacterial ammonia oxidizing community from a Nitrosomonas oligotropha-dominated community to a mixed community including also Nitrosomonas ureae-like ammonia oxidizers. This was likely a response to differences in NH(4)(+)-N and organic loading.
Article
A strain YZN-001 was isolated from swine manure effluent and was identified as Pseudomonas stutzeri. It can utilise not only nitrate and nitrite, but also ammonium. The strain had the capability to fully remove as much as 275.08 mg L(-1) NO(3)(-)-N and 171.40 mg L(-1) NO(2)(-)-N under aerobic conditions. Furthermore, At 30°C, the utilization of ammonium is approximately 95% by 18 h with a similar level removed by 72 h and 2 weeks at 10 and 4°C, respectively. Triplicate sets of tightly sealed serum bottles were used to test the heterotrophic nitrifying ability of P. stutzeri YZN-001. The results showing that 39% of removed NH(4)(+)-N was completely oxidised to nitrogen gas by 18 h. Indicating that the strain has heterotrophic nitrification and aerobic denitrification abilities, with the notable ability to remove ammonium at low temperatures, demonstrating a potential using the strain for future application in waste water treatment.
Article
Explosives used in mining, such as ammonium nitrate fuel oil (ANFO), can cause eutrophication of the surrounding environment by leakage of ammonium and nitrate from undetonated material that is not properly treated. Cold temperatures in mines affect nitrogen removal from water when such nutrients are treated with bioreactors in situ. In this study we identified bacteria in the bioreactors and studied the effect of temperature on the bacterial community. The bioreactors consisted of sequential nitrification and denitrification units running at either 5 or 10°C. One nitrification bioreactor running at 5°C was fed with salt spiked water. From the nitrification bioreactors, sequences from both ammonia- and nitrite-oxidizing bacteria were identified, but the species were distinct at different temperatures. The main nitrifiers in the lower temperature were closely related to the genera Nitrosospira and Candidatus Nitrotoga. 16S rRNA gene sequences closely related to halotolerant Nitrosomonas eutropha were found only from the salt spiked nitrification bioreactor. At 10°C the genera Nitrosomonas and Nitrospira were the abundant nitrifiers. The results showed that bacterial species richness estimates were low, <150 operational taxonomic units (OTUs), in all bioreactor clone libraries, when sequences were assigned to operational taxonomic units at an evolutionary distance of 0.03. The only exception was the nitrification bioreactor running at 10°C where species richness was higher, >300 OTUs. Species richness was lower in bioreactors running at 5°C compared to those operating at 10°C.
Article
The aim of this work was to compare denitrification activity of three types of encapsulated biomass containing pure culture of Paracoccus denitrificans or Pseudomonas fluorescens or mixed culture of psychrophilic denitrifiers cultivated at 5 °C from activated sludge. The experiments were held with synthetic wastewater containing 50 mg L(-1) N-NO(3)(-) under the temperature 15, 10, 8 and 5 °C. Specific denitrification rates related to the weight of pellets and to the protein content were calculated and the temperature coefficients describing the dependence of denitrification rate on the temperature were determined. Although the mixed culture showed the highest denitrification rate at the temperatures below 10 °C, using of pellets containing pure culture is recommended as the mixed culture has slow growth rate and its activity at temperatures above 10 °C is very low.
Article
Partial nitrification to nitrite has been frequently obtained at high temperatures, but has proved difficult to achieve at low temperatures when treating low strength domestic wastewater. In this study, the long-term effects of temperature on partial nitrification were investigated by operating a sequencing bath reactor with the use of aeration duration control. The specific ammonia oxidation rate decreased by 1.5 times with the temperature decreasing from 25 to 15 degrees C. However, low temperature did not deteriorate the stable partial nitrification performance. Nitrite accumulation ratio was always above 90%, even slightly higher (above 95%) at low temperatures. The nitrifying sludge accumulated with ammonia-oxidizing bacteria (AOB), but washout of nitrite-oxidizing bacteria (NOB) was used to determine the short-term effects of temperature on ammonia oxidation process. The ammonia oxidation rate depended more sensitively on lower temperatures; correspondingly the temperature coefficient theta was 1.172 from 5 to 20 degrees C, while theta was 1.062 from 20 to 35 degrees C. Moreover, the larger activation energy (111.5 kJ mol(-1)) was found at lower temperatures of 5-20 degrees C, whereas the smaller value (42.0 kJ mol(-1)) was observed at higher temperatures of 20-35 degrees C. These findings might be contributed to extend the applicability of the partial nitrification process in wastewater treatment plants operated under cold weather conditions. It is suggested that the selective enrichment of AOB as well as the washout of NOB be obtained by process control before making the biomass slowly adapt to low temperatures for achieving partial nitrification to nitrite at low temperatures.
Article
To obtain economically sustainable wastewater treatment, advanced nitrogen removal from municipal wastewater and the feasibility of achieving and stabilizing short-cut nitrification and denitrification were investigated in a pilot-plant sequencing batch reactor (SBR) with a working volume of 54 m(3). Advanced nitrogen removal, from summer to winter, with effluent TN lower than 3 mg/L and nitrogen removal efficiency above 98% was successfully achieved in pulsed-feed SBR. Through long-term application of process control in pulsed-feed SBR, nitrite accumulation reached above 95% at normal temperature of 25 degrees C. Even in winter, at the lowest temperature of 13 degrees C, nitrite was still the end production of nitrification and nitrite accumulation was higher than 90%. On the basis of achieving advanced nitrogen removal, short-cut nitrification and denitrification was also successfully achieved. Compare to the pulse-feed SBR with fixed time control, the dosage of carbon source and energy consumption in pulsed-feed SBR with process control were saved about 30% and 15% respectively. In pulsed-feed SBR with process control, nitrogen removal efficiency was greatly improved. Moreover, consumption of power and carbon source was further saved.
Article
To understand the effect of low temperature on the formation of aerobic granules and their nutrient removal characteristics, an aerobic granular sequencing batch airlift reactor (SBAR) has been operated at 10 degrees C using a mixed carbon source of glucose and sodium acetate. The results showed that aerobic granules were obtained and that the reactor performed in stable manner under the applied conditions. The granules had a compact structure and a clear out-surface. The average parameters of the granules were: diameter 3.4mm, wet density 1.036 g mL(-1), sludge volume index 37 mL g(-1), and settling velocity 18.6-65.1 cm min(-1). Nitrite accumulation was observed, with a nitrite accumulation rate (NO(2)(-)-N/NO(x)(-)-N) between 35% and 43% at the beginning of the start-up stage. During the stable stage, NO(x) was present at a level below the detection limit. However, when the influent COD concentration was halved (resulting in COD/N a reduction of the COD/N from 20:1 to 10:1) nitrite accumulation was observed once more with an effluent nitrite accumulation rate of 94.8%. Phosphorus release was observed in the static feeding phase and also during the initial 20-30 min of the aerobic phase. Neither the low temperature nor adjustment of the COD/P ratio from 100:1 to 25:1 had any influence on the phosphorus removal efficiency under the operating conditions. In the granular reactor with the influent load rates for COD, NH(4)(+)-N, and PO(4)(3-)-P of 1.2-2.4, 0.112 and 0.012-0.024 kg m(-3)d(-1), the respective removal efficiencies at low temperature were 90.6-95.4%, 72.8-82.1% and 95.8-97.9%.
Article
Four samples of natural ecosystems and one sample from an activated sludge treatment plant were mixed together and progressively adapted to alternating aerobic/anoxic phases in the presence of nitrate in order to enrich the microflora in aerobic denitrifiers. Aerobic denitrifying performances of this mixed ecosystem at various dissolved oxygen concentrations and various carbon-nitrogen loads were evaluated and compared to those obtained with the aerobic denitrifier Microvirgula aerodenitrificans. The consortium and the pure strain exhibited an aerobic denitrifying activity at air saturation conditions (7 mg dissolved oxygen 1(-1)), i.e. there was co-respiration of the two electron acceptors with significant specific nitrate reduction rates. Dissolved oxygen concentrations had no influence on denitrifying performances above a defined threshold: 0.35 mg l(-1) for the consortium and 4.5 mg l(-1) for M. aerodenitrificans respectively. Under these thresholds, decreasing the dissolved oxygen concentrations enhanced the denitrifying activity of each culture. The higher the carbon and nitrogen loads, the higher the performance of the aerobic denitrifying ecosystem. However, for M. aerodenitrificans, the nitrate reduction percentage was affected more by variations in nitrogen load than in carbon load.
Article
Potential starch degrading denitrifying microorganisms that can grow at 4 degrees C were isolated from lake sediments to remove nitrate from groundwater. Initial screening using soluble starch as the sole carbon source confirmed that two out of twenty-five isolates (strain no. 2 and 47) significantly reduced nitrate in the medium and liberated nitrogen gas during culture. In a second screening, several commercially available starch based materials and different kinds of starch were tested. Strain 47 was found to have the best denitrification performance compared with strain 2. Using starch based carrier C (a commercial packing material) as carbon source, strain 47 could completely reduce the nitrate nitrogen in the medium after one week of batch culture even at 10 degrees C. Strain 47 could remove nitrate even without trace element supplementation, and it could perform optimally at 1X (10ml l(-1) of trace element solution) level of trace element supplement. The best temperature for denitrification for strain 47 was 15 degrees C and 20 degrees C, but it could also remove nitrate nitrogen at 10 degrees C and 30 degrees C, although at a slower rate. Reactor studies in a simulated treatment well (a cylindrical reciprocating basket reactor) in a repeated fed batch mode showed a good stable denitrification performance as long as substrate limitation is avoided by adequate supply of starch based carrier. Although the similarity score obtained was not enough for phylogenic identification, the results of 16SrRNA sequences analysis for the strain 47 showed a dose relation to Janthinobacterium lividum or Pseudomonas (Janth) mephitica (95.77%).
Article
Bioaugmentation of nitrifying bacteria for short solids retention time (short-SRT) nitrification is an attractive alternative for wastewater treatment plants in cold climates or for those in the process of upgrading to include nitrification. One possible source of ammonia for the production of nitrifying bacteria is the liquor generated during the dewatering of anaerobically digested sludges. The objectives of this study was to determine the impact of sudden decrease in temperature on nitrification rates and to determine if nitrification could be accomplished in sequencing batch reactors (SBRs) at 10 degrees C by seeding nitrifying bacteria acclimated to 20 degrees C. In this research, biomass produced during warm nitrification of dewatering liquor was seeded into cold SBRs at various hydraulic retention times from 43.3 to 96 h. The average decreases in nitrification rates were 58%, 71% and 82% for biomass cooled to 10 degrees C when the biomass was acclimated to 20 degrees C, 25 degrees C and 30 degrees C, respectively. The seeded SRTs of the cold SBRs were raised above the minimum solids retention time (SRT(min)) required for nitrification. Full ammonia nitrogen removal was achieved in cold SBRs that were operated at an apparent SRT less than SRT(min).
Article
The cause of seasonal failure of a nitrifying municipal landfill leachate treatment plant utilizing a fixed biofilm was investigated by wastewater analyses and batch respirometric tests at every treatment stage. Nitrification of the leachate treatment plant was severely affected by the seasonal temperature variation. High free ammonia (NH3-N) inhibited not only nitrite oxidizing bacteria (NOB) but also ammonia oxidizing bacteria (AOB). In addition, high pH also increased free ammonia concentration to inhibit nitrifying activity especially when the NH4-N level was high. The effects of temperature and free ammonia of landfill leachate on nitrification and nitrite accumulation were investigated with a semi-pilot scale biofilm airlift reactor. Nitrification rate of landfill leachate increased with temperature when free ammonia in the reactor was below the inhibition level for nitrifiers. Leachate was completely nitrified up to a load of 1.5 kg NH4-N m(-3)d(-1) at 28 degrees C. The activity of NOB was inhibited by NH3-N resulting in accumulation of nitrite. NOB activity decreased more than 50% at 0.7 mg NH3-N L(-1). Fluorescence in situ hybridization (FISH) was carried out to analyze the population of AOB and NOB in the nitrite accumulating nitrifying biofilm. NOB were located close to AOB by forming small clusters. A significant fraction of AOB identified by probe Nso1225 specifically also hybridized with the Nitrosomonas specific probe Nsm156. The main NOB were Nitrobacter and Nitrospira which were present in almost equal amounts in the biofilm as identified by simultaneous hybridization with Nitrobacter specific probe Nit3 and Nitrospira specific probe Ntspa662.
Article
Alcaligenes faecalis no. 4 has heterotrophic nitrification and aerobic denitrification abilities. By taking the nitrogen balance under different culture conditions, 40-50% of removed NH4+-N was denitrified and about one-half of removed NH4+-N was converted to intracellular nitrogen. The maximum ammonium removal rate of no. 4 (28.9 mg-N/l/h) and its denitrification rate at high-strength NH4+-N of about 1200 ppm in aerated batch experiments at a C/N ratio of 10 were 5-40 times higher than those of other bacteria with the same ability. Only a few percent of the removed ammonium was converted to nitrite, and the main denitrification process was speculated to be via hydroxylamine which was produced by ammonium oxidation.
Article
To establish an environmentally friendly groundwater bioremediation process using a cellulose carrier combined with cellulose-utilizing, denitrifying microorganisms, a novel psychrophilic bacterium, designated CL-5, which can degrade a commercial-based cellulose carrier as the sole carbon source, was screened. Since the denitrification capability of CL-5 is low, complex microbial systems were constructed together with other denitrifying bacteria designated NR-1 and NR-2 that were also isolated from soil. The nitrate-reducing activities of mixed cultures were much higher than those of the pure cultures of CL-5, NR-1 and NR-2. The highest N(2)O and N(2) formation activities were observed in the mixed culture of CL-5+NR-2.
Article
Two reactors, initially operated at 14 and 23+/-1 degrees C (RA and RB, respectively), were inoculated with a bacterial consortium enriched and acclimatized to the respective temperatures over 4 months. The biofilms, formed in the reactors, were studied using scanning electron microscopy, cultivation of the biofilm microflora, and physiological analysis of the isolates. Two bacteria able to mineralize chlorophenols under a large range of temperature (10-30 degrees C) were isolated from the biofilm communities of reactors RA and RB and characterized as Alcaligenaceae bacterium R14C4 and Cupriavidus basilensis R25C6, respectively. When temperature was decreased by 10 degrees C, the chlorophenols removal capacity was reduced from 51.6 to 22.8 mg l(-1) h(-1) in bioreactor RA (from 14 to 4 degrees C) and from 59.3 to 34.7 mg l(-1) h(-1) in bioreactor RB (from 23+/-1 to 14 degrees C). Fluorescence in situ hybridization (FISH) of the biofilm communities showed that, in all temperatures tested, the beta-proteobacteria were the major bacterial community (35-47%) followed by the gamma-proteobacteria (12.0-6.5%). When the temperature was decreased by 10 degrees C, the proportions of gamma-proteobacteria and Pseudomonas species increased significantly in both microbial communities.
Article
We hypothesize that activated-sludge processes having stable and complete nitrification have significant and similar diversity and functional redundancy among its ammonia- and nitrite-oxidizing bacteria, despite differences in temperature, solids retention time (SRT), and other operating conditions. To evaluate this hypothesis, we examined the diversity of nitrifying bacterial communities in all seven water-reclamation plants (WRPs) operated by Metropolitan Water Reclamation District of Greater Chicago (MWRDGC). These plants vary in types of influent waste stream, plant size, water temperature, and SRT. We used terminal restriction fragment length polymorphism (T-RFLP) targeting the 16S rRNA gene and group-specific ammonia-monooxygenase functional gene (amoA) to investigate these hard-to-culture nitrifying bacteria in the full-scale WRPs. We demonstrate that nitrifying bacteria carrying out the same metabolism coexist in all WRPs studied. We found ammonia-oxidizing bacteria (AOB) belonging to the Nitrosomonas europaea/eutropha, Nitrosomonas oligotropha, Nitrosomonas communis, and Nitrosospira lineages in all plants. We also observed coexisting Nitrobacter and Nitrospira genera for nitrite-oxidizing bacteria (NOB). Among the factors that varied among the WRPs, only the seasonal temperature variation seemed to change the nitrifying community, especially the balance between Nitrosospira and Nitrosomonas, although both coexisted in winter and summer samples. The coexistence of various nitrifiers in all WRPs is evidence of functional redundancy, a feature that may help maintain the stability of the system for nitrification.