Improvement in ammonium removal efficiency in wastewater treatment by mixed culture of Alcaligenes faecalis no. 4 and L1

Hydroxylamine production by Alcaligenes faecalis challenges the paradigm of heterotrophic nitrification

Heterotrophic nitrifiers continue to be a hiatus in our understanding of the nitrogen cycle. Despite their discovery over 50 years ago, the physiology and environmental role of this enigmatic group remain elusive. The current theory is that heterotrophic nitrifiers are capable of converting ammonia to hydroxylamine, nitrite, nitric oxide, nitrous oxide, and dinitrogen gas via the subsequent actions of nitrification and denitrification. In addition, it was recently suggested that dinitrogen gas may be formed directly from ammonium. Here, we combine complementary high-resolution gas profiles, 15N isotope labeling studies, and transcriptomics data to show that hydroxylamine is the major product of nitrification in Alcaligenes faecalis. We demonstrated that denitrification and direct ammonium oxidation to dinitrogen gas did not occur under the conditions tested. Our results indicate that A. faecalis is capable of hydroxylamine production from an organic intermediate. These results fundamentally change our understanding of heterotrophic nitrification and have important implications for its biotechnological application.

Characterization of Enrichment Cultures of Anammox, Nitrifying and Denitrifying Bacteria Obtained from a Cold, Heavily Nitrogen-Polluted Aquifer

Anammox bacteria related to Candidatus Scalindua were recently discovered in a cold (7.5 °C) aquifer near sludge repositories containing solid wastes of uranium and processed polymetallic concentrate. Groundwater has a very high level of nitrate and ammonia pollution (up to 10 and 0.5 g/L, respectively) and a very low content of organic carbon (2.5 mg/L). To assess the potential for bioremediation of polluted groundwater in situ, enrichment cultures of anammox, nitrifying, and denitrifying bacteria were obtained and analyzed. Fed-batch enrichment of anammox bacteria was not successful. Stable removal of ammonium and nitrite (up to 100%) was achieved in a continuous-flow reactor packed with a nonwoven fabric at 15 °C, and enrichment in anammox bacteria was confirmed by FISH and qPCR assays. The relatively low total N removal efficiency (up to 55%) was due to nonstoichiometric nitrate buildup. This phenomenon can be explained by a shift in the metabolism of anammox bacteria towards the production of more nitrates and less N₂ at low temperatures compared to the canonical stoichiometry. In addition, the too high an estimate of specific anammox activity suggests that N cycle microbial groups other than anammox bacteria may have contributed significantly to N removal. Stable nitrite production was observed in the denitrifying enrichment culture, while no "conventional" nitrifiers were found in the corresponding enrichment cultures. Xanthomonadaceae was a common taxon for all microbial communities, indicating its exclusive role in this ecosystem. This study opens up new knowledge about the metabolic capabilities of N cycle bacteria and potential approaches for sustainable bioremediation of heavily N-polluted cold ecosystems.

Simultaneous heterotrophic nitrification and aerobic denitrification potential of Paenibacillus sp. strain GLM-08 isolated from lignite mine waste and its role ammonia removal from mine waste water

Paenibacillus sp. strain GLM-08 was isolated from a lignite mine waste site in the Barmer basin, Rajasthan, India. The strain is efficient in heterotrophic nitrification and aerobic denitrification. This bacterium could remove approximately more than 95% of NH₄⁺, NO₃^-, and NO₂^- in 24 h. The average nitrogen (N) removal rate of the strain was found to be 4.775 mg/L/H, 5.66 mg/L/H, and 5.01 mg/L/H for NH₄⁺, NO₃^-, and NO₂^-, respectively. Bioaugmentation of mine wastewater with Paenibacillus sp. strain GLM-08 demonstrated N removal of 86.6% under conditions of a high load of NH₄⁺. The presence of potential genetic determinants (nxrB, nirS, and nosZ) having role in heterotrophic nitrification and aerobic denitrification was confirmed by PCR based analysis. The findings show that this bacterium performs simultaneous nitrification and denitrification and has a high nitrogen removal efficiency indicating the potential application of the strain in the treatment of wastewater.

Bioremediation of organic/heavy metal contaminants by mixed cultures of microorganisms: A review

Although microbial remediation has been widely used in the bioremediation of various contaminants, in practical applications of biological remediation, pure cultures of microorganisms are seriously limited by their adaptability, efficiency, and capacity to handle multiple contaminants. Mixed cultures of microorganisms involve the symbiosis of two or more microorganisms. Such cultures exhibit a collection of the characteristics of each microorganism species or strain, showing enormous potential in the bioremediation of organic or heavy metal pollutants. The present review focuses on the mixed cultures of microorganisms, demonstrating its importance and summarizing the advantages of mixed cultures of microorganisms in bioremediation. Furthermore, the internal and external relations of mixed culture microorganisms were analyzed with respect to their involvement in the removal process to elucidate the underlying mechanisms.

Application of response surface methodology for COD and ammonia removal from municipal wastewater treatment plant using acclimatized mixed culture

This study aimed to optimize conditions influencing the removal of chemical oxygen demand (COD) and ammonia-N in municipal wastewater by using acclimatized mixed culture (AMC). Two-level factorial analysis was used to investigate the factors affecting the degradation of COD and ammonia-N (%); ratio of synthetic wastewater (SW) to acclimatized mixed culture (AMC) (1:1 and 3:1), presence and absence of support media (Yes and No), agitation (0 rpm and 100 rpm) and hydraulic retention time (HRT) (2 and 5 days). A central composite design (CCD) under response surface methodology (RSM) determined the optimum agitation (0 rpm and 100 rpm) and retention time (2 and 5 days). The best conditions were at 3:1 of SW: AMC ratio, 100 rpm agitation, without support media, and 5 days retention time. COD and ammonia-N removal achieved until 57.23% and 43.20%, respectively. Optimization study showed the optimum conditions for COD and ammonia-N removal were obtained at 150 rpm agitation speed and 5 days of retention time, at 70.41% and 64.29% respectively. This study discovers the conditions that affect the COD and ammonia-N removal in the municipal wastewater using acclimatized mixed culture.

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Removal of COD and ammonia-N using acclimatized mixed culture.

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Central composite design was used to optimize process condition.

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The maximum COD removal was found to be 70.41%.

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The maximum ammonia-N removal was found to be 64.29%.

Simultaneous Heterotrophic Nitrification and Aerobic Denitrification of Water after Sludge Dewatering in Two Sequential Moving Bed Biofilm Reactors (MBBR)

Water after sludge dewatering, also known as reject water from anaerobic digestion, is recycled back to the main wastewater treatment inlet in the wastewater treatment plant Porsgrunn, Norway, causing periodic process disturbance due to high ammonium of 568 (±76.7) mg/L and total chemical oxygen demand (tCOD) of 2825 (±526) mg/L. The main aim of this study was the simultaneous treatment of reject water ammonium and COD using two pilot-scale sequential moving bed biofilm reactors (MBBR) implemented in the main wastewater treatment stream. The two pilot MBBRs each had a working volume of 67.4 L. The biofilm carriers used had a protected surface area of 650 m²/m³ with a 60% filling ratio. The results indicate that the combined ammonia removal efficiency (ARE) in both reactors was 65.9%, while the nitrite accumulation rate (NAR) and nitrate production rate (NPR) were 80.2 and 19.8%, respectively. Over 28% of the reject water’s tCOD was removed in both reactors. The heterotrophic nitrification and oxygen tolerant aerobic denitrification were the key biological mechanisms found for the ammonium removal in both reactors. The dominant bacterial family in both reactors was Alcaligenaceae, capable of simultaneous heterotrophic nitrification and denitrification. Moreover, microbial families that were found with equal potential for application of simultaneous heterotrophic nitrification and aerobic denitrification including Cloacamonaceae, Alcaligenaceae, Comamonadaceae, Microbacteriaceae, and Anaerolinaceae.

A review of research progress of heterotrophic nitrification and aerobic denitrification microorganisms (HNADMs)

Traditional nitrogen removal relies on the autotrophic nitrification and anaerobic denitrification process. In the system, autotrophic microorganisms achieve nitrification under aerobic condition and heterotrophic microorganisms complete the denitrification in anaerobic condition. As the two types of microorganisms have different tolerance on oxygen concentration, nitrification and denitrification are normally set in two compartments for high nitrogen removal. Therefore, large land occupying is required. In fact, there is a special type of microorganism called heterotrophic nitrification & aerobic denitrification microorganisms (HNADMs) which can oxidize ammonium nitrogen, and perform denitrification in the presence of oxygen. HNADMs have been reported in many environments. It was found that HNADMs could simultaneously achieve nitrification and denitrification. In addition, some HNADMs not only have the ability to remove nitrogen, but also have the ability to remove phosphorus. It suggests that HNADMs have great potential for pollution removal from wastewater. So far, individual work on single strain was carried out. Comprehensive summary of the HNADMs would provide a better picture for understanding and directing its application. In this paper, the studies related on HNADMs were reviewed. The nitrogen metabolism pathway of HNADMs was summarized. The impact of pH, DO, carbon source, and C/N on HNADMs growth and metabolism were discussed. In addition, the extracellular polymeric substance (EPS) production, quorum sensing (QS) secretion and P removal by HNADMs were displayed.

Potential of Bacterial Strains Isolated from Coastal Water for Wastewater Treatment and as Aqua-Feed Additives

Bacteria have various and sustained effects on humans in various fields: molecular biology, biomedical science, environmental/food industry, etc. This study was conducted to evaluate the wastewater treatment capacity and feed-additive fish-growth effect of four strains of bacteria: Pseudoalteromonas mariniglutinosa, Psychrobacter celer, Bacillus albus, and Bacillus safensis. In a wastewater degradation experiment, (i) nitrate-N and nitrite-N were removed within 1 h in all of the 4 bacterial strains; (ii) the removal rates of TAN and TN were higher in all of the strains relative to the B. subtilis. In a feed-additive experiment (5% Kg-1), (i) the growth of fish was higher in all of the 4 bacterial strains with the B. subtilis relative to the commercial feed; (ii) there was no significant growth difference for B. albus and B. safensis relative to the B. subtilis, but growth was higher in P. mariniglutinosa and P. celer. The results indicated that the 4 bacterial strains can be effectively utilized for biological wastewater treatment processes and as aqua-feed.

Application of glucose for improving NH4+-N removal in micro-polluted source water by immobilized heterotrophic nitrifiers at low temperature

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.

The application of Marinobacter hydrocarbonoclasticus as a bioaugmentation agent for the enhanced treatment of non-sterile fish wastewater

Wastewaters generated by fish processing are characterised by salt concentrations similar to or greater than that of seawater together with high nutrient concentrations (e.g. organic carbon and total nitrogen) due to the presence of blood, oil, and fish tissues. Fish processing wastewater entering rivers and oceans have become a key factor leading to the pollution of receiving waters; the adequate treatment of this wastewater is, therefore, crucial to a sustainable fish industry. The present study aimed to determine whether augmentation of fish wastewater with either Marinirhabdus sp., Marinobacter hydrocarbonoclasticus or a consortium of the two halobacteria, could successfully enhance the removal of both chemical oxygen demand (COD) and total nitrogen (TN) from fish wastewater. Following 9 days of incubation, the bioaugmentation treatment resulted in a significant reduction in COD, 88%, 91%, and 92% in fish wastewater augmented with either Marinirhabdus sp., Marinobacter hydrocarbonoclasticus respectively, or a consortium of the two halobacteria compared with the control (non-bioaugmented) treatment (77% removal). In tall bioaugmentation treatments (79-88%) TN removal was also significantly greater than the control treatment (57%). After 9 days of incubation, the COD and TN in bioaugmentation reached the European Union's (EU) wastewater discharge standard (Level B, COD < 120 mg L^-1, TN < 70 mg L^-1). The addition of monoculture was effective in enhancing the removal of COD, while co-culture significantly improved TN removal. Results of 16S rDNA sequence analysis investigating the survival of these introduced bacteria showed that only Marinobacter hydrocarbonoclasticus was detected at the end of the treatment, constituting 36% of the total bacterial population when added alone to the wastewater. This study confirms the effectiveness of bioaugmentation in removing COD and TN in saline fish wastewater. The ability of Marinobacter hydrocarbonclasticus to enhance the treatment and dominate the bacterial community suggests the commercial potential of this organism for bioaugmentation of aquaculture wastewater without the need for further bioaugmentation.

Heterotrophic nitrification and related functional gene expression characteristics of Alcaligenes faecalis SDU20 with the potential use in swine wastewater treatment

A new heterotrophic nitrifying bacterium was isolated from the compost of swine manure and rice husk and identified as Alcaligenes faecalis SDU20. Strain SDU20 had heterotrophic nitrification potential and could remove 99.7% of the initial NH₄⁺-N. Nitrogen balance analysis revealed that 15.9 and 12.3% of the NH₄⁺-N were converted into biological nitrogen and nitrate nitrogen, respectively. The remaining 71.44% could be converted into N₂ or N₂O. Single-factor experiments showed that the optimal conditions for ammonium removal were the carbon source of sodium succinate, C/N ratio 10, initial pH 8.0, and temperature 30 °C. Nitrification genes were determined to be upregulated when sodium succinate was used as the carbon source analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Strain SDU20 could tolerate 4% salinity and show resistance to some heavy metal ions. Strain SDU20 removed 72.6% high concentrated NH₄⁺-N of 2000 mg/L within 216 h. In a batch experiment, the highest NH₄⁺-N removal efficiency of 98.7% and COD removal efficiency of 93.7% were obtained in the treatment of unsterilized swine wastewater. Strain SDU20 is promising in high-ammonium wastewater treatment.

Colonization kinetics and implantation follow-up of the sewage microbiome in an urban wastewater treatment plant

The Seine-Morée wastewater treatment plant (SM_WWTP), with a capacity of 100,000 population-equivalents, was fed with raw domestic wastewater during all of its start-up phase. Its microbiome resulted from the spontaneous evolution of wastewater-borne microorganisms. This rare opportunity allowed us to analyze the sequential microbiota colonization and implantation follow up during the start-up phase of this WWTP by means of regular sampling carried out over 8 months until the establishment of a stable and functional ecosystem. During the study, biological nitrification–denitrification and dephosphatation occurred 68 days after the start-up of the WWTP, followed by flocs decantation 91 days later. High throughput sequencing of 18S and 16S rRNA genes was performed using Illumina's MiSeq and PGM Ion Torrent platforms respectively, generating 584,647 16S and 521,031 18S high-quality sequence rDNA reads. Analyses of 16S and 18S rDNA datasets show three colonization phases occurring concomitantly with nitrification, dephosphatation and floc development processes. Thus, we could define three microbiota profiles that sequentially colonized the SM_WWTP: the early colonizers, the late colonizers and the continuous spectrum population. Shannon and inverse Simpson diversity indices indicate that the highest microbiota diversity was reached at days 133 and 82 for prokaryotes and eukaryotes respectively; after that, the structure and complexity of the wastewater microbiome reached its functional stability. This study demonstrates that physicochemical parameters and microbial metabolic interactions are the main forces shaping microbial community structure, gradually building up and maintaining a functionally stable microbial ecosystem.

Evaluating performance of nitrogen and organic carbon removal in a single reactor by using A. faecalis strain NR aerobically

The performance of nitrogen and organic carbon removal in a single reactor (R₁) operating with A. faecalis strain NR aerobically was assessed. Under 150 mg/L influent NH₄⁺-N, 91.3%, 71.4% and 90.9% of NH₄⁺-N, TN and TOC were removed, presenting much higher efficiency than a control bioreactor inoculating activated sludge (R₀). The amoA gene expression from strain NR in R₁ was 7.8 times higher than that from activated sludge in R₀, demonstrating the role of strain NR in removing NH₄⁺. The analysis of microbial community composition revealed that strain NR was the dominant species and outcompeted ammonium oxidizing bacterium (AOB) under high organic carbon as well as ammonium. Simultaneous ammonium and organic carbon removal still maintained for a long-term operation with NH₄⁺-N loadings of 300 and 450 mg/L in R₁. Nitrogen balance showed that stripped NH₃ only occupied a few percentages and aerobic denitrification played a significant role in nitrogen removal.

One-Step Removal of Calcium, Magnesium, and Nickel in Desalination by Alcaligenes aquatilis via Biomineralization

In desalination, a high level of calcium (Ca) and magnesium (Mg) ions in seawater can cause scale deposition on the reverse osmosis membranes and water treatment systems. This process can significantly affect the efficiency of desalination. In addition, heavy metals in seawater affect human health. Therefore, Alcaligenes aquatilis from seawater was used to remove Ca, Mg, and nickel (Ni) by microbial-induced carbonate precipitation (MICP). The purification system was then analyzed by ionic analysis and surface characterization. This study shows that the bacteria can utilize amino acids to produce carbonate and form precipitates with a high removal rate. MICP via A. aquatilis removed 91.8%, 68.5%, and 92.2% of the initial soluble Ca, Mg, and Ni, respectively. Furthermore, A. aquatilis can remove ammonium after the MICP process under oxygen-rich conditions. Therefore, we provide interesting insight into the use of Alcaligenes (in the absence of urea) to improve the seawater quality in the process of desalination.

Optimizing Suitable Conditions for the Removal of Ammonium Nitrogen by a Microbe Isolated from Chicken Manure

Strain C was isolated from chicken manure, and its phenotypic characteristics were gram-stain negative, yellow-pigmented, aerobic bacterium, heterotrophic, non-motile, chemoorganotrophic, non-gliding as well as non-spore-forming. A 16S rRNA gene sequence analysis showed that strain C occupied a distinct lineage within the family of the genus Chryseobacterium, and it shared highest sequence similarity with Chryseobacterium solincola strain 1YB-R12 (80%). The new isolate has been studied for removing ammonium-nitrogen (NH4-N) and the optimization of suitable conditions. The strain C was able to degrade over 42.8% of NH4-N during its active growth cycle. Experimental study of the effect of temperature and pH on NH4-N removal showed that the temperature and pH optima for NH4-N removal were 30–35℃ and 4–8, respectively. The results indicated that strain C shows a potential application for wastewater treatment.

Aerobic denitrifiers with petroleum metabolizing ability isolated from caprolactam sewage treatment pool

To improve the biological nitrogen removal efficiency of petrochemical wastewater, three aerobic denitrifiers were isolated from caprolactam sewage treatment pool. They were identified as Acinetobacter sp. YY1, Sphingomonas sp. YY2 and Pseudomonas sp. YY3, respectively. The nitrification and denitrification enzyme genes could be detected using polymerase chain reaction (PCR). Moreover, the strain YY2 was a novel aerobic denitrifier belongs to genus of Sphingomonas, which showed great ability for metabolizing aromatic hydrocarbons. In the nitrification and denitrification process, the total nitrogen (TN) removal efficiency after 48 h was 94.22% and 90.10%, respectively. In the process of simultaneous nitrification and denitrification in mixed N-source, ammonia nitrogen was preferentially utilized. Furthermore, the strain YY2 exhibited excellent extracellular polymer secretion properties and excellent aerobic denitrification capacity using petroleum refractory organic compounds, which are beneficial for the formation of bacterial micelles and the engineering applications for the treatment of petrochemical wastewater.

Nitrogen Removal in Oligotrophic Reservoir Water by a Mixed Aerobic Denitrifying Consortium: Influencing Factors and Immobilization Effects

Nitrogen pollution in reservoirs has received increasing attention in recent years. Although a number of aerobic denitrifying strains have been isolated to remove nitrogen from eutrophic waters, the situation in oligotrophic water environments has not received significant attention. In this study, a mixed aerobic denitrifying consortium screened from reservoir samples was used to remove nitrogen in an oligotrophic denitrification medium and actual oligotrophic source water. The results showed that the consortium removed 75.32% of nitrate (NO₃--N) and 63.11% of the total nitrogen (TN) in oligotrophic reservoir water during a 24-h aerobic cultivation. More initial carbon source was helpful for simultaneous removal of carbon and nitrogen in the reservoir source water. NO₃--N and TN were still reduced by 60.93% and 46.56% at a lower temperature (10 °C), respectively, though the rates were reduced. Moreover, adding phosphorus promoted bacterial growth and increased TN removal efficiency by around 20%. The performance of the immobilized consortium in source water was also explored. After 6 days of immobilization, approximately 25% of TN in the source water could be removed by the carriers, and the effects could last for at least 9 cycles of reuse. These results provide a good reference for the use of aerobic denitrifiers in oligotrophic reservoirs.

Simultaneous nitrification and denitrification without nitrite accumulation by a novel isolated Ochrobactrum anthropic LJ81

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.

Characteristics of a heterotrophic nitrogen removal bacterium and its potential application on treatment of ammonium-rich wastewater

Nitrogen and organic carbon are major pollutants in wastewater causing environmental problems. Alcaligenes faecalis strain NR, isolated from activated sludge, exhibited the ability to remove ammonium and organic carbon from wastewater simultaneously under sole aerobic conditions in batch culture. Changes in carbon type, C/N ratio, oxygen concentration and inorganic ions significantly affected the treatment efficiency. Furthermore, a continuous bioreactor, solely inoculated with A. faecalis strain NR, was conducted to assess its feasibility for simultaneous nitrogen and organic matter removal in a single aerated reactor. Approximately 66.7-78.3% of NH₄⁺-N and 85.8-92.2% of TOC were removed by using synthetic wastewater with 150-200mg/L of NH₄⁺-N and 1350-2000mg/L of TOC. This research would be valuable to develop an innovative treatment method for ammonium-rich wastewater under aerobic conditions.

Nitrogen removal by Providencia rettgeri strain YL with heterotrophic nitrification and aerobic denitrification

Providencia rettgeri strain YL shows the capability of nitrogen removal under sole aerobic conditions. By using isotope ratio mass spectrometry, (15)N-labelled N2O and N2 were detected in aerobic batch cultures containing [Formula: see text], [Formula: see text] or [Formula: see text]. Strain YL converted [Formula: see text], [Formula: see text] and [Formula: see text] to produce more N2O than N2 in the presence of [Formula: see text]. An (15)N isotope tracing experiment confirmed that the nitrogen removal pathway of strain YL was heterotrophic nitrification-aerobic denitrification. The optimal treatment conditions for nitrogen removal were pH of 8, C/N ratio of 12, temperature of 25°C and shaking speed of 105 rpm. A continuous aerobic bioreactor inoculated with strain YL was developed. With an influent [Formula: see text] concentration of 90-200 mg/L, the [Formula: see text] removal efficiency ranged from 80% to 97% and the total nitrogen removal efficiency ranged from 72% to 95%. The nitrogen balance in the continuous bioreactor revealed that approximately 35-52% of influent [Formula: see text] was denitrified aerobically to form gaseous nitrogen. These findings show that the P. rettgeri strain YL has potential application in wastewater treatment for nitrogen removal under sole aerobic conditions.

Potential application of Alcaligenes faecalis strain No. 4 in mitigating ammonia emissions from dairy wastewater

This research examined the potential mitigation of NH3 emissions from dairy manure via an enhanced aerobic bio-treatment with bacterium Alcaligenes faecalis strain No. 4. The studies were conducted in aerated batch reactors using air and pure oxygen. Aeration with air and oxygen removed approximately 40% and 100% total ammoniacal nitrogen (TAN), respectively. Intermittent oxygenation (every 2 or 4 h) reduced oxygen consumption by 95%, while attaining nearly identical TAN removal to continuous aeration. The results revealed that adequate oxygen supply and supplementing dairy wastewater with carbon are essential for this bioprocess. Based on the nitrogen mass balance, only 4% of TAN was released as NH3 gas, while the majority was retained in either the microbial biomass (58%) or converted to nitrogen gas (36%). The mass balance results reveal high potential for environmentally friendly bio-treatment of dairy wastewater using A. faecalis strain No. 4 with respect to NH3 emissions.

Marinobacter strain NNA5, a newly isolated and highly efficient aerobic denitrifier with zero N2O emission

An efficient aerobic denitrification bacterium, strain NNA5, was isolated and identified as Marinobacter sp. NNA5. NNA5 did not perform heterotrophic nitrification. GC/IRMS analysis revealed that (15)N2 was produced from Na(15)NO2 and K(15)NO3. GC/MS and quantitative analyses showed that no N2O emission occurred when nitrite or nitrate was used as substrate. Single factor experiments indicated that optimal conditions for aerobic denitrification were: sodium succinate or sodium pyruvate as carbon source, temperature 35 °C, NaCl concentration 2-4%, C/N ratio 6-8, pH 7.5, rotation speed 150 rpm (giving dissolved oxygen concentration 6.08 mg/L), NO3(-)-N concentration ranging from 140 to 700 mg/L. NNA5 displayed highly efficient aerobic denitrifying ability, with maximal NO3(-)-N removal rate 112.8 mg/L/d. In view of its ability to perform aerobic denitrification with zero N2O emission, NNA5 has great potential for future application in aerobic denitrification processes in industrial and aquaculture wastewater treatment systems.

Toxicity of TiO₂ nanoparticle to denitrifying strain CFY1 and the impact on microbial community structures in activated sludge

The antibacterial activity of titanium dioxide nanoparticles (TiO2 NPs) is well described, but little is known of their impact on specific microbial functions such as denitrification, nor on microbial community structure. In this study, a denitrifier (named as Pseudomonas stutzeri CFY1), which was isolated from the activated sludge and could remove up to 111.68 mg/L of NO3(-)-N under aerobic conditions, was utilized to evaluate the influences of TiO2 NPs on its nitrogen removal ability and associated gene expression under aerobic conditions. The variations of the bacterial diversity of activated sludge were also observed. The results showed that antibacterial activity increased with increasing concentrations of TiO2 NPs. Increased production of reactive oxygen species was responsible for TiO2 NPs toxicity. An up-regulation of denitrification genes was observed with increasing concentrations of TiO2 NPs under aerobic conditions. Accordingly, denitrification by P. stutzeri was accelerated when the concentration of TiO2 NPs was increased to 50 mg/L. However, the denitrification of CFY1 was inhibited at low concentrations of TiO2 NPs (5-25 mg/L), indicating that assimilatory and dissimilatory denitrification were synchronized in P. stutzeri CFY1; the latter process plays a major role in denitrification. Further study of the community using 454 pyrosequencing showed that after 7 days of exposure to 50 mg/L TiO2 NPs, the microbial composition of the activated sludge was significantly different and had a lower diversity compared to the controls.

Removal of nitrogen by heterotrophic nitrification-aerobic denitrification of a phosphate accumulating bacterium Pseudomonas stutzeri YG-24

Phosphate accumulating bacterium Pseudomonas stutzeri YG-24 exhibited efficient heterotrophic nitrification and aerobic denitrification ability. Single factor experiments showed that both heterotrophic nitrification and aerobic denitrification occurred with sodium citrate as carbon source and lower C/N ratio of 8. High average NH4(+)-N, NO2(-)-N and NO3(-)-N removal rates of 8.75, 7.51 and 7.73 mg L(-1)h(-1) were achieved. The application of strain YG-24 in wastewater samples resulted in TN, NH4(+)-N, NO2(-)-N, NO3(-)-N and P removal efficiencies of 85.28%, 88.13%, 86.15%, 70.83% and 51.21%. Sequencing and quantitative amplification by real-time PCR of napA, nirS and ppk showed that nitrogen removal pathway of strain YG-24 was achieved through heterotrophic ammonium nitrification coupled with fast nitrite denitrification (NH4(+)-N to NO2(-)-N and then to gaseous nitrogen) directly. These results demonstrated the strain as a suitable candidate to simultaneously remove both nitrogen and phosphate in wastewater treatment.

Simultaneous nitrification and denitrification using a polypyrrole/microbial cellulose electrode in a membraneless bio-electrochemical system

In this study, the feasibility of ammonium and total nitrogen removal from aqueous solution using a simultaneous nitrification and denitrification process was studied in a membraneless bio-electrochemical system with a novel electrode.

Marinobacter hydrocarbonoclasticus NY-4, a novel denitrifying, moderately halophilic marine bacterium

The isolation and characterization of a novel halophilic denitrifying marine bacterium is described. The halophilic bacterium, designated as NY-4, was isolated from soil in Yancheng City, China, and identified as Marinobacter hydrocarbonoclasticus by 16S rRNA gene sequence phylogenetic analysis. This organism can grow in NaCl concentrations ranging from 20 to 120 g/L. Optimum growth occurs at 80 g/L NaCl and pH 8.0. The organism can grow on a broad range of carbon sources and demonstrated efficient denitrifying ability (94.2% of nitrate removal and 80.9% of total nitrogen removal in 48 h). During denitrification by NY-4, no NO₂^--N was accumulated, N₂ was the only gaseous product and no harmful N₂O was produced. Because of its rapid denitrification ability, broad carbon use range and ability to grow under high salinity and pH conditions, NY-4 holds promise for the treatment of saline waste waters.

Characteristics of an aerobic denitrifier that utilizes ammonium and nitrate simultaneously under the oligotrophic niche

INTRODUCTION

An aerobic denitrifier was isolated from the Hua-Jia-Chi pond in China and identified as Pseudomonas mendocina 3-7 (Genbank No. HQ285879). This isolated strain could express periplasmic nitrate reductase which is essential for aerobic denitrification occurred when the dissolved oxygen (DO) level maintains at 3-10 mg L(-1).

METHODS

To determine whether the ability of isolated strain is exhibited in the bioremediation of polluted drinking source water, the heterotrophic nitrification and aerobic denitrification characteristics of P. mendocina 3-7 under different cultural conditions such as oxygen level, nitrate and organic concentrations were studied from the nitrogenous balance in the paper.

RESULTS AND CONCLUSIONS

By measuring the nitrogen balance in all experiments under different culture conditions, the removal of total organic carbon and ammonium was positively correlated with total nitrogen removal, especially under high substrate level. With substrate concentration decreasing, ammonium and nitrate removal occurred separately, and ammonium was completely utilized first under low substrate concentration. Compared to that under high substrate level, the specific growth rate of P. mendocina 3-7 was not low under the low substrate level and the pollutant removal efficiencies remained high, which implies the stronger nitrogen removal and acclimatization capacities of the strain in oligotrophic niches.

Removal of nitrate using Paracoccus sp. YF1 immobilized on bamboo carbon

Paracoccus sp. strain YF1 immobilized on bamboo carbon was developed for the denitrification. The results show that denitrification was significantly improved using immobilized cells compared to that of free cells, where denitrification time decreased from 24h (free cells) to 15 h (immobilized cells). The efficiency of denitrification increased from 4.57 mg/(Lh) (free cells) to 6.82 mg/(Lh) (immobilized cells). Kinetics studies suggest that denitrification by immobilized YF1 cells fitted well to the zero-order model. Scanning electron microscopy (SEM) demonstrated that firstly, the bacteria became stable on the inside and exterior of the bamboo carbon particles and secondly, they formed biofilm after adhesion. Various factors and their influences on biological denitrification were investigated, namely temperature, pH, initial nitrate concentrations and carbon sources. The immobilized cells exhibited more nitrate removal at various conditions compared to free cells since bamboo carbon as a carrier protects cells against changes in environmental conditions. Denitrification using the YF1 immobilized in bamboo carbon was also maintained 99.8% after the tenth cycle reuse, thus demonstrating excellent reusability. Finally, wastewater was treated using the immobilized cells and the outcome was that nitrogen was completely removed by bamboo-immobilized YF1.

Simultaneous heterotrophic nitrification and aerobic denitrification by bacterium Rhodococcus sp. CPZ24

Rhodococcus sp. CPZ24 was isolated from swine wastewater and identified. Batch (0.25 L flask) experiments of nitrogen removal under aerobic growth conditions showed complete removal of 50 mg L(-1) ammonium nitrogen within 20 h, while nitrate nitrogen removal reached 67%. A bioreactor (50 L) was used to further assess the heterotrophic nitrification and aerobic denitrification abilities of Rhodococcus sp. CPZ24. The results showed that 85% of the ammonium nitrogen (100 mg L(-1)) was transformed to nitrification products (NO(3)(-)-N and NO(2)(-)-N) (13%), intracellular nitrogen (24%), and gaseous denitrification products (48%) within 25 h. The ammonium nitrogen removal rate was 3.4 mg L(-1)h(-1). The results indicate that the strain CPZ24 carries out simultaneous nitrification and denitrification, demonstrating a potential use of the strain for wastewater treatment.

Isolation and nitrogen removal characteristics of an aerobic heterotrophic nitrifying-denitrifying bacterium, Bacillus subtilis A1

Bacterium A1, isolated to enhance nitrogen removal from ammonium-rich wastewater in situ, exhibited an amazing ability to convert ammonium to gaseous nitrogen compounds under fully aerobic conditions, while growing autotrophically or heterotrophically. A1 was identified as Bacillus subtilis by morphological and physiological characteristics, and phylogenetic analysis of its 16S rDNA gene sequence. Nitrogen removal by A1 was analyzed in relation to the ammonium concentration, presence of organic carbon, carbon source, and carbon-to-nitrogen ratio (C/N). The nitrogen balance during 120 h of autotrophic growth in the presence of 104.12±1.27 mg/L NH4+N showed that 20.4±2.7% of NH4+N was removed as gaseous nitrogen compounds, and A1 removed 58.4±4.3% of NH4+N within 60 h of growth in acetate medium at a C/N of 6. A mean ammonium removal rate of 3.52 mg NH4+N/(L h) was achieved in an open wastewater system, indicating great potential of A1 for future full-scale applications.

Heterotrophic nitrification-aerobic denitrification by novel isolated bacteria

Three novel strains capable of heterotrophic nitrification-aerobic denitrification were isolated from the landfill leachate treatment system. Based on their phenotypic and phylogenetic characteristics, the isolates were identified as Agrobacterium sp. LAD9, Achromobacter sp. GAD3 and Comamonas sp. GAD4, respectively. Batch tests were carried out to evaluate the growth and the ammonia removal patterns. The maximum growth rates as determined from the growth curve were 0.286, 0.228, and 0.433 h(-1) for LAD9, GAD3 and GAD4, respectively. The maximum aerobic nitrification-denitrification rate was achieved by the strain GAD4 of 0.381 mmol/l h, followed by LAD9 of 0.374 mmol/l h and GAD3 of 0.346 mmol/l h. Moreover, hydroxylamine oxidase and periplasmic nitrate reductase were successfully expressed in all the isolates. The relationship between the enzyme activities and the aerobic nitrification-denitrification rates revealed that hydroxylamine oxidation may be the rate-limiting step in the heterotrophic nitrification-aerobic denitrification process. The study results are of great significance to the wastewater treatment systems where simultaneous removal of carbon and nitrogen is desired.