Nitrite Conversion Rate Research Articles

Partial denitrification-anammox granular sludge domesticated from high-strength anammox granules and the high-efficiency performance in treating low-nitrogen wastewater

Partial denitrification (PD) is an effective approach to supply nitrite for the anaerobic ammonium oxidation (anammox) reaction, and the PD-anammox process can achieve nearly 100 % nitrogen removal when denitratation, denitritation and anammox processes are well balanced. However, most of the previous studies initiated the PD-anammox process by a mixed inoculation of denitrification and anammox sludges, leading to low anammox bacteria abundance and a risk of unstable operation in the long-term. To address this, this study used high-strength anammox granules as seed sludge for rapid PD-anammox process start-up. During the continuous operation, nitrogen removal efficiencies of 97.6 ± 1.6 % and 91.0 ± 2.0 % were attained under influent conditions of 159.4 ± 3.4 mg N/L and 78.1 ± 3.5 mg N/L, respectively. In addition, the nitrite conversion rate of the sludge reached 5.34 ± 0.37 g N/g VSS/d during the operation, and the anammox activity was stable at 0.27–0.41 g N/g VSS/d, indicating a synergistic PD-anammox relationship. Furthermore, PD bacteria were efficiently enriched in the reactor within a short period of time, with Thauera accounting for 7.6 % of the relative abundance. Notably, the abundances of dominating anammox bacteria, Ca. Brocadia and Ca. Kuenenia were 16.6 % and 4.9 %, respectively, which were among the highest of the reported PD-anammox processes. High anammox microbial abundance is conducive to ensuring the dominance and stability of the anammox reaction, enabling efficient nitrite conversion and nitrogen removal throughout the continuous operation. Finally, nitrogen removal pathways based on mass balance were proposed to clarify the fate of different nitrogen compounds in the PD-anammox system.

Evaluation of biofilter performance with alternative local biomedia in pilot scale recirculating aquaculture systems

Plastic is commonly used as biofilter media in recirculating aquaculture systems. Because plastic is relatively expensive and may erode and emit microplastics to the environment, efforts are being made to test and develop more sustainable materials. Five alternative locally available biofilter media were compared with commercial plastic media and evaluated in duplicate in 1 m3 two pilot scale Recirculation aquaculture system. Ammonium chloride and sodium nitrite were added to the systems for 4 weeks followed by stocking 20 kg of Nile tilapia in each system. Volumetric total ammonia nitrogen (TAN), nitrite and oxygen conversion rates were assessed for ten weeks. All biofilters with local media matured and reached full capacity after six weeks, while commercial plastic biomedia matured after seven weeks. This study found that the performance of commercial plastic biomedia was similar to performance of coconut shells in terms of volumetric TAN conversion rate (VTR), volumetric nitrite conversion rate (VNR) and volumetric oxygen conversion rate (VOCR). The highest VTR recorded in this study was 599 ± 15.8 g TAN/m3/d from coconut shells while the lowest was 343 ± 8.9 g TAN/m3/d from cattle horns. Biofilters with commercial plastic media had the highest VNR (704 ± 50.3 g NO2–N/m3/d) while media made of cattle horns was the lowest (457 ± 46.1 g NO2–N/m3/d). Biofilters containing coconut shells demonstrated the highest oxygen consumption around 3.0 g/m3/d and biofilters containing charcoal consumed less than 1.0 g/m3/d of oxygen. This study suggests that coconut shells can be used in place of plastic materials in simple recirculation aquaculture system biofiltration. This study also recommends further studies on comparing coconut shells with other biomedia and assessing its effects on water quality parameters and durability.

Fabrication of cadmium indium sulfide/cadmium sulfide/polyoxo-titanium cluster composite nanofibers with enhanced photocatalytic activity for nitrite degradation

Photocatalytic removal of nitrite is a convenient and green method. Photocatalytic technology has been limited, however, by its light absorption range and unsuitable conduction and valence bands, which affect the photocatalytic efficiency and nitrogen selectivity. In this work, we synthesized a cadmium indium sulfide/cadmium sulfide/polyoxo-titanium cluster composite nanometer photocatalyst with a visible light response, and further fixed the photocatalyst to fibers to form electrospun film. The samples were characterized using direct reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, Fourier-transform infrared spectroscopy, N2 adsorption–desorption isotherms, and the transient photocurrent response. The photocatalytic activity of the prepared photocatalyst was evaluated based on the transformation of nitrite under simulated sunlight. The photocatalytic results showed that the nitrite conversion rate was as high as 98% within 2 h and had about a 63% selectivity of nitrogen. The combination of CdS and Cdln2S4 better captured visible light and could be adjusted to an appropriate oxidation–reduction potential energy after loading with polyoxo-titanium clusters. Subsequently, the results of cycling experiments indicated that the Cdln2S4/CdS/polyoxo-titanium clusters composite nanofibers maintained a fairly consistent photocatalytic performance. The effects of electron and hole scavengers were investigated and the possible photocatalytic mechanism was elucidated by studying the products during the photocatalytic degradation.

A kinetics study on anammox bacteria with a disproportionate substrate concentration

AbstractBACKGROUNDAnaerobic ammonia oxidation, or anammox, is one of the most efficient techniques to dispose of sewage ammonia nitrogen and nitrite nitrogen within a reactor. Kinetics equations of anammox have been studied under proportions of ammonia nitrogen and nitrite nitrogen in the laboratory, however, in wastewater treatment, the reaction conditions are variable and unstable.RESULTSTwo strains of anammox bacteria, Candidatus Brocadia fulgida and Candidatus Brocadia caroliniensis, were identified by PCR and assigned the formal bacterial serial numbers: KR005667 and KR005668, respectively. The degradation curves of the two anammox bacteria were drawn by calculating the kinetics parameters using the Michaelis–Menten equation, and the ammonia oxidation rates, nitrite conversion rates and Km values of ammonia and nitrite were close to or identical to the known data range of the kinetics of anammox bacteria metabolism.CONCLUSIONA hypothesis regarding the role of extracellular polymeric substance (EPS) was proposed and the reaction mechanism of anammox bacteria was deduced in the case of a disproportionate substrate concentration. © 2017 Society of Chemical Industry

Change of Ammonium Nitrogen Removal Rate and Nitrite Conversion Rate according to Change of Retention Time using Recycle Water

Change of Ammonium Nitrogen Removal Rate and Nitrite Conversion Rate according to Change of Retention Time using Recycle Water

Correlation between nitrite accumulation and the concentration of AOB in a nitritation reactor

Nitritation is an innovative biological nitrogen removal method in wastewater, and it has the advantages of energy and economy. The correlation between a nitrite conversion rate and the gene copy numbers of ammonia oxidizing bacteria (AOB) in a nitritation reactor was examined to measure the effectiveness of removing a nitrogen content in a biological nitrogen removal process, using a biological process of nitritation. A laboratory scale reactor was prepared and operated for over a year, using digester supernatant to induce a stable nitritation, and to optimize the operational conditions by adjusting various operating factors. The relationship between operational results of nitritation reactor and the AOB gene copies was approximated through identification and quantitative analysis of AOB. A stable nitritation can be artificially led with the control of SRT, while treating anaerobic digester supernatant from MWTPs. And AOB gene copies showed a correlation with free ammonia (FA) inhibition and performance of nitritation, and AOB activity. Thus, AOB gene copies were found important when it comes to analyzing nitritation.

하수처리장 혐기 소화 상징액과 돈사폐수를 이용한 장기간에 걸친 실험실 규모 아질산화 반응 연구

본 연구에서는 혁신적인 질소 제거 방법인 아질산화 반응을 통해 혐기 소화 상징액 및 돈사폐수에 함유된 고농도의 질소를 제거하기 위한 실험실 규모 아질산화 반응조를 운전하였다. 약 970일의 장기간에 걸친 반응조 운전을 통하여 안정적인 아질산화 반응을 유도하고, 아질산화 반응의 유도 인자를 연구하였다. 연구 결과 혐기 소화 상징액 및 돈사폐수 모두 안정적인 아질산화 반응을 유도 할 수 있었다. 유입수의 pH, Alkalinity, COD 범위 내에서 아질산화 반응은 큰 영향을 받지 않는 것으로 나타났다. 반면 SRT의 경우 그 변화에 따라 아질산화율이 크게 변화하는 것으로 나타나 SRT는 아질산화 반응에 큰 영향을 미치는 것으로 나타났다. 또한 아질산화 반응은 암모니아성 질소 제거 반응에 비해 SRT에 더 민감하게 반응하는 것으로 판단된다. 본 논문의 연구 결과는 하수처리장에 아질산화 반응을 적용 시킬 시 중요한 자료로 사용될 수 있을 것으로 판단된다. In this study, the laboratory scale reactor was operated for high strength ammonium nitrogen in anaerobic digestion supernatant and piggery wastewater through nitritation that is an innovative process of nitrogen removal. From the laboratory scale reactor for about 970 days, a stable nitritation was induced, and the operation factor of induced was analysed nitritation. As a result, a stable nitritation could be successfully induced from anaerobic digestion supernatant and piggery wastewaters. It appeared that nitritation wasn't affected seriously within the range of pH, Alkalinity and COD in influent. In case of SRT, it found that nitrite conversion rate was changed according to SRT condition change, so it showed that SRT had effected on nitritation. In addition, compared to ammonium nitrogen removal, it clearly revealed that nitrite conversion rates more sensitive to SRT. The conclusion in this study, it could be used as an important data when applying nitritation to municipal wastewater treatment plants(MWTPs).

Effect of oxygen on the anaerobic methanotroph ‘Candidatus Methylomirabilis oxyfera’: kinetic and transcriptional analysis

'Candidatus Methylomirabilis oxyfera' is a denitrifying methanotroph that performs nitrite-dependent anaerobic methane oxidation through a newly discovered intra-aerobic pathway. In this study, we investigated the response of a M. oxyfera enrichment culture to oxygen. Addition of either 2% or 8% oxygen resulted in an instant decrease of methane and nitrite conversion rates. Oxygen exposure also led to a deviation in the nitrite to methane oxidation stoichiometry. Oxygen-uptake and inhibition studies with cell-free extracts displayed a change from cytochrome c to quinol as electron donor after exposure to oxygen. The change in global gene expression was monitored by deep sequencing of cDNA using Illumina technology. After 24 h of oxygen exposure, transcription levels of 1109 (out of 2303) genes changed significantly when compared with the anoxic period. Most of the genes encoding enzymes of the methane oxidation pathway were constitutively expressed. Genes from the denitrification pathway, with exception of one of the putative nitric oxide reductases, norZ2, were severely downregulated. The majority of known genes involved in the vital cellular functions, such as nucleic acid and protein biosynthesis and cell division processes, were downregulated. The alkyl hydroperoxide reductase, ahpC, and genes involved in the synthesis/repair of the iron-sulfur clusters were among the few upregulated genes. Further, transcription of the pmoCAB genes of aerobic methanotrophs present in the non-M. oxyfera community were triggered by the presence of oxygen. Our results show that oxygen-exposed cells of M. oxyfera were under oxidative stress and that in spite of its oxygenic capacity, exposure to microoxic conditions has an overall detrimental effect.

돈사 폐수의 아질산화 반응에 따른 유기물 성상 변화

안정적으로 유도되는 아질산화 반응을 통해 고농도의 질소를 함유한 돈사폐수 내 질소를 제거하고, 운전 조건 변화에 따른 아질산화 반응 변화를 분석하기 위해 실험실 규모 아질산화 반응조를 운전하였다. 운전 결과 아질산화 반응은 SRT에 민감하게 반응하는 것으로 나타났다. 또한 아질산화 반응조 유입 유출수에 함유된 유기물을 미생물 호흡률을 기초로 하여 분류하였다. 돈사폐수 유입수 내 함유된 유기물은 <TEX>$X_S$</TEX>성분이 가장 큰 부분을 차지하고 있었고, 혐기 소화를 거친 돈사폐수의 경우에는 <TEX>$S_I$</TEX>성분이 가장 큰 부분을 차지하고 있었다. 아질산화 반응조 유출수의 경우에는 암모니아성 질소 제거율과 아질산화율에 따라 유출수 내 유기물 성상이 변화하는 것을 파악하였다. 또한 다중 상관성 분석을 통하여 아질산화 반응을 거친 돈사폐수의 유기물 성상을 예측하는데 중요한 자료로 제공될 수 있을 것이다. To remove high strength ammonium nitrogen in piggery wastewater through stable nitritation and to analyze nitrite conversion rate under the change of operating condition, laboratory scale reactor was operated with stable nitritation process. As the result, it is observed that nitritation is sensitively affected by SRT. Also, the organic matters in the influent and effluent of laboratory scale reactor were classified according to microbial respirometric method. In the organic matter contained in the raw piggery wastewater, Xs is the most part. But effluent of anaerobic digester form piggery wastewater, <TEX>$S_I$</TEX> is the most part. In case of effluent of laboratory scale reactor, it is observed that the property of the organic matter fraction in the effluent is being changed according to ammonia removal rate and nitrite conversion rate. Through multiple correlation analysis, this finding also would be important data to predict the property of organic matters fraction in piggery wastewater through nitritation process.

Anaerobic ammonium oxidation by Nitrosomonas spp. and anammox bacteria in a sequencing batch reactor

A sequencing batch reactor (SBR) was inoculated with mixed nitrifying bacteria from an anoxic tank at the conventional activated sludge wastewater treatment plant in Nongkhaem, Bangkok, Thailand. This enriched nitrifying culture was maintained under anaerobic conditions using ammonium (NH 4 +) as an electron donor and nitrite (NO 2 −) as an electron acceptor. Autotrophic ammonium oxidizing bacteria survived under these conditions. The enrichment period for anammox culture was over 100 days. Both ammonium and nitrite conversion rates were proportional to the biomass of ammonium oxidizing bacteria; rates were 0.08 g N/g VSS/d and 0.05 g N/g VSS/d for ammonium and nitrite, respectively, in a culture maintained for 3 months at 42 mg N/L ammonium. The nitrogen transformation rate at a ratio of NH 4 +–N to NO 2 −–N of 1:1.38 was faster, and effluent nitrogen levels were lower, than at ratios of 1:0.671, 1:2.18, and 1:3.05. Fluorescent in situ hybridization (FISH) was used to identify specific autotrophic ammonium oxidizing bacteria ( Nitrosomonas spp., Candidatus Brocadia anammoxidans, and Candidatus Kuenenia stuttgartiensis). The ammonium oxidizing culture maintained at 42 mg N/L ammonium was enriched for Nitrosomonas spp. (30%) over Candidati B. anammoxidans and K. stuttgartiensis (2.1%) while the culture maintained at 210 mg N/L ammonium was dominated by Candidati B. anammoxidans and K. stuttgartiensis (85.6%). The specific nitrogen removal rate of anammox bacteria (0.6 g N/g anammox VSS/d) was significantly higher than that of ammonium oxidizing bacteria (0.4 g N/g Nitrosomonas VSS/d). Anammox bacteria removed up to 979 mg N/L/d of total nitrogen (ammonium:nitrite concentrations, 397:582 mg N/L). These results suggest significant promise of this approach for application to wastewater with high nitrogen but low carbon content, such as that found in Bangkok.

Effect of inorganic carbon on nitrite accumulation in an aerobic granule reactor

Pilot scale experiments were performed to evaluate the potential of nitrite type nitrification process with an airlift reactor and granular biomass. Initially, oxygen limitation was used as the main control parameter for accumulating nitrite in the effluent. After 30 d operation, the maximum nitrite conversion rate reached 2.5 kgNO2-N m(-3) d(-1), average diameter of the granule was 0.7 mm. Nitrite type reaction continued over 100 d, but nitrate formation increased after 150 d of operation. Once nitrate formation increased, oxygen limitation could not eliminate nitrite oxidising bacteria from granule. To overcome nitrate formation, laboratory scale batch experiments were conducted and it revealed a high concentration of inorganic carbon which had a significant effect on nitrite accumulation. Following this new concept, inorganic carbon was fed to the pilot scale reactor by changing pH adjustment reagent from NaOH to Na2CO3 and nitrite accumulation was recovered successfully without changing DO concentration. These results show that a high concentration of inorganic carbon is one of the control parameters for accumulating nitrite in biofilm nitrification system.

Operation of a nitrite-type airlift reactor at low DO concentration

Laboratory scale experiments were performed to evaluate the feasibility and potential of nitrite-type nitrification process with an airlift reactor having aerobic granular biomass. Oxygen limitation was selected as the main control parameter for inhibiting the growth of nitrite oxidizer and thus achieving only nitritation. To enhance granule formation, seeding of methanogenic anaerobic granules was used to serve as an initial carrier material. After 90 days of operation at low DO concentration of less than 1.0 mg/l, the maximum nitrite conversion rate of 2.6 g NO2-N/L/d could be achieved. During the continuing year-long stable operation, the granular mass of nitritation granules increased to about 15 g VSS/L with an average granule size of 0.7 mm. Nitrate-N concentration was observed to be below 10 mg/L during the whole operational period. From the results of the experiments, it is concluded that a granule-type airlift reactor with DO control is feasible for achieving stable nitritation.

Organic Matter and Hydraulic Loading Effects on Nitrification Performance in Fixed Film Biofilters with Different Filter Media

Nitrification performance of fixed film biofilters using coarse sand, loess bead, or styrofoam beads in biofilter columns 1 meter high and 30cm in diameter were studied at different hydraulic and organic matter loading rates. Synthetic wastewater was supplied to the culture tank in order to maintain desired TAN concentrations in inlet water to biofilters. All the biofilters were conditioned 5 months before start of sampling. TAN and conversion rates increased with an increase in the hydraulic loading rate (HLR). However, the improvement in biofilter performance was not linearly correlated to HLR in styrofoam bead filters. This is mainly due to the characteristics of the styrofoam beads used. TAN conversion rates of sand filters increased with the increase of HLR up to . per day. No increase in the TAN conversion rate was observed at the highest HLR since flooding on the media surface took place. HLR had a significant impact on the TAN conversion rates in loess bead filter up to the highest HLR tested (P per day than those without the addition of organic matter in styrofoam bead filters. The addition of glucose resulted in a reduction of the TAN conversion rate from 540 to 284g per day. No significant difference of TAN conversion rates between the two organic matter loading rates was found (p. per day, a great reduction of TAN conversion rates was observed in sand filters and loess bead filters. Clearly, organic matter can be one of the most Important Impacting factors on nitrification. conversion rates showed a similar trend for TAN. Based on the TAN and nitrite conversion rates, styrofoam beads showed the best performance among the three filter media tested. Also, the low gravity and price of styrofoam beads make the handling easier and more cost-effective for commercial application. The results obtained at the highest organic matter loading rates can be used in the biofilter design in recirculating aquaculture system.

Use of floating bead filters to recondition recirculating waters in warmwater aquaculture production systems

Floating bead filters (FBFs) are expandable granular filters that display a bioclarification behavior similar to sand filters. They function as a physical filtration device (or clarifier) by removing solids, while simultaneously encouraging the growth of bacteria that remove dissolved wastes from the water through biofiltration processes. Presently, there are two classes of FBFs that exist. Hydraulic and air washed units fall into the ‘gently washed’ category, which display reduced biofilm abrasion during backwashing and must be washed at a high frequency. Conversely, propeller-washed and paddle-washed filters inflict damage to a relatively heavy biofilm during backwashing, and are considered ‘aggressively washed’. FBFs capture solids through four identifiable mechanisms: straining, settling, interception, and adsorption. In the biofiltration mode, bead filters are classified as fixed film reactors, where each bead becomes coated with a thin film of bacteria that extracts nutrients from the recirculating water as it passes through the bed. In this paper the authors first establish application categories and parameters for recirculating system use, then give criterion for the sizing of recirculating system components in tabular form. Sizing variables for FBFs are normalized to the feed application rates, and the primary method for the sizing is based on a volumetric organic loading rate. Evaluation parameter equations are also given for comparison of bioclarifier performance. These equations include volumetric TAN conversion rate (VTR), the volumetric nitrite conversion rate (VNR), and the volumetric oxygen consumption rate of the bioclarifier (OCF).

Thermodynamic Model of Nitrification Kinetics

The ammonia oxidation rate of Nitrosomonas spp. is tested at various nitrite concentrations from 14 to 296 mg‐N/L in fresh water at 28.4 °C. The nitrite oxidation rate of Nitrobacter spp. is tested at various nitrate concentrations of 11–250 mg N/L. The oxidation rates of both bacteria are found to be linearly correlated to free‐energy changes (δG) with coefficients of determination of 0.841 and 0.934. It is shown that the Monod kinetic model with end‐product inhibition can be more simply and precisely modeled by a proposed thermodynamic model. At the same ratio of ammonia/nitrite and nitrite/nitrate over the range of 0.001–0.1, the ammonia conversion rate is about double that of the nitrite conversion rate. Management strategies can be devised to maximize the nitrite removal rate. Further, by knowing the thermodynamic model's parameters, the reactor's performance can be optimized during the peak loading period while minimizing nitrite pulses in the effluent.