Nitrite accumulation characteristics of high strength ammonia wastewater in an autotrophic nitrifying biofilm reactor

Selective nitrification was carried out to accumulate nitrite from high strength ammonia wastewater in an autotrophic nitrifying biofilm reactor. Nitrification efficiencies and nitrite accumulation characteristics were investigated at various operating conditions such as ammonium load, oxygen supply and free ammonia concentration. The biofilm reactor showed very stable nitrification efficiencies of more than 90% at up to 2 kg NH₄‐N m^?3 d^?1 and the nitrite content was maintained at around 95%. Inhibition by free ammonia on nitrite oxidizers seems to be the major factor for nitrite accumulation. Batch kinetic analyses of ammonium and nitrite oxidation showed that nitrite oxidation activity was selectively inhibited in the presence of free ammonia. However, the activity recovered quickly as the free ammonia concentration decreased below the threshold inhibition concentration. Examination of specific ammonia and nitrite oxidation activities and the most probable number indicated that the number of nitrite‐oxidizing microorganisms in the nitrite‐accumulating system was less than that in the normal nitrification system due to long‐term free ammonia inhibition of the nitrite oxidizers. The reduced population of nitrite oxidizers in the biofilm system was also responsible for the accumulation of nitrite in the biofilm reactor. © 2003 Society of Chemical Industry     

Sustained nitrite accumulation in a membrane‐assisted bioreactor (MBR) for the treatment of ammonium‐rich wastewater

A membrane‐assisted bioreactor (MBR) for sustained nitrite accumulation is presented, treating a synthetic wastewater with total ammonium nitrogen (TAN) concentrations of 1 kg N m^?3 at a hydraulic retention time down to 1 day. Complete biomass retention was obtained by microfiltration with submerged hollow fibre membranes. A membrane flux up to 189.5 dm³ day^?1 m^?2 could be maintained at a suction pressure below 100 kPa. Nitrification was effectively blocked at the nitrite stage (nitritation), and nitrate concentration was less than 29 g N m^?3. The rate of aeration was reduced to obtain a mixture of ammonium and nitrite, and after adjusting this rate the TAN/NO₂‐N ratio in the reactor effluent was kept around unity, making it suitable for further treatment by anaerobic oxidation of ammonium with nitrite. After increasing again the rate of aeration, complete nitrification to nitrate recovered after 11 days. It is suggested that nitrite accumulation resulted from a combination of factors. First, the dissolved oxygen (DO) concentration in the reactor was always limited with concentrations below 0.1 g DO m^?3, thereby limiting nitrification and preventing significant nitrate formation. The latter is attributed to the fact that ammonium‐oxidising bacteria cope better with low DO concentrations than nitrite oxidisers. Second, the MBR was operated at a high ammonia concentration of 7–54 g N m^?3, resulting in ammonia inhibition of the nitrite‐oxidising microorganisms. Third, a temperature of 35 °C was reported to yield a higher maximum growth rate for ammonium‐oxidising bacteria than for nitrite‐oxidising bacteria. Nitrite oxidisers were always present in the MBR but were out‐competed under the indicated process conditions, which is reflected in low concentrations of nitrate. Oxygen limitation was shown to be the most important factor to sustain nitrite accumulation. Nevertheless, nitritation was possible at ambient temperature (22–24 °C), lower ammonia concentration (<7 g N m^?3) and when using raw nitrogenous wastewater containing some biodegradable carbon. Overall, application of the MBR for nitritation was shown to be a reliable technology. © 2003 Society of Chemical Industry     

Carbon- and nitrogen-limited growth of Penicillium chrysogenum in fed batch culture: The optimal ammonium ion concentration for penicillin production

Fed batch culture was used to investigate penicillin production when the growth of Penicillium chrysogenum was limited by the supply of either sucrose and or ammonium ions. It was found that a ‘quasi steady state’ (in which the growth rate was virtually equal to the dilution rate) could be established under these conditions. Some metabolic parameters (specific sucrose consumption rate and growth yields) were dependent on the ratio of sucrose: ammonium ions in the feed medium over a range of ammonium concentrations both above and below the double substrate-limited point. The maximum specific rate of penicillin production required the supply of a large excess of ammonium ion, about five times the growth-limiting level. That is, the ratio of ammonium-nitrogen: sucrose, fed to the (sucrose-limited) culture, was 0.11 and the residual ammonium ion concentration was in excess of 18 mmol dm^?3, at a dry biomass concentration of 0.6%.     

Phenol biodegradation in a bioreactor considering different geometries and process parameters

In this study, a three-dimensional coupled lattice Boltzmann model and cellular automata platform was developed to simulate biofilm growth and phenol biodegradation as an effective and sustainable way to remove phenolic contaminants in aquatic systems. Two three-dimensional bioreactors with cubic or spherical obstacles at varying inlet phenol concentrations and flow velocities were examined. The results showed that the cubic-bioreactor had higher phenol reduction than the spheric-bioreactor due to the greater effects of cubic obstacles on flow patterns. The biofilm concentration in bioreactors decreased up to 36.4% as inlet velocity increased and in the spheric-bioreactor at the same inlet phenol concentration. The cubic-bioreactor had the highest normalized reduction rate of 1.194 at the lowest inlet phenol concentration, while the spheric-bioreactor had the lowest one of 0.871 at the highest inlet phenol concentration. The results proved the accuracy of the model to assess the performance of wastewater treatment bioreactors under different conditions.     

移动床生物膜反应器SHARON工艺半亚硝化特性

采用移动床生物膜反应器（MBBR）对城市垃圾渗滤液进行SHARON工艺研究。主要研究了该反应器的启动情况和氨氮浓度、溶解氧（DO）以及pH等因素对反应器半亚硝化效果的影响。结果表明,在控制HRT=1 d、温度30℃、DO=0.5～1.0 mg·L^-1、pH=7.5左右、无污泥回流等条件下,经过4周的运行,成功地选择培养出亚硝化型生物膜,实现了短程硝化。研究表明通过控制进水氨氮浓度、DO和pH,可以达到出水半亚硝化的处理效果。当进水氨氮浓度为500 mg·L^-1时,出水半亚硝化的控制条件是pH=7.0,DO=1.5 mg·L^-1;而在进水氨氮浓度为300 mg·L^-1时,控制pH=7.0,DO=1.0 mg·L^-1,出水也可实现半亚硝化。最大可能计数法（MPN）测定发现,亚硝化菌在数量上的绝对优势是反应器能始终保持高效稳定的亚硝氮积累的主要原因。     

Effects of free ammonia and dissolved oxygen on nitrification and nitrite accumulation in a biofilm airlift reactor

The purpose of this research is to find out the effects of free ammonia concentration and dissolved oxygen on nitrification and nitrite accumulation in a biofilm airlift reactor. Free ammonia seriously inhibited the activity of nitrite oxidizers at the concentration higher than 0.1 mg NH₃-N/L and it was very effective for nitrite accumulation. Dissolved oxygen limitation in the biofilm also caused nitrite accumulation. Long term inhibition decreased the growth rate for nitrite oxidizers, and ammonia oxidizers were the dominant nitrifiers in the wastewater nitrification. Selective accumulation of ammonia oxidizers in the biofilm could be another reason for nitrite accumulation. Free ammonia inhibited nitrite oxidizers immediately, and adaptation to free ammonia was not observed. Therefore, the optimum control of free ammonia and dissolved oxygen concentration is critical for nitrite accumulation and the strategy can be used for selective accumulation of ammonia oxidizers in a bioreactor system.     

Increased hydrazine during partial nitritation process in upflow air-lift reactor fed with supernatant of anaerobic digester effluent

The optimal balance of ammonium and nitrite is essential for successful operation of the subsequent anammox process. We conducted a partial nitritation experiment using an upflow air-lift reactor to provide operational parameters for achieving the optimal ratio of ammonium to nitrite, by feeding supernatant of anaerobic digester effluent, highnitrogen containing rejection water. Semi-continuous operation results show that HRT should be set between 15 and 17 hours to achieve the optimum ration of 1.3 of NO₂-N/NH₄-N. In the UAR, nitritation was the dominant reaction due to high concentration of ammonia and low biodegradable organics. The influent contained low concentrations of hydroxylamine and hydrazine. However, hydrazine increased during partial nitritation by ～60–130% although there was no potential anammox activity in the reactor. The partial nitritation process successfully provided the ratio of nitrogen species for the anammox reaction, and relived the nitrite restraint on the anammox activity by increasing hydrazine concentration.     

光合细菌生物膜反应器葡萄糖降解及产氢特性实验

对光合细菌生物膜制氢反应器在挂膜启动期间以及稳定运行时以葡萄糖为唯一底物的降解特性进行了实验研究,获得了光照强度、光波长、进口底物浓度、温度和底物溶液pH值等参数对生物膜光生物制氢反应器降解性能的影响规律。实验结果表明：在反应器挂膜期间,反应器葡萄糖消耗量随着反应器中填料表面的生物膜的生长逐渐趋于稳定。反应器挂膜启动完成后的降解效率随着底物浓度、光照强度、温度和底物溶液pH值的增加而增加,直到降解效率达到一个峰值后开始下降。光波长对反应器的降解效率也具有明显的影响。     

厌氧氨氧化反应的影响因素研究

以厌氧氨氧化活性污泥作为接种物,以无机盐培养液作为实验用水,考察了溶解氧、进水NO2--N与NH4＋-N的比值对厌氧氨氧化反应的影响。反应体系中硝酸盐的产生量随溶解氧浓度增加而增大,总氮去除率则随溶解氧浓度的增加而降低,除氧实验时出水NO3--N浓度平均为67.2mg/L,总氮去除率平均为73.9%;不除氧时出水NO3--N浓度平均为83.0mg/L,总氮去除率平均为67.8%;当进水NO2--N与NH4＋-N比值为1.16时,利于厌氧氨氧化反应的进行,总氮去除率为62.78%。     

Numerical and experimental study on the biofiltration of toluene vapor

We have solved both steady state and transient problems on the biofiltration of toluene vapor. The effect of inlet toluene concentration and inlet gas-flow rate on the removal rate of toluene and the elimination capacity of a lab-scale biofilter has been investigated. In this study, the effectiveness factor was a function of pollutant concentration. The dynamic solutions show good agreement with experimental results. At an inlet toluene concentration of 100 ppm, the diffusion of toluene into biofilm was obviously a rate determining step. Above 200 ppm, however, biofilm already showed full activity. The steady-state simulation confirmed that the change of elimination capacity obtained by increasing only inlet toluene concentration was the same as that obtained by increasing only flow rate of contaminated air. The maximum possible performance is about 20 g/m³h with no addition of nutrients.     

Nitrogen removal characteristics of heterotrophic nitrification-aerobic denitrification by Alcaligenes faecalis C16

Alcaligenes faecalis C16 was found to have the ability to heterotrophically nitrify and aerobical y denitrify. In order to further understand its nitrogen removal ability and mechanism, the growth and ammonium removal response were investigated at different C/N ratios and ammonium concentrations in the medium with citrate and acetate as carbon source separately. Furthermore, experiments of nitrogen sources, production of nitrogen gas and enzyme assay were conducted. Results show that the bacterium converts NH4+-N and produces NH2OH during the growing phase and nitrite accumulation is its distinct metabolic feature. A. faecalis C16 is able to tolerate not only high ammonium concentration but also high C/N ratio, and the ammonium tolerance is associated with carbon source and C/N ratio. The nitrogen balance under different conditions shows that approximately 28%–45%of the initial ammonium is assimilated into the cells, 44%–60%is denitrified and several percent is converted to nitrification products. A. faecalis C16 cannot utilize hydroxylamine, nitrite or nitrate as the sole nitrogen source for growth. However, nitrate can be used when ammonium is simultaneously present in the medium. A possible pathway for nitrogen removal by C16 is suggested. The preliminary enzyme assay provides more evidence for this nitrogen removal pathway.     

限氧条件下亚硝化的稳定运行及动力学

采用高氨氮人工配水和序批式反应器,在限氧(0.2～0.3mg/L)条件下,研究了进水氨氮负荷、游离氨和游离亚硝酸对氨氮转化率、亚硝化率和亚硝氮生成速率的影响及游离氨对氨氧化菌的基质抑制动力学。结果表明,在进水氨氮负荷逐步提升过程中,由于高浓度游离氨的抑制作用及负荷冲击的影响,亚硝化效果易出现波动,且负荷越高,亚硝化性能恢复的时间越长。反应系统最终可达到的氨氮容积负荷为3.60kg/(m³·d),亚硝氮生成速率为2.98kg/(m³·d),亚硝化率始终维持在85%左右。反应体系中较高的游离氨浓度(24.4～85.8mg/L)和低浓度溶解氧是维持亚硝化工艺稳定运行的主要因素。游离氨对氨氧化菌的抑制动力学符合Haldane模型,拟合得到最大氨氧化速率为6.71gN/(gVSS·d),游离氨半饱和常数和抑制常数分别为3.2mg/L和27.8mg/L。     

基于基质浓度的厌氧氨氧化工艺运行策略

考察了不同操作模式对厌氧氨氧化工艺性能的影响。采用高基质浓度运行厌氧氨氧化反应器,设置出水回流（回流比R为1.07）,最大基质氮去除速率为3.78 kg·m^-3·d^-1;采用低基质浓度运行厌氧氨氧化反应器,不设出水回流,最大基质氮去除速率可达25.04 kg·m^-3·d^-1;两者的最大基质氮去除速率相差6.62倍,低基质浓度操作模式明显优于高基质浓度操作模式。亚硝酸盐的毒性强于氨,反应器运行中可控制氨氮适当过量,同时应根据反应器对亚硝酸盐的转化能力来控制亚硝酸盐负荷,以避免亚硝酸盐过载所致的抑制作用。在处理高浓度含氮废水时,可采用出水回流来缓解基质抑制,也可配水稀释,使NO^-₂-N浓度低于临界抑制浓度。     

Monitoring and control of biogas desulphurization using oxidation reduction potential under denitrifiying conditions

BACKGROUND: Hydrogen sulphide (H₂S) present in biogas can be oxidized to elemental sulphur (S₀) or sulphate (SO₄^2?) using nitrate and nitrite. Both nitrate and nitrite are normally available in most wastewater treatment plants and could be used to oxidize H₂S depending on the molar loading ratio of wastewater and biogas. A control approach is required in order to minimize the fluctuations in inlet and outlet H₂S concentrations in biogas, and the oxidation potential of the wastewater used. RESULTS: A control scheme has been developed for biogas desulphurization using oxidation reduction potential under industrial conditions. The redox potential was maintained at about + 50 to + 100 mV in the activated sludge plant to monitor the performance of the nitrification process. The redox potential in the bioscrubber was related to sulphide removal from biogas. More than 90% of the hydrogen sulphide was removed from the biogas. CONCLUSION: The oxidation reduction potential can be used as a key parameter for monitoring and controlling biogas cleaning. Fluctuations of the inlet H₂S concentration in biogas can be compensated by manipulating the flowrates of wastewater used in order to achieve consistent and desired H₂S concentrations in treated biogas. Copyright © 2011 Society of Chemical Industry     

好氧氨氧化生物膜内氧传质特性及影响因素

采用理论计算和实验测试相结合的方法,对流化床反应器中好氧氨氧化生物膜内溶解氧传质特性及影响因素进行了分析。建立了综合考虑反应-扩散-对流作用的一维模型,计算结果表明:溶解氧所能到达的生物膜厚度受渗流速度等因素的影响;增大渗流速度、扩散系数和进水底物浓度均可以提高膜内溶解氧浓度的最大值。建立了序批式流化床生物膜反应器,获得了高于80%的氨氮转化率,实现了好氧氨氧化生物膜的成功挂膜,获得生物膜厚度为0.1～0.3 mm,采用微电极测试了膜内溶解氧浓度。实验测试和模型计算结果表明,溶氧浓度沿生物膜厚度方向均呈现出抛物线形的不均匀下降趋势,且当扩散系数为2.2×10–4 m2/s和渗流速度为6.0 mm/s时,测试结果和计算数值具有较好的吻合度。     

缺氧FNA对氨氧化菌和亚硝酸盐氧化菌的选择性抑菌效应

为了研究缺氧条件下游离亚硝酸（FNA）对氨氧化菌（AOB）和亚硝酸盐氧化菌（NOB）的选择性抑菌效应,通过批次试验考察活性污泥经缺氧FNA（0.27 mg HNO₂^--N·L^-1）处理6 h后,其氨氧化速率与亚硝酸盐氧化速率的变化及AOB和NOB活性恢复情况。结果表明：经缺氧FNA处理的活性污泥,NOB活性下降83.57%,而AOB的活性仅下降22.34%。此污泥在正常条件下运行34个周期后,NOB的活性仍未得到恢复,且硝化过程中亚硝酸盐积累率逐渐增加,最后稳定在90%以上。典型周期内氮化合物浓度变化研究表明,即使在过曝气2 h的条件下,亚硝酸盐积累并未遭到破坏。上述试验结果表明基于缺氧FNA选择性抑菌效应有望稳定实现城市污水短程硝化,为城市污水短程硝化厌氧氨氧化提供基础。     

亚硝酸盐对厌氧产酸耦合反硝化工艺的影响

以木薯酒精废水为碳源,通过批次实验研究了亚硝酸盐对厌氧产酸耦合反硝化系统的影响。结果表明,投加600 mg·L^-1 后的最终产酸量与空白反应器相差不大,但是投加相同浓度亚硝酸盐后产酸受到严重抑 制,最终产酸量仅为空白反应器的1.8%。而硝酸盐还原过程中厌氧产酸受到抑制可能是由于反硝化中间产物亚硝酸盐的存在,低投加量的亚硝酸盐即可对厌氧产酸产生强烈的抑制作用并具有持续性,且对各产酸组分的影响作用：正丁酸>丙酸>乙酸。随着 的降低,亚硝酸盐的还原率由74.9%降低至22.2%。当游离亚硝酸（free nitrous acid, FNA）浓度为0.05 mg·L^-1以上时,亚硝酸盐还原几乎被完全抑制（90%以上）。此外,随着 的增加,反硝化所占的比例逐渐减小,而DNRA过程（dissimilatory nitrate reduction to ammonium,异化硝酸盐还原为铵）逐渐占优势。     

Autotrophic biological nitrogen removal from saline wastewater under low DO

BACKGROUND: This study was conducted to investigate the feasibility and performance of nitrogen removal through the complete autotrophic nitrogen removal over nitrite (CANON) process for saline wastewater in a continuous reactor, and to characterize microorganisms in the sludge from the reactor using DNA‐based techniques. RESULTS: The nitrogen removal experiment in the reactor was operated over five phases for 286 days treating a synthetic sewage of 1.2% salinity at 21–25 °C. At dissolved oxygen (DO) concentrations of 0.5–1.0 mg L^?1 and in the presence of glucose, NO₂^? was accumulated, indicating the activity of ammonia‐oxidizing bacteria (AOB). At DO concentration of 0.5 mg L^?1 without organic substrate, the anaerobic ammonium oxidation (Anammox) process was the major pathway responsible for nitrogen removal, with a total nitrogen removal of 70% and an ammonium conversion efficiency of 96%. A maximum ammonium removal rate of 0.57 kg‐N m^?3 d^?1 was achieved during the experimental period. The concentrations of AOB and Anammox bacteria were monitored over the operation of reactor using quantitative real‐time polymerase chain reaction (qRT‐PCR). CONCLUSION: In this study, autotrophic nitrogen removal process was achieved under salinity condition in a one‐reactor system. An over 100 fold increase of AOB was found due to the increased supply of ammonium at the beginning, then AOB concentration decreased temporarily in correspondence with the decreased DO, and the AOB resumed their concentration at the last phase. The Anammox bacteria abundance was about 150 fold higher than that at the beginning, indicating the successful enrichment of Anammox bacteria in the reactor. Copyright © 2010 Society of Chemical Industry     

The effect of nitrogen on root growth and nutrient uptake of young tea plants (Camellia sinensis L.) grown in sand culture

Root growth and nutrient uptake of a tea clone were studied in a sand culture experiment using ammonium sulphate, ammonium nitrate and urea each at 35, 70 and 105 ppm N. Results show that increasing N levels regardless of forms increased the proportion of white roots and decreased brown root weight.As to the composition of the aerial parts (plant tops) enhanced N supply increased concentrations of Ca and NO₃, while K and H₂PO₄ concentration decreased. Use of ammonium sulphate increased the sulphate levels. Increased N level through urea increased Cl concentration, while the reverse was true with both ammonium sulphate and ammonium nitrate. Concentrations of Mg and Na remained unaffected by N fertilization, though the former tended to increase with increased level of N irrespective of forms. The organic acid concentration measured as the difference of sum equivalents of cations and that of anions increased with an increase supply of N in any of the three forms.The white:brown root ratio was correlated positively with growth, Ca:K ratio and organic acid content of plant tops.     

Influence of Salt Concentration and Nitrogen Source on Growth and Productivity of Anaerobiosprillum succiniciproducens

The influence of salts and organic nitrogen sources on the growth and acid production of Anaerobiosprillum succiniciproducens was studied. In shake flask experiments, maximum specific growth rate and acid production increased by reducing the salt concentration. Additionally, growth and acid production were affected by the type of organic nitrogen source and by the pH value. Through the optimization, optical density could be increased from 1.9 ± 0.1 to 3.0 ± 0.1 and succinic acid concentration from 4.0 ± 0.2 to 6.5 ± 0.1 g L^–1. In fed‐batch experiments with the optimized medium, the final succinic acid concentration was 25.6 % higher compared to the reference. Also, the succinic acid/acetic acid ratio was affected by the optimization. The experimental results indicated that A. succiniciproducens consumed only organic nitrogen sources because growth and productivity were not influenced by the addition of ammonium sulfate.