Determination of the nitrous oxide emission potential of deammonification under anoxic conditions

Various studies have been performed to determine nitrous oxide (N2O) emissions from conventional biological nitrogen removal processes in wastewater treatment like nitrification and denitrification in the main stream. However, with respect to the overall emissions of a wastewater treatment plant, part-stream treatment for high-strength wastewater (e.g., sludge liquor) is also expected to hold a significant emission potential because of high concentrations and extreme boundary conditions. This paper presents results from a laboratory-scale study on nitrous oxide production by biomass from a deammonification process (nitritation + anammox) under anoxic conditions. It was discovered that N2O formation results from incomplete endogenous denitrification rather than anammox and is dependent on substrate availability. Based on direct measurements of the dissolved N2O concentrations in a sequencing batch reactor, the dynamic behavior of N2O production is characterized in more detail. The results show that, during anoxic conditions, the N2O emission potential of deammonification is significantly lower than from conventional denitrification.     

Nitrogen removal via the nitrite pathway during wastewater co-treatment with ammonia-rich landfill leachates in a sequencing batch reactor

The biological treatment of ammonia-rich landfill leachates due to an inadequate C to N ratio requires expensive supplementation of carbon from an external carbon source. In an effort to reduce treatment costs, the objective of the study was to determine the feasibility of nitrogen removal via the nitrite pathway during landfill leachate co-treatment with municipal wastewater. Initially, the laboratory-scale sequencing batch reactor (SBR) was inoculated with nitrifying activated sludge and fed only raw municipal wastewater (RWW) during a start-up period of 9 weeks. Then, in the co-treatment period, consisting of the next 17 weeks, the system was fed a mixture of RWW and an increasing quantity of landfill leachates (from 1 to 10 % by volume). The results indicate that landfill leachate addition of up to 10 % (by volume) influenced the effluent quality, except for BOD₅. During the experiment, a positive correlation (r ²?=?0.908) between ammonia load in the influent and nitrite in the effluent was observed, suggesting that the second step of nitrification was partially inhibited. The partial nitrification (PN) was also confirmed by fluorescence in situ hybridisation (FISH) analysis of nitrifying bacteria. Nitrogen removal via the nitrite pathway was observed when the oxygen concentration ranged from 0.5 to 1.5 mg O₂/dm³ and free ammonia (FA) ranged from 2.01 to 35.86 mg N-NH₃/dm³ in the aerobic phase. Increasing ammonia load in wastewater influent was also correlated with an increasing amount of total nitrogen (TN) in the effluent, which suggested insufficient amounts of assimilable organic carbon to complete denitrification. Because nitrogen removal via the nitrite pathway is beneficial for carbon-limited and highly ammonia-loaded mixtures, obtaining PN can lead to a reduction in the external carbon source needed to support denitrification.     

Effect of biochar on nitrous oxide emission and its potential mechanisms

Extensive use of biochar to mitigate nitrous oxide (N₂O) emission is limited by the lack of understanding on the exact mechanisms altering N₂O emission from biochar-amended soil. Biochars produced from rice straw and dairy manure at 350 and 500 °C by oxygen-limited pyrolysis were used to investigate their influence on N₂O emission. A quadratic effect of biochar levels was observed on the N₂O emissions. The potential mechanisms were explored by terminal restriction fragment length polymorphism (T-RFLP) and real-time polymerase chain reaction (qPCR). A lower relative abundance of bacteria, which included ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), was observed at 4% biochar application rate. Reduced copy numbers of the ammonia monooxygenase gene amoA and the nitrite reductase gene nirS coincided with decreased N₂O emissions. Therefore, biochar may potentially alter N₂O emission by affecting ammonia-oxidizing and denitrification bacteria, which is determined by the application rate of biochar in soil.

Implications:Biochar research has received increased interest in recent years because of the potential beneficial effects of biochar on soil properties. Recent research shows that biochar can alter the rates of nitrogen cycling in soil systems by influencing nitrification and denitrification, which are key sources of the greenhouse gas nitrous oxide (N₂O). However, there are still some controversial data. The purpose of this research was to (1) examine how applications of different dose of biochar to soil affect emission of N₂O and (2) improve the understanding of the underlying mechanisms.     

污水硝化过程中N2O逸出控制的理论与实践

在污水生物脱氮工艺中,硝化过程是由自养硝化菌和异养硝化菌共同完成的.2类细菌的N2O生成机理及逸出量与系统中溶解氧的高低密切相关.了解硝化系统中的典型菌种自养菌Nitrosomonas europaea和异养菌Alcaligenesfaecalis生成N2O的机理是控制硝化过程中N2O逸出的理论基础,通过筛选优势菌种构建同步硝化-反硝化作用则是控制N2O逸出的新途径.     

Treatment efficiency and stoichiometry of a high-strength graywater.

The transit mission wastewater may represent a future graywater, in which toilet waste is separated from other household waste streams, and dilution water is minimal. A loading rate study indicated that denitrification is stoichiometrically limited, and nitrification was kinetically limited. Denitrification stoichiometry was developed by deriving hypothetical molecular formulas of organic carbon inputs to be represented by the relative proportions of carbon, hydrogen, oxygen, and nitrogen. The derived stoichiometry was validated against experimental data by adjusting the values of fe and fs and multiplying the total dissolved organic carbon loss across the system by the overall R equation and then comparing the total nitrogen removed in the reaction to experimentally observed total nitrogen removal. The nitrification stoichiometry was similarly validated by multiplying the R equation by the ammonium-nitrogen removed and then comparing the NO(x)-N formed in the equation to actual NO(x)-N production values. The fs values for the denitrifying and nitrifying bacteria were 0.33 and 0.15, respectively.     

Kinetics of ammonium removal with suspended and immobilized nitrifying bacteria in different reactor systems

The degradation of ammonium by free and immobilized bacteria in different reactor systems was investigated. It was found that the start-up of a nitrifying system is enhanced if a reservoir of immobilized bacteria is present. It was also found that in a single stage system with suspended nitrifying bacteria a stable ammonium removal > 95 % could be established up to an influent ammonium concentration of 1000 mg/1 and a volumetric loading rate (VLR) of 2.3 kg NH₄⁺ m⁻³ d⁻¹. The oxygen uptake rate (OUR) due to nitrification processes was greatly enhanced with increasing volumetric loading rates. Using nitrifying bacteria immobilized on Siran material it was demonstrated that the ammonium degradation rate was directly proportional to the initial ammonium concentration.     

废水的硝化作用

硝化作用是废水生物脱氮中的关键。本文介绍了硝化作用的生化反应、硝化细菌的类群、硝化反应动力学和影响硝化作用的主要环境因子：溶解氧、ｐＨ、温度和毒物。     

Chemical and microbial hypotheses explaining the effect of wastewater treatment plant discharges on the nitrifying communities in freshwater sediment

Nitrification is a microbial key step of the nitrogen cycle, which performs the oxidation of ammonium to nitrate, via nitrite. In aquatic environments, it mainly takes place in the sediment or is associated with suspended particles. Wastewater treatment plant (WTP) discharges in rivers may disrupt sediment nitrification: this impact is related to nitrogen inputs (mainly NH(4)(+) and organic nitrogen) but could also depend on the nitrifying bacteria inputs which have been proved to survive downstream WTP discharge points. The aim of the present study was to assess the effect of NH(4)(+) and nitrifying bacteria inputs on the two steps of nitrification in freshwater sediments.To avoid natural sites constraints and to control the main environmental parameters, we used microcosms to simulate a river receiving different types of WTP discharges. These microcosms were composed of five glass dual-walls reactors (6 l) containing sediment and continuously filled (controlled flow) with river water and WTP effluent. Two types of effluents were tested: a non-nitrified one (high NH(4)(+) input, very few nitrifying bacteria) and a nitrified one (low NH(4)(+) input, more nitrifying bacteria), at different effluent/freshwater ratios (0/100, 20/80, 40/60 and 80/20). Changes in the ammonium- and nitrite-oxidizing communities were assessed by the Most Probable Number method, and changes in potential ammonium-oxidizing activity and potential nitrite-oxidizing activity were determined by incubations with specific inhibitors (sodium chlorate and allylthiourea).In most of the cases the presence of effluent induced significant changes of the nitrifying bacteria densities and potential activities in the sediment. This effect indicates generally a loss of specific potential activity and in most of the time is significant for a high effluent/river water ratio (40% to 80%). In our experimental conditions and in the case of a large WTP discharge, the nitrifying potential in freshwater sediments could thus be significantly modified.     

呼吸法测定硝化菌产率系数实验研究

基于硝化过程中合成代谢和能量代谢耦合原理,分析硝化过程中的电子流,建立自养硝化菌细胞生长与氨氮氧化耗氧量之间的关系。采用间歇实验方法,通过电解质呼吸仪测定硝化过程的累积耗氧量和耗氧速率,使用M ann-Ken-dell趋势检验方法确定实验中硝化菌进入内源呼吸的时刻以及内源呼吸过程中的耗氧速率,估算出氨氮氧化的耗氧量。计算结果表明本实验中硝化菌产率系数为0.2345±0.0115 mg COD/mg NH4+-N。     

低COD/N-NH_4比废水的同时硝化反硝化生物处理策略

从生化反应计量学出发 ,提出了对低 COD/ N- NH4比废水可以通过控制营养配比、调控溶解氧浓度和控制生物硝化及生物反硝化 ,经过 NO- 2 途径进行同时硝化反硝化的生物处理策略。对香港低 COD/ N- NH4比的垃圾渗漏水用同时硝化反硝化处理的成功实例进行了讨论     

SFBR工艺顺序进行硝化和反硝化的动力学研究

采用序半连续式反应器(sequencing fed-batch reactor,简称SFBR)对人工合成废水顺序地进行硝化和反硝化动力学进行了研究.硝化和反硝化所用微生物为活性污泥.反应器在不同的操作条件进行操作,获得了用于确定动力学常数的数据;获得动力学参数um=0.05 h-1,KNO=2.0 mg/L,y=0.47 mg X/mg N,a=0.001 h-1.类似地确定了反硝化动力学参数kD=0.01 h-1和KD,NO=0.4 mg/L.在一定范围内硝化和反硝化速率随着氨浓度和硝酸盐浓度的增加而增加.实验数据表明,硝化和反硝化的动力学符合Monod动力学方程.     

短程硝化—厌氧氨氧化组合工艺在脱氮领域的研究进展

基于全程硝化反硝化的传统生物脱氮工艺在硝化过程中需要大量氧气供应,反硝化过程需要有机物作为碳源,存在能耗与药耗过大的问题.为了降低废水脱氮的成本,短程硝化(PN)—厌氧氨氧化(ANAMMOX)组合工艺(PNA工艺)得到了高速发展.综述了PNA工艺的影响因素,重点介绍了4种基于PN与ANAMMOX原理开发的衍生PNA工艺...     

好氧颗粒污泥处理高浓度氨氮废水的研究

在不同接种源污泥颗粒化过程中污泥理化性状对比研究的基础上,采用成熟好氧颗粒污泥处理高浓度氨氮废水,对其脱氮行为以及不同C/N条件下好氧颗粒污泥微生物的比耗氧速率、好氧颗粒污泥对氨氮的比降解速率随时间的变化等进行了研究.实验结果表明,在进水氨氮质量浓度较高(480 mg/L)、温度30℃左右的条件下,稳定运行15 d,氨氮的去除率维持在85%左右;进水氨氮的浓度越高,随着微生物对环境的逐渐适应,硝化菌的活性也逐步增加;随着进水氨氮浓度的提高,好氧颗粒污泥对氨氮的比降解速率也逐渐上升.     

Influence of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on ammonia-oxidizing bacteria and archaea in rhizosphere and bulk soil

In agricultural plant production nitrification inhibitors like 3,4-dimethylpyrazole phosphate (DMPP) are used to retard the microbial nitrification process of fertilized ammonium to enhance the nitrogen supply for cultivated crops and to reduce nitrogen losses from the production system. Besides the well-known ammonia-oxidizing bacteria (AOB) it is known for a few years that also ammonia-oxidizing archaea (AOA) are able to perform the first step in nitrification, hence being also a target for a nitrification inhibitor. However, so far no information are available concerning the effectiveness of DMPP and its extent towards AOB and AOA, neither in bulk soil nor in the root-rhizosphere complex. We investigated in a field experiment performed according to agricultural practice the effect of DMPP on the abundance of AOB and AOA two, four and eight weeks after fertilization. We observed impaired abundances of AOB but not of AOA in both soil compartments that were still visible eight weeks after application, possibly indicating a reduced effectiveness of the nitrification inhibitor in our study.     

Microbiology of high-sodium-nitrite-wastewater treatment

A microbiological study conducted as a complement to kinetic studies of biological denitrification as a process for treating high-sodium-nitrite wastewaters generated from ship-boiler-tube cleaning is described. The number, genera, and denitrifying capabilities of the organisms inhabiting anoxic suspended-growth reactors used in the kinetic studies were evaluated for four experimental phases. The results regarding the enumeration of bacteria supported the findings of the kinetic studies as follows: (i) the better nitrite-removal efficiencies observed in the nitrification/denitrification system as compared with direct denitrification were confirmed by the presence of larger populations of organisms capable of completely reducing nitrate or nitrite; (ii) the presence of metals in concentrations associated with boiler-tube wastewater did not affect removal performance in the nitrification/denitrification systems, nor did it affect the density of complete denitrifiers; (iii) increasing sludge ages resulted in increasing nitrite-removal efficiencies as well as populations of complete denitrifiers; and (iv) a decrease in nitrate-removal efficiencies when the actual wastewater was introduced to a system that had been acclimated to the synthetic wastewater coincided with a reduction in the number of complete denitrifiers. Regarding the types of organisms found in this study, denitrifying strains of Alcaligenes and Pseudomonas were always present in the anoxic reactors along with other denitrifying and non-denitrifying bacteria of the same genera, or other genera such as Acinetobacter and Flavobacterium. However, members of the genus Alcaligenes were the only complete denitrifiers found in the anoxic reactors, and hence they are likely to play a key role in the denitrification process.     

Feasibility of a membrane-aerated biofilm reactor to achieve single-stage autotrophic nitrogen removal based on Anammox

A laboratory-scale membrane-aerated biofilm bioreactor (MABR) equipped with non-woven fabrics support around the gas-permeable carbon tube was developed for single-stage autotrophic nitrogen removal based on partial nitrification and anaerobic ammonium oxidization. This reactor allowed air to be supplied through the microporous carbon tube wall to the biofilm that was supported by non-woven fabrics. The partial nitrification and consumption of dissolved oxygen occurred in the inner layer and Anammox in the anoxic outer layer of the non-woven fabrics, thus realizing autotrophic nitrogen removal in a single reactor. After 116d of operation, the maximal nitrogen removal of 0.77kgNm(-3)d(-1) at a volumetric ammonium loading rate of 0.87kgNm(-3)d(-1) was achieved. The spatial profiles of the ammonia-oxidizing bacteria and Anammox bacteria were evaluated by fluorescence in situ hybridization. This study demonstrated that MABR was a very suitable experimental set-up for the operation of the single-stage autotrophic nitrogen removal process.     

同步硝化反硝化工艺中DO浓度对N2O产生量的影响

采用序批式生物膜反应器（SBBR）,在连续曝气全程好氧的运行条件下,考察不同溶解氧浓度对同步硝化反硝化脱氮性能及N2O产量的影响。控制溶解氧浓度恒定在1、2、2.5和3 mg/L。结果表明,DO为2 mg/L和2.5 mg/L时,氨氮去除率分别为97.9%和98.5%,同步硝化反硝化率均为99%。DO为2 mg/L时,系统中N2O产生量最低,为0.423 mg/L,占氨氮去除量的1.4%;DO为3 mg/L时N2O的产生量最高,为2.01 mg/L,是DO为2 mg/L时的4.75倍。系统中亚硝酸盐的存在可能是高溶解氧条件下N2O产量增加的主要原因,同步过程中没有NOx-的积累即稳定的SND系统有利于降低生物脱氮过程中N2O的产生量。     

生物沸石球强化吸附氨氮废水的动力学研究

用一种具有多孔结构特征的沸石球作为载体固定化硝化细菌强化吸附氨氮废水。结果表明,沸石球能快速固定化硝化细菌,吸附动力学表明150 min对氨氮吸附容量达到2.816 mg/g,而且还有继续增加的趋势。假二级动力学方程和Elovich模型的精确拟合说明,生物沸石球对氨氮的吸附过程可能是非均相扩散起作用及以化学吸附反应为主的复杂转化过程。扩散拟合结果表明,氨氮在生物沸石球的吸附是以液膜扩散和颗粒内扩散为吸附速率的控制步骤,活性的硝化细菌对氨氮的硝化使氨氮在微孔的吸附得到了强化。     

A/O1/H/O2工艺处理焦化废水硝化过程的实现及其抑制

针对焦化废水中的有毒污染物会对敏感易受干扰的硝化细菌产生不利影响从而破坏硝化过程稳定性的现象,采用A/O1/H/O2工艺处理焦化废水的实际工程为研究对象,根据工程运行的水质监测数据分析,发现几种主要污染物的浓度变化会对二级好氧段的硝化过程产生抑制影响。序批式毒性抑制实验结果表明,苯酚、硫氰化物和喹啉对硝化过程具有毒性抑制作用,半抑制浓度EC50分别为34.26、278.5和73.24 mg/L。当二级好氧工艺段运行正常时（C/N约4.3/1,pH8～8.5,DO 4～4.5 mg/L）,出水氨氮浓度可低于5 mg/L,是由于焦化废水经厌氧/好氧/水解工艺后毒物浓度大幅下降,毒性得到削减,表明焦化废水生物处理A/O1/H/O2组合流化床工艺具有较强抵抗毒物抑制并实现高效的硝化作用。     

一株高效异养硝化-好氧反硝化菌的分离鉴定及脱氮性能

从经驯化的污泥中筛选出一株异养硝化-好氧反硝化细菌，编号为TN-05，通过形态学特征观察，生理生化特征试验和核酸序列分析鉴定其为门多萨假单胞菌（pseudomonasmendocina）。同时对其进行脱氮性能研究，结果表明，TN-05具有较好的异养硝化能力，菌株在培养至48h时对总氮和氨氮去除率均能达95％以上。通过反硝化能力验证实验发现，菌株对NO3-N和N0f—N也分别具有较好的去除效率。将菌株应用于人工合成废水中，发现对废水中氨氮优先利用并能在24h时使去除率接近100％，对硝态氮和亚硝态氮也具有一定的去除效率。因此，菌株TN-05是一株同时具备异养硝化和好氧反硝化能力的高效菌株。