Volatile fatty acids carbon source for biological denitrification

In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrification rate than single VFA C-source consisting of them. When VFA were used as carbon source, consumed carbon quantity for denitrification was closed to 1. 07 mg VFA-C/mg NO-N. About 20% of the applied C/N was used for assimilative purposes. As rising up influent C/N by increasing the C load ,the sludge yield YN increased. The part of carbon consumption increased and the effluent oxidized nitrogen decreased. At pH 7. 5, 25℃ and sludge yield 0.72 mg VSS/mg NO-N, the calculated influent VFA-C /NO critical value was 1. 43 for complete denitrification.

Simultaneous nitrification and denitrification in step feeding biological nitrogen removal process

The simultaneous nitrification and denitrification in step-feeding biological nitrogen removal process were investigated under different influent substrate concentrations and aeration flow rates. Biological occurrence of simultaneous nitrification and denitrification was verified in the aspect of nitrogen mass balance and alkalinity. The experimental results also showed that there was a distinct linear relationship between simultaneous nitrification and denitrification and DO concentration under the conditions of low and high aeration flow rate. In each experimental run the floc sizes of activated sludge were also measured and the results showed that simultaneous nitrification and denitrification could occur with very small size of floc.

Performance of simultaneous nitrification and denitrification in lateral flow biological aerated filter

A new wastewater treatment facility—lateral flow biological aerated filter (LBAF) was developed aiming at solving energy consumption and operational problems in wastewater treatment facilities in small towns. It has the function of nitrification and removing organic substrate. In this study, we focused on the denitrification performance of LBAF and its possible mechanism under thorough aeration. We identified the existence of simultaneous nitrification and denitrification (SND) by analyzing nitrogenous compounds along the flow path of LBAF and supportive microbial microscopy, and studied the effects of air/water ratio and hydraulic loading on the performance of nitrogen removal and on SND in LBAF to find out the optimal operation condition. It is found that for saving operation cost, aeration can be reduced to some degree that allows desirable removal efficiency of pollutants, and the optimal air/water ratio is 10:1. Hydraulic loading less than 0.43 m h?1 hardly affects the nitrification and denitrification performance; whereas higher hydraulic loading is unfavorable to both nitrification and denitrification, far more unfavorable to denitrification than to nitrification.

Biological Nutrient Removal in a Full Scale Anoxic/Anaerobic/Aerobic/ Pre-anoxic-MBR Plant for Low C/N Ratio Municipal Wastewater Treatment

A novel full scale modified A2O （anoxic/anaerobic/aerobic/pre-anoxic）-membrane bioreactor （MBR） plant combined with the step feed strategy was operated to improve the biological nutrient removal （BNR） from low C/N ratio municipal wastewater in Southern China. Transformation of organic carbon, nitrogen and phosphorus, and membrane fouling were investigated. Experimental results for over four months demonstrated good efficiencies for chemical oxygen demand （COD） and NH4^＋-N removal, with average values higher than 84.5%and 98.1%, re-spectively. A relatively higher total nitrogen （TN） removal efficiency （52.1%） was also obtained at low C/N ratio of 3.82, contributed by the configuration modification （anoxic zone before anaerobic zone） and the step feed with a distribution ratio of 1：1. Addition of sodium acetate into the anoxic zone as the external carbon source, with a theoretical amount of 31.3 mg COD per liter in influent, enhanced denitrification and the TN removal efficiency in-creased to 74.9%. Moreover, the total phosphate （TP） removal efficiency increased by 18.0%. It is suggested that the external carbon source is needed to improve the BNR performance in treating low C/N ratio municipal waste-water in the modified A^2O-MBR process.

Enhanced Nutrient Removal with Upflow Biological Aerated Filter for Reclaimed Water

A two-stage upflow biological aerated filter was designed as an advanced treatment process to optimize the operating parameters and study the correlative factors influencing the efficiency of nitrification, denitrification and phosphorus removal. The experimental results showed that the final effluent of the two-stage upflow biofilter process operated in series could meet the stringent limits of the reclaimed water for the total nitrogen of 2 mg/L, and total phosphorus of 0.3 mg/L. The high treatment efficiency allowed the reactor operating at very high hydraulic loadings and reaching nearly complete nitrification and denitrifieation.

Influence of Pyrolytic Biochar on Settleability and Denitrification of Activated Sludge Process

Biochar is a massively produced by-product of biomass pyrolysis to obtain renewable energy and has not been fully used. Incomplete separation of sludge and effluent and insufficient denitrification of sewage are two of main factors that influence the efficiency of activated sludge process. In this work, we proposed a new utilization of biochar and investigated the effect of biochar addition on the performance of settleability and denitrification of activated sludge. Results show that the addition of biochar can improve the settleability of activated sludge by changing the physicochemical characteristics of sludge （e.g., flocculating ability, zeta-potential, hydrophobicity, and extracellular polymeric substances constituents）. Moreover, the dissolved organic carbon released from biochar obtained at lower pyrolysis temperature can improve the nitrate removal efficiency to a certain extent.

Research progress and prospect of low-carbon biological technology for nitrate removal in wastewater treatment

Wastewater treatment plants are the major energy consumers and significant sources of greenhouse gas emissions,among which biological nitrogen removal of wastewater is an important contributor to carbon emissions.However,traditional heterotrophic denitrification still has the problems of excessive residual sludge and the requirement of external carbon sources.Consequently,the development of innovative low-carbon nitrate removal technologies is necessary.This review outlines the key roles of sulfur autotrophic denitrification and hydrogen autotrophic denitrification in low-carbon wastewater treatment.The discovered nitrate/nitrite dependent anaerobic methane oxidation enables sustainable methane emission reduction and nitrogen removal by utilizing available methane in situ.Photosynthetic microorganisms exhibited a promising potential to achieve carbon-negative nitrate removal.Specifically,the algal-bacterial symbiosis system and photogranules offer effective and prospective low-carbon options for nitrogen removal.Then,the emerging nitrate removal technology of photoelectrotrophic denitrification and the underlying,photoelectron transfer mechanisms are discussed.Finally,we summarize and prospect these technologies,highlighting that solar-driven biological nitrogen removal technology is a promising area for future sustainable wastewater treatment.This review has important guiding significance for the design of low-carbon wastewater treatment systems.

Correlation of anaerobic ammonium oxidation and denitrification

The feasibility of the nitrous organic wastewater treated was studied in seven anaerobic sequencing batch reactors（ASBRs） （0^#-6^#） which had been run under stable anaerobic ammonium oxidation （Anammox）. By means of monitoring and data analysis of COD, NH4^#-N, NO2^--N, NO3^--N and pH, and of microbial test, the results revealed that the optimal Anammox performance was achieved from 2^# reactor in which COD/NH4^＋ -N was 1.65, Anammox bacteria and denitrification bacteria could coexist, and Anammox reaction and denitrification reaction could occur simultaneously in the reactors. The ratio of NH4^＋-N consumed ： NO2^- -N consumed ： NO3^- -N produced was 1：1.38：0.19 in 0^# reactor which was not added glucose in the wastewater. When different ratio of COD and NH4^＋-N was fed for the reactors, the ratio of NO2^- -N consumed： NH4^＋-N consumed was in the range of 1.51-2.29 and the ratio of NO;-N produced： NH4^＋ -N consumed in the range of 0 -0.05.

Tentative Study on a New Way of Simultaneous Desulfurization and Denitrification

Thiobacillus denitrificans, a kind of autotrophic facultative bacteria, can oxidize sulfide into elemental sulfur or sulfate when nitrate was adopted as its electron accepter and carbon dioxide as its carbon resource under anoxic or anaerobic environment. In this way, nitrate is converted into nitrogen. In addition, ThiobaciWus denitrificans can accumulate sulfur extracellularly. In this study, in a process of simultaneous desulfurization and denitrification, a strain of Thiobacillus denitriificans is employed as sulfur-producer in the treatment of wastewater containing sulfide and nitrate. The key factors affecting this process are investigated through batch tests. The experimental results indicate that the sulfide concentration and the ratio of sulfide to nitrate (S2-/NO3-) in the influent are the key factors, and their suitable values are suggested to be 5/3 and no more than 300mg·L-1, respectively, in order to achieve high conversion of sulfur.

Nitrification and denitrification in biological activated carbon filter for treating high ammonia source water

Since the ammonia in the effluent of the tradi-tional water purification process could not meet the supply demand,the advanced treatment of a high concentration of NH4+-N micro-polluted source water by biological activated carbon filter(BACF)was tested.The filter was operated in the downflow manner and the results showed that the remov-ing rate of NH_(4)^(+)-N was related to the influent concentration of NH_(4)^(+)-N.Its removing rate could be higher than 95%when influent concentration was under 1.0 mg/L.It could also decrease with the increasing influent concentration when the NH_(4)^(+)-N concentration was in the range from 1.5 to 4.9 mg/L and the dissolved oxygen(DO)in the influent was under 10 mg/L,and the minimum removing rate could be 30%.The key factor of restricting nitrification in BACF was the influent DO.When the influent NH_(4)^(+)-N concentration was high,the DO in water was almost depleted entirely by the nitrifying and hetetrophic bacteria in the depth of 0.4 m filter and the filter layer was divided into aerobic and anoxic zones.The nitrification and degradation of organic matters existed in the aerobic zone,while the denitrification occurred in the anoxic zone.Due to the limited carbon source,the denitrifica-tion could not be carried out properly,which led to the accu-mulation of the denitrification intermediates such as NO_(2)^(−).In addition to the denitrification bacteria,the nitrification and the heterotrophic bacteria existed in the anoxic zone.

Denitrification from nitrogen-fixing biologically crusted soils in a cool desert environment,southeast Utah,USA

Introduction:Nitrogen fixation by microorganisms within biological soil crust(“biocrust”)communities provides an important pathway for N inputs in cool desert environments where soil nutrients are low and symbiotic N-fixing plants may be rare.Estimates of N fixation in biocrusts often greatly exceed that of N accretion rates leading to uncertainty regarding N loss pathways.Methods:In this study we examined nitrogen fixation and denitrification rates in biocrust communities that differed in N fixation potential(low N fixation=light cyanobacterial biocrust,high N fixation=dark cyanolichen crust)at four temperature levels(10,20,30,40°C)and four simulated rainfall levels(0.05,0.2,0.6,1 cm rain events)under controlled laboratory conditions.Results:Acetylene reduction rates(AR,an index of N fixation activity)were over six-fold higher in dark crusts relative to light crusts.Dark biocrusts also exhibited eight-fold higher denitrification rates.There was no consistent effect of temperature on denitrification rates,but there was an interactive effect of water addition and crust type.In light crusts,denitrification rates increased with increasing water addition,whereas the highest denitrification rates in dark crusts were observed at the lowest level of water addition.Conclusions:These results suggest that there are no clear and consistent environmental controls on short-term denitrification rates in these biologically crusted soils.Taken together,estimates of denitrification from light and dark biocrusts constituted 3 and 4%of N fixation rates,respectively suggesting that losses as denitrification are not significant relative to N inputs via fixation.This estimate is based on a previously published conversion ratio of ethylene produced to N fixed that is low(0.295),resulting in high estimates of N fixation.If future N fixation studies in biologically crusted soils show that these ratios are closer to the theoretical 3:1 ratio,denitrification may constitute a more significant loss pathway relative to N fixed.

固定化异养硝化-好氧反硝化菌在污水生物强化中的研究进展

异养硝化-好氧反硝化(Heterotrophic nitrification-aerobic denitrification,HN-AD)菌可以在有机碳存在的好氧条件下实现同时硝化和反硝化,广泛应用于各类污水处理过程中。综述了HN-AD菌株的脱氮特性和代谢途径,总结了其在污水处理中的应用和研究现状,比较了不同载体材料的优缺点,重点讨论了固定HN-AD菌株提高反应器处理效果和稳定性的作用机理。最后,展望了固定化HN-AD菌株在污水处理中面临的挑战和未来的研究方向。

结晶磷回收联合A/O工艺处理猪场沼液工艺特性

厌氧发酵广泛用于猪场废水的前端处理,该过程将产生大量沼液。在中国受土地消纳能力限制,相当一部分猪场沼液不得不经处理后达标排放。猪场沼液含有高浓度污染物,目前仍缺少高效的处理工艺。化学磷回收与A/O工艺均已有较好应用基础,该研究尝试联合结晶磷回收与A/O系统设计了一套具有工程可行性的猪场沼液处理工艺,并以实际猪场沼液为处理对象,探究了该工艺的污染物去除效能与机制。A/O系统缺氧、好氧反应器水力停留时间(HRT,hydraulic retention time)分别为3.4、8.6 h,硝化液回流比为200%,结晶反应器HRT为15min。试验结果表明,所设计工艺获得了较好的污染物去除效果,TP(总磷)、NH_(4)^(+)-N、TN(总氮)、COD(化学需氧量)的去除率分别达到91.20%、94.67%、83.28%和96.18%;工艺同时实现了磷的高效回收,磷回收率(结晶单元对TP去除的贡献率)达到93.44%。缺氧、好氧单元对COD、TN、NH_(4)^(+)-N的去除贡献率分别为75.24%、47.66%、17.30%与24.76%、30.92%、62.75%;该工艺条件下,缺氧单元发生了明显的厌氧氨氧化过程,好氧单元可能通过同步硝化反硝化、厌氧氨氧化等过程实现了部分TN的去除。结晶单元主要结晶产物为MgNH_(4)PO_(4),同步去除了部分TN、NH_(4)^(+)-N,去除贡献率分别为21.39%、19.92%。该研究可为猪场沼液处理及资源回收提供参考。

小麦淀粉生物基水凝胶合成及其辅助NO_(2)^(-)-N的去除

针对小麦淀粉(CS)凝胶力学性能较差的缺陷,利用小麦淀粉与聚乙烯醇(PVA)、硼砂(B)、海藻酸钠(SA)等天然/无机材料通过物理/化学交联合成了PVA/B/CS和SA/B/CS 2种生物基水凝胶,考察其力学性能和溶胀性能;并制备生物基水凝胶包埋反硝化菌剂,考察其对水体中亚硝酸盐氮(NO_(2)^(-)-N)的去除性能。结果表明:合成的2种生物基水凝胶均具有良好的力学性能,PVA/B/CS水凝胶的拉伸断裂伸长率最高可达1088%,SA/B/CS水凝胶的拉伸断裂伸长率最高可达562%;PVA/B/CS2.7水凝胶包埋反硝化菌剂(D-PVA/B/CS2.7)去除水中NO_(2)^(-)-N 30 h后,去除效率为94.81%;SA/B/CS2.7水凝胶包埋反硝化菌剂(D-SA/B/CS2.7)去除水中NO_(2)^(-)-N 40 h后,去除效率为94.99%,说明所合成的生物基水凝胶具有辅助去除水体中氨氮的效果。

高大毛壳对硝化纤维素的降氮机理

针对废旧火药存在严重的安全隐患问题,通过对硝化纤维素(Nitrocellulose,NC)生产的废液处理池及其周边进行采样、富集、驯化和分离纯化,获得5株能够降低NC含氮量的微生物,并对其中降氮效果最佳的高大毛壳进行时间优化实验,发现随着时间的延长,NC含氮量可从13.06%降至10.83%,X射线光电子能谱结果显示NC表面氮元素含量逐渐降低;利用傅里叶变换红外光谱、显微共聚焦拉曼仪和凝胶渗透色谱仪对NC分子结构和分子量进行表征,红外光谱表明高大毛壳与O—NO 2发生水解反应,导致NC在3400 cm^(-1)左右的—OH峰强逐渐增大,拉曼光谱图显示NC含能基团(O—NO 2)的强度发生了显著降低,同时通过凝胶色谱发现,高大毛壳可使NC的数均分子质量和重均分子质量分别降低2.34%和6.40%。为进一步确定作用于NC的生物酶,利用胞外酶、胞内酶的分离以及硫酸铵梯度沉淀实验,证明0~30%硫酸铵沉淀的胞外酶能够有效降低NC的含氮量;高大毛壳对降低NC含氮量的显著作用,使其在废旧火药的再利用、高渐增发射药的生物脱硝等方面具有广阔的应用前景。

一株耐碱好氧反硝化菌的分离鉴定及其脱氮性能

为改善强碱环境下微生物脱氮效率低下的问题,从上海市稻田土壤中分离出一株具有强碱适应能力的好氧反硝化菌。经细胞形态学观察及16S rDNA分析,鉴定其为琼氏不动杆菌(Acinetobacter junii),并命名为琼氏不动杆菌5-2。结合单因素影响试验考察该菌株在不同环境条件下的脱氮效果,发现其在一定pH值(7.0~12.0)及盐质量浓度范围(10~30 g/L)内,均能保持较高的硝氮去除率(>90%)。在以乙酸钠为碳源、硝酸钾为氮源、碳氮质量比(m(C)/m(N))值为12、温度为35℃、转速为90 r/min、初始pH值为10.0、初始硝氮质量浓度为41.07 mg/L的条件下培养120 h后,该菌株对硝氮及总氮的去除率分别为97.83%及65.85%,同时,对该菌株好氧反硝化相关酶活性及基因进行检测。研究结果表明,琼氏不动杆菌5-2具有高效好氧反硝化能力,有望应用于处理实际含氮废水。

不同粒径零价铁对微氧脱氮系统的影响

构建了部分硝化反硝化厌氧氨氧化(SNAD)微氧体系,并定期向体系内投加120 mg不同粒径的零价铁(ZVI),从反应器运行情况、微生物性能以及群落结构来探究不同粒径ZVI对微氧系统的影响。研究结果表明,在50 nm粒径ZVI(50 nZVI)的介导下,系统的TIN去除率最终稳定在83.591%,电子传递活性(ETSA)是接种污泥的1.48倍,均高于其他粒径ZVI的影响。越小粒径ZVI越能促进胞外聚合物的产生,有利于活性污泥结构稳定。这都源于粒径越小的ZVI更容易被微生物吸附、利用。微生物群落结构与功能分析结果表明,在粒径越小的ZVI介导下的微生物群落多样性越高,群落结构也越复杂。ZVI介导会促进对氧需求不敏感的微生物的富集,样品中主要检测出Candidatus_Brocadia和Candidatus_Kuenenia两种厌氧氨氧化菌(AnAOB),且在50 nZVI影响下丰度最高,分别为4.650%和0.692%。nZVI介导下,AnAOB与Gemmobacter和norank_f_Comamonadaceae两种兼性厌氧型反硝化菌共同作用构成SNAD的脱氮途径。而在mZVI介导下,兼性厌氧型反硝化为主要脱氮途径。

污水处理系统中厌氧氨氧化细菌的富集策略

厌氧氨氧化(Anammox)工艺有利于实现可持续的污水生物处理,自发现以来就引起了人们的极大兴趣,与传统的生物脱氮技术相比,其优势在于节约充氧电耗与外加碳源所需的运行费用,以及较低的剩余污泥产量。然而,厌氧氨氧化细菌(AnAOB)的生长速率极其缓慢,限制了Anammox工艺的大规模应用。综述了以往富集AnAOB的研究,主要介绍了以下3个方面:接种污泥选择、载体与反应器设计以及外加化学物质。该文将有助于研究人员规划和设计一个合适的AnAOB富集策略,有利于拓宽Anammox工艺在污水生物处理中的应用。

污水生物脱氮外加碳源的开发与应用

外加碳源在污水生物脱氮过程中发挥着重要作用。根据外加碳源参与生物反硝化反应的作用机制及利用速率的差异性,可将其分为速效碳源、缓释碳源和迟效类碳源,其中后两者合称为复合型碳源。文章第一部分总结了速效碳源的不同种类对反硝化性能和污泥性状的影响。第二部分阐述了以天然植物基质浸出液和可生物降解聚合物为代表的缓释碳源。第三部分介绍了以餐厨垃圾发酵液、污水厂污泥水解液及高浓度有机废水发酵液为代表的迟效碳源。基于降低脱氮成本和废物资源化利用等目的,概述这两类复合碳源的制备过程、生物脱氮性能以及实际应用的可行性等方面内容,提出其质量和性能提升的潜在路径。最后指出建立新型复合碳源的综合性能评价体系是开发利用生物脱氮用新型外加碳源的前提和保障。

复合固相碳源材料强化生物绳脱氮效果

总氮超标的微污染水体中有机碳源较少,投加外部碳源可促进反硝化脱氮,固体碳源因能克服传统碳源缺点而备受关注.以农业废弃物玉米芯和高分子材料作为碳源,以聚乙烯醇和海藻酸钠作为骨架载体,利用交联法制备2种复合固相碳源PSPC-Ⅰ和PSPC-Ⅱ,并研究释碳特性及强化生物绳脱氮效果.结果表明,28 d内两种固相碳源持续释碳且未达到释碳平衡,最高释碳量分别达6.3和8.7 mg/g(以溶解性有机碳计);三维荧光结果显示释放碳源以微生物易降解的可溶性微生物代谢产物和芳香蛋白类物质为主;与不投加碳源的生物绳(生物量200 ng/g,以三磷酸腺苷计)相比,2种固相碳源均显著增加了生物绳挂膜生物量(PSPC-Ⅰ和PSPC-Ⅱ的生物量分别为400~600和300~500 ng/g,以三磷酸腺苷计);2种固相碳源均显著增强了反硝化作用,对照组未脱氮,2种固相碳源脱氮率达80.4%和75.0%.