Comparative study of two biological nitrogen removal processes:A/O process and step-feeding process

Two biological nitrogen removal processes are compared in the aspect of nitrogen removal, process operation and energy saving. Results show that when the returned sludge ratio is 50% of the inflow rate, the step-feeding process achieves over 80% total nitrogen （TN） removal efficiency, but the TN removal efficiency of the A/O process is only 40%. Moreover, filamentous sludge bulking can be well restrained in the step-feeding process. Given the conditions of a returned sludge ratio of 100% and a nitrifying liquor recycle ratio of 200%, the TN removal efficiency is 78.32% in the A/O process, but the sludge volume index （SVI） value increases to 143 mL/g. In the step-feeding process, the SVI is only 94.4 mL/g when the TN removal efficiency reaches 81. 1%. The step-feeding process has distinct advantages over the A/O process in the aspects of practicability, nitrogen removal and operating stability.

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.

Enhanced biological nutrient removal in modified carbon source division anaerobic anoxic oxic process with return activated sludge pre-concentration

A pilot-scale modified carbon source division anaerobic anoxic oxic(AAO) process with pre-concentration of returned activated sludge(RAS) was proposed in this study for the enhanced biological nutrient removal(BNR) of municipal wastewater with limited carbon source. The influent carbon source was fed in step while a novel RAS pre-concentration tank was adopted to improve BNR efficiency, and the effects of an influent carbon source distribution ratio and a RAS pre-concentration ratio were investigated. The results show that the removal efficiency of TN is mainly influenced by the carbon source distribution ratio while the TP removal relies on the RAS pre-concentration ratio. The optimum carbon source distribution ratio and RAS pre-concentration ratio are 60% and 50%, respectively, with an inner recycling ratio of 100% under the optimum steady operation of pilot test, reaching an average effluent TN concentration of 9.8 mg·L-1with a removal efficiency of 63% and an average TP removal efficiency of 94%. The mechanism of nutrient removal is discussed and the kinetics is analyzed. The results reveal that the optimal carbon source distribution ratio provides sufficient denitrifying carbon source to each anoxic phase, reducing nitrate accumulation while the RAS pre-concentration ratio improves the condition of anaerobic zone to ensure the phosphorus release due to less nitrate in the returned sludge. Therefore, nitrifying bacteria, denitrifying bacteria and phosphorus accumulation organisms play an important role under the optimum condition, enhancing the performance of nutrient removal in this test.

Fuzzy Control of Nitrate Recirculation and External Carbon Addition in A/O Nitrogen Removal Process

Nitrogen and phosphorous concentrations of effluent water must be taken into account for the design and operation of wastewater treatment plants. In addition, the requirement for effluent quality is becoming strict. Therefore, intelligent control approaches are recently required in removing biological nutrient. In this study, fuzzy control has been successfully applied to improve the nitrogen removal. Experimental results showed that a close relationship between nitrate concentration and oxidation-reduction potential (ORP) at the end of anoxic zone was found for anoxic/oxic (A/O) nitrogen removal process treating synthetic wastewater. ORP can be used as online fuzzy control parameter of nitrate recirculation and external carbon addition. The established fuzzy logic controller that includes two inputs and one output can maintain ORP value at - 86 mV and - 90 mV by adjusting the nitrate recirculation flow and external carbon dosage respectively to realize the optimal control of nitrogen removal, improving the effluent quality and reducing the operating cost.

Study of control strategy and simulation in anoxic-oxic nitrogen removal process

The control strategy and simulation of external carbon addition were specially studied in an anoxic-oxic(A/O) process with low carbon: nitrogen(C/N) domestic wastewater. The control strategy aimed to adjust the flow rate of external carbon dosage to the anoxic zone, thus the concentration of nitrate plus nitrite(NOx--N) in the anoxic zone was kept closed to the set point. The relationship was studied between the NOx--N concentration in the anoxic zone(S_ NO) and the dosage of external carbon, and the results showed that the removal efficiency of the total nitrogen(TN) could not be largely improved by double dosage of carbon source when S_ NO reached about 2 mg/L. Through keeping S_ NO at the level of about 2 mg/L, the demand of effluent quality could be met and the carbon dosage could be optimized. Based on the Activated Sludge Model No.1(ASM No.1), a simplified mathematical model of external carbon dosage was developed. Simulation results showed that PI controller and feed-forward PI controller both had good dynamic response and steady precision. And feed-forward PI controller had better control effects due to its consideration of influent disturbances.

Nitrogen removal for low-carbon wastewater in reversed A^2/O process by regulation technology

Full scale experimental study on nitrogen removal for low-carbon wastewater was conducted in reversed A2/O process in Jiguanshi waste water treatment plant in Chongqing,in order to aid the operation and maintenance of similar WWTP. When the proposed measures,such as using 0.1% (volume fraction of wastewater) landfill leachate,shortening HRT by 2/3 in the primary sedimentation tank and controlling DO at 0.5 mg/L in the 3rd section of aerobic zone,are applied,15% of the carbon source can be complemented,the favorable property of activated sludge is achieved,and the nitrogen removal effect is significantly improved. The effluent NH3-N is 2 mg/L and the removal rate is 90%. The effluent TN is 17 mg/L and the removal rate is 54%. The up-to-standard discharge of the effluent is achieved. And after the optimization,the unit electricity consumption also reaches 0.21 kW/h and saves 20%.

Development and Study on Nitrogen Removal Controller in A/O Process

In this paper three controllers for A/O process are developed, including a DO cascade controller, an external carbon flow rate controller and an internal recycling flow rate controller. The objective of the different controllers is to control the nitrate and ammonia concentration. Simulation study demonstrated that these controllers could efficiently control nitrogen removal and meet stricter effluent quality standards at a minimum cost.

Removal of nitrogen and phosphorus in a combined A^2/O-BAF system with a short aerobic SRT

A bench-scale anaerobic/anoxic/aerobic process-biological aerated filter （A^2/O-BAF） combined system was carded out to treat wastewater with lower C/N and C/P ratios. The A^2/O process was operated in a short aerobic sludge retention time （SRT） for organic pollutants and phosphorus removal, and denitrification. The subsequent BAF process was mainly used for nitrification. The BAF effluent was partially returned to anoxic zone of the A^2/O process to provide electron acceptors for denitrification and anoxic P uptake. This unique system formed an environment for reproducing the denitdfying phosphate-accumulating organisms （DPAOs）. The ratio of DPAOs to phosphorus accumulating organisms （PAOs） could be maintained at 28% by optimizing the organic loads in the anaerobic zone and the nitrate loads into the anoxic zone in the A^2/O process. The aerobic phosphorus over-uptake and discharge of excess activated sludge was the main mechanism of phosphorus removal in the combined system. The aerobic SRT of the A^2/O process should meet the demands for the development of aerobic PAOs and the restraint on the nitrifiers growth, and the contact time in the aerobic zone of the A^2/O process should be longer than 30 min, which ensured efficient phosphorus removal in the combined system. The adequate BAF effluent return rates should be controlled with 1--4 mg/L nitrate nitrogen in the anoxic zone effluent of A^2/O process to achieve the optimal nitrogen and phosphorus removal efficiencies.

Effect of carbon source and nitrate concentration on denitrifying phosphorus removal by DPB sludge

Effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by DPB sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in anoxic phase increased with the high initial anaerobic carbon source addition. However once the initial COD concentration reached a certain level, which was in excess to the PHB saturation of poly-P bacteria, residual COD carried over to anoxic phase inhibited the subsequent denitrifying phosphorus uptake. Simultaneously, phosphate uptake continued until all nitrate was removed, following a slow endogenous release of phosphate. High nitrate concentration in anoxic phase increased the initial denitrifying phosphorus rate. Once the nitrate was exhausted, phosphate uptake changed to release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the denitrificaion and anoxic phosphorus uptake operations.

Theoretical evaluation on nitrogen removal of step-feed anoxic/oxic activated sludge process

Evaluation on nitrogen removal of step-feed anoxic/oxic activated sludge process at the standpoint of reaction kinetics and process kinetics was conducted. Theoretical biological nitrogen removal efficiency was deduced based on the mass balance of nitrate in the last stage. The comparison of pre-denitrification process and step feed process in the aspects of nitrogen removal efficiency, volume of reactor and building investment was studied, and the results indicated that step-feed anoxic/oxic activated sludge process was superior to pre-denitrification process in these aspects.

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.

Effects of different external carbon sources and electron acceptors on interactions between denitrification and phosphorus removal in biological nutrient removal processes

The effects of two different external carbon sources （acetate and ethanol） and electron acceptors （dissolved oxygen, nitrate, and nitrite） were investigated under aerobic and anoxic conditions with non-acclimated process bi- omass from a full-scale biological nutrient removal-activated sludge system. When acetate was added as an external carbon source, phosphate release was observed even in the presence of electron acceptors. The release rates were 1.7, 7.8, and 3.5 mg P/（g MLVSS.h） （MLVSS： mixed liquor volatile suspended solids）, respectively, for dissolved oxygen, nitrate, and nitrite. In the case of ethanol, no phosphate release was observed in the presence of electron acceptors. Results of the experiments with nitrite showed that approximately 25 mg NO2-N/L of nitrite inhibited anoxic phosphorus uptake regardless of the concentration of the tested external carbon sources. Furthermore, higher deni- trification rates were obtained with acetate （1.4 and 0.8 mg N/（g MLVSS.h）） compared to ethanol （1.1 and 0.7 mg N/ （g MLVSS.h）） for both anoxic electron acceptors （nitrate and nitrite）.

侧流与主流磷回收工艺对比及调控因子分析

从污水中回收磷是缓解磷资源危机的有效途径,目前,污水处理厂常用的磷回收工艺主要为从剩余污泥中回收磷的侧流工艺,存在工艺复杂、回收效率低等问题.以生物膜为主体的主流磷回收工艺可实现磷的同步去除与富集,工艺简单且高效,因此更具发展前景.两种工艺在运行原理及模式上存在显著差异,因此对两者的调控措施不尽相同.本文分别以A^(2)O工艺和生物膜序批式反应器工艺为代表,对比了侧流和主流磷回收工艺在运行原理及模式上的异同,并以聚磷菌的代谢机理为基础,总结了温度、pH值、水力停留时间、溶解氧、碳源和蓄磷量等调控因子对两种工艺产生的影响,并阐述了其差异化机制,以期为生物膜磷回收工艺的进一步发展提供参考.

生物增效低曝气BC-BAF处理低碳高氨氮废水的性能研究

为改善传统曝气生物滤池(BAF)对低碳高氨氮比猪场沼液脱氮除磷效果差的困境,采用生物炭(Biochar,BC)为BAF载体填料,接种课题组前期驯化好的脱氮除磷功能菌泥,低曝气条件下构建生物增效BC-BAF工艺。研究该工艺对猪场沼液脱氮除磷的效能,并基于高通量测序技术分析启动前后微生物种群的组成变化,最后结合启动后污泥样品的能谱分析(EDS),探讨其强化脱氮除磷机理。结果表明,启动成功后的生物增效BC-BAF工艺对低碳高氨氮猪场沼液的NH4+-N、TN和TP的平均去除率分别达到了65.27%、60.31%和63.20%;与脱氮除磷功能相关的优势菌属Nitrosomonas(2.12%),Candidatus_Brocadia(3.24%),Acinetobacter(3.88%),Micropruina(24.72%),norank_o_RBG-13-54-9(11.71%),JGI_0001001-H03(1.77%)和unclassified_f_Burkholderiaceae(1.11%)在反应体系中实现了很好的富集。微曝气生物增效BC-BAF工艺处理猪场沼液反应体系中存在短程硝化、厌氧氨氧化以及反硝化脱氮等多种途径,而对于总磷的去除主要以生物除磷和吸附沉淀的联合方式进行。

基于碳减排的厌氧氨氧化脱氮工艺应用及强化调控进展

随着我国“双碳”目标的提出和水处理行业提标改造的重点落在生物脱氮,污水处理厂从关注满足排放许可限制转向实现碳中和、能量自给及资源回收。厌氧氨氧化(Anammox)技术凭借无需外加有机碳源、占地面积小、污泥产量少以及脱氮效率高等节能降耗与碳减排优势,代表着未来污水生物脱氮的发展方向。基于已有研究成果,梳理对比了传统脱氮与Anammox反应的发展历程;重点综述了新兴短程硝化耦合Anammox(PN-A)工艺、短程反硝化耦合Anammox(PD-A)工艺和甲烷型反硝化耦合Anammox(DAMO-Anammox)工艺在城市主流工况的应用进展;详细探讨了主流Anammox工艺面临低温、进水负荷不均和光照等环境因素冲击时,可施行的“侧流污泥补充至主流”“侧流污水间歇性补充至主流”“驯化生物膜颗粒”等内源性以及外源性的强化调控策略及内在机制;最后围绕分子生物学技术、材料科学、数字信息技术和管理政策,对加快Anammox生物脱氮技术的创新发展与推广应用进行了展望。

可生物降解聚合物作为固相反硝化碳源的研究进展

碳源是生物反硝化法处理低碳氮比硝酸盐污水的必要物质.传统的水溶性碳源投加量难以控制,易导致出水水质恶化,需要寻找一种释碳稳定、安全高效的替代碳源.可生物降解聚合物(biodegradable polymers,BDPs)是一类人工合成的高分子有机物,已被证实可作为新型的反硝化缓释碳源.其具有反硝化效率高、安全稳定、操作简单等优点,近年来被广泛报道.归纳总结了BDPs碳源类型及其体系的反硝化性能和影响因素,讨论了BDPs体系脱氮机制及生物膜群落结构与功能,评价了BDPs反硝化脱氮的成本.提出发展成本相对低廉的BDPs复合碳源、阐明运行条件对BDPs反硝化的影响机制、通过优化微生物群落来构建高效BDPs反硝化系统以及加强共存污染物去除等未来重点研究方向,以期为可生物降解聚合物的反硝化脱氮研究和应用提供参考和依据.

污水生化处理工艺发展阶段化技术特征及未来趋势

百余年来,伴随人类社会和科技日新月异,污水生化处理技术也在实现快速发展与不断迭代,新工艺与新反应器、新功能微生物与新生化代谢途径不断被提出、发现和解析,并进一步推动了污水处理技术的进步与升级。回顾了过去百余年污水生化处理技术发展历程,就典型污水生化工艺,结合技术研发进展、技术成熟度及案例应用情况,给出了不同生化处理工艺代际划分与技术发展期“S曲线”,分析了近些年来新涌现出的一些革新性污水生化处理工艺的技术原理、技术特征,结合实际案例分析了工艺技术特征、技术优势与总体效能,从工艺强化、绿色低碳与集约高效等方面总结了未来污水处理发展的技术趋势,以期为“双碳背景”下排水系统提质增效工作、未来国内前瞻性污水厂工艺设计与运行提供参考和借鉴。

磁环境下AAO工艺中的微生物群落演替规律

将AAO反应器置于5 mT大小的平均磁场环境,文中研究了磁场对AAO工艺效能的影响,并从分子生物学的角度对其影响机理进行了初步探究。结果表明,在5 mT磁场环境下,AAO工艺启动阶段的平均总氮去除率有较明显提升,比对照组上升6%;AAO反应器启动时间较对照组缩短了5 d;AAO中以固氮螺旋菌(Azospira)为代表的反硝化菌群的相对丰度占比明显提升,丝硫菌属(Thiothrix)的相对丰度占比大幅降低,对污泥膨胀的抑制作用较明显;通过基因功能预测发现磁环境下细胞运动类基因相对丰度相对无磁场条件提升75%,膜运输类基因大幅下降,从而提高了AAO的启动速度,提升了脱氮效能。

活性碳介导厌氧铁氨氧化脱氮效能及影响因素

厌氧铁氨氧化(Feammox)是一种以Fe^(3+)为电子受体的自养型脱氮工艺。利用活性碳(AC)作为电子穿梭体增加铁还原细菌的胞外电子转移速率和Feammox脱氮效率。考察了p H值、溶解氧、碳酸盐和硫酸盐浓度等对AC介导Feammox脱氮效能的影响。结果表明,p H值为6~7时有助于提升出水NH4+-N去除率。间隙曝气可以促进Fe^(3+)再生从而使得Feammox持续脱氮。当碳酸盐、硫酸盐质量浓度分别为250,150 mg/L时,NH4+-N和TN去除率分别达到94%和91%。Feammox强化人工湿地对农村生活污水NH4+-N去除率达到95%,具有微动力、运行稳定的特点。

曝气生物滤池影响因素及脱氮除磷研究进展

曝气生物滤池(BAF)是一种集吸附、过滤和生物氧化为一体的新型污水生物处理技术。本文介绍了影响BAF运行效果的因素(如填料、水力负荷、气水比、反冲洗、C/N和温度等),综述了BAF在去除水中各类污染物质的最新研究进展,并就该工艺在有机及悬浮物去除、硝化除氨、脱氮除磷、耦合其他工艺等方面所具备的优势与不足进行了阐述,为BAF的发展与应用研究提供一定的科学参考。