Stoichiometric deduction of activated sludge process for organic carbon and nitrogen removal

The activated sludge process （ASP） is the most generally applied biological wastewater treatment method. The ASP for the removal of organic carbon and nitrogen can be looked as the combination of eight processes. In order to set up an ASP model, the stoichiometric coefficients should be deduced so that the stoichiometric matrix can be presented. The important assumptions and simplifications behind the model for ASP are enumerated. Using the matrix, mass balance equation and consistent units, the stoichiometric coefficients in the eight processes are exclusively deduced one by one.

Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations

The impact of the organic carbon to nitrogen ratio （chemical oxygen demand （COD）/N） in wastewater and dissolved oxygen （DO） concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria （AOB） communities in activated sludge in constantly aerated sequencing batch reactors （SBRs） was determined. At DO of 0.5 and 1.5 mg O2/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination （above 50%） was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O2/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.

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.

Applying real-time control to enhance the performance of nitrogen removal in CAST system

A bench-scale reactor（72 L） red with domestic sewage, was operated more than 3 months with three operation modes： traditional mode, modified mode and real-time control mode, so as to evaluate effects of the operation mode on the system performance and to develop a feasible control strategy. Results obtained from fixed-time control study indicate that the variations of the pH and oxidation-reduction potential（ORP） profiles can represent dynamic characteristics of system and the cycle sequences can be controlled and optimized by the control points on the pH and ORP profiles. A control strategy was, therefore, developed and applied to real-time control mode. Compared with traditional mode, the total nitrogen（TN） removal can be increased by approximately 16% in modified mode and a mean TN removal of 92% was achieved in real-time control mode. Moreover, approximately 12.5% aeration energy was saved in real- time control mode. The result of this study shows that the performance of nitrogen removal was enhanced in modified operation mode. Moreover, the real-time control made it possible to optimize process operation and save aeration energy.

Effects of low temperature on sludge settleability and nutrients removal performance treating domestic wastewater

In order to investigate the effect of temperature on activated sludge systems,sludge settleability,nitrogen and phosphorus removal processes were investigated by changing temperature variation patterns using 4 sequencing batch reactors (SBR).The results showed that no matter temperature changes in the range of 15-22 ℃ (decrease or increase) gradually or sharply,it has little effect on nitrogen and phosphorus removal processes.But when temperature decreases to 12 ℃,biochemical reactions will be inhibitted obviously.At least 1 sludge retention time (SRT) is needed for nitrification adapt to new temperature envirionment,and more time is necessary for phosphorus removal process.When temperature increases from 12 ℃ to 22 ℃ sharply,nitrification process deteriorates seriously,but phosphorus removal process shows no change.In addition,sludge settleability deteriorates when temperature changes sharply (decrease or increase),but the reasons are different.Under temperature decrease condition,it is mainly caused by the increase of accumulated extracellular polymeric substances (EPS).Under temperature increase condition,the loosing sludge flocs' configuration is the main reason.It should be pointed out that the filamentous bacteria content during the entire experiment keeps almost constant,and the sludge settleability variations are the reflection of the change of sludge physicochemical characteristics.

Characteristics of Nutrients Removal under Viscous Sludge Bulking Treating Synthetic Wastewater

Viscous sludge bulking is a rare phenomenon in activated sludge process.The performances of nutrients removal were investigated with normal sludge and viscous bulking sludge.The results showed that when COD loading and C/N ratio were around 0.13 mg COD/(mg MLSS·d)and 7.67,the effect of viscous sludge bulking on the maximum specific oxidation rates of NH_(4)^(+)⁃N was very little,while the maximum specific oxidation rates of NO_(2)^(-)⁃N decreased from 24.69 mg/(g·h)to 1.20 mg/(g·h).Compared with normal sludge,viscous bulking sludge had bigger particle size and more extracellular polymeric substances(EPS).The mass transfer resistance in sludge flocs might be the main cause of the difference in NO-2⁃N oxidation rates.Therefore,this study demonstrates that viscous sludge bulking is beneficial to enhance simultaneous nitrification and denitrification(SND),and excessive EPS will exhibit storage function during phosphorus removal process.

Simultaneous nitrogen and phosphorus removal under low dissolved oxygen conditions

A full-scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of CODCr, TN and TP varied in a range of 352.9 mg/L-1338.2 mg/L, 34.4 mg/L-96.3 mg/L, and 2.21 mg/L-24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively. During the test period of two months, effluent meas of CODCr,, BOD5, NH3-N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L respectively. The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency. It is very convenient to retrofit the conventional activated sludge process with the above process.

Nitrogen and phosphorus removal under intermittent aeration conditions

A practice wastewater treatment plant was operated using intermittent aeration activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of COD Cr , BOD 5, TN, TP, NH 3\|N, TKN, and SS varied in a range of 207.5—1640 mg/L, 61.8—637 mg/L, 28.5—75.6 mg/L, 4.38—20.2 mg/L, 13.6—31.9 mg/L, 28.5—75.6 mg/L, and 111—1208 mg/L, the effluent means were less than 50 mg/L, 20 mg/L, 5 mg/L, 1.0 mg/L, 5 mg/L, 10 mg/L, and 20 mg/L, respectively. Based on a long time of operating results, this process is very suitable for nutrient biological removal for treating the municipal wastewater those water characteristics are similar as that of the Songjiang Municipal Waste Water Treatment Plant(SJMWTP).

Long-and short-chain AHLs affect AOA and AOB microbial community composition and ammonia oxidation rate in activated sludge

Quorum sensing(QS)regulation of the composition of ammonia-oxidising archaea(AOA)and ammonia-oxidising bacteria(AOB)communities and functions in wastewater treatment was investigated.Specifically,we explored the role of N-acyl-L-homoserine lactones(AHLs)in microbial community dynamics in activated sludge.On average,the specific ammoniaoxidising-rate increased from 1.6 to 2.8 mg NH_4^+-N/g MLSS/hr after treatment with long-chain AHLs for 16 days,and the addition of AHLs to sludge resulted in an increased number of AOA/AOB amoA genes.Significant differences were observed in the AOA communities of control and AHL-treated cultures,but not the AOB community.Furthermore,the dominant functional AOA strains of the Crenarchaeota altered their ecological niche in response to AHL addition.These results provide evidence that AHLs play an important role in mediating AOA/AOB microbial community parameters and demonstrate the potential for application of QS to the regulation of nitrogen compound metabolism in wastewater treatment.

温度对垃圾渗滤液生化处理过程中氨氮去除的影响研究

为解决垃圾渗滤液处理工程中常出现夏季高温导致生化污泥失活、出水氨氮不达标的问题,利用杭州市某垃圾中转站的渗滤液和活性污泥,探究了温度对垃圾渗滤液生化处理过程中氨氮去除的影响。通过小试试验探究得出,高温条件下活性污泥对氨氮的去除效果随温度的升高而逐渐降低;当生化系统温度小于40℃时,简单的降温措施即可恢复污泥的活性;当活性污泥受到40℃以上的高温损伤后,生物膜结构受到破坏而彻底失活,生化系统对氨氮的去除率降至20%以下,此时仅通过降温措施并不能有效恢复活性,需重新接种污泥或添加硝化菌剂方能快速恢复氨氮去除功能。因此,在垃圾渗滤液处理工程中,应通过设置冷却塔等措施避免活性污泥处于40℃以上的高温环境中。

邻苯二甲酸二乙酯对厌氧/好氧/缺氧工艺脱氮除磷的影响

邻苯二甲酸二乙酯(DEP)是水生态系统内高频检出污染物,然而DEP对新工艺厌氧-好氧-缺氧运行效能的影响至今尚不清楚。为了填补空白,本工作考察了DEP对新工艺处理低C/N废水的影响并分析了相关作用机制。结果表明,DEP显著抑制了新工艺内COD及脱氮除磷效率,且DEP浓度越高,COD去除抑制越显著。典型周期发现DEP能抑制厌氧阶段和缺氧阶段COD的消耗而对好氧阶段COD去除影响不显著。DEP降低了厌氧释磷和好氧吸磷过程导致生物除磷效率下降。DEP提高AOA工艺内胞外聚合物(EPS)含量,并促进了主要组分蛋白质和多糖的分泌。微生物学揭示高浓度DEP降低了Patescibacteria、Bacteroidetes和Nitrospirae门水平上关键微生物的相对丰度。研究结果对AOA高效去除新污染物DEP提供了数据支持。

活性污泥对磺胺二甲嘧啶的去除及其脱氮除磷的影响

抗生素被广泛应用于生物医疗和畜牧养殖中,其对环境的污染问题引起了广泛关注。本文以常用的抗生素磺胺二甲嘧啶(SM2)为研究对象,考察了活性污泥降解SM2的特性。结果显示:活性污泥能够降解水体中的SM2,在初始接菌量OD600=0.60、温度为30℃、pH=7.0时,经20 d反应后,SM2初始浓度为5、10、30 mg·L^(-1)的条件下其SM2降解率分别为50.65%、39.65%和32.15%。在反应前期,活性污泥主要通过吸附去除SM2;在反应后期,活性污泥主要通过生物降解去除SM2。SM2能够一定程度抑制活性污泥的脱氮除磷能力。

不同调控措施对低负荷污水脱氮除磷影响分析

利用中试试验装置模拟低负荷状态下SBR生化池的运行调控,通过对现状SBR工艺进行改进(主反应区增加搅拌),同时研究不同的调控措施对SBR工艺脱氮除磷的影响,探究低负荷污水处理厂高效、经济运行方式。

四环素长期暴露对脱氮系统性能及微生物群落结构的影响

本实验通过构建序批式反应器(SBR),研究四环素浓度为0~35 mg/L的废水对硝化脱氮系统性能及微生物群落结构的影响。实验结果表明,四环素浓度≤20 mg/L时,硝化菌的活性随着暴露周期的增加而逐渐恢复。在四环素浓度为35 mg/L时,硝化菌失去活性,硝化系统崩溃。通过微生物群落结构分析可知,四环素的存在使Proteobacteria菌门产生一定的耐药性。随着四化素的浓度增加,对Ferribacterium和Nitrospira菌属的抑制程度越来越强,对Zoogloea和Pseudoxanthomonas菌属的抑制作用越来越弱。另外,四环素浓度为5 mg/L时利于Thauera菌属的生长。四环素浓度为35 mg/L时Nitrosomonas菌属全部失活。

生物膜与活性污泥工艺在污水处理中的应用对比研究

污水处理厂建设是解决污水污染问题的有效手段,目前我国污水厂大多集中于城市,随着城镇工业企业的迅速发展,未经处理污水大量排放成为水环境主要污染源。生物膜法作为一项新兴污水好氧生物处理工艺,可以大幅提升反应池生物含量,降低污泥负荷率,有效去除污水中碳、磷氮含量,提升水质。本文以该工艺为研究对象,对其和活性污泥法在给排水工程中的应用进行生产性对比研究,结合工艺去除污染物特点及污水处理厂运行状态评估,进行工程实践指导。

Process Adaption and Modifications of a Nutrient Removing Wastewater Treatment Plant in Sri Lanka Operated at Low Loading Conditions

The Sri Lankan national water authority, that is The National Water Supply and Drainage Board (NWS&DB) has taken a new wastewater treatment plant into operation at Ja Ela, North of Colombo. The plant has been in operation since September 2011. In April 2012, it was concluded how a test of the aeration efficiency and a performance test should be carried out. The tests have been based on the actual loading of the plant and the analysis results from the daily process control. The evaluation of the aeration efficiency is not reported in this paper. The paper presents the overall performance of the water treatment part of the plant during start-up conditions, from fall 2011 through the first five months of 2012. The results from the operation are found in Table 1. An important circumstance at the plant is the current very low loading in comparison with the design load. This fact has resulted in an introduction of an intermittent mode of the aeration (nitrification) reactor. Based on operation figures, during more than a month (May 2012), it has been possible to give a realistic assessment of the overall performance. The most striking results are summarized as follows: 1) The intermittent operation has enabled an energy efficient operation of the plant. By the introduction of the intermittent aeration, the energy consumption has been reduced by around 75%, compared with the continuous operation mode;2) The plant performance during the intermittent operation has been improved with respect to virtually all important pollution variables. The most striking improvement is the discharge total P level, reflecting that a substantial enhanced biological phosphorus removal takes. The typical discharge levels found during May 2012, were compared with the earlier obtained values. It is important to underline that the loading on the plant has slightly increased during May as compared with the previous operation period.

油菜秸秆生物炭强化好氧活性污泥体系污水脱氮效能研究

为提高好氧活性污泥体系的污水脱氮效能,向序批式反应器内分别投加300,500,700℃条件下热解制备的油菜秸秆生物炭(RBC_(300)、RBC_(500)、RBC_(700)),并考察其强化脱氮效果。结果表明,当RBC_(700)投加量为1.0 g/L时,好氧活性污泥体系的平均NH_(4)^(+)-N、TN去除率分别为95.1%、84.5%,比未投加RBC_(700)时分别提升了19.2,51.8个百分点。RBC_(700)对NH_(4)^(+)-N的吸附量分别是RBC_(300)、RBC_(500)的1.8,1.3倍,载膜量分别是RBC_(300)、RBC_(500)的4.5,1.9倍,为同步硝化反硝化的发生创造了有利条件,因而投加RBC_(700)的好氧活性污泥体系可在更短的时间内获得更高的脱氮效率和更好的污泥沉降性能。因此,700℃条件下热解制备的油菜秸秆生物炭应用于好氧活性污泥体系强化脱氮具有良好的可行性。

不同来源生物炭对活性污泥特性及脱氮除磷影响机理研究

在中温(20~25℃)条件下,研究不同生物质原料在500℃热解温度下分别制得稻壳生物炭(RHB)、玉米秸秆生物炭(CSB)、鸡粪生物炭(CMB),投加至序批式反应器(SBR)中,探究了生物炭对SBR系统污泥特性和污水处理效果的影响。结果表明:生物炭强化了活性污泥的沉降性,使污泥稳定性增强,提高了污泥MLVSS,有利于微生物的增殖。相较于对照组K0,添加生物炭的组别有利于溶解性微生物代谢产物(SMP)含量的降低和污水出水水质改善。此外,生物炭还提高了污泥胞外聚合物(EPS)含量,在RHB、CSB和CMB的组别中,EPS含量分别升高至114.20、118.17和113.37 mg·g^(-1),均显著高于K0,生物炭存在提高了EPS内PN/PS比值。通过对EPS测定三维荧光(EEM)分析可知,相较于K0,添加生物炭的活性污泥EPS中含有更多的芳香类、多芳香类蛋白和腐殖质类物质。生物炭的存在有效提高SBR系统对氨氮、总氮和总磷的去除效率,生物炭存在的组别内出水总氮(TN)的质量浓度基本维持在9.14~13.6 mg·L^(-1),均明显低于对照组。

城镇污水厂新兴强化生化处理工艺综述

当前城镇污水处理厂正面临日趋严格的高排放标准挑战,二级处理过程的效能挖潜是当下污水处理提标改造的重点,除了对传统二级处理进行优化改良,现阶段更是涌现出一系列新兴强化生化处理工艺,实现对传统工艺的突破和污水处理的提质增效。文中通过分析生物处理效率提升的途径,总结了快速生化污水处理(RPIR)、载体活性污泥、以芽孢杆菌为优势菌的生物反应器工艺(BBR)、生物倍增、好氧颗粒污泥等已实现规模化应用的新工艺与新技术,介绍了其原理和工艺特点,并结合相关应用案例,对其潜在优势进行了分析和讨论。新兴工艺多采用模块化、一体化装备,在省占地、降投资、减工期等方面具有显著优势,相较现有成熟工艺,新兴工艺虽然还处在发展阶段,但仍可以为未来城市水环境治理提供新思路。

低碳源生活污水生物脱氮工艺研究进展

针对低碳源生活污水总氮脱除的难题,分别从传统生物脱氮工艺、新型生物脱氮工艺、碳源对污水脱氮的影响进行了综述。传统生物脱氮工艺主要包括活性污泥法、生物膜法、泥膜复合法,相较于单一的传统活性污泥法或生物膜法,泥膜复合工艺对低碳源生活污水可以获得较高的脱氮效果;新型生物脱氮工艺主要包括短程硝化反硝化、厌氧氨氧化、同步硝化反硝化及自养反硝化,其中短程硝化反硝化需严格控制运行条件以获得较高的总氮去除率;厌氧氨氧化无须外碳源,但需要严格控制环境条件以保持厌氧氨氧化菌的活性;同步硝化反硝化工艺运行参数的波动对处理效果影响显著;自养反硝化节省了外碳源的投入,但保持自养反硝化微生物的活性是关键;碳源作为污水生物脱氮反硝化过程的重要影响因素,主要有外投加单一碳源、外投加组合碳源及利用内源碳,需要根据具体处理的污水水质水量情况,以及可利用的碳源情况进行选择。为此,对低碳源生活污水脱氮技术提出了展望,可从微观角度重点研究新型生物脱氮工艺的机制机理;通过工艺的组合优化,合理选择外碳源,充分利用污水中内碳源;新型生活污水脱氮工艺进行组合,对各运行参数进行优化,以期获得高效化、低碳化的脱氮技术。