Kinetics model of aerobic phase in hybrid anoxic-oxic process

Kinetics models of COD degradation,biomass growth of the anoxic-oxic ( A/O) system as well as NH3-N degradation in aerobic phase were presented according to the mass balance theory,reaction-diffusion theory and Fick law. Then these models were testified by comparson with experimental results. It is demonstrated that the variation trends of theoretical and experimental values for COD degradation and biomass growth are similar. The deviation rate between theoretical and experimental values is always under 20% even it increases along with the fluctuation of influent organic loading. In terms of NH3-N degradation,nitrification can also be well simulated by the model as the substrates of influent are sufficient. It indicates that the model can accurately reflect the reaction in hybrid A/O process. Models presented herein provide a theoretical basis for the design, operation and control of hybrid A/O process.

Characteristics of anoxic phosphors removal in sequence batch reactor

The characteristics of anaerobic phosphorus release and anoxic phosphorus uptake were investigated in sequencing batch reactors using denitrifying phosphorus removing bacteria （DPB） sludge. The lab-scale experiments were accomplished under conditions of various nitrite concentrations （5.5, 9.5, and 15 mg/L） and mixed liquor suspended solids （MLSS） （1844, 3231, and 6730 mg/L）. The results obtained confirmed that nitrite, MLSS, and pH were key factors, which had a significant impact on anaerobic phosphorus release and anoxic phosphorus uptake in the biological phosphorous removal process. The nitrites were able to successfully act as electron acceptors for phosphorous uptake at a limited concentration between 5.5 and 9.5 mg/L. The denitrification and dephosphorous were inhibited when the nitrite concentration reached 15 mg/L. This observation indicated that the nitrite would not inhibit phosphorus uptake before it exceeded a threshold concentration. It was assumed that an increase of MLSS concentration from 1844 mg/L to 6730 mg/L led to the increase of denitrification and anoxic P-uptake rate. On the contrary, the average P-uptake/N denitrifying reduced from 2.10 to 1.57 mg PO4^3--P/mg NO3^--N. Therefore, it could be concluded that increasing MLSS of the DEPHANOX system might shorten the reaction time of phosphorus release and anoxic phosphorus uptake. However, excessive MLSS might reduce the specific denitrifying rate. Meanwhile, a rapid pH increase occurred at the beginning of the anoxic conditions as a result of denitrification and anoxic phosphate uptake. Anaerobic P release rate increased with an increase in pH. Moreover, when pH exceeded a relatively high value of 8.0, the dissolved P concentration decreased in the liquid phase, because of chemical precipitation. This observation suggested that pH should be strictly controlled below 8.0 to avoid chemical precipitation if the biological denitrifying phosphorus removal capability is to be studied accurately.

Effects of loading rate and hydraulic residence time on anoxic sulfide biooxidation

The optimal operation conditions in an anoxic sulfide oxidizing (ASO) bioreactor were investigated. The maximal removal rates for sulfide and nitrate were found to be 4.18 kg/(m3·d) and 1.73 kg/(m3·d), respectively. The volumetrical volumetric loading rates (LRs) observed through decreasing hydraulic retention time (HRT) at fixed substrate concentration are higher than those by increasing substrate concentration at fixed HRT. The sulfide oxidation in ASO reactor was partially producing both sulfate and sulfur; but the amount of sulfate produced was approximately one third that of sulfur. The process was able to tolerate high sulfide concentration, as the sulfide removal percentage always remained near 99% when influent concentration was up to 580 mg/L. It tolerated relatively lower nitrate concentration because the removal percentage dropped to 85% when influent con- centration was increased above 110 mg/L. The process can tolerate shorter HRT but careful operation is needed. Nitrate conversion was more sensitive to HRT than sulfide conversion since the process performance deteriorated abruptly when HRT was decreased from 3.12 h to 2.88 h. In order to avoid nitrite accumulation in the reactor, the influent sulfide and nitrate concentrations should be kept at 280 mg/L and 67.5 mg/L respectively. Present biotechnology is useful for removing sulfides from sewers and crude oil.

Effect of short-term atrazine addition on the performance of an anaerobic/anoxic/oxic process

In this study,an anaerobic/anoxic/oxic(A^(2)O)wastewater treatment process was implemented to treat domestic wastewater with short-term atrazine addition.The results provided an evaluation on the effects of an accidental pollution on the operation of a wastewater treatment plant(WWTP)in relation to Chemical Oxygen Demand(COD)and biological nutrient removal.Domestic wastewater with atrazine addition in 3 continuous days was treated when steady biological nutrient removal was achieved in the A^(2)O process.The concentrations of atrazine were 15,10,and 5 mg%L–1 on days 1,2 and 3,respectively.The results showed that atrazine addition did not affect the removal of COD.The specific NH4þoxidation rate and NO3–reduction rate decreased slightly due to the short-term atrazine addition.However,it did not affect the nitrogen removal due to the high nitrification and denitrification capacity of the system.Total nitrogen(TN)removal was steady,and more than 70%was removed during the period studied.The phosphorus removal rate was not affected by the short-term addition of atrazine under the applied experimental conditions.However,more poly-hydroxy-alkanoate(PHA)was generated and utilized during atrazine addition.The results of the oxygen uptake rate(OUR)showed that the respiration of nitrifiers decreased significantly,while the activity of carbon utilizers had no obvious change with the atrazine addition.Atrazine was not removed with the A^(2)O process,even via absorption by the activated sludge in the process of the short-term addition of atrazine.

A novel multistage anoxic/aerobic process with sludge regeneration zone (R-MAO) for advanced nitrogen removal from domestic sewage

To achieve advanced nitrogen removal from actual municipal sewage,a novel multistage anoxic/aerobic process with sludge regeneration zone(R-MAO)was developed.The reactor was used to treat actual domestic sewage and the nitrogen removal capacity of the sludge regeneration zone(R zone)was investigated during the long-term operation.The best performance was obtained at the R zone’s Oxidation-Reduction Potential(ORP)of-50±30 mV and hydraulic residence times(HRT)of 1.2 hr.The average effluent COD,TN,NH_(4)^(+)-N and NO_(3)^(−)-N of the R-MAO process were 18.0±2.3,7.5±0.6,1.0±0.5 and 4.6±0.4 mg/L,respectively,with the corresponding removal efficiency of COD,TN and NH_(4)^(+)-N were 92.9%±1.0%,84.1%±1.5% and 97.5%±1.1%.Compared to the sole MAO system,the TN removal efficiency of the R-MAO increased by 10.1%.Besides,under the optimal conditions,the contribution of the R zone in the R-MAO that removal COD,TN,NH_(4)^(+)-N and NO_(3)^(−)-N were 0.36,0.15,0.032 and 0.82 g/day.High-throughput sequencing results showed that uncultured_bacterium_f_Burkholderiaceae(5.20%),OLB8(1.04%)and Ottowia(1.03%)played an important role in denitrification in the R zone.This study provided effective guidance for the design and operation of the R-MAO process in domestic sewage treatment.

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.

Anaerobic degradation of xenobiotic organic contaminants(XOCs):The role of electron flow and potential enhancing strategies

In groundwater,deep soil layer,sediment,the widespread of xenobiotic organic contaminants(XOCs)have been leading to the concern of human health and eco-environment safety,which calls for a better understanding on the fate and remediation of XOCs in anoxic matrices.In the absence of oxygen,bacteria utilize various oxidized substances,e.g.nitrate,sulphate,metallic(hydr)oxides,humic substance,as terminal electron acceptors(TEAs)to fuel anaerobic XOCs degradation.Although there have been increasing anaerobic biodegradation studies focusing on species identification,degrading pathways,community dynamics,systematic reviews on the underlying mechanism of anaerobic contaminants removal from the perspective of electron flow are limited.In this review,we provide the insight on anaerobic biodegradation from electrons aspect-electron production,transport,and consumption.The mechanism of the coupling between TEAs reduction and pollutants degradation is deconstructed in the level of community,pure culture,and cellular biochemistry.Hereby,relevant strategies to promote anaerobic biodegradation are proposed for guiding to an efficient XOCs bioremediation.

Effect of Sludge Retention Time on the Fate of Proteins and Polysaccharides in AAO Process

Effect of sludge retention time( SRT) on the removal of potential and polysaccharides in an anaerobic / anoxic / aerobic( AAO) process was investigated. The Lowry method and anthrone method were used to detect proteins and polysaccharides. Total removal efficiency of proteins at SRT of 10 to 25 d in the AAO system was higher than 90%. Polysaccharides removal efficiencies were above 80% when SRT was increased from 15 to 25 d,whereas only 81% of polysaccharides was removed at SRT of 10 d. The biodegradation part of proteins and polysaccharides increased from87. 40% to 93% and from 74. 22% to 86. 94% with increasing SRTs.The ratios of polysaccharides and proteins in extracellular polymer substances( EPSs) were around 1. 5-3 in different SRTs. As SRT increasing,polysaccharides and proteins discharged with residual sludge decreased gradually. The amount of EPSs decreased with increasing SRTs.

一体化厌氧-变级数缺氧/好氧循环流污水处理装置中试研究

针对现有村镇污水处理技术与装备的不足,开发出适用于村镇污水处理的新型一体化厌氧-变级数缺氧/好氧循环流(A-(AO)_n)同步脱氮除磷、沉淀分离技术与装备,以长沙某污水提升泵站沉砂池的出水作为处理对象开展中试实验。对好氧区不同溶解氧、填料填充比和分区进水条件下装置污水处理效能的变化进行研究,结果表明:当好氧区溶解氧控制在1.5~2.0 mg/L,好氧区填料填充比为30%时,装置的脱氮除磷效果最佳。在不外加碳源且不投加化学除磷药剂的条件下,出水水质优于《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级A标准。高通量测序结果显示,好氧区投加悬浮球填料后,系统中微生物总量和多样性明显提高,为系统中发生同步硝化反硝化(SND)现象创造了条件。

有机负荷率对新型厌氧/好氧/缺氧工艺的影响机制探究

为了探究进水有机负荷对新型厌氧/好氧/缺氧工艺(AOA)工艺的影响,构建了新型AOA生物脱氮除磷反应器,通过控制进水COD考察了有机负荷率(OLR)对AOA工艺对污染物和营养盐去除的影响,并通过分析不同OLR工况影响下污泥特征及胞内聚合物的变化规律、微生物群落特征揭示了OLR对AOA工艺的影响机制。结果表明进水OLR由200 mg/L提高至400 mg/L,AOA工艺具有良好的去除效率,COD、TN和SOP的去除效率分别达到93.6%~96.2%、82.45%~85.1%和94.2%~98.5%。进水OLR提高了污泥往胞外聚合物含量,且显著提高了PN含量。在进水OLR为400 mg/L时,聚羟基脂肪酸酯(PHA)最大积累量为5.98 mmol/g,糖原质含量下降至6.03 mmol/g。OLR能影响AOA工艺内微生物群落结构,适量提高OLR促进了Proteobacteria和Firmicutes在污泥内的占比。研究结果为AOA工艺处理不同进水OLR的废水提供一定的数据支撑和理论依据。

AA-RPIR工艺应用于某污水处理厂工程设计与实践

东莞市某污水处理厂现状一期、二期总规模为15万m^(3)/d。因片区污水处理需求逐步增长,污水厂面临高负荷运行及雨季超负荷运行问题。为缓解该厂日益紧迫的污水处理压力,需进行三期扩建工程,其扩建规模为土建10万m^(3)/d,近期设备安装为5万m^(3)/d。三期工程采用一种新型快速生化污水处理技术-反应沉淀一体式环流生物反应器(RPIR),以该技术组合成“厌氧-缺氧-RPIR(AA-RPIR)”核心污水处理工艺。文章主要介绍该工程的设计特点及实际运行效果。该工艺AARPIR生化池部分的用地指标为0.110 m^(2)/(m^(3)·d^(-1)),相比传统“AAO+二沉池”工艺节约用地约0.019 m^(2)/(m^(3)·d^(-1)),后段深度处理采用“高效沉淀池+精密滤池”工艺,整个工艺对污染物去除效果较佳,其对COD_(Cr)、TN、TP、SS及氨氮的最大去除率分别为95.5%、72.8%、96.9%、97.9%及98.2%。此工程为RPIR工艺在市政污水处理厂的应用提供了设计案例,实际运行效果可为其他类似污水厂提标或扩建设计提供参考。

废油漆桶清洗废水处理工程设计

根据废油漆桶清洗废水高pH值、高COD和悬浮物、可生化性较差的水质特点,设计采用加酸中和-气浮-混凝沉淀-臭氧氧化-水解酸化-缺氧-好氧-MBR组合工艺进行处理。工程运行结果表明,在进水COD、BOD_(5)、SS质量浓度分别为3750、900、450 mg/L,色度为420度时,相应出水分别为110、15、5 mg/L和15度,排水水质满足GB/T 19923—2005《城市污水再生利用工业用水水质》表1规定的洗涤用水标准。该工艺具有运行稳定,操作简单,投资及运行成本低且节约水资源等特点,实现了良好的经济效益和环境效益。

污水处理厂中“AAO+深度处理”工艺减污降碳研究

针对当前污水处理过程中的碳排放问题,设计“AAO(厌氧—缺氧—好氧)+深度处理”的污水处理工艺,并以某污水处理厂为例,将“AAO+深度处理”工艺应用其中,对污水处理效果进行分析,并对该项工艺的降碳和经济性进行探究。

生物脱氮除磷工艺厌氧/缺氧环境倒置效应

厌氧、缺氧环境是生物脱氮除磷工艺必不可少的重要组成部分，就该两种环境的先后顺序及其对工艺性能的影响进行机理研究。结果表明：常规工艺厌氧（Ａ１）／缺氧（Ａ２）／好氧（Ｏ）布置方式的合理性是值得再探讨的。把常规工艺的厌氧、缺氧环境倒置过来，即以缺氧（Ａ２）／厌氧（Ａ１）／好氧（Ｏ）方式运行可明显提高工艺的氮磷脱除效果。在同等条件下，Ａ２／Ａ１／Ｏ系统的出水Ｏｒｔｈｏ－Ｐ比常规Ａ１／Ａ２／Ｏ系统低５０％，而比反硝化速率却比后者高４０－５０％。

水解酸化/AAO工艺的同步脱氮除磷及污泥减量研究

针对传统活性污泥法脱氮除磷效率低、污泥产量高的缺点，提出了水解酸化／缺氧-厌氧-好氧（HAAO）污水、污泥一体化处理工艺，研究了该工艺去除COD、氮、磷和污泥减量的效果及其主要影响因素。试验结果表明，在进水COD为286-425mg／L、NH4^＋ -N为36-58mg／L、PO4^3- -P为4-12mg／L、总水力停留时间为11．5h及无外加碳源和碱度的条件下，系统对COD、NH4^＋ -N、TN、PO4^3- -P的去除率分别可达95％、98％、84％、87％。好氧段的DO浓度、固体停留时间（SRT）和剩余污泥回流比对系统的运行效果有重要影响。将污水和剩余污泥同时进行水解酸化，既可有效地改善污水的可生化性，提高系统对碳源的利用效率，又可实现污泥的减量化，试验条件下系统的污泥减量率达56．5％。

碳源对缺氧/厌氧/好氧工艺脱氮除磷效果的影响

通过投加有机碳源改变进水的碳氮比,考察了不同碳氮比条件下缺氧/厌氧/好氧工艺的脱氮除磷效果。结果表明:在污泥回流比为120%的条件下,当C/N值为7、C/P值为75时,缺氧/厌氧/好氧工艺对污水的脱氮除磷效果最佳,对TP、NH4+-N和TN的去除率分别可达95%以上、98%和67%。

基于数学模型的多模式AAO系统运行优化研究

构建了综合考虑出水水质、污泥产量和系统能耗的运行成本指数CPI,并利用数学模型对多模式厌氧/缺氧/好氧（AAO）系统的AAO、倒置AAO（RAAO）和缺氧/好氧（AO）3种模式进行对比优化研究.在处理成本相近的前提下,在污泥龄5-25d范围内AAO模式的污染物去除效率和聚磷菌浓度明显高于RAAO和AO模式.在运行模式筛选的基础上,通过回流比优化确定了排放标准约束下AAO工艺的达标运行区域和最佳运行工况.动态模拟结果表明,优化工况能够显著改善出水水质,出水高于一级A的时间由78.4%下降至37.7%,CPI降低3.9%.

短程硝化反硝化去除高氨氮猪场废水中的氮

对比分析了运用缺氧／好氧SBR工艺处理2种COD／N不同的废水的脱氮效果，结果表明，2种废水的脱氮主要是通过短程硝化反硝化实现的，反应器中的NH4^+-N浓度和pH值是控制亚硝酸型硝化的重要因素，经过部分厌氧消化的废水由于保持了较高的COD／N，脱氮效果明显好于完全厌氧消化废水，NH4^+-N去除率达到98％以上，但出水反硝化不完全，投加乙酸钠后出水NOx^--N由100-120mg／L减少到10-20mg／L，乙酸钠投加量以275mg／L为宜．

SBR工艺交替硝化反硝化运行方式的可行性研究

将交替好氧、缺氧运行方式应用于间歇式污水处理系统(SBR工艺),分别在原水碱度充足和碱度不足情况下考察该运行方式的可行性.结果表明:原水碱度充足时,交替硝化反硝化的运行方式在处理效率上并没有体现出优势;原水碱度不足时,交替硝化反硝化与传统硝化反硝化相比,处理效率与出水水质明显提高,出水氨氮可以达到检测水平.当原水碱度的不足量低于所需碱度理论值的1 3时,采取交替硝化反硝化,无需额外补充碱度就可以达到原水碱度充足情况下的处理效率.如果原水碱度的不足量已超过1 3,采取交替硝化反硝化可最大限度节省额外投加碱度的量,降低处理成本,是一种理想的运行方式.

草甘磷废水处理技术

对经电解预处理后的草甘磷废水采用选择性生物反应器 - UASB- CAAS组合工艺进行处理。试验结果表明 :当进水 COD为 2 6 5 0 0～ 30 0 0 0 mg/ L,Cl-为 5 6 78～ 7892 m g/ L 时 ,处理后出水 COD小于 15 0 mg/ L,COD平均去除率达到 99%以上 。