Enhanced Biological Nutrients Removal in Modified Step-feed Anaerobic/Anoxic/Oxic Process

In order to enhance phosphorus removal in traditional step-feed anoxic/oxic nitrogen removal process,a modified pilot-scale step-feed anaerobic/anoxic/oxic(SFA 2/O) system was developed,which combined a reactor similar to UCT-type configuration and two-stage anoxic/oxic process.The simultaneous nitrogen and phosphorus removal capacities and the potential of denitrifying phosphorus removal,in particular,were investigated with four different feeding patterns using real municipal wastewater.The results showed that the feeding ratios(Q1)in the first stage determined the nutrient removal performance in the SFA 2/O system.The average phosphorus removal efficiency increased from 19.17% to 96.25% as Q1 was gradually increased from run 1 to run 4,but the nitrogen removal efficiency exhibited a different tendency,which attained a maximum 73.61%in run 3 and then decreased to 59.62%in run 4.As a compromise between nitrogen and phosphorus removal,run 3 (Q1=0.45Qtotal) was identified as the optimal and stable case with the maximum anoxic phosphorus uptake rate of 1.58 mg·(g MLSS)-1 ·h-1.The results of batch tests showed that ratio of the anoxic phosphate uptake capacity to the aerobic phosphate uptake capacity increased from 11.96% to 36.85% with the optimal influent feeding ratio to the system in run 3,which demonstrated that the denitrifying polyP accumulating organisms could be accumulated and contributed more to the total phosphorus removal by optimizing the inflow ratio distribution.However,the nitrate recirculation to anoxic zone and influent feeding ratios should be carefully controlled for carbon source saving.

Transformation of phthalic acid diesters in an anaerobic/anoxic/oxic leachate treatment process

Transformations of di-n-butyl phthalate(DBP) and di(2-ethylhexyl) phthalate(DEHP) have been investigated in anaerobic/anoxic/oxic(A/A/O) leachate treatment processes. Although the DBP removal processes are different when the DBP initial concentration is different, the overall system DBP removal efficiencies are high(N 94%).DEHP is much more difficult to remove than DBP. The removal efficiency of DEHP is approximately 75%–78%.The results of mass balance calculations indicate that approximately 33.7%–50.7% of the DBP is degraded by the activated sludge, 48.9%–64.9% accumulates in the system, and 0.4%–1.4% is contained in the final effluent. Approximately 15.0%–19.0% of the DEHP is degraded by activated microcosms, 75.8%–79.0% accumulates in the system, and 5.2%–6.0% is contained in the final effluent. Biodegradation and adsorption to the activated sludge are the main mechanisms for DBP removal and adsorption to the activated sludge is the main mechanism for DEHP removal. The different removal mechanisms of the two PAEs may be related to their different molecular structures. However, PAEs are not really removed when they adsorb onto the sludge. Therefore, methods for decreasing PAEs adsorption and increasing the biodegradation efficiencies of the leachate treatment processes should be further investigated.

Electricity Generation Performance of Microbial Fuel Cell Embedded in Anaerobic-Anoxic-Oxic Wastewater Treatment Process

Microbial fuel cell (MFC) embedded in anaerobic-anoxic-oxic (A2/O) process has positive effects on wastewater treatment, which can enhance the efficiencies of pollutants’ removal, along with electricity production. But the electricity generation performance and its optimization of MFC embedded in A2O process still needs to be further investigated. In this study, in order to optimize the contaminants removal and electricity production of the MFC-A2/O reactor, a lab-scale corridor-style MFC-A2/O reactor, which could simulate the practical A2/O biological reactor better, was designed and operated. The removal efficiencies of chemical oxygen demand, total nitrogen and total phosphorus were continuously monitored so as the electricity generation. In addition, the influences of the structural parameters’ changes of MFC on the output voltage, including electrode material, the directly connected area and the distance between electrodes, were also studied. The results elucidated that the effluent quality of A2/O reactor could be improved when MFC was embedded, and all the investigated structural factors were closely related to the electricity generation performance of MFC to some extent.

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.

The first metagenome of activated sludge from full-scale anaerobic/anoxic/oxic(A2O) nitrogen and phosphorus removal reactor using Illumina sequencing

The anaerobic/anoxic/oxic（A2O） process is globally one of the widely used biological sewage treatment processes. This is the first report of a metagenomic analysis using Illumina sequencing of full-scale A2O sludge from a municipal sewage treatment plant.With more than 530,000 clean reads from different taxa and metabolic categories, the metagenome results allow us to gain insight into the functioning of the biological community of the A2O sludge. There are 51 phyla and nearly 900 genera identified from the A2O activated sludge ecosystem. Proteobacteria, Bacteroidetes, Nitrospirae and Chloroflexi are predominant phyla in the activated sludge, suggesting that these organisms play key roles in the biodegradation processes in the A2O sewage treatment system.Nitrospira, Thauera, Dechloromonas and Ignavibacterium, which have abilities to metabolize nitrogen and aromatic compounds, are most prevalent genera. The percent of nitrogen and phosphorus metabolism in the A2O sludge is 2.72% and 1.48%, respectively. In the current A2O sludge, the proportion of Candidatus Accumulibacter is 1.37%, which is several times more than that reported in a recent study of A2O sludge. Among the four processes of nitrogen metabolism, denitrification related genes had the highest number of sequences（76.74%）, followed by ammonification（15.77%）, nitrogen fixation（3.88%） and nitrification（3.61%）. In phylum Planctomycetes, four genera（Planctomyces, Pirellula, Gemmata and Singulisphaera） are included in the top 30 abundant genera, suggesting the key role of ANAMMOX in nitrogen metabolism in the A2O sludge.

水解酸化+A2/O+AO+芬顿氧化工艺处理工业园区污水

针对工业园区的污水排放企业种类较多、进水水量水质波动较大、污染物复杂且可生化性差、排放标准高的特征,以浙江省德清县某工业园区实际污水处理工程为对象,分析了水解酸化+A2/O+AO+芬顿氧化工艺处理以印染、食品制造、金属加工企业为主的废水排放的技术经济可行性.实践结果显示,出水水质的COD、NH_(3)-N、TN及TP能稳定达到《城镇污水处理厂主要染物排放标准》(DB33/2169—2018)中的限值,其余指标达到《城镇污水处理厂染物排放标准》(GB18918—2002)的一级A标准;工程投资金额为8200元/m^(3),实际直接运行成本为2.39元/m^(3).

提标升级对乡镇污水处理厂碳排放特征的影响

在碳达峰、碳中和和流域水污染防治的背景下,乡镇污水处理厂减污降碳协同势在必行。基于成都市某乡镇市政污水处理厂2016—2022年水质水量数据,分析提标升级前后化学需氧量、氨氮、总磷、总氮的时间变异性,利用《IPCC 2006国家温室气体清单指南》(2019年修订版)、《城镇水务系统碳核算与减排路径技术指南》评估直接、间接碳排放强度特征,探究提标升级前后碳排放量对季节、水质及污染物削减量的响应。结果表明:1)污水处理厂主体工艺从周期循环活性污泥法(CASS)升级为厌氧-缺氧-好氧-膜生物反应器法(AAO-MBR)后,出水水质满足DB 51/2311—2016《四川省岷江、沱江流域水污染物排放标准》,升级后通过增加碳源、利用MBR膜截留污泥等措施,使出水水质指标更加稳定,对污染物的处理效率更高;2)提标升级后,直接、间接碳排放强度分别为0.296和1.082 kg/m^(3)(以CO_(2)当量计),分别增加41.59%和105.70%,且夏季碳排放强度显著低于其他季节(P<0.01),升级前后的间接碳排放强度均高于直接碳排放强度;3)提标升级后,总碳排放强度增加了0.643 kg/m^(3)(以CO_(2)当量计),工艺升级导致的电耗增加,使得间接碳排放强度变化更显著。乡镇污水处理厂提标升级在提高处理效能的同时也增加了碳排放量,建议在工艺改造中协同考虑污染物去除与能耗控制,以实现减污降碳协同增效。

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。

基于复杂用地条件的地下式污水处理厂精细化设计

广州市黄埔区某水质净化厂二期工程需要在不规则的用地形状、复杂的场地周边环境、较低的建设用地指标及地上高水平建设开发的预期下,实现规模为5万m^(3)/d地下式污水处理厂的设计工作。工艺设计上通过采用“厌氧-缺氧-好氧+膜生物反应器(AAO+MBR)”工艺提升节地效率;结构设计上通过处理单元构筑物的共壁、错层实现“地尽其用”;平面设计上通过优化池体上部建(构)筑物布局、设施设备设置、交通物流规划、管线综合排布来提高操作空间的使用率。本工程项目用地负荷率比同类项目提高了36%,工程直接费用的建设单位成本低于广州市同等规模同类型项目8.5%的情况下,实现了工程设计目标,为同类项目的设计提供了良好示范。

山羊皮加工废水处理工艺设计

开封市某皮革企业年加工山羊皮600万张,从事由毛皮到成皮的全流程生产。厂区建有1座污水处理站,主要包括含铬废水预处理单元、含硫废水预处理单元和综合废水处理单元。结合污水处理站的设计规模和进出水水质,分析废水处理的工艺流程和主要设计参数,从而指导类似企业有效降低投资和运行成本,提高经济效益和环境效益。

A^(2)O+MBR工艺处理低碳氮比污水的效果研究

污水处理厂通常面临进水碳氮比偏低的问题,为确保出水水质达标,一般采取超量投加碳源的策略,但是这会导致运行成本上升。北京市某污水处理厂将厌氧-缺氧-好氧(Anaerobic-Anoxic-Oxic,A^(2)O)+膜生物反应器(Membrane Bio-Reactor,MBR)工艺作为主体工艺,进水由生活污水(占30%)和工业废水(占70%)组成。该污水处理厂向缺氧池投加葡萄糖溶液作为碳源,辅助脱氮。试验分别测定进出水化学需氧量(Chemical Oxygen Demand,COD)、总氮(Total Nitrogen,TN)和反应池混合液悬浮固体(Mixed Liquid Suspended Solids,MLSS)的浓度,分析外加碳源对脱氮效果和污泥产生量的影响,并进行碳源投加前后的成本对比。研究表明,进水COD/TN小于7时,适量投加碳源有助于提升脱氮效率,而COD/TN大于7时,要优化其他环节来加强脱氮效果,以保证出水水质稳定符合相关标准。通过精细化过程控制和改变运行管理方式,污水处理厂可以有效降低运行成本,避免进行工程化改造。

改进型A^(2)O+MBR工艺在污染地表水处理中的应用

南方某园区受污染地表水存在化学需氧量(Chemical Oxygen Demand,COD)和总氮超标等问题,对下游城市河道水环境质量造成影响。结合受污染水质情况,工程采用改进型厌氧-缺氧-好氧(Anaerobic-Anoxic-Oxic,A^(2)O)与膜生物反应器(Membrane Bio-Reactor,MBR)相结合处理工艺,强化脱氮和难降解有机物处理,出水指标稳定达到《地表水环境质量标准》(GB 3838—2002)Ⅳ类标准,详细介绍了该组合工艺的处理流程、主要构筑物及配套设备设计参数,为修复受损水体工程提供参考。

6000 m^(3)/d明胶废水处理工程设计与实践

明胶废水与常见的工业废水有较大不同,其成分更加复杂,处理难度更大。以某明胶生产企业为例,结合废水处理站设计处理规模和进出水水质,对不同废水处理工艺进行比选。经比选,废水处理站选用“初沉池+气浮池+水解池+厌氧好氧生化池+二沉池”组合工艺处理明胶废水。经该工艺处理后,出水的化学需氧量、生化需氧量和氨氮等主要指标均达到设计要求,满足《污水综合排放标准》(GB 8978—1996)的一级标准。

A^(2)/O工艺中溶解性有机氮的分子转化与生物有效性特征

本研究探究了厌氧/缺氧/好氧(A^(2)/O)工艺沿程溶解性有机氮(DON)浓度分布及其分子转化规律,并运用多种方法表征了各单元污水DON的生物有效性特征.结果表明,DON浓度由进水(5.3±0.3)mg/L沿厌氧池、缺氧池分别下降至(2.0±0.1),(1.8±0.2)mg/L,而有意思的是好氧池中DON浓度反而升高至(1.9±0.1)mg/L,去除率竟为(-5.6±0.6)%.傅里叶变换离子回旋共振质谱(FT-ICR-MS)分析DON分子组成特征显示,各单元活性DON分子(H/C≥1.5)占比为:厌氧池(38%)<缺氧池(41%)<好氧池(42%),表明好氧池出水DON最不稳定,易被受纳水体中藻类微生物摄取利用.同时在各单元产生的DON分子中,以蛋白/氨基糖类化合物为特征的微生物源DON占比沿程上升,由厌氧池24.77%分别上升至缺氧池29.12%、好氧池33.11%,表明微生物源DON分子是导致好氧池出水DON生物有效性升高的原因.进一步地,采用藻类生物测定厌氧池、缺氧池和好氧池沿程DON生物有效性,分别为(33.2±3.0)%、(34.9±7.0)%和(42.1±4.0)%,该结果证实了FT-ICR-MS的测定结论.此外,主成分分析表明,相比于厌氧池和缺氧池,温度对好氧池DON分子组成具有显著影响,且冬季好氧池出水DON生物有效性(49.3%±2%)高于夏季(42.1%±4.0%).因此,冬季好氧池出水DON具有更高的富营养化潜在风险.

A^(2)/O-BAF工艺短程硝化模式下反硝化除磷效能

采用厌氧/缺氧/好氧-曝气生物滤池(A^(2)/O-BAF)工艺处理低C/N城市污水,研究硝化液回流比为0、50%、100%、150%和200%时该工艺脱氮除磷效能。结果表明,在A^(2)/O中控制污泥龄(SRT)为15d,水力停留时间(HRT)为10h,好氧段溶解氧(DO)为2.0mg/L;BAF中控制HRT为3h、好氧/缺氧曝停时间比为50min∶10min以及硝化液回流比R=200%的条件下,进水COD、TN、NH_(4)^(+)-N和PO_(4)^(3-)-P的浓度分别为232.61mg/L、53.99mg/L、52.20mg/L和5.54mg/L,系统出水中COD、TN、NH_(4)^(+)-N和PO_(4)^(3-)-P的浓度分别为34.11mg/L、12.44mg/L、1.01mg/L和0.34mg/L,亚硝积累率(Ni AR)高达95.20%。出水NO_(2)^(-)-N回流至A^(2)/O缺氧段后,缺氧段出水的PO_(4)^(3-)-P含量下降至2.68mg/L,反硝化除磷(DPR)对系统PO_(4)^(3-)-P的去除贡献达75.42%。批次试验表明,A^(2)/O反应器中的除磷菌在厌氧120min后释磷量达到36.35mg/L,缺氧条件下以NO_(2)^(-)-N为电子受体的反应中吸磷量为26.28mg/L,吸磷率为72.30%,以NO_(2)^(-)-N为电子受体的反硝化除磷菌(DPB)占总除磷菌的72.91%。

水解酸化+AAO+混凝沉淀+臭氧-BAF工艺在综合产业园废水处理中的应用

针对综合产业园废水处理项目进水水质成分复杂、可生化性较差、水质水量波动较大的特点,以潜江某综合产业园废水处理项目为例,介绍了该工程的废水特性、废水处理工艺、主要设计参数和运行效果,分析了不同工况下的污水处理运行费用。污水经“水解酸化+AAO+混凝沉淀+臭氧-BAF”工艺处理后,出水主要污染物指标可稳定达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A标准。污水处理厂投资为4826元/m^(3),设计工况下运行费用为1.399元/m^(3),实际低进水水质工况下的运行费用为0.755元/m^(3)。相关经验可为排水企业种类较多、具有相似水质特征的综合产业园污水处理厂提供参考。

A^(2)/O+MBR+潜流湿地在南方小流域环境综合整治中的应用

受制于该流域用地指标及用地性质的影响,结合流域环境整治的景观需求,采用了灰绿结合的A^(2)/O+MBR+潜流湿地组合工艺形式作为流域治理的水质净化处理工艺对流域收集的污水进行处理。工程运行四年来,出水主要指标稳定达到《地表水环境质量标准》(GB3838-2002)Ⅳ类水质标准(TN≤10 mg/L),其中再生水厂COD、BOD5、NH_(3)-N、TN、TP、SS平均去除率分别达到91.18%、98.27%、97.83%、62.74%、91.29%和99.04%;潜流湿地NH_(3)-N、TN、TP平均去除率分别达到38.44%、12.15%和33.04%。工程实践表明,该组合工艺不仅满足了流域水质要求、节约占地,同时也起到了很好的景观效果。