A2O工艺处理低C/N比生活污水的试验研究

采用52.5 L的A²O试验装置处理实际生活污水,研究了A²O工艺在处理低C/N比生活污水时的脱氮除磷特性,并探讨了如何通过强化缺氧吸磷来提高系统的脱氮除磷效率。试验结果表明：在厌氧/缺氧/好氧体积比为1/1/2、HRT为8 h、污泥回流比为70%、内回流比为300%的工况下处理C/N为7.89的生活污水,TN和SOP去除率分别能够达到85.4%和93.3%,系统中存在反硝化除磷,缺氧吸磷占总吸磷量的25.3%。同样的运行条件下处理C/N为4.20的生活污水时,SOP去除几乎不受影响,但TN去除率降低至62.2%,平均出水TN浓度也超过20 mg•L^-1。维持厌氧区体积不变,增大缺氧区体积,使得缺氧/好氧体积比为5/8时,TN去除率可上升到70.7%,缺氧吸磷占总吸磷量的55.2%。同时改变内回流比的试验表明250%的内回流比能最大程度地强化反硝化除磷的作用,此时TN去除率可提高至77.3%。强化A²O工艺中的反硝化除磷,能克服碳源不足对脱氮除磷的影响,显著提高低C/N比污水的脱氮除磷效率。     

Pilot‐scale anaerobic/anoxic/oxic/oxic biofilm process treating coking wastewater

BACKGROUND: Biological treatment efficiency of coking wastewater is rather poor, especially for chemical oxygen demand (COD) and ammonia‐nitrogen (NH$_{4}^{+}$ ‐N) removal due to its complex composition and high toxicity. RESULTS: A pilot‐scale anaerobic/anoxic/oxic/oxic (A²/O²) biofilm system has been developed to treat coking wastewater, focusing attention on the COD and NH$_{4}^{+}$ ‐N removal efficiencies. Operational results over 239 days showed that hydraulic retention time (HRT) of the system had a great impact on simultaneous removals of COD and NH$_{4}^{+}$ ‐N. At HRT of 116 h, total removal efficiencies of COD and NH$_{4}^{+}$ ‐N were 92.3% and 97.8%, respectively, reaching the First Grade discharge standard for coking wastewater in China. Adequate HRT, anoxic removal of refractory organics and two‐step aerobic bioreactors were considered to be effective measures to obtain satisfactory coking effluent quality using the A²/O² biofilm system. The correlation between removal characteristics of pollutants and spatial distributions of biomass along the height of upflow bioreactors was also revealed. CONCLUSION: The study suggests that it is feasible to apply the A²/O² biofilm process for coking wastewater treatment, achieving desirable effluent quality and steady process performance. © 2012 Society of Chemical Industry     

Performance and microbial population variation in a plug‐flow A2O process treating domestic wastewater with low C/N ratio

BACKGROUND: In this study, a plug‐flow A²O (anaerobic/anoxic/oxic) reactor, with a working volume of 52.5 L, was employed to investigate the performance of biological nutrients removal and microbial population variations when treating low C/N ratio domestic wastewater. RESULTS: Results showed that TN removal was significantly affected by the shortage of carbon source while phosphorus removal was only slightly affected. The effluent soluble orthophosphate‐phosphorus (SOP) concentration was lower than 0.50 mg L^?1 but the TN concentration was over 20 mg L^?1 when the C/N ratio was 4.43. There was denitrifying phosphorus removal in the anoxic reactor and this was enhanced by increasing the volume ratio of anoxic reactor and maintaining appropriate mixed liquor recycle rate. More than 60% of the SOP were removed in anoxic reactors by denitrifying phosphorus removal when the volume ratio of anaerobic/anoxic/oxic was 1/1.4/1.6 and the mixed liquor recycle rate was 250%. The TN concentration of effluent decreased to 11.34 mg L^?1 and SOP concentration was still lower than 0.5 mg L^?1 in this condition. The main microorganisms found in the process by polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and the functional biodiversity are discussed. CONCLUSION: Traditional design and operating parameters of A²O are not appropriate for treating low C/N wastewater. Enhancing the denitrifying phosphorus removal ratio in an A²O process is an effective way to increase the removal rate of N and P from low C/N wastewater. Copyright © 2010 Society of Chemical Industry     

Performance evaluation of a modified step-feed anaerobic/anoxic/oxic process for organic and nutrient removal

A pilot scale modified step-feed process was improved to increase nutrient(N and P)and organic removal operations from municipal wastewater.It combined the step-feed process and a method named "University of Cape Town(UCT)".The effect of nutrient ratios and inflow distribution ratios were studied.The highest uptake efficiency of 95% for chemical oxygen demand(COD)has been achieved at the inflow distribution ratio of 40/35/25.However,maximum removal efficiency obtained for total nitrogen(TN)and phosphorus at 93% and 78%,respectively.The average mixed liquor suspended solids(MLSS)was 5500 mg·L~(-1).In addition,convenient values for dissolved oxygen(DO)concentration,and p H were obtained throughout different stages.The proposed system was identified to be an appropriate enhanced biological nutrient removal process for wastewater treatment plants owing to relatively high nutrient removal,sturdy sludge settle ability and COD removal.     

Optimisation of anaerobic/anoxic/oxic process to improve performance and reduce operating costs

A laboratory‐scale anaerobic/anoxic/oxic reactor system was used to treat synthetic brewery wastewater for 1 year. The objectives were to enhance denitrifying phosphorus removal, improve biological nutrient removal and reduce operating costs. Three operational strategies were tested: (1) controlling nitrate recirculation to stimulate the growth of denitrifying phosphate‐accumulating organisms; (2) adjusting the volume ratio of the anaerobic/anoxic/oxic zones to enhance anoxic P uptake; (3) bypassing a part of the influent flow into the anoxic zone to maximise anoxic P uptake and denitrification. The results showed that not only was anoxic P uptake enhanced but also energy consumption for aeration could be reduced when the anoxic effluent NO₃^?‐N concentration was controlled between 1 and 3 mg L^?1. The optimal volume ratio of the anaerobic/anoxic/aerobic zones in this system was found to be 1:1:2. The optimal bypass flow ratio was 0.32. The results indicated that the optimal strategies could improve treatment performance and reduce operational costs, but there was still a challenge to treat wastewater with low C/N ratio. Copyright © 2006 Society of Chemical Industry     

A study of A2/O process in El-Berka WWTP by replacing the anaerobic selector with UASB and adopting a hybrid system in the oxic zone

ABSTRACT

A multistage system comprising an upflow anaerobic sludge blanket (UASB) followed by anoxic unit and then oxic activated sludge (AS) with biofilm is studied in El-Berka WWTP, Egypt. Different organic loading wastewaters of chemical oxygen demand (COD) less than 500 mg/L till 3000 mg/L are tested during the study. The hydraulic retention time (HRT) varies for each loading from 7.5 to 10 to 15 h. The UASB reactor accomplishes the removal efficiency of 50%–70% of influent COD. The overall system performs the removal efficiency of 95% of influent COD and NH₄-N. Also, the results are verified by a modified mathematical model.     

Biological nutrient removal characteristics of low strength municipal wastewater

Most Korean community represents the primary effluent of 180 mg/L COD, 80 mg/L BOD, 25 mg/L TKN and 4 mg/L TP. A/O, A²/O and MUCT (Modified University of Cape Town) systems were applied to laboratory scale reactor with a temperature of 10 to 20°C. A total of 6 hour hydraulic retention time including anaerobic, anoxic and aerobic zones was used with a maximum 3,000 mg/L MLSS to simulate the existing municipal plants. All BNR systems represented effluent BOD less than 10 mg/L. MUCT produced better quality; 0.5 mg/L SP (soluble phosphorus) with 10 mg/L TN vs 1.8 mg/L SP with 12 mg/L TN for A²/O with the same internal recycle ratio. Performance of BNR systems would suggest the primary effluent used for this study represents a nature of slowly biodegradable COD. As that result, anaerobic fraction must be increased to attain lower effluent P concentrations. However, prefermentation to increase Premoval was not necessary since P was also limited. Microbial mass fractions computed from COD and nitrogen mass balances suggested that poly-P microbes were about 33% in A/O and MUCT, denitrifier fractions were about 30% in A²/O and MUCT. Nitrifier fractions were about 2%.     

多点进水改良型复合A2/O处理低C/N污水

以低C/N比城市生活污水为研究对象,重点考查了改良A²/O工艺的脱氮除磷性能。原水按一定比例分配给厌氧池和缺氧池,以合理分配厌氧释磷和缺氧反硝化所需的碳源;在好氧池和缺氧池中分别投加填料,以稳定系统的硝化和反硝化效果,提高系统的脱氮性能;厌氧池和缺氧池出水都直接进入好氧池。在进水COD/TN平均为5.54,HRT为11 h,SRT为15 d,MLSS为3000～4000 mg·L^-1,污泥回流比为50%条件下,通过三种不同进水分配比以及三种混合液回流比的对比试验研究,得到系统最佳进水分配比5:5,对分配脱氮和除磷所需碳源更加合理;而混合液回流比为200%,过高会破坏缺氧池的溶解氧环境,过低又会导致缺氧池反硝化作用不能充分发挥。在最优工况下COD、NH₃-N、TN和TP出水水质分别为29.7、0.1、11.8和0.42 mg·L^-1,平均去除率分别达到87.8%、99.7%、72.4%和91.3%,出水优于国家GB 18918-2002一级A排放标准,并且在缺氧池中发生了明显的反硝化除磷现象。     

UASB-A/O工艺处理化工园区废水的试验研究

针对某化工园区废水水质变化大、污染物种类多、难生物降解、处理难度大的特点,采用UASB-A/O联合工艺处理该化工园区废水。研究结果表明,该联合工艺对CODCr、NH3-N、TP的去除率分别可达到83.0%、74.5%、93.1%,出水水质达到GB 8978—1996《污水综合排放标准》一级排放标准的要求。通过UASB厌氧反应器的进一步水解酸化作用,废水的可生化性得到了提高,UASB与A/O工艺联合,提高了系统对CODCr、NH3-N、TP的去除效果,有利于该工艺的推广和使用。     

改良型A~2/O工艺对低碳源城市污水的脱氮除磷效果

以城市污水为原水,考察了一种分点进水的改良型A2/O工艺的脱氮除磷效果。试验结果表明,原水按照6∶4的体积比分别进入厌氧池和缺氧池后,增加了缺氧池的碳源浓度,提高了该系统的脱氮效果。当进水中碳氮质量比平均为6.84、硝化液回流比为200%,CODCr、TN、NH3-N和TP的平均质量浓度分别为237.02、36.39、22.99和4.98mg/L时,出水CODCr、TN、NH3-N和TP的平均质量浓度分别为34.29、10.70、0.18和0.46mg/L,去除率分别为85.53%、70.60%、99.22%和90.76%。     

臭氧氧化-A~2/O工艺处理含吡啶有机废水的研究

采用臭氧氧化-A~2/O组合工艺对某企业含吡啶有机废水进行处理。小试试验确定臭氧氧化工艺的最佳反应条件:反应时间为120 min,反应初始pH为5,臭氧投加量为1.20 g/L。此时,废水中吡啶和TOC的去除率分别达到35%和36%,B/C由0.22提高至0.36。经臭氧氧化-A~2/O组合工艺处理后,出水中的吡啶、TOC、COD质量浓度分别稳定在20、90、350 mg/L以下,出水水质达到《污水综合排放标准》(GB 8978—1996)中的三级标准,可以排入该企业所在的化工园区集中污水处理厂进行后续处理。     

流量分配比对改良A/O分段进水脱氮除磷特性的影响

采用改良A/O分段进水工艺处理我国南方低浓度、低碳氮比城市生活污水。在进水COD/TN为5.16,HRT为8.7 h,SRT为15 d,MLSS为5.66 g·L^-1,污泥回流比为75%,厌氧/缺氧/好氧体积比为4∶8∶10条件下,通过设置6种不同进水流量分配比,控制各好氧段DO为1～1.5 mg·L^-1,经过150 d的连续运行,得到系统最佳流量分配比为20%∶35%∶35%∶10%;在此工况下COD、氨氮、总氮、总磷出水水质分别为33.05 mg·L-1、0.58 mg·L^-1、9.26 mg·L^-1、0.46 mg·L^-1,出水优于国家GB 18918-2002一级A排放标准。原水COD绝大部分作为厌氧释磷和反硝化脱氮所需碳源,系统对碳源有效利用率达74%;DO和ORP 的协同控制可以作为系统厌氧放磷段的控制参数;同时亦可作为缺氧段反硝化完成和好氧段硝化完成的指示性参数。     

Evaluation of the parameters affecting nitrogen and phosphorus removal in anaerobic/anoxic/oxic (A/A/O) biological nutrient removal systems

Considerable research has been performed on biological nutrient removal (BNR) systems which remove the problematic nutrients, nitrogen and phosphorus, that cause eutrophication. This research focussed on setting up two laboratory‐scale anaerobic/anoxic/oxic (A/A/O) systems and investigating their reliability while undergoing various parameter changes. Pump failure, in the first trial, R1, led to a decrease in pH, exposure of the sludge to relatively low nitrate concentrations and reduction of the suspended solids concentration within the system. This adversely affected the phosphorus removal efficiency. Shock loading the system with increased influent phosphate concentrations for 56 days was shown to aid remediation of the phosphorus removal efficiency to values between 65 and 70% (w/w). The second trial, R2, highlighted the presence of bacteria capable of P‐uptake under anoxic conditions (in the presence of nitrate). The characteristic anaerobic P‐release was also evident. The bacteria responsible for phosphate uptake under anoxic conditions are thought to be the denitrifying phosphate removing bacteria (DPB). However, the presence of higher nitrate concentrations retarded the P‐removal efficiency to some extent. Secondary release of P was evident in the clarifier of the A/A/O system during the R2 trial and especially during times of increased nitrate concentrations in the system. Between 20 and 40% (w/w) of the P taken up in the oxic stage of the system was released in the clarifier at various stages throughout the trial. © 2000 Society of Chemical Industry     

两级A/O工艺处理生活污水脱氮除磷试验

针对传统A2/O工艺存在的泥龄矛盾,将脱氮和除磷分置于前后2套不同的A/O系统中,第一级A/O采用活性污泥法除磷;第二级A/O采用生物膜法脱氮。以生活污水为处理对象进行试验研究。结果表明,在泥龄为6 d、水温为22～28℃,进水NH3-N、TP、COD的质量浓度分别为40～70、2.0～6.0、150～320 mg/L条件下,出水NH3-N、TP、COD的平均质量浓度分别为5.9、1.0、40 mg/L,均达到了城镇污水处理厂污染物排放标准(GB18918-2002)中的一级排放标准,其去除率分别为82.5%、69.7%、83.1%。     

改性填料强化A^2/O工艺处理低温市政污水效果的研究

采用向好氧池投加改性填料的方法,提升A^2/O工艺低温条件下的脱氮能力及CODCr降解能力。结果表明,在冬季水温为10～12℃的条件下,生化系统对CODCr、氨氮和总氮的去除率分别为91.3%、99.6%和79.7%,出水水质达到了GB 18918—2002《城镇污水处理厂污染物排放标准》中的一级A标准。     

物化预处理+厌氧+两级A/O工艺处理农药废水

采用物化(电催化氧化、铁炭微电解)预处理高、中浓度混合废水后,利用厌氧+两级A/O工艺处理综合废水,处理量为300 m3/d。运行实践表明:物化预处理对COD的去除率为32%,整个工艺处理后出水COD低于500 mg/L,氨氮低于35 mg/L,盐分低于0.6%,出水水质达到接管要求,工艺处理效果明显。     

改性硅酸钙用于养殖废水厌氧处理过程中除磷研究

为了实现在养殖废水厌氧处理的过程中同时除磷,自行制备改性硅酸钙(MCS),并对其物相和微观进行了表征;随后将其投加到正在运行的厌氧反应装置中,以考察其对养殖废水厌氧处理过程中除磷效果的影响。结果表明:制备的MCS纯度高、粒径小,为半结晶低有序度的水合硅酸钙单相,磷吸附量高达111.04 mg/g。重要的是,MCS的投入不仅未对UASB反应的运行和处理效果产生不良影响,而且可以提高反应器中污泥的活性,并可大幅提高反应器中磷去除率到99.5%,而未投加MCS的对照组中磷去除率仅为50%。     

改良倒置A~2/O工艺脱氮效率的研究与分析

对改良倒置A2/O工艺进行了讨论,并对其脱氮效率以及进入缺氧池和厌氧池的污水分配系数进行了研究分析,对于典型城市污水得出:①系统的脱氮效率为84.5%,出水硝态氮浓度为6.2 mg/L;②进入缺氧池的污水分配系数β≥37.2%~62%,厌氧池污水分配系数α≥40%。     

A/O结合循环式活性污泥法处理海产品加工废水

针对海产品加工废水氨氮含量较高的特点。舟山兴业有限公司的污水处理工程采用两段A/O结合循环式活性污泥法工艺，工程验收合格后运行一年多来，排放废水的各项污染指标均达到国家《污水综合排放标准》（GB8978-1996）的二级标准，处理系统具有很好的抗冲击能力和脱氮效果。