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     

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     

单级SBR厌氧/好氧/缺氧处理中期垃圾渗滤液深度脱氮

为了考察单级SBR处理实际中期垃圾渗滤液深度脱氮的可行性,采用单级SBR在“厌氧/好氧/缺氧”(AOA)运行方式下处理实际中期垃圾渗滤液。试验发现,厌氧/好氧/缺氧交替运行下驯化的微生物能在厌氧段消耗胞内糖原,并将水中部分溶解性有机物以聚羟基脂肪酸酯(PHAs)形式储存;在好氧段微生物消耗胞内PHAs,转化为胞内糖原,氨氧化的同时也伴随着同步硝化反硝化脱氮;好氧段氨氧化结束后贮存的碳源(PHAs和糖原)能为后置缺氧反硝化提供碳源。经长期试验研究,进水COD、NH₄⁺-N、TN浓度分别为6430～9372 mg·L^-1、1025.6～1327 mg·L^-1、1345.7～1853.9 mg·L^-1,出水COD、NH₄⁺-N、TN浓度能达到525～943 mg·L^-1、1.2～4.2 mg·L^-1、18.9～38.9 mg·L^-1。在未投加外碳源的情况下,SBR法AOA运行方式下能够实现中期垃圾渗滤液的深度脱氮,出水TN<40 mg·L^-1。其中,好氧段(DO<1 mg·L^-1)通过同步硝化反硝化去除TN占总去除量的1/3左右;缺氧后置反硝化去除的TN占总去除量的2/3左右。     

Combined adsorption and Chemical precipitation process for pretreatment or post-treatment of landfill leachate

Performances of combined adsorption and chemical precipitation were evaluated as one of the options for pretreatment or post-treatment of a municipal solid waste (MSW) landfill leachate and leachate from an industrial solid waste landfill. The COD and color removals of the leachate from a MSW landfill were 35% and 33% at an alum dose of 300 mg/L with preceding PAC (powdered activated carbon) dose of 200 mg/L, respectively. For MSW leachate, the combined adsorption and coagulation process showed 2.3 times higher COD removal at PAC dose of 200 mg/L and alum dose of 500 mg/L than the unit process of adsorption with poor settleability. The COD removal was accomplished mainly by adsorption, while coagulation was a key mechanism of color removal. The COD and color of the biologically treated leachate from an industrial solid waste landfill were removed up to 32% and 68%, respectively, at addition of 490 mgAlum/L and 1,000 mgPAC/L in adsorption-coagulation process with pH control. Combined adsorption and coagulation process with pH control showed better COD and color removal than the process without pH control. The color removal was influenced greatly by pH control, while COD removal was not. No difference in removal efficiency was observed between adsorption-coagulation and coagulation-adsorption. Maximum net increases in the COD and color removals by the adsorption-coagulation process were 40% and 46%, respectively, compared with the removals by sole chemical precipitation. The Freundlich isotherm exclusively described the adsorption of leachate components on the PAC. Thus, a combined adsorption and coagulation process was considered to be effective for pre-treatment or post-treatment of landfill leachate, and has distinct features of simple, flexible, stable and reliable operation against fluctuation of leachate quality and flowrate.     

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.     

垃圾焚烧发电厂沥滤液处理工艺

垃圾焚烧发电厂产生的垃圾渗沥滤液由于浓度高成分复杂一直是污水处理中的难点。通过介绍深圳市宝安垃圾焚烧发电厂二期配套沥滤液处理项目所采用的零排放组合处理工艺,以期解决垃圾沥滤液处理的难题,并在全国范围内进行推广。     

Performance evaluation of a modified anaerobic/anoxic/oxic (A/O) process treating low strength wastewater

A full scale modified A²/O process which combined pre-anoxic selector and the staging strategy treating low strength wastewater was investigated. In South China, domestic wastewater is always low in strength due to the high level of groundwater and setting of septic tank at the beginning of wastewater collection system. The results suggested that inadequate denitrification could result in deterioration of phosphorus removal. In addition, influent phosphorus concentration had effect on phosphorus removal. The pre-anoxic selector in modified A²/O process changed the distribution of nitrogen denitrified in different tanks. Characteristics of 3-stage aeration tanks were also studied. The simplified design of rectangular aeration tank could also perform as plug flow as conventional channel aeration tank. In 3-stage aeration tanks, mixed liquid suspended solid (MLSS) increased from one tank to another, while specific oxygen uptake rate (SOUR) of sludge, chemical oxygen demand (COD) and total phosphorus (TP) removal rate decreased, however ammonia nitrogen (NH₃-N) and nitrate nitrogen (NO₃-N) reaction rate remained constant. Furthermore, high MLSS concentration was not suitable for treating low strength wastewater. Waste sludge discharge could improve removal efficiency of COD, NH₃-N, and TP. Without waste sludge discharge, nitrite accumulated in settler.     

Evaluation of treatment and recovery of leachate by bipolar membrane electrodialysis process

Recovery studies are frequently carried out for electrodialysis (ED) processes. In this study, beyond examining the recovery of leachate components in an electrodialysis process, the use of that process to treat leachate-containing wastewater was simultaneously tested. Leachates were initially pre-treated (ultra filtration + cation exchange) to prevent clogging and harmful effect to the bipolar electrodialysis membranes. Optimum operating conditions were determined at the end of the experimental studies. Online observations during the electrodialysis process included the temperature-dependent reaction time, conductivity and changes of molar concentrations of H⁺ and OH⁻ ions in both the anolyte and catholyte compartments in which removed ions were collected. The most important contaminants in leachates are organic substances and nitrogen compounds. For this reason, representations of organic substances, such as the chemical oxygen demand (COD), and nitrogenous compounds, such as total Kheldahl nitrogen (TKN) and ammonia-nitrogen (NH₃-N), were also monitored in the electrodialysis effluent. Under the optimum operating conditions, removal of NH₃-N, TKN and COD were determined in the effluent at 96.2%, 92.8% and 86.7%, respectively. The conductivity value was determined to be 1.97 mS/cm at the end of the study.     

单一缺氧/厌氧UASB同步反硝化产甲烷与A/O组合工艺处理实际晚期渗滤液

以实际高氮晚期渗滤液为研究对象,应用缺氧/厌氧UASB-A/O组合工艺重点研究有机物和氮的去除特性,同时考察了A/O系统内短程硝化实现途径及稳定方法。试验结果表明,该生化系统可实现有机物和氮的同步、深度去除。在原液COD平均为6537 mg·L^-1,NH⁺₄-N为2021 mg·L^-1的条件下,系统最终出水分别为300 mg·L^-1和15.6 mg·L^-1,去除率分别为95.4%和99.2%。UASB反应器的平均COD负荷为6.5 kg COD·m^-3·d^-1,去除速率为5.3 kg COD·m^-3·d^-1。在单一UASB反应器内,发生了缺氧反硝化和厌氧产甲烷的双重生化反应,UASB反应器内获得了几乎100%的反硝化率。通过高游离氨（FA）和游离亚硝酸（FNA）的协同作用,使A/O反应器实现并维持了稳定的短程硝化,通过99%以上的亚硝化率实现高效的氨氮去除。     

苄基磺酸官能化介孔分子筛催化合成邻苯二甲酸二乙二醇双甲基丙烯酸酯

以苄基磺酸官能化的介孔分子筛（MCM-41-B-S）为催化剂,以邻苯二甲酸酐（PA）、一缩二乙二醇（DEG）、甲基丙烯酸（MA）为原料,经两步酯化法合成了邻苯二甲酸一缩二乙二醇双甲基丙烯酸酯（PA-DEG-DMA）。结果表明,合成PA-DEG-DMA的反应温度在85～90℃,催化剂用量为DEG质量的4.5%,MA与邻苯二甲酸一缩二乙二醇酯（DEGP）的物质的量比为1.1∶1,带水剂甲苯用量为反应总质量的40%,阻聚剂4-甲氧基酚的用量为DEG质量的1.0%和回流时间为6h的优化条件下,获得了最佳反应结果,产品总收率可达83.4%,纯度大于98%。且产品外观质量好,反应后处理方便。并用X-射线衍射（XRD）、红外光谱（IR）、差示扫描量热（DSC）和Hammett指示剂对催化剂的结构和酸强度进行了表征和测定。     

厌氧/好氧/缺氧模式的SBR处理生活污水

采用厌氧/好氧/缺氧SBR处理生活污水,研究了泥龄、温度、曝气量对处理效果的影响,确定了特定水质条件下的最佳运行工况:污泥龄25 d,温度25℃,曝气量64 L/h。在此工况下,该系统对COD、NH4+-N、TN、TP的去除率较高,分别为92.9%、90.8%、82.9%、97.8%,出水中的COD、NH4+-N、TN、TP均可以达到《城镇污水处理厂污染物排放标准》的一级A标准。通过连续培养运行,系统中存在反硝化除磷现象。     

大冶有色冶炼厂污酸处理工艺改造实践

介绍了大冶有色金属有限责任公司冶炼厂污酸处理工艺流程及石灰中和钙砷渣煅烧工艺流程.石灰除砷控制pH值12,气浮除砷pH值8～9.试运行处理后污水ρ（As）0.27～0.39 mg/L,含砷废渣安全填埋处理.     

单级好氧脉冲式SBR处理垃圾渗滤液深度脱氮

为了考察单级好氧工艺处理垃圾渗滤液的可行性和脱氮性能,采用脉冲进水式SBR工艺处理高氨氮实际垃圾渗滤液。脉冲SBR运行周期共分为4个缺氧段和3个好氧段,采用3次等量进水模式。缺氧₄(An₄)不投加外碳源,利用微生物内碳源将NO₂^--N 还原为N₂。结果表明,经过4个不同进水TN阶段(118 d)的连续运行,获得了稳定和高效的脱氮性能。在进水COD为733~3971 mg·L^-1的条件下,出水COD稳定在298 ~888.15 mg·L^-1;在进水TN为299.78~1100.34 mg·L^-1的条件下,出水TN稳定在13.89~36.27 mg·L^-1。An₄的平均理论内源反硝化速率(TDNR_m)达到1.53 mg N·h^-1·(g MLVSS)^-1。运行阶段的单个周期内,An₄内源反硝化速率(DNR)分为快(DNR₁)和慢(DNR₂)两部分。其中阶段2(Ph₂)中的一个周期内DNR₁可达2.80 mg N·h^-1·(g MLVSS)^-1。在没有物化预处理和不投加外加碳源的情况下,实现单级好氧系统对垃圾渗滤液的深度脱氮。     

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     

Comparison of granular activated carbon bio-sorption and advanced oxidation processes in the treatment of leachate effluent

Landfill leachate is a toxic effluent of a decomposing landfill that is produced when rainwater percolates through the landfill leaching out contaminants and pollutants. Untreated leachate is a potential source for the contamination of soil, surface and ground water. In this study, the treatment processes such as granular activated carbon (GAC) adsorption/bio-sorption (batch), and advanced oxidation processes (AOP) viz. photocatalysis and Fenton’s process were evaluated and compared by using synthetic landfill leachate (SLL) as a contaminant. TiO₂ was used as a catalyst in photocatalysis, and Fenton’s reagent (H₂O₂/Fe⁺²) was used in Fenton’s process. The degradation of SLL effluent by the three above-mentioned processes was characterized by the % TOC removal. The % TOC removed by photocatalysis, Fenton oxidation and bio-sorption (which includes adsorption and biodegradation) was 30, 60 and 85%, respectively. The bio-sorption increased with the increasing GAC dose. The optimum dose of Fenton’s reagent in advanced oxidation was 15 and 400 milli moles of Fe⁺² and H₂O₂, respectively. The Fenton’s process showed faster degradation kinetics compared to biodegradation and photocatalysis.     

Pressurized hot water extraction of benzoic acid and phthalic anhydride from petrochemical wastes using a modified supercritical fluid extractor and a central composite design for optimization

Using the pressurized hot water extraction technique, benzoic acid and phthalic anhydride were selectively removed from solid petrochemical wastes (called molten phthalic anhydride). A statistical experimental design based on “central composite design” was applied for obtaining optimized conditions for the semi-continuous extraction of phthalic anhydride and benzoic acid from their mixture with benzoic acid, maleic acid, phthalic acid, phthalic anhydride, aldehydes, phthaldehyde, toluic acid, and some minor impurities. Variables such as pressure (60-220 bar), temperature (60-140 °C), dynamic time (5-45 min), and flow rate (0.2-1 mL/min) were used.     

Development of microbial fuel cell with anoxic/oxic design for treatment of saline seafood wastewater and biological electricity generation

BACKGROUND: Sustainable technologies need to be developed to treat saline seafood wastewater (SSW) efficiently. This study focused on the feasibility of a continuously operated microbial fuel cell (MFC) with modified anoxic/oxic (A/O) architecture (A/O–MFC) for power generation and treatment of SSW simultaneously. RESULTS: Hydraulic retention time (HRT) was shown to have an impact on polarization and power output of the A/O–MFC and the maximum power density of 16.2 W m^?3 was obtained at a current density of 41.7 A m^?3 and HRT of 4.2 h. High salinity together with advective flow mode enabled a low and constant internal resistance of approximately 100 Ω throughout the experiments. Besides, pH of waste stream in both compartments was found always near neutral level. Increasing HRT could improve eliminability of soluble chemical oxygen demand (sCOD) and biological nitrification. CONCLUSIONS: This study provides a proof‐in‐concept demonstration to utilize an MFC for effective and sustainable treatment of SSW along with recovery of electrical energy. Copyright © 2010 Society of Chemical Industry     

A_2SBR工艺反硝化除磷系统的快速启动与稳定运行

为了实现废水同时脱氮除磷的目的,采用A2SBR工艺进行了长期的实验室实验,考察反硝化除磷系统的启动与运行效果。结果表明:在进水COD质量浓度200 mg/L,磷酸盐质量浓度4—11 mg/L,缺氧段硝酸盐质量浓度从25 mg/L提高到55 mg/L的条件下,采用"厌氧(2.5 h)-沉淀排水(1 h)-缺氧(3.5 h)-沉淀排水(1 h)"的周期性运行方式,可在31 d内成功启动A2SBR反硝化除磷系统,厌氧段COD、硝态氮和磷酸盐去除效率分别为77%,90%和84.96%。稳定运行后硝态氮和磷酸盐去除效率分别达到92%和91%,COD去除率高于80%,其出水磷酸盐质量浓度接近于0,表现出良好的反硝化脱氮和除磷性能。