厌氧-缺氧-ALMBR法处理焦化废水的试验研究

采用厌氧—缺氧—ALMBR工艺处理焦化废水。在充填了横断面具有蜂窝胞壁结构纤维滤料的厌氧池和缺氧池中收集池内出气作为气源回曝气池中,在缺氧的条件下形成气升循环。好氧池为气提升三相循环流化床结构的MBR(ALMBR),不设二沉池,MLSS高达11～12 g/L。连续3个月的试验表明,焦化废水进水COD_(Cr)1950 mg/L、NH_3—N 150 mg/L时,出水COD_(Cr) 144 mg/L、NH_3—N 9.8 mg/L。工艺具有良好的抗冲击负荷能力,能够维持较高的污泥浓度,运行稳定,操作简单且管理方便。装有蜂窝胞壁填料的缺氧池COD_(Cr)去除率明显高于装有软性纤维填料缺氧池。     

AO—BPBC—MBR组合工艺处理化工园区废水的试验研究

应用AO—BPBC—MBR组合工艺处理某化工园区废水,考察了其对COD_(Cr)、BOD_5、NH_3—N和TP的去除效果及影响因素。试验结果表明,AO—BPBC—MBR组合工艺对该化工废水具有良好的处理效果,COD_(Cr)、BOD_5、NH_3—N和TP的平均去除率分别为92.67%、85.67%、82%和92%。出水水质可以稳定达到《污水综合排放标准》(GB 8978—1996)一级B要求。综合处理费用约2.4元/m~3,系统运行可靠,为化工园区难降解综合废水的达标处理提供了一种稳定、简便和经济的解决方案。     

BAF-混凝-沉淀-过滤工艺在中水回用中的应用

采用曝气生物滤池(BAF)—混凝—沉淀—过滤工艺对城市污水处理厂二级出水进行深度处理,以实现污水的回用。试验结果表明:当聚硫酸铁(PFS)投加量为30 mg/L,石灰投加量为150～240mg/L时,沉淀物质的量最大;该组合工艺对COD_(Cr)、NH_3-N、TP的平均去除率分别为49.9%、96.2%、92%,出水COD_(Cr)、NH_3—N、TP分别稳定在30mg/L、1 mg/L、0.5 mg/L以下;该工艺同时对其他水质指标也具有良好的去除效果,出水SS<5 mg/L;出水总硬度(以CaCO_3计)<110 mg/L。     

多级生化法处理抗生素制药废水的中试研究

采用多级A/O~2生化工艺对抗生素制药废水进行了中试处理研究。结果表明缺氧池DO<0.5mg/L、好氧池DO2～3/L、温度16～30℃、有机负荷1.4～2kg COD_(Cr)/(MLSS·d)时该生化系统具有较好的去除效果,COD_(Cr)总去除率可达到80%～94%,NH_3—N总去除率达98%。     

改良氧化沟工艺强化脱氮除磷试验研究

采用改良氧化沟试验装置处理生活污水。为了提高脱氮除磷效率,对改良氧化沟的曝气量进行了优化,在氧化沟的前三个廊道设置缺氧区,将其运行方式改变为缺氧—厌氧—缺氧好氧,在提高氮磷去除效率的同时降低了能耗。试验结果表明,稳定运行阶段,二沉池出水COD_(Cr)、TN、NH3 N和TP的平均浓度分别为37 mg/L、8.9 mg/L、0.5 mg/L和0.39 mg/L,平均去除率分别为92%、83%、99%和92%,均稳定达到了《城镇污水处理厂污染物排放标准》(GB 18918 2002)一级A标准要求。     

溶解氧浓度对硅藻土移动床复合生物反应器处理城市污水的影响

利用硅藻土移动床复合生物反应器处理城市污水。以复配硅藻土作为微生物的载体,在连续流小试中,考察溶解氧浓度对反应器处理城市污水效果的影响。当溶解氧浓度为1.85～2.38 mg/L时,处理出水TN为13～16mg/L,满足《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级B标准,其他出水指标如COD_(Cr)为12～22mg/L,NH_3—N为0.5～2.6mg/L;出水TP为0.2～0.9mg/L,都满足GB 18918—2002一级A标准。表明该反应器在中小规模污水处理方面是一个有前途的污水处理工艺单元。     

混凝—吸附法深度处理城市生活污水再生利用的中试研究

以北京市城市排水集团某污水处理厂MBR出水为处理对象,研究在城市生活污水深度处理中水回用中,絮凝-吸附法对TP、PO_4—P、COD、TN、NO_3~-—N、NH_3—N和浊度等的处理效果。该试验装置连续运行约105 d,试验结果表明,该方法对TP、PO_4~(3-)—P具有很好的处理效果,除TN、NO_3~-—N外,其他监测指标均达到了景观环境用水的再生水水质指标(GB/T 18921—2002)。     

A /O泳动床反应器脱氮性能研究

基于A/O工艺与泳动床工艺技术的联合,开发出A/O泳动床生物膜反应器.A/O泳动床系统表现出高效去除COD_(Cr)、NH_3-N和TN以及较好的抗负荷冲击能力.在HRT=12.5 h,回流比为300%,进水COD_(Cr)、NH_3-N平均浓度分别为343.4 mg/L、94.1 mg/L时,COD_(Cr)和NH3-N平均去除率分别为84.6%, 86.8%;COD_(Cr)的容积负荷与去除负荷现良好的线性关系,R~2=0.970 4;系统在较低的C/N下,TN平均去除率为70.8%.     

低C/N冲击对A~2/O处理功能影响及修复方法研究

研究了低C/N对A~2/O系统产生的冲击效应及修复方法.结果表明,C/N为2时对系统冲击效应明显,可使系统硝化功能、COD_(Cr)去除率和TP去除率分别下降40%、50%和30%,同时会导致少量污泥上浮和产生轻微污泥膨胀问题;而采用加大回流比(R和r都提高2倍)的修复方法可显著增强系统处理功能,修复期NH_3-N平均去除率可提高20%,TN平均去除率提高约7.4%,COD_(Cr)平均去除率提高约5.4%.并且加大回流比可有效缩短修复运行时间,使系统的NH_3-N、TN和COD_(Cr)去除功能提前约3～4 d恢复.     

人工快速渗滤系统处理高速公路服务区污水

利用人工快速渗滤系统(CRI)处理高速公路服务区生活污水,工程试验结果表明:在水力负荷不小于1m/d的条件下,CRI系统对服务区生活污水具有较强的抗冲击负荷能力和较好的污染物去除效果。其对SS、COD_(Cr)和NH_3—N的平均去除率分别为92.74%、91.12%和84.34%;处理出水中SS、COD_(Cr)和NH_3—N的平均浓度分别为5.25mg/L、25.7mg/L、4.32mg/L。     

Nitrification and denitrification in partially aerated biological aerated filter (BAF) with dual size sand media.

A 104-mm (4-inch) diameter pilot-scale biological aerated filter (BAF) with a media depth of 2.5 m (8.3 feet) was operated with an anaerobic, anoxic and oxic zone at a temperature of 23 degrees C. The medium for the anaerobic and anoxic zones was 10 mm diameter sand while the medium for the oxic zone was 5 mm diameter sand. The influent sCOD and total nitrogen concentrations in the feedwater were approximately 250 mg/L and 35 mg N/L, respectively. sCOD removal at optimum hydraulic retention time (HRT) of 3 h with recirculation rates of 100, 200 and 300% in the column was above 96%. Nitrification was found to be more than 96% for 3 h HRT at 200 and 300% recirculation. Total nitrogen removal was consistent at more than 80% for 4 and 6 h HRT at 300% recirculation. For 3 h HRT and 300% recirculation, total nitrogen removal was approximately 79%. The ammonia loading rates for maximum ammonia removed were 0.15 and 0.19 kg NH3-N/m3-day for 100 and 200% recirculation, respectively. The experimental results demonstrated that the BAF can be operated at an HRT of 3h with 200-300% recirculation rates with more than 96% removal of sCOD and ammonia and at least 75% removal of total nitrogen.     

Enhanced removal of chemical oxygen demand, nitrogen and phosphorus using the ameliorative anoxic/anaerobic/oxic process and micro-electrolysis

Synthetic wastewater was treated using a novel system integrating the reversed anoxic/anaerobic/oxic (RAAO) process, a micro-electrolysis (ME) bed and complex biological media. The system showed superior chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal rates. Performance of the system was optimised by considering the influences of three major controlling factors, namely, hydraulic retention time (HRT), organic loading rate (OLR) and mixed liquor recirculation (MLR). TP removal efficiencies were 69, 87, 87 and 83% under the HRTs of 4, 8, 12 and 16 h. In contrast, HRT had negligible effects on the COD and TN removal efficiencies. COD, TN and TP removal efficiencies from synthetic wastewater were 95, 63 and 87%, respectively, at an OLR of 1.9 g/(L·d). The concentrations of COD, TN and TP in the effluent were less than 50, 15 and 1 mg/L, respectively, at the controlled MLR range of 75-100%. In this system, organics, TN and TP were primarily removed from anoxic tank regardless of the operational conditions.     

Improvement of existing nightsoil treatment plant for nitrogen removal.

This study was performed to increase the treatment efficiency and to reduce operation and maintenance costs of the existing nightsoil treatment plant. The existing nightsoil plant was not established by the nitrogen removal process, and was operated ineffectively with deterioration of treatment efficiency rate, and according to the demand of many operators, the expenses of operation and maintenance have become excessive. Modified plant has been changed through two steps. The first step, liquid decayed tank using closed oxidation ditch is operated to increase retention time only for nitrification. The second step, modified liquid decayed tank including anoxic tank is operated, it has an excellent nitrogen removal rate. In first step, when HRT was increased from 10 days to 13 days in liquid decayed tank including aeration tank using closed oxidation ditch, TN concentration of effluent appeared below 51 mg/L less than discharge limit, 60 mg/L. In second step, when anoxic tank and oxic tank were installed, HRT has been increased to 13 days and 26 days, respectively. Then average TN concentration of effluent was detected less than 13 mg/L for over one year. The simple process modified the existing two processes resulted in the reduction of costs for operation and maintenance in the personnel, chemical, and filter change sphere.     

Two-stage entrapped mixed microbial cell process for simultaneous removal of organics and nitrogen for rural domestic sewage application.

A two-stage entrapped mixed microbial cell ((2S)EMMC) process which separates nitrification and denitrification phases by the installation of the anoxic and oxic EMMC reactors packed with EMMC carriers was operated with 6, 4, 3, and 2 hours of hydraulic retention time (HRT) using simulated domestic wastewater. The activated sludge was immobilized using cellulose acetate for the EMMC carriers. Similar soluble chemical oxygen demand (SCOD) removal efficiencies of 90-97% were observed for all HRTs (SCOD loading rate of 0.84-2.30 g/L/d) applied. In order to achieve more than 80% of TN removal efficiency, the HRT should be maintained higher than 4 hours (less than 0.24 g/L/d of TN loading rate). Denitrification was a rate-limiting step which controlled overall TN removal efficiency at TN loading rate of 0.15-0.31 g/L/d although nitrification efficiencies achieved 97-99%. The effluent TSS of less than 25 mg/L in the (2S)EMMC process was maintained at the SCOD loading rate of less than 1.23 g/L/d with back-washing intervals of 5 and 10 days in the anoxic and oxic EMMC reactors, respectively. The minimum HRT of 4 hours is required for high removal efficiencies of organics (average 95.6%) and nitrogen (average 80.5%) in the (2S)EMMC process with 3 times of recirculation ratio.     

Integration of sulphate reduction, autotrophic denitrification and nitrification to achieve low-cost excess sludge minimisation for Hong Kong sewage.

An integrated anaerobic-aerobic treatment system of sulphate-laden wastewater was proposed here to achieve low sludge production, low energy consumption and effective sulphide control. Before integrating the whole system, the feasibility of autotrophic denitrification utilising dissolved sulphide produced during anaerobic treatment of sulphate rich wastewater was studied here. An upflow anaerobic sludge blanket reactor was operated to treat sulphate-rich synthetic wastewater (TOC=100 mg/L and sulphate=500 mg/L) and its effluent with dissolved sulphide and external nitrate solution were fed into an anoxic biofilter. The anaerobic reactor was able to remove 77-85% of TOC at HRT of 3 h and produce 70-90 mg S/L sulphide in dissolved form for the subsequent denitrification. The performance of anoxic reactor was stable, and the anoxic reactor could remove 30 mg N/L nitrate at HRT of 2 h through autotrophic denitrification. Furthermore, sulphur balance for the anoxic filter showed that more than 90% of the removed sulphide was actually oxidised into sulphate, thereby there was no accumulation of sulphur particles in the filter bed. The net sludge productions were approximately 0.15 to 0.18 g VSS/g COD in the anaerobic reactor and 0.22 to 0.31 g VSS/g NO3- -N in the anoxic reactor. The findings in this study will be helpful in developing the integrated treatment system to achieve low-cost excess sludge minimisation.     

Knowledge-based fuzzy system for diagnosis and control of an integrated biological wastewater treatment process.

A supervisory expert system based on fuzzy logic rules was developed for diagnosis and control of a laboratory- scale plant comprising anaerobic digestion and anoxic/aerobic modules for combined high rate biological N and C removal. The design and implementation of a computational environment in LabVIEW for data acquisition, plant operation and distributed equipment control is described. A step increase in ammonia concentration from 20 to 60 mg N/L was applied during a trial period of 73 h. Recycle flow rate from the aerobic to the anoxic module and bypass flow rate from the influent directly to the anoxic reactor were the output variables of the fuzzy system. They were automatically changed (from 34 to 111 L/day and from 8 to 13 L/day, respectively), when new plant conditions were recognised by the expert system. Denitrification efficiency higher than 85% was achieved 30 h after the disturbance and 15 h after the system response at an HRT as low as 1.5 h. Nitrification efficiency gradually increased from 12 to 50% at an HRT of 3 h. The system proved to react properly in order to set adequate operating conditions that led to timely and efficient recovery of N and C removal rates.     

Nitrogen removal from piggery waste with anaerobic pretreatment.

Aerobic degradation of high strength piggery waste elevated the reactor temperature inhibiting nitrification. This study included anaerobic pretreatment with various influent by-pass rates to control the temperature and to minimize the external carbon requirement for denitrification. To find the optimum operating conditions, both lab-scale AnSBR (anaerobic sequencing batch reactor) and Ax/Ox (anoxic/oxic) SBR were operated at 35 degrees C. The heat energy released from Ax/Ox SBR was assumed to be used for heating the AnSBR, with which the Ax/Ox reactor temperature could successfully be controlled below 40 degrees C. The optimum rates of by-pass were 1.0 for winter, 0.4 for spring/fall and 0.2-0.4 for summer, respectively. Applying the correction factors for the measured AUR2 (nitrite nitrification rate) and AUR (nitrate nitrification) at the predicted temperatures, the required oxic HRTs were computed. The required Ax/Ox HRT ratios were respectively 0.5 for COD/TKN>8, 1.0 for COD/TKN ratio of 5.5-8 and 3.5 for below 5.5. The optimum HRTs were 16 days for AnSBR and 17 days for Ax/Ox SBR with the corrected AUR2.     

Biological nutrient removal in simple dual sludge system with an UMBR (upflow multi-layer bioreactor) and aerobic biofilm reactor.

In this study, a simple dual sludge process was developed for small sewage treatment. It is a hybrid system that consists of upflow multi-layer bioreactor (UMBR) as anaerobic and anoxic reactor with suspended growth microorganisms and post aerobic biofilm reactor with inclined plates. UMBR is a multifunction reactor that acts as primary sedimentation tank, anaerobic reactor, anoxic reactor, and thickener. The sludge blanket in the UMBR is maintained at a constant level by automatic control so that clear water (30 mg-SS/L) can flow into the post aerobic biofilm reactor. It leads to improving performance of the biofilm reactor due to preventing of excess microbial attachment on the media surface and no requirment for a large clarifier caused by low solid loading. The HRT in the UMBR and the aerobic biofilm reactor were about 5.8 h and 6.4 h, respectively. The temperature in the reactor during this study varied from 12.5 degrees C to 28.3 degrees C. The results obtained from this study show that effluent concentrations of TCOD, TBOD, SS, TN, and TP were 29.7 mg/L, 6.0 mg/L, 10.3 mg/L, 12.0 mg/L, and 1.8 mg/L, which corresponded to a removal efficiency of 92.7%, 96.4%, 96.4%, 74.9%, and 76.5%, respectively. The sludge biomass index (SBI) of the excess sludge in the UMBR was about 0.55, which means that the sludge in the UMBR was sufficiently stabilized and may not require further treatment prior to disposal.     

Grey water treatment in upflow anaerobic sludge blanket (UASB) reactor at different temperatures

The treatment of grey water in two upflow anaerobic sludge blanket (UASB) reactors, operated at different hydraulic retention times (HRTs) and temperatures, was investigated. The first reactor (UASB-A) was operated at ambient temperature (14-25 degrees C) and HRT of 20, 12 and 8 h, while the second reactor (UASB-30) was operated at controlled temperature of 30 degrees C and HRT of 16, 10 and 6 h. The two reactors were fed with grey water from 'Flintenbreite' settlement in Luebeck, Germany. When the grey water was treated in the UASB reactor at 30 degrees C, total chemical oxygen demand (CODt) removal of 52-64% was achieved at HRT between 6 and 16 h, while at lower temperature lower removal (31-41%) was obtained at HRT between 8 and 20 h. Total nitrogen and phosphorous removal in the UASB reactors were limited (22-36 and 10-24%, respectively) at all operational conditions. The results showed that at increasing temperature or decreasing HRT of the reactors, maximum specific methanogenic activity of the sludge in the reactors improved. As the UASB reactor showed a significantly higher COD removal (31-64%) than the septic tank (11-14%) even at low temperature, it is recommended to use UASB reactor instead of septic tank (the most common system) for grey water pre-treatment. Based on the achieved results and due to high peak flow factor, a HRT between 8 and 12 h can be considered the suitable HRT for the UASB reactor treating grey water at temperature 20-30 degrees C, while a HRT of 12-24 h can be applied at temperature lower than 20 degrees C.