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活性污泥法—人工湿地联合处理城市污水研究
Research on Activated Sludge Process-Constructed Wetland Combinative Technology Treating Municipal Wastewater
【作者】 付国楷;
【导师】 周琪;
【作者基本信息】 同济大学 , 环境工程, 2007, 博士
【摘要】 针对我国南方城市污水有机污染物浓度偏低,氮磷含量相对较高,水质、水量随季节变化的特点,采用活性污泥法与人工湿地相结合的联合处理工艺,分别在100m3/d规模的生产性试验和10000m3/d规模的示范工程中,以实际城市污水为处理对象进行研究。试验重点考察了原水水质水量特征、污染物存在形态及去除规律、不同工艺条件下碳源分配情况,确定了高效生物反应器在不同季节时段的运行模式;研究了不同构型人工湿地中污染物的去除效率及池型、填料、负荷、温度、植物对其的影响,计算了反应动力学参数,确定了适宜的湿地构型及负荷调控方法;在此基础上提出了基于q-t曲线图的双向输入/输出联合调控模式,确定了活性污泥法-人工湿地联合处理工艺及负荷分配。示范工程依据试验结果,针对实际水质变动情况灵活调控,考察了工程规模的联合处理工艺对各种污染物质的去除情况。试验原污水平均COD、NH4+-N、TN、TP为129mg/L、25.6mg/L、31.5mg/L、3.38mg/L,C/N值和C/P值为4.3和39.5,脱氮除磷所需碳源严重不足。在不同的季节,原水水质有较大变化,雨季原水污染物浓度只有旱季浓度60%左右,春、夏季暴雨时原水污染物浓度接近排放标准。因此,生物反应器需要根据水温的变化、水质的波动、降雨的多寡采用不同的运行模式,才能在有限碳源条件下实现最大限度的脱氮除磷。通过不同季节多种工艺的比较,确定了高效生物反应器运行模式:春季时段采用改良型A2/O工艺,夏季晴天/小雨时段采用预缺氧+倒置A2/O工艺,夏季连续暴雨时段采用多点进水工艺,秋季时段采用低氧/常氧交替运行的倒置A2/O工艺,冬季时段采用常规倒置A2/O工艺。通过分析各种工艺中有机物、氮、磷的去除规律,比较其碳源分配情况,说明碳源能否合理分配及充分利用是评价工艺优劣的重要标准。人工湿地系统对COD、NH4+-N、TN、TP的去除效率受负荷明显影响,随着水力负荷和面积负荷增加,湿地对污染物的去除效率呈下降趋势,同时污染物面积去除量的增量随着面积负荷的增加逐渐减少。另外,随着水温的升高,湿地对NH4+-N、TN的去除效率明显上升,模拟小试试验还证明,湿地系统总氮面积去除量与进水硝态氮的比例成正的线性关系,提高进水中硝态氮比例有利于总氮的去除。生物量大的湿地植物对污染物的吸收总量最高,单位干重的氮磷含量不能作为评价植物污染物吸收能力的主要指标。在较低污染物浓度水平条件下,湿地对污染物的去除可以用一级推流动力学模型近似模拟。在相同负荷条件下,潜流湿地对COD和TP的去除效率高于表面流湿地及潜流/表面流组合湿地,页岩和钢渣的应用明显提高了湿地对磷的去除能力。表面流湿地对NH4+-N的去除效率高于潜流湿地和组合流湿地,在硝态氮比例大于0.25时,潜流湿地对总氮的去除优于表面流湿地。组合流湿地的优势在于其去除效率受温度的影响最小。整体来说,采用页岩和钢渣作为基质的潜流湿地最适宜于城市污水的深度处理,其COD、NH4+-N、TN、TP的面积反应速率常数分别为0.32m/d、0.065m/d、0.176m/d、0.29m/d。根据试验结果,总结了活性污泥法/人工湿地联合处理的方法和原则,利用q-t曲线图进行设计和调控,提出了双向输入/输出的活性污泥法-人工湿地联合调控模式,并进行了实例分析。示范工程生物反应器通过改良型A2/O工艺、预缺氧+倒置A2/O工艺、局部低氧倒置A2/O工艺的切换运行,使出水水质稳定达到《城镇污水处理厂污染物排放标准》一级B标准,部分指标达到一级A标准。在水力负荷为0.3m/d~0.35m/d条件下,示范工程人工湿地系统出水COD、BOD、NH4+-N、TP可以达到《地表水环境质量标准》,TN浓度可以下降到7mg/L左右。
【Abstract】 There are some difficulties in treating municipal wastewater in Southern Chinabecause of the weak carbon concentration, comparative strong nitrogen andphosphorus concentration, seasonal changing quality and quantity. To solve theproblem the activated sludge process-constructed wetland combinative technologywas invented. The research focus on real municipal wastewater treatment in a pilotscale system with capacity of 100m3/d and a demonstrating plant with capacity of10000m3/d. In the pilot scale experiment the study involves the influent quality andquantity, the pollutant form and removal efficiency, the COD distribution in differentprocesses. With these studies the operating modes of the interactive reactor indifferent seasons were confirmed. Meanwhile the pollutant removal efficiency andkinetic constants in different types of constructed wetland were investigated and theeffecting factors such as packing medium, load, temperature and plant species werealso researched. Thereout the appropriate type and load of constructed wetland can beconfirmed. Further more the bidirectional input/output adjusting mode forbiological-ecological comnination based on q-t figure was proposed as well as theload distribution. In the full scale experiment the demonstrating reactor was adjustedwith the fluctuating influent quality and the polluent removal efficiency wasinvestigated.The influent concentratons of COD, NH4+-N, TN and TP of pilot system were129mg/L、25.6mg/L、31.5mg/L、3.38mg/L respectly. The needed carbon for nitrogenand phosphorus removal was lacking because of the low C/N and C/P ratios. Theinfluent quality fluctuates with the alternation of season and the pollutantconcentration in rainy weather was about 60% of that in dry weather. Even thepollutant concentration was so weak that close to the discharge standard in rainy dayin spring and summer. So the biological reactor must be adjusted accoding to thechanges of temperature, influent quality and precipitation for making the most ofnitrogen and phosphorus removal with the limited carbon resource. By comparing different processes in the same period, following operting modeof interactive reactor was recommend: enhanced A2/O process fits on spring period,pre-anoxic inverted A2/O process was recommend in dry/mizzle weather in summerperiod, step aeration process was adopted in rainy weather in summer period,alternating oxygen concentration inverted A2/O process was appropriate in autumnperiod, and normal inverted A2/O process was better in winter period. The analysis ofthe organic matter, nitrogen and phosphorus removal rule and the carbon resourcedistribution shows that the preferable process can betterly distribute and utilize thelimited carbon resource.The removal efficiencies of COD, NH4+-N, TN and TP in constructed wetlandwrer remarkably affected by loading. The removal efficiencies were decreased withthe increasing hydraulic loading and areal loading. The increment of areal removalmass was reduced with the increasing areal loading. Otherwise the removalefficiencies of NH4+-N and TN were observably increased with the climbingtemperature. The lab-scale experiment shows that the TN areal removal mass waslinearly related to the NOx--N/TN ratio. So increasing the NOx--N/TN ratio canimprove the TN removal. The aquatic plants with bigger biomass have strongercapacity to assimilating the pollutant so the concentrations of nitrogen andphosphorus in dry plant should not be the exponent for evaluating assimilatedpollutant by plant. On the condition of low influent concentration the pollutantremoval rules in constructed wetland can be simulated by first-order K-C model.The removal efficiencies of COD and TP in subsurface flow wetland (SSFW)were higher than that in surface flow wetland (SFW) and SSFW/SFW combinedwetland with the same loading. Using shale and slag as medium can enhance theremoval of phosphorus. The removal efficiency of NH4+-N in SFW was higher thanthat in SSFW and SSFW/SFW combined wetland. When the NOx--N/TN ratio wasmore than 0.25 the removal efficiencies of TN in SSFW was higher than that in SFW.The advantage of SSFW/SFW combined wetland was less infection by lowtemperature. Eventually the shale/slag filled SSFW was recommended for advancedtreating municipal wastewater and the first-order areal rate constants of COD,NH4+-N, TN and TP were 0.32m/d, 0.065m/d, 0.176m/d and 0.29m/d respectly. Accoding to the pilot experiment results the guidelines of biological-ecologicalcombination was proposed for managing the demonstrating plant. And thebidirectional input/output adjusting mode for biological-ecological comnination basedon q-t figure was builted. A case for the adjusting mode focus on the pilot scalesystem was analyzed. The operation modes of demonstrating reactor were switchedby using enhanced A2/O process, pre-anoxic inverted A2/O process and partialy lowoxygen concentration inverted A2/O process. The effluence quality of demonstratinginteractive reactor can reach the standard of grade B, class one in Discharge Standardof Pollutants for Municipal Wastewater Treatment Plant. Some of them can reach thegrade A standard. When the hydraulic loading of demonstrating SSFW was about0.3m/d to 0.35m/d the effluence concentration of COD, BOD, NH4+-N and TP canreach the Environmental quality standards for surface water, the effluenceconcentration of TN can be declined to 7mg/L.