基于模型的低负荷运行村镇污水处理厂问题诊断分析

DIAGNOSIS AND ANALYSIS BASED ON MATHEMATICAL MODEL ON PROBLEMS IN SEWAGE TREATMENT PLANTS IN VILLAGES AND TOWNS WITH LOW LOAD OPERATION

我国村镇污水处理厂普遍存在进水量和进水浓度偏低的问题,导致村镇污水厂运行稳定性差。为防止低负荷运行影响污水处理厂处理效能的发挥,以临太湖村镇污水厂多点进水倒置AAO工艺为研究对象,以数学模型为基础,建立污水厂水质水量动态响应模型。以数学模拟为主要研究手段,试验作为补充方法,通过模型诊断发现,该厂夏季曝气过剩,活性污泥ρ(MLVSS)/ρ(MLSS)=0.37。试验结果表明:该厂进水ρ(ISS)=57~92 mg/L,ρ(ISS)/ρ(SS)为0.71~0.82,ρ(ISS)/ρ(COD)为0.50~0.84。进入AAO系统的ISS粒径为36~52μm,而小粒径的ISS组分是导致活性污泥MLVSS/MLSS偏低的主要原因。通过优化进水ISS/COD、泥龄、污泥回流比、曝气量,使得出水水质稳定达到GB 18918—2002《城镇污水处理厂污染物排放标准》一级A标准,污泥活性提高到0.7,全年曝气成本可节省约10%。

The problems of low influent flow and concentration generally existed in sewage treatment plants in villages and towns in China, which led to the poor operation stability of sewage treatment plants in villages and towns. In order to prevent the low load operation from affecting treatment performance, taking the inverted AAO process of multiple points in the sewage treatment plant in villages and towns near Taihu Lake as the research object, based on mathematical model, a dynamic response model of sewage treatment plant was established. With mathematical simulation as the main research method and experiment as the supplementary method, the simulation results showed that aeration was excessive in summer, and then MLVSS/MLSS was 0.37. The results of the experiment showed that the influent ISS concentration was 57~92 mg/L, ISS/SS was 0.71~0.82 and ISS/COD was 0.50~0.84. The ISS particle size entered AAO system ranged from 36 μm to 52 μm. Small particle sized ISS was the main reason for low MLVSS/MLSS in the activated sludge. By optimizing influent ISS/COD, sludge retention age, returned sludge ratio and aeration velocity, the effluent quality reached grade A in standard GB 18918—2002 stably, sludge activity was increased to 0.7, and aeration cost was reduced by about 10%.