The Technology Upgrading And Operation Optimizing Of Small Municipal Sewage Treatment Plant

In order to meet the strict effluent standards for the municipal sewage treatment plants (STPs), existing STPs are required to be upgraded, especially for removal of NH3-N, TN, TP, SS and chroma in the effluent. As the influents of most STPs in China were mixed with high ratio of industrial wastewaters with complex contents, it is difficult for the existing STPs to be upgraded. In this study, Zhoupu STP in Shanghai was selected as an example to illuminate the details of upgrade. Before upgrade, the influent of this STP contains35%industrial wastewater, including those discharged from printing and dyeing plant, washing plant and traditional Chinese medicine plant, which led the quality and quantity of influent changed greatly from time to time. To improve the performance of this STP and make the effluent to meet the national standard of first class B, NH3-N, TN, TP and SS in influent have to be decreased with the upgrading process. But during the trial run of upgrade process, the effluent quality could not be stable and meet the standards, due to the low nitrification in winter, non-filamentous bulking, as well as the exceeding standards of TP, chroma and SS. Concerning the decrease of nitrification in winter, the industrial wastewaters were checked, the wastewater that might decrease the nitrification efficiency was determined by the nitrification experiment in low temperature. Therefore, nitrification was improved significantly by supervisory control of this wastewater discharge, the adding pretreatment and operation optimizing of the STP. In addition, the performances of synchronization and postpositional dephosphorization were compared, the decoloration effects of chemicals and ozone for tail water were incestigated and filter performance of multilayer high density metal mesh for tail water was confirmed. Based on these results, the units for synchronization dephosphorization, reagent decoloration and multilayer high density metal mesh were set up to make the quality of effluent be stable and meet the national standard of first class B, including NH3-N, TN, TP, SS and chroma. This work might be an applicable reference for the upgrade and optimization of STPs in small towns with mixed industrial wastewaters in the influent.