OPERATION EVALUATION OF URBAN SEWAGE TREATMENT PLANTS IMPLEMENTING GRADE I-A STANDARD AND ANALYSIS ON EMPASSIS AND DIFFICULTIES IN UPGRADING THE STANDARD

By the end of 2019, a total of 2913 urban wastewater treatment plants (WWTPs) in China had implemented the Grade I-A Discharge Standard in China's national standard GB 18918-2002, which accounted for 53.2% of the total WWTPs in China. The Grade I-A Standard has become the most widely implemented discharge standard for WWTPs in China. Based on the deep investigation of 204 WWTPs implementing the Grade I-A Standard of Taihu Basin in recent 6 years, in combination with whole process analysis of more than 100 WWTPs in China, this paper firstly evaluated the operational performance of WWTPs implementing the Grade I-A Standard. Results showed that total amount of pollutants reduction of WWTPs in Taihu Basin had been significantly increased due to the continuous increase of water inflow, and the continuous decrease of effluent concentration after the upgrading of Grade I-A Standard, positively contributing to the emission reduction of organic matter, nitrogen, phosphorus and the eutrophication control in Taihu Basin. Then the common problems in the operation process of WWTPs were summarized. Influent water quality, process design, selection and maintenance of equipment and facilities, as well as the performance control of functional bacterial group in activated sludge still had further improvement and optimization space. Meanwhile, targeted optimization operation measures were put forward. At last, key and difficult points and strategies in the new round of upgrading work were discussed. It is suggested that attention should be paid to improving the quality and efficiency of the wastewater collection system, and the quality and transmission efficiency of the pipe network. And the whole process analysis should be carried out before upgrading. Then the process optimization or engineering measures could be confirmed.