中文摘要：

郑州上街污水厂原有工艺主体为CASS工艺,日处理水量3.5万t。分析原CASS工艺存在的问题,并结合工程实际情况提出生物处理工艺的改进思路和设计方案。改造过程中,对原有CASS池重新分隔,将CASS工艺改造成A2/O工艺,将中间沉淀池改造为二沉池。改造后,出水水质达到《城镇污水处理厂污染物排放标准》（GB 18918—2002）一级A标准。

英文摘要：

CASS process was used in Shangjie Wastewater Treatment Plant with the treatment capacity of 35 000m3/ d. This paper analyzes the existing problems of the original CASS technology,and puts forward the improvement ideas and design scheme of the biological treatment process according to the actual situation of the project. During the transformation process,the original CASS pool is redivided,and the CASS process is transformed into A2/ O technology. The intermediate sedimentation tank is transformed into two settling tank. After the transformation,the water quality meets the effluent standard of A level in the First Grade of Urban Sewage Disposal Plant Contamination Integrated Discharge Standard（ GB 18918—2002）.