Notice of Retraction: Preliminary study on sewage treatment process of small town in northeast China

For small towns in northeast China, there are many different characteristics of sewage condition comparing with big cities and south China cities, including discharge scale, waste water quality, temperature, changeable load, easily being effected by environment, and so on. It causes some confusion to designers in choosing the suitable sewage treatment processes for small towns. What is the best one? This work was focusing on discussing the good processes to give advice to solve this problem. Through investigation, we found there are some problems in present operating sewage plants, they should upgrade their processes techniques and enhance the management level. We summarized the conditions of the present operating processes which have been operated in small town sewage treatment plants. We got information from books, reports, specialists, and internet, and analyzed processes' Advantages and shortages theoretically. Finally, we compared the feasible processes comprehensively. After summed up all the prior discussions, we obtained the recommended processes. According to the results of our research, the CASS process and improved A2/O process are supportive processes for small town sewage treatment plants in northeast China. In this paper, we comment on the improvements of the sewage treatment processes application in small town sewage treatment plants, especially in 50∼500 thousands of tons sewage plants, and make suggestions on the development directions in order to provide the reference for further systematic researches.