Abstract:
Discharge standard of water pollutants for rural domestic sewage treatment facilities is an important basis for rural environmental management, which is related to the choice of sewage treatment technologies and processes, and the costs of construction, operation and maintenance of sewage treatment facilities. The present study conducted a detailed contrastive analysis of the discharge standards of rural sewage treatment facilities in Beijing City, Chongqing City and Zhejiang Province, etc., and the results indicated that existing standards exhibit some shortages such as unclear scope of applications, incomplete classification and grading ideas, and unreasonable types of control indicators. Therefore, three suggestions are proposed to optimize the formulation of pollutant discharge standards for rural domestic sewage treatment facilities:(1) Clearly state that the standards are applicable to rural domestic sewage treatment facilities under 500 m
3/d. (2) Classification according to variations of drainage direction and treatment facility scale. (3) Add pH, SS, COD
Cr, NH
3-N, TN, TP and animal and vegetable oils as control indicators. Among them, total nitrogen and total phosphorus are suitable for the treatment facilities where the effluent is directly discharged into closed water bodies or where the limiting factors are nitrogen and phosphorus, while animal and vegetable oils are suitable for treatment facilities containing catering wastewater. The qualified region can appropriately add some control indicators (such as anionic surfactants, fecal coliform flora and chroma)based on those control indicators proposed in this study. Meanwhile, some suggestions are put forward, such as acting according to circumstances, revising the standard in time, improving the evaluation method of rural domestic sewage treatment technologies and strengthening the financial guarantee of the treatment facilities, to ensure the smooth implementation of the standards and effectively reduce pollutant discharge.