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5.3.1 Introduction
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5.3.1 Introduction

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Both local environmental, geological, meteorological and economic conditions, as well as effluent discharge standards shall be fully taken into consideration when designing the wastewater treatment process. The Ministry of Ecology and Environment has issued the Guideline for Establishment of Wastewater Discharge Standards for Rural Wastewater Treatment Facilities in 2019. The Guideline indicated that: (i) effluent to be discharged into Class II or Class III surface water bodies (GB 3838) shall at least meet the Class IB standards in GB 18918; (ii) effluent to be discharged into Class IV or Class V surface water bodies shall at least meet the Class II standards in GB 18918; (iii) effluent to be discharged into natural water bodies indirectly (e.g., through constructed wetland) shall at least meet the Class III standards in GB 18918. Generally, effluent from a system consisting of a septic tank and ecological approaches (e.g., leach field, or constructed wetlands) can meet Class III standards in GB 18918. To further decrease the pollutant concentrations in wastewater, biological approaches (e.g., activated sludge, or trickling filter) shall be introduced. The combination of a septic tank and biological approaches can make the effluent meet Class II standards in GB 18918, and additional ecological approaches after biological approaches can further reduce the pollutant concentrations to meet Class IB standards in GB 18918 or even higher requirements.

 

This section introduces three widely applied wastewater treatment processes to illustrate their applicability, key design considerations, and the do’s and don’ts during construction, commissioning and operation. Except for the three processes, the Practice Guideline users can design the most suitable treatment process by combination of different treatment technologies according to actual situations and practical experiences. It needs to be emphasized that although biological membrane has high pollutants removal capacity, it is not recommended for rural wastewater treatment due to (i) high O&M cost for cleaning and replacing membrane; (ii) complexity of O&M; and (iii) high requirements on the technical capacity of operators.

 

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