According to the requirements of standards and specifications such as "Technical Specifications for Monitoring of Surface Water and Wastewater" and "Technical Specifications for Monitoring of Total Emission of Pollutants", the principles for the layout of monitoring points for pollution sources' wastewater are as follows:
For the first type of pollutants, the sampling points are set at the discharge outlets of workshops or workshop treatment facilities, or at the discharge outlets of facilities specifically designed to handle such pollutants;
For the second type of pollutants, the sampling points are set at the external discharge outlets of the polluting units or the discharge outlets of the plant treatment facilities. All discharge outlets must have separate sampling points; the sampling points for wastewater entering centralized sewage treatment plants and those entering the urban sewage network should be determined according to the requirements of the local environmental protection administrative department. In the layout of sampling points for efficiency monitoring of sewage treatment facilities, when monitoring the overall efficiency of sewage treatment facilities, sampling points should be set at various entrances into the sewage treatment facilities and the total discharge outlet of the facilities; when monitoring the efficiency of each sewage treatment unit, sampling points should be set at the entrances of various sewage flows entering the treatment facilities and the outlets of the facility units.