Water pollution sources include industrial waste water source and domestic sewage source. Before formulating the monitoring plan, the first step is to conduct investigation and research, collect relevant data, check the water use, the type of wastewater or sewage, the main pollutants and the discharge direction and discharge, the number and location of the sewage outlets in the workshop, factory or area, the wastewater treatment, whether it is discharged into the river, river, lake and sea, and whether there are seepage pits in the area. Then, the comprehensive analysis is carried out to determine the monitoring items, monitoring points, sampling time and frequency, sampling and monitoring methods and technologies, and quality assurance procedures, measures and implementation plans are formulated. （1） Layout of sampling points one   industrial waste water (1) The first type of pollutants shall be sampled at the discharge port of the workshop or workshop treatment facilities; The second type of pollutants are sampled at the unit total discharge port; (2) In the internal monitoring of industrial enterprises, the sampling is usually selected at the total discharge port, the discharge port of workshop or workshop and the discharge point of relevant processes or equipment; (3) For factories with existing wastewater treatment facilities, sampling points shall be set at discharge orifice of treatment facilities. In order to understand the effect of wastewater treatment, sampling points can be set at the inlet and outlet respectively; (4) In the sewage discharge channel, the sampling point shall be located in the place where the channel is relatively straight, the water quantity is stable and there is no sewage inflow upstream. two   domestic sewage (1) Urban sewage pipe network: sampling point shall be set at the inspection well where the branch pipe of non resident domestic drainage is connected to the main pipe of urban sewage; Different locations of the main sewage pipes in cities; Different positions of sewage entering the water body; (2) Urban sewage treatment plant: set sampling points at the sewage inlet and the total discharge orifice. If the treatment efficiency of each sewage treatment unit needs to be monitored, sampling points can be set at the inlet and outlet of each treatment unit. In addition, sludge sampling points should be set. （2） Sampling time and frequency one   industrial waste water The pollutant content and discharge of industrial wastewater are often different with the process conditions and the starting rate. Therefore, the selection of sampling time, cycle and frequency is a more complex problem. For the pollution sources with discharge of wastewater ≥ 5000t / D, automatic on-line water quality monitoring instrument shall be installed, and continuous automatic monitoring shall be conducted at any time; The main pollution sources with wastewater discharge of 1000-5000t / d need to be installed with equal proportion automatic sampler and flow measuring device, and the monitoring shall be conducted once / day; The pollution source with wastewater discharge ≤ 1000t / D shall be monitored for 3-5 times / month. Monitoring water quality and water quantity simultaneously; The monitoring frequency of unstable pollution sources depends on the production cycle and the pollution discharge. two   domestic sewage For the sewage of urban pipe network, the mixed sample of flow ratio can be collected from the total discharge outlet in the rainy, flat and dry seasons of one year, and sampling can be conducted once every day and night and every 4 hours. In the municipal sewage treatment plant, in order to regulate the treatment process parameters and supervise the external drainage water quality, the sewage samples shall be collected from the treatment unit and the main discharge port every day to conduct routine monitoring on the index items.