Development of Monitoring Plan for Water Pollution Sources

Water pollution sources include industrial wastewater sources, domestic sewage sources, etc. Before formulating a monitoring plan, it is necessary to conduct investigation and research, collect relevant information, clarify the water use situation, types of wastewater or sewage generated, main pollutants and their discharge destinations and amounts, the number and location of sewage outlets in workshops, factories or areas, the treatment status of wastewater, whether it is discharged into rivers, lakes, seas, and whether there are seepage pits in the areas it flows through. Then, a comprehensive analysis is conducted to determine the monitoring items and monitoring points, select the sampling time and frequency, sampling and monitoring methods and techniques, and develop quality assurance procedures, measures, and implementation plans.

（1） Layout of sampling points

1. Industrial wastewater

(1) The first type of pollutant is sampled at the discharge outlet of the workshop or workshop treatment facility; The second type of pollutant is sampled at the unit's total discharge outlet;

(2) When conducting internal monitoring in industrial enterprises, samples are usually taken from the total discharge outlet of the factory, the discharge outlet of the workshop or section, and the discharge points of relevant processes or equipment;

(3) Factories with existing wastewater treatment facilities should set up sampling points at the discharge outlets of the treatment facilities. To understand the effectiveness of wastewater treatment, sampling points can be set up separately at the inlet and outlet;

(4) On the sewage discharge channel, the sampling point should be located in a place where the channel is relatively straight, the water volume is stable, and there is no sewage flowing into the upstream.

2. Domestic sewage

(1) Urban sewage pipeline network: Sampling points should be located at inspection wells where non residential domestic drainage branch pipes are connected to urban sewage main pipes; Different locations of urban sewage main pipes; Different locations where sewage enters the water body;

(2) Urban sewage treatment plant: Set up sampling points at the sewage inlet and main discharge outlet. To monitor the treatment efficiency of each sewage treatment unit, sampling points can be set up at the inlet and outlet of each treatment unit. In addition, sludge sampling points should be set up.

（2） Sampling time and frequency

1. Industrial wastewater

The pollutant content and discharge amount of industrial wastewater often vary greatly with different process conditions and operating rates, so the selection of sampling time, cycle, and frequency is a complex issue. For pollution sources with a general wastewater discharge of ≥ 5000t/d, automatic online water quality monitoring devices need to be installed for continuous and automatic monitoring at any time; The main source of pollution with a wastewater discharge of 1000-5000t/d requires the installation of proportional automatic samplers and flow measuring devices for monitoring once a day; Pollution sources with wastewater discharge of ≤ 1000t/d shall be monitored 3-5 times per month. Simultaneous monitoring of water quality and quantity; The monitoring frequency of unstable pollution sources depends on the production cycle and pollutant discharge situation.

2. Domestic sewage

For urban pipe network sewage, a flow ratio mixed sample can be collected from the total discharge outlet during the wet, normal, and dry seasons of one year for one day and one night, and sampled every 4 hours. In urban sewage treatment plants, in order to guide the adjustment of treatment process parameters and supervise the quality of external drainage, sewage samples are collected daily from the treatment unit and the main discharge outlet for routine monitoring of indicator items.