Environmental monitoring data reflects the true situation of water quality at pollution sources. Sampling of water quality at pollution sources is a very important part of the environment. If the water samples collected by the samplers are not representative, they will not be able to reflect the time situation of water quality at pollution sources. In this case, even if the data analyzed in the laboratory is very accurate and the quality control is very good, The data obtained from the tests actually cannot reflect the true situation of the water quality at the pollution source. Therefore, no matter how much is done, it will be in vain.
First, enhance the sense of responsibility and professional quality of sampling personnel, and ensure that all practitioners are certified before taking up their posts
The purpose of sampling is to collect representative samples from the water samples to be tested to analyze and infer whether the batch of samples has been contaminated. Therefore, the quality of sampling work directly affects the quality of environmental monitoring work. Taking representative samples is one of the foundation and most crucial links of environmental monitoring. Based on years of water quality sampling practice, it can be seen that although sampling seems simple, it is not the case in reality. Not everyone can engage in environmental monitoring sampling work. Sampling personnel should have a sense of responsibility and professional quality for environmental monitoring work, as well as the spirit of hard work and endurance. Moreover, one must undergo strict theoretical knowledge training and assessment before taking up the post, as well as practical sampling work assessment. Only after passing the assessment can one officially start working. It is essential to master the sampling techniques and the basic knowledge of some other industries, and be familiar with the technical requirements for sample collection, transportation, and sampling of routine monitoring parameters. Colleagues should have a sense of safety protection and be responsible for sampling safety protection work.
Second, formulate a sampling plan
The basis and prerequisite for formulating a sampling plan is that the on-site investigation should be as detailed and accurate as possible. Based on a comprehensive on-site investigation, verify relevant materials. In light of specific circumstances, determine the monitoring items, reasonable sampling sections, sampling points, sampling cycles and sampling frequencies in accordance with the on-site investigation results and review of relevant materials. Formulate quality control and assurance measures, implementation plans and safety protection measures.
Formulating a detailed sampling plan can help eliminate randomness and blindness during sampling, thereby ensuring the representativeness and completeness of the samples. The person in charge of sampling should fully understand the purpose and requirements of the monitoring task before formulating the plan. It is necessary to have a clear understanding of the conditions of the pollution sources to be sampled (such as the process flow, type of sewage, discharge pattern, and the direction of the sewage network, etc.). And be familiar with sampling methods, the selection of containers for holding water samples, the preservation and transportation of samples. If there are on-site measurement projects, one should understand the relevant on-site measurement techniques. The sampling plan should include: determining the sampling points, the items and quantities to be measured, the quality assurance measures for sampling, the sampling time and route, the sampling personnel and their division of labor, the sampling equipment, the on-site monitoring equipment and transportation means, and the guarantee of safety protection measures, etc.
Iii. Determination of Sampling Location
In accordance with the requirements of standards and norms such as the "Technical Specifications for Monitoring Surface Water and Wastewater" and the "Technical Specifications for Monitoring Total Discharge of Water Pollutants", the layout principles of wastewater monitoring points from pollution sources are as follows:
The sampling points for the first category of pollutants are set at the discharge outlets of workshops or workshop treatment facilities or facilities specifically for treating such pollutants.
The sampling points for the second category of pollutants are set at the external discharge outlets of the pollutant-discharging units or the discharge outlets of the treatment facilities within the factory area. Sampling points must be set up separately at all discharge outlets. The sampling points for sewage entering centralized sewage treatment plants and urban sewage networks should be determined in accordance with the requirements of the local environmental protection administrative department. In the layout of sampling points for monitoring the efficiency of sewage treatment facilities, when monitoring the overall efficiency of the sewage treatment facilities, sampling points should be set up at various entrances to the sewage treatment facilities and the total discharge outlets of the sewage treatment facilities. When monitoring the efficiency of each sewage treatment unit, sampling points should be set up at the inlets of sewage entering the treatment facility units and the outlets of the facility units.
Iv. Quality Control in the Sampling Process
Quality control during the sampling process runs through the entire sampling process, covering aspects such as sampling personnel, sampling methods, sampling points, sampling containers, sample preservation and transportation, full procedure blanks and transportation blanks, on-site parallel samples, the surrounding conditions of sampling points, and original sampling records.
First, sampling personnel should pass the assessment and hold relevant certificates to work.
Second, the setting of sampling sections and points, as well as the sampling containers used, should all comply with the technical specifications for environmental monitoring. The sampling frequency, time and method should be carried out in accordance with the requirements of the monitoring object and the analysis method, and in compliance with the corresponding technical specifications.
Thirdly, when sampling, it is necessary to have a detailed understanding of the production status of the polluting entity, including water consumption, process flow, source of wastewater, treatment capacity and operation status of wastewater treatment facilities, etc. Special attention should be paid to whether there are any abnormal situations.
Fourth, during each monitoring process, no less than 10% of the on-site parallel samples should be collected.
The on-site fixed monitoring items should be fixed in accordance with the environmental monitoring technical specifications and sent to the laboratory as soon as possible within the valid retention period. When water samples are sent to the laboratory, the sample handover work should be completed in a timely manner, and both the sender and the recipient should sign.
Fifth, for the determination of suspended SS, pH, BOD, oil, sulfides, radioactivity, residual chlorine, microorganisms and other items, separate sampling is required. The water samples for the determination of BOD5, sulfides and organic pollutants must fill the containers. The determination of pH, water temperature, conductivity, DO and ORP should be carried out on-site. When sampling, except for items with special requirements such as total bacterial count, coliform bacteria, oil, BOD, organic matter, and residual chlorine, the sampler and water sample container should be rinsed 2 to 3 times with sampling water first. Then, the water sample should be collected into the container and the corresponding fixative should be added immediately as required, and the label should be affixed. Regular self-adhesive labels should be used.
Sixth, fill in the sampling record carefully. The main contents include: the name of the pollutant-discharging entity, the category of the sample, the purpose of sampling, the sampling date, the sample number, the sampling location, the sampling time, the monitoring items and the name of the preservative added, the description of the apparent characteristics of the wastewater, the flow rate, the flow volume, and the sampler, etc. Ensure that sampling is timely, accurate and safe; Before the sampling is completed, the sampling records and water samples should be carefully inspected. If any samples are missed or do not comply with the regulations, they should be immediately supplemented or re-sampled.
V. Sampling for acceptance Monitoring of Wastewater pollution sources
The acceptance monitoring of wastewater from pollution sources should be carried out under stable production conditions and when the production load reaches more than 75% of the designed production capacity. Where national or local emission standards have separate provisions on production load, such provisions shall prevail. If the overall production conditions fail to meet the prescribed requirements, the conditions can be adjusted in parts for monitoring based on the process of the pollution source and the production facilities. Where it is truly impossible to adjust to meet the specified working conditions, with the consent of the administrative department for environmental protection, monitoring shall be conducted under the condition that the production facilities are operating stably, and an explanation shall be provided in the monitoring results. During the monitoring period, there should be a dedicated person responsible for supervising the working conditions and recording parameters such as production time and working condition load during the monitoring period. The production equipment and treatment facilities of the pollution source should all be in normal operating conditions. The frequency of sampling for pollution source acceptance monitoring shall be determined in accordance with the following principles:
The monitoring frequency should be able to reflect the actual pollutant discharge situation and the treatment effect of environmental protection and governance facilities, and should minimize the workload.
For emission sources with stable production and regular pollutant emissions, the production cycle should be taken as the sampling cycle. Sampling should be no less than two cycles, and the number of samplings within each cycle should generally be 3 to 5 times, but no less than 3 times.
For construction projects with sewage treatment facilities that are operating normally or with regulating tanks, if the sewage is to be discharged stably, instantaneous samples can be taken, but not less than three times. The sampling frequency for testing the treatment efficiency of sewage treatment facilities can be appropriately reduced.
4. For unstable emission sources and those from large key projects, the method of intensive monitoring must be adopted.