【Weekly Topic】(33) June 27, 2015: Briefly describe the methods for collecting water samples and the precautions to take

1) The water sampling valve must be opened and allowed to drain for more than 3 minutes before sampling can be performed. 2). The sampler can be a colorless ground-mouthed hard glass flask or a polyethylene plastic bottle. Specialized analysis requires dedicated sampling bottles; for example, plastic bottles should not be used for measuring oil content, while glass bottles are not suitable for measuring trace amounts of silica, trace sodium ions, or low hardness levels ； For dissolved oxygen sampling, there are dissolved oxygen sampling bottles; for carbon dioxide analysis, sealed carbon dioxide sampling bottles are used, etc. 3). The sampling bottle must be cleaned thoroughly; rinse it with the water sample at least three times before sampling. During sampling, water should flow into the sampling bottle slowly; it should not be filled to the brim, with a gap (of more than 1 mm) remaining between the water surface and the bottle stopper to prevent the stopper from being pushed out due to changes in water temperature.

1. Sampling: For collecting surface water samples, the sampler can be placed 0.3 to 0.5 meters below the water surface to take samples; immediately after sampling, the container should be covered tightly to prevent exposure to air； Deep-water sampling can be carried out using a suction pump; a vessel or similar craft is used to navigate to the desired sampling location, the sampling tube is lowered to the specified depth, and water samples are then drawn up using the pump. Simple water sampler: Lower it to the desired depth (which can be determined from the scale on the pull rope), pull up the rope to open the stopper, and then lift it out once the sampling bottle is filled with water. Rapid current water sampler: It consists of a long steel tube fixed to an iron frame; a rubber tube is placed inside the tube, with its upper end clamped by a clip and its lower end connected to a short glass tube on a stopper. Another long glass tube extends from this stopper to near the bottom of the sampling bottle. Before sampling, tighten the rubber stopper, then extend it vertically along the hull to the desired water depth. Open the upper rubber clamp, and the water sample will flow into the sample bottle through the long glass tube, while the air in the bottle is expelled through the short glass tube and the rubber tube. Water samples collected in this way can also be used to determine dissolved gases in water, as they are isolated from air. 2. Precautions for sampling: (1) After the water sample is collected or placed in a container, preservatives should be added immediately as specified in the table above. (2) Oil sampling: Before sampling, any existing oil film is broken apart. A glass container is placed in the holder of a vertical water sampler, which is then lowered to a depth of 300 mm. Water is collected while the sampler is raised upward, leaving an appropriate amount of space at the surface. Sampled separately, all used for testing. Furthermore, the sampling bottle (container) must not be rinsed with the water sample collected. (3) Do not disturb the sediment at the bottom of the water during sampling. (4) When sampling, it is necessary to ensure the accurate location of the sampling points. Use a locator (GPS) for positioning when necessary. (5) Fill out the “Water Quality Sampling Record Form” carefully; make the entries on-site using a signature pen or a hard pencil. The handwriting should be neat and clear, with all items completed. (6) Ensure sampling is carried out on time, accurately, and safely. (7) Before the sampling is completed, verify the sampling plan, records, and water samples; if there are any errors or omissions, additional sampling or resampling should be carried out immediately. (8) If the water body at the sampling site is highly uneven and it is not possible to obtain representative samples, the extent of this unevenness as well as the actual sampling conditions should be recorded in detail for those who will use this data. And report this on-site situation to the environmental protection administrative authorities. (9) When measuring parameters such as dissolved oxygen, biochemical oxygen demand, and organic pollutants, the water sample must fill the container completely, with no space at the top, and it should be sealed with water. (10) If the water sample contains settleable solids (such as sediment), they should be separated and removed. The separation method is as follows: Shake the collected water sample well and pour it into a cylindrical glass container (such as a 1–2 L measuring cylinder); let it stand for 30 minutes. Then, transfer the water sample, which contains no sedimentary solids but does contain suspended solids, into a sample storage container and add a preservative. Except for water samples used to determine water temperature, pH, DO, conductivity, total suspended solids, and oils. (11) When determining the COD, permanganate index, chlorophyll a, total nitrogen, and total phosphorus in lake and reservoir water, let the water sample stand for 30 minutes, then take the sample using a pipette once or several times; the tip of the pipette should be inserted at a depth of 50 mm below the surface of the water sample, after which a preservative is added to preserve it. (12) Separate sampling is required for the determination of parameters such as oils, BOD5, DO, sulfides, residual chlorine, fecal coliforms, suspended solids, and radioactivity.

Water sample collection methods, washing of sampling containers: 1. For the determination of general physical and chemical parameters, the container is cleaned with water and detergent to remove dust and oil residues, then rinsed thoroughly with tap water. It is subsequently soaked in 10% *ao acid or salt acid for 8 hours; after that, it is taken out, drained, rinsed 3 times with tap water, and finally thoroughly washed with distilled water.  2. Determination of microbiological indicators: ① Container washing: Same as the washing of sampling containers for the determination of general physical and chemical indicators ； ②Container sterilization: Autoclaving is used, requiring a temperature of 121°C for 15 minutes. If the containers are not used immediately after autoclaving, the condensation water inside them should be dried at 60°C. The sterilized containers should be used within 2 weeks.    Sampling of water samples: 1. Water from sources: ① Sampling points should generally be selected at the locations where water is drawn ； ②Springing spring water can be sampled directly at the source ； When collecting spring water that does not flow spontaneously, the water trapped in the pumping pipe should be removed first, and sampling should be carried out after fresh water has taken its place. ③ When collecting well water, it should be done after sufficient pumping (more than twice the amount of water stored), to ensure the representativeness of the water sample.  2. Water leaving the plant: The sampling point should be located before the water enters the transmission pipeline, and sampling should be conducted after fresh water has taken its place.  3. Peripheral water: Sampling points should be located at the pipeline network (at the users’ end). When sampling, the faucets should be left open for a few minutes; after fresh water has replaced the old water, disinfect the faucets, and then collect 400 milliliters of sample for microbiological testing ； Then, water samples for physical and chemical parameters are collected.  4. Secondary water supply: includes the inlet and outlet of water tanks or reservoirs.  5. Decentralized water supply: Determined based on actual usage.    Precautions for water sample collection: 1. Do not disturb the sediment at the bottom of the water during sampling.   2. When collecting water samples for several types of test indicators from the same source at the same time, the samples intended for microbiological testing should be collected first. Sampling should be done directly; the sterilized sampling bottles must not be cleaned with a water brush, and care should be taken to prevent fingers and other objects from contaminating the bottle openings.   2. For water samples used in the testing of physical and chemical parameters, rinse the container and stopper 2–3 times with the sample to be tested before sampling.   3. Volatile and semi-volatile organic compounds: Fill to just before overflowing; no bubbles should be present. Seal with a stopper covered by a polytetrafluoroethylene membrane or an appropriate compatible stopper, and the sealed sample bottle must be free of bubbles.   4. Water samples that have been tested on-site cannot be taken back to the laboratory for testing other parameters.

This post was last edited by ljtjbx on 2015-6-28 at 16:36. Briefly describe the methods for collecting water samples and the precautions to take 1) The water sampling valve must be opened and allowed to drain for more than 3 minutes before sampling can be performed. 2). The sampler can be a colorless ground-mouthed hard glass flask or a polyethylene plastic bottle. Specialized analysis requires dedicated sampling bottles; for example, plastic bottles should not be used for measuring oil content, while glass bottles are not suitable for measuring trace amounts of silica, trace sodium ions, or low hardness levels ； For dissolved oxygen sampling, there are dissolved oxygen sampling bottles; for carbon dioxide analysis, sealed carbon dioxide sampling bottles are used, etc. 3). The sampling bottle must be cleaned thoroughly; rinse it with the water sample at least three times before sampling. During sampling, water should flow into the sampling bottle slowly; it should not be filled to the brim, with a gap (of more than 1 mm) remaining between the water surface and the bottle stopper to prevent the stopper from being pushed out due to changes in water temperature.

1) The water sampling valve must be opened and allowed to drain for more than 3 minutes before sampling can be performed. 2). The sampler can be a colorless ground-mouthed hard glass flask or a polyethylene plastic bottle. Specialized analysis requires dedicated sampling bottles; for example, plastic bottles should not be used for measuring oil content, while glass bottles are not suitable for measuring trace amounts of silica, trace sodium ions, or low hardness levels ； For dissolved oxygen sampling, there are dissolved oxygen sampling bottles; for carbon dioxide analysis, sealed carbon dioxide sampling bottles are used, etc. 3). The sampling bottle must be cleaned thoroughly; rinse it with the water sample at least three times before sampling. During sampling, water should flow into the sampling bottle slowly; it should not be filled to the brim, with a gap (of more than 1 mm) remaining between the water surface and the bottle stopper to prevent the stopper from being pushed out due to changes in water temperature. Learned it*:D

1 For wastewater with unstable water quality that changes throughout the day, water samples need to be collected multiple times within a single day (the standard approach is three times in the morning and three times in the afternoon, with an interval of one hour between each collection). 2 Do not use only the raw water; samples should be taken from multiple locations such as the water inlet, flow regulation tank, and hydrolysis-acidification tank. For renovation projects, water sampling is also required at the original outlet. 3 When collecting water, try to use the upper layer liquid, and avoid using water from the middle or lower layers. If necessary, water can be collected multiple times and then mixed together. 4 For wastewater containing both industrial and domestic effluents, sampling should be taken at the main outlet.

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