Rules for sampling water for laboratory research
In accordance with GOST R “Water. General requirements for sampling", GOST R "Drinking water. Sampling" for chemical-analytical control of water quality, you must follow the following recommendations:
· Samples are taken in containers made of polymer materials approved for contact with water - PET bottles (example Fig. 1), or other materials intended for contact with food products. Sampling can also be carried out in chemical-resistant glass containers.
· The sample volume must be at least 3 liters.
· Before sampling, the sampling containers must be rinsed at least twice with water to be analyzed. Sampling containers should be thoroughly washed to minimize possible contamination of the sample.
· During transportation, containers are placed inside a container (container, box, case, etc.), which prevents contamination and damage to containers with samples. The container must be designed in such a way as to prevent the spontaneous opening of container caps.
· A water sample for chemical analytical control must be delivered on the day of collection. If this is not possible, the selected sample is cooled (in a refrigerator at a temperature of 4 C), but not more than 24 hours.
· When taking samples from a well or reservoir, it is necessary to drain water for at least 10 minutes (to drain stagnant water).
· Information about the sampling location and the conditions under which they were taken is indicated on the label and attached to the sampling container.
In accordance with GOST R “Water. Sampling for microbiological analysis" when taking samples to determine microbiological parameters, it is necessary to:
· Used for sampling clean sterile containers made of glass (example Fig. 2)
· Sampling containers must be equipped with tightly closing stoppers (silicone, rubber). Issued at the Laboratory.
Immediately before sampling, the faucet is sterilized, preferably by flambéing (treating the faucet with a burning swab moistened with 96% ethyl alcohol). The quality of flambéing is determined by the appearance of a hissing sound upon contact with water after opening the tap.
· Before directly collecting a sample, you must wash your hands with soap.
An open container for sampling is placed under the tap in a stream of water and filled to the mark, avoiding contact of the surface of the tap with the container. While filling the container, it is not allowed to change the water pressure (by closing or opening the tap).
It is not allowed to take samples from faulty faucets with water leaks.
· The sample must be taken in such a way that a layer of air remains under the plug.
Water samples from flowing wells are taken from the wellhead.
Water sampling from springs is carried out at the outlet of the capture structure or, if there is none, at the point where the head of the spring (“griffin”) exits the surface of the earth.
· A water sample for microbiological analysis must be delivered within 6 hours from the moment of sampling.
When taking samples to determine radon:
Samples are taken in containers made of polymer materials approved for contact with water - PET bottles with a volume of 1.5 liters.
Containers made of polymer material can be permeable to radon. If possible, fill the container by immersing it in water and closing it under water, without leaving any air bubbles.
The sample is transported with the lid turned down.
Sample freezing is not allowed.
Selection rules
in accordance with the requirements of GOST R 51592-2000 "Water. General requirements for sampling", GOST R 53415-2009 (ISO 19458:2006) "Water. Sampling for microbiological analysis", MP 0100/13609-07-34 "Sampling and preparation of water samples to determine radiological indicators of drinking water."
1. General requirements for sampling
When collecting water samples at the same point for different purposes, samples are taken first for microbiological analysis.
When sampling from a tap (well), the time to drain the water before sampling depends on the purpose of sampling. If the purpose of sampling is to assess the quality of consumed water, then samples should be taken without first draining the water. To assess the quality of water in a water point (well, well) to establish equilibrium conditions before sampling, 5 minutes of draining the water is sufficient.
The water supply system from wells and wells in which the pump is permanently installed must have a metal tap or outlet. An open container for sampling is placed under a tap in a stream of water and filled (in a thin stream along the wall of the container). While filling the container, it is not allowed to change the water pressure (by closing or opening the tap).
Sampling from wells and wells at the point of consumption that do not have a permanently installed pump is carried out using a bucket, can or ladle, etc., which are filled with water, after which the water is poured into sampling containers.
Water sampling from springs is carried out at the outlet of the capture structure or, if there is none, at the point where the head of the spring ("griffin") exits the surface of the earth.
For transportation, it is preferable to cool the samples to a temperature of 2-5 °C (for example, using cold accumulators). During transportation, containers must be protected from contamination, damage and spontaneous opening of caps.
The analysis of water samples must begin on the same working day on which the samples were taken. The storage time of water samples from collection to the beginning of their analysis includes the duration of transportation, registration and preparation of samples for analysis. The maximum storage period for samples is 6 hours. Increasing this period may reduce the reliability of the results. By agreement with the Customer, it is possible to increase the maximum sample storage period to 8 hours.
2. Sampling water intended for microbiological analysis, carried out with disinfected [for example, treatment with ethyl alcohol 70% or disinfectant wipes for personal use] immediately before sampling with hands or with sterile gloves in a sterile container (volume 0.5 l, which must be obtained in advance from the laboratory).
Immediately before sampling, the faucet is sterilized, preferably by flambéing (treating the faucet with a burning swab moistened with 96% ethyl alcohol). The quality of flambéing is determined by the appearance of a hissing sound upon contact with water after opening the tap. (Superficially burning the faucet with a lighter is not enough to disinfect it). Only if flame sterilization is not possible, the neck of the tap is disinfected by immersion for 2-3 minutes in a glass with 70% ethyl alcohol. After sterilization, the tap is opened to provide the minimum flow of water necessary to flush away the disinfectant that was used on the tap, after which water samples are taken.
When sampling, aseptic conditions must be ensured and samples must be protected from dust and splashes.
The sterile sampling container is opened immediately before sampling, removing the stopper along with the sterile cap. The stopper and edges of the container should not touch foreign surfaces. Not allowed Rinse sterile sampling containers!
After filling, the container is immediately closed with a sterile stopper, which ensures tightness and does not get wet during transportation, and a sterile cap. When filling the container, there should be space between the stopper and the surface of the poured water so that the stopper does not become wet during transportation and to ensure mixing of the sample before analysis.
3. When sampling water intended for chemical analysis, 2 containers with a volume of 1.5 liters (or 1 container with a volume of 5 liters) made of polymer material intended for contact with food products are rinsed at least three times with the water to be analyzed and the containers are filled to the top with it.
4. When sampling water intended for determining radiological indicators, incl. specific activity of radon ( 222 Rn), a 1.5 liter container made of polymer material intended for contact with food products is pre-rinsed at least three times with water to be analyzed. After filling the container with water to the top, you need to squeeze it so that the water is at the very edge of the neck, and then screw on the lid. The sample is transported with the lid turned down. The maximum sample storage period is no more than 48 hours.
- To take samples, prepare a clean plastic drinking water bottle: 1.5 - 2 liters in volume. You cannot use bottles of beer, Pepsi-Cola, kvass and other sweet drinks.
- A sample from the well should be taken after the water has been drained for a long time. On average, you will need to drain 3 liters of water for every 10 meters of well depth.
- Before collecting water, it is necessary to thoroughly rinse the bottle several times with the analyzed water.
- The bottle is filled to the neck. It is very important that the water does not become agitated and does not come into contact with atmospheric air. For this purpose, one end of the siphon hose is lowered to the sampling point, and the other to the bottom of the bottle. While filling the container, it is not allowed to change the water pressure (by closing or opening the tap). The bottle is filled to the top and then the water being analyzed is continued to pass through it until the water in the bottle is changed several times. Then immediately close the bottle with a stopper, squeezing out the remaining air bubble. This method of collecting a sample allows you to reduce the saturation of water with atmospheric oxygen and, as a result, prevents chemical reactions from occurring!
- The sample taken is ready for chemical analysis of the water, but remember: the faster the sample gets to the laboratory, the more accurate the result will be.
This image shows how the organoleptic characteristics of a water sample from a well change over a short period of time. After just over four hours, analyzing the water of this sample becomes meaningless.
When taking water samples from a surface reservoir or a mine well, its temperature is measured using a special thermometer (Fig. 16.1.) or a conventional chemical thermometer, the reservoir of which is wrapped in several layers of gauze bandage. The temperature is determined directly at the water source. The thermometer is lowered into the water for 5-8 minutes, then quickly pulled out and the water temperature is taken.
Rice. 16.1. Thermometer for measuring water temperature in reservoirs, wells (a), bathometers for taking water samples for analysis (b).
Sampling of water from surface reservoirs and wells is carried out using bottles of various designs, which are provided with double twine: for lowering the device to a given depth and for opening the plug of the vessel at this depth (Fig. 16.1-b).
To take water samples from flowing reservoirs (rivers, streams), a bottlemeter with a stabilizer is designed, which directs the neck of the vessel against the flow.
A water sample from a water tap or equipped drainage system is taken:
for bacteriological analysis, after preliminary burning the outlet of the tap or captage with an alcohol torch, draining water from the tap for at least 10 minutes, into a sterile bottle with a capacity of 0.5 liters, with a cotton-gauze stopper, wrapped on top with a paper cap. In order not to soak the cotton-gauze stopper, fill the bottle about three-quarters full so that 5-6 cm of air space remains under the stopper.
Dishes with a cotton-gauze stopper are sterilized in advance in an oven at 160 0 C for an hour;
During sampling, a covering letter is drawn up, in which they note: the type, name, location, address of the water source (surface reservoir, artesian borehole, mine well, captage, water tap, standpipe); its brief description; weather conditions at the time of sampling and during the previous 10 days; the reason and purpose of sampling (routine examination, unfavorable epidemic situation, population complaints about the deterioration of the organoleptic properties of water); the laboratory where the sample is sent; the required amount of research is noted (short, full sanitary-chemical analysis, bacteriological analysis, identification of pathogenic microorganisms); date and time of sample collection; results of studies performed during sample collection (temperature); who took the sample (name, position, institution); signature of the official who took the sample.
Samples are delivered to the laboratory as quickly as possible. Bacteriological studies should begin within 2 hours after sampling or, if stored in a refrigerator at a temperature of 1-8°C, no later than 6 hours. Physico-chemical analysis is carried out within 4 hours after taking the sample or, if stored in a refrigerator at 1-8°C, no later than 48 hours. If it is impossible to conduct research within the specified time frame, the samples must be preserved (except for samples for physical, organoleptic and bacteriological studies, as well as BOD determination, which must be carried out within the above time frame). The samples are preserved with a 25% solution of H 2 SO 4 at the rate of 2 ml per 1 liter of water or in another way, depending on the indicators that will be determined.
An accompanying form is attached to the selected sample, which indicates the address, type of water source where the sample is sent, the purpose of the analysis, the date and time of sampling, and the signature of the official who took the sample.
1. For chemical analysis take a water sample:
· in cleanly washed dishes (bottles), previously rinsed with the same water,
capacity 1 l with cork or rubber stopper.
2. Water sample for bacteriological analysis take:
· in a bottle with a capacity 0.5 l, pre-sealed with a cotton plug and sterilized (in an oven at 1600 C for 1 hour) in the laboratory.
· After sterilization is completed, the neck of the bottle is closed to protect against contamination sterile paper cap .
Taking a water sample from mine well For chemical analysis
To take a water sample from mine well For chemical analysis more often use the bucket available at the well.
1. First 4-6 buckets The water is drained and then the bottle is filled with water for chemical analysis.
2. Pre-bottle at least 3 times rinse with selected water, and then fill it so that under the stopper there was little air space left(5-6 cm).
Taking a water sample from mine well For bacteriological analysis
Before collecting a water sample for bacteriological analysis,
1. holding the paper cap with your hand, remove the plug;
2. using alcohol torch (a cotton swab moistened with alcohol) burn the neck
3. and fill a bottle with water (without adding approximately 50-100 ml),
4. close with a stopper and fix the cap, tying it.
When collecting a water sample from a well, equipped with a pump , standpipe or water supply tap at first:
1. burn the tap with an alcohol torch,
2. then drain the water for 15 minutes with the tap fully open
3. and fill the bottle in compliance with the previously listed rules.
Stick on bottleslabel, on which it is noted:
· date, time and place of water collection and purpose of analysis,
then test with accompanying form sent to the laboratory as soon as possible.
INaccompanying formindicate:
1. name, location and address of the water source;
2. characteristics of the water source (type, depth, means of water lifting, sanitary condition of the surrounding area);
3. the reason for sampling (routine research, control after repair, infectious disease, etc.) and the purpose of the analysis;
4. data from studies performed at the source, if any;
5. date, hour of sample collection, who took it, signature.
At the sampling site, determine:
· water temperature,
presence of an oily film on its surface,
· transparency,
· color,
· smell (see table 15).
· If a sample of chlorinated water is taken, then it is determined on site residual chlorine content.
1. Determining the smell of water
Fill the bottle 2/3 full with the water being tested,
Seal with a clean cork stopper.
And shake vigorously.
After removing the cork, immediately draw air from the bottle into your nose and notice the smell.
The strongest odor is felt when first detected..
Check nature of the smell :
earthy, musty, swampy, woody, putrid, moldy, vague
and him intensity , in points using the table. 15
To enhance the smell of water, 100 ml of water is poured into a flask, covered with glass, and heated to 60 degrees. In a water bath, remove the glass and determine the smell.
2. Determining the taste of water.
· Boil water in a flask,
· then cool it to room temperature
· and, taking small portions into your mouth,
mark
flavor character:
Salty, bitter, ferrous, metallic, astringent, etc.
Andintensity it in points, using the table. 15.
The taste of water is determined by confidence in its safety.
3. O determination of residual chlorine.
Add to a glass of water 5 drops of 5% potassium iodide solution And 10 drops of 1% starch solution.
· If no blueness, Means residual chlorine absent ,
· bluish color - less than 0.3 mg/l,
· slight blue discoloration - from 0.3 to 0.5 mg/l, - №
· intense - more than 0.5 mg/l residual chlorine.
T able 15. Intensity of smell (taste) in points
3 data 2. Determination of the dose of chlorine for water disinfection (field method ).
Dose of chlorine required for water disinfection (chlorine demand), determined by test chlorination.
For this purpose, equal volumes of test water add different amounts1% bleach solution .
After 30-minute contact of chlorine with water in all vessels determine the content of residual chlorine.
- Chlorine dose equals that amount bleach , which was added to the vessel, where after trial chlorination there remained0.3-0.5 mg/l residual chlorine.
Preparation of a 1% bleach solution
1. Measure into the cylinder up to 99 ml distilled or transparent well water.
2. Weigh on a pharmacy scale 1 g bleach(the one you will use to disinfect the water).
3. Transfer weighed in a porcelain cup or mortar,
4. add more from the cylinder a few drops of water to wet the bleach and with a glass rod or pestle rub it thoroughly until homogeneous pulp.
5. After this, add a small amount of water again and Continue rubbing the bleach until the lumps disappear.
6. Then, pouring water from the cylinder, transfer the bleach suspension into a beaker or flask.
7. Rinse the cup with all the water from the cylinder, pouring the rinsing water into the same cup.
8. Later 10-15 min filter the received 1% bleach solution through paper filter, preferably in a dark bottle with a ground stopper.
Date added: 2015-07-23 | Views: 1830 | Copyright infringement
| | | | 5 | | | | | | |
