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Back to Water quality
1. Testselection and water preparation for analysis
To conduct physics-chemical analysis of water it is necessary to carry out the test selection in a proper way.
Depending on the purpose of your investigation, the test of water for your analysis can be obtained by several processes:
- by way of single collection of the whole amount of water, necessary for the analysis;
- by mixing tests collected in definite time intervals in the same place of the basin under;
- by mixing tests collected from different places of the basin under research but at the same time.
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When collecting test water it is necessary to use colorless glass dishes or polythene, permissible for contact with drinking water. The dish must be thoroughly washed by dish-washing liquid, many times rinsed out by running and distilled water, and just before the test the dish is thoroughly rinsed out by the water under study.
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It is desirable to use stoppers made of glass or polythene, rubber corks must be covered by polythene.
In practice it is convenient to use a jar or a bottle. If the access to water is difficult, the jar or the bottle can be fixed to pole. To make a test from a definite depth a bathometer is used. If this device is not available, you can use a self-made one, consisting of a bottle (1 L) with a thin firm cord of the necessary length fixed to it. The bottle is closed by a stopper with cord and is placed into the cover with weight and a loop. The cord with marks is fixed to the loop, these marks point out the depth of immerse. On the necessary depth the stopper is pulled out of the bottle and after the latter is filled with water it is lifted.
Water test selection in flowing streams is made 1 km above the nearest point of water usage (pump house, beaches, settlement territory) an in stagnants and reservoirs - 1 km in both sides from the point of water usage.
Usually the tests are selected in 3 points (by both shores and in fairways); at limited technical abilities or in small basins test selection in 1-2 points is allowed (in the places pf the strongest stream). Most often tests are selected in 5-10 m from the shore at a depth of 50 cm. A matter of special attention are polluted rivers.
If there is a sewage spill of industrial enterprises, farms etc. Water test selection is made 500 m below the spill, that allows to control the level of water pollution (for comparison a test should be also made 500 m above the sewage spill).
If it is supposed that in the result of sewage spill there accumulate subsided pollutants in fore-bottom layers, which can become the source of the second water pollution, fore bottom tests are made at a distance of 3-50 cm from the bottom.
In reservoirs, lakes, ponds where water flow is sharply slowed down, water quality in different parts can be irregular (here the appearance of second sources of pollution is possible), that is why in such basins usually a number of tests at a depth is made.
Just after you have taken the tests it is necessary to make notes about the conditions of selection, wind direction, point the date and the time (hour) of water selection.
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Setting water for analysis
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To provide exact results analysis should be made as quickly as possible. In water there are processes of oxidation-restoration, physical-chemical. Biochemical, caused by microorganisms activity, sorptions, desorption, sedimentations etc. Such water qualities as smell, colour ets. can change as well. Some substances are able to adsorb on the walls of vessels (Ferrum, Alluminium, Copper, Cadmium, Manganese etc.) and some microelements can be leached from the bottles glass.
Table 1
Terms of water analysis
| Indicators of water quality |
The shelf life |
| Taste and touch of |
2 h. |
| Smell |
2 h. |
| Transparency |
4 h. |
| Colour |
6 h. |
| Suspensions substances |
4 h. |
| рН |
during the selection |
| Hardness |
2 days |
| Nitrates |
4 h. |
| Nitrites |
4 h. |
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