SAMPLING OF WATER
Water samples are collected from their sources and tested in laboratories to assess their quality and
suitability for different uses. The quality of water varies from place to place and season to season.
Hence the samples for analysis should be collected frequently and over a long period of time so that
they may be truly representative of the actual quality of water being used.
GRAB SAMPLES:
These are the water samples collected more or less instantaneously and analyzed separately. The
no. of samples to be collected and the frequency of sampling are decided judiciously by the analyst.
COMPOSIT SAMPLES:
These are the samples collected in the sources where fluctuations are rapid. These samples are
collected in regular intervals say 15 to 30 minutes and pooled into one large sample over a period of
24 hours.
METHOD OF OBTAINING SAMPLES FOR TESTING
For example, examination, water can be collected in fully cleaned buckets or plastic cans. If the
water is to be collected for chemical tests, the container is thoroughly washed and cleaned. Glass
bottles of minimum 2 liters capacity should be used. For bacteriological tests 200 to 500 CC capacity
bottles are sufficient for collection of samples.
The following precautions should be kept in view while collecting the samples.
1. If the water is to be collected from a tap of faucet, sufficient quantity of water should be
allowed to pass through the tap, before collecting sample from it, to eliminate the stagnant
water if any.
2. If the water is to be collected from the surface stream or river, it should be collected about
40-50 cm below the surface to avoid the collection of surface impurities, oils, tree leaves and
other floating matter.
3. If the water is to be collected from the under-ground sources i.e., through wells of tube
wells, sufficient quantity of water should be pumped out before collecting the samples.
4. In the case of samples for bacteriological analysis the bottles and stoppers are properly
sterilized. Also if the water to be collected is tap water, the mouth of the tap or faucet is
flamed by the application of burning methylated spirit to kill all pathogens sticking on it.
Water samples are collected from their sources and tested in laboratories to assess their quality and
suitability for different uses. The quality of water varies from place to place and season to season.
Hence the samples for analysis should be collected frequently and over a long period of time so that
they may be truly representative of the actual quality of water being used.
GRAB SAMPLES:
These are the water samples collected more or less instantaneously and analyzed separately. The
no. of samples to be collected and the frequency of sampling are decided judiciously by the analyst.
COMPOSIT SAMPLES:
These are the samples collected in the sources where fluctuations are rapid. These samples are
collected in regular intervals say 15 to 30 minutes and pooled into one large sample over a period of
24 hours.
METHOD OF OBTAINING SAMPLES FOR TESTING
For example, examination, water can be collected in fully cleaned buckets or plastic cans. If the
water is to be collected for chemical tests, the container is thoroughly washed and cleaned. Glass
bottles of minimum 2 liters capacity should be used. For bacteriological tests 200 to 500 CC capacity
bottles are sufficient for collection of samples.
The following precautions should be kept in view while collecting the samples.
1. If the water is to be collected from a tap of faucet, sufficient quantity of water should be
allowed to pass through the tap, before collecting sample from it, to eliminate the stagnant
water if any.
2. If the water is to be collected from the surface stream or river, it should be collected about
40-50 cm below the surface to avoid the collection of surface impurities, oils, tree leaves and
other floating matter.
3. If the water is to be collected from the under-ground sources i.e., through wells of tube
wells, sufficient quantity of water should be pumped out before collecting the samples.
4. In the case of samples for bacteriological analysis the bottles and stoppers are properly
sterilized. Also if the water to be collected is tap water, the mouth of the tap or faucet is
flamed by the application of burning methylated spirit to kill all pathogens sticking on it.
