5.1 Signs of contaminated waterIt is important for the EHP, or whoever is in charge of the water supply within the community, to constantly monitor the quality of the water.
One sign that the water supply might be contaminated is when several people from different families in the community become sick at the same time. A contaminated community water supply can make lots of people sick at the same time. Remember, however, such sickness may also be caused by contaminated food or vectors carrying disease-causing germs.
It is, therefore, a good idea to occasionally check the complete water supply system for any problems. If any are found they must be fixed. It might be necessary to call the water supplier for help in locating and fixing the problem. Where contamination by germs is suspected, sampling of the entire water supply system is recommended to find the contamination source. This is done by working through the water supply system and sampling at different places.
The results of these samples will show which parts of the system are contaminated and where the contamination may be happening.
It is important that every water tank is inspected regularly for signs of water contamination. These are signs that the water in the tank is contaminated:
- The water is a green or brown in colour
- Green slime is growing on the sides or bottom of the tank
- Faeces, rotting leaves or dead animals are in the water
- Live animals, such as frogs, are in the water
- There is no lid on the tank
- The lid of the tank is not on tightly or is rusty and has holes in it
Fig. 6.29: Contaminated water tank.
If any of these problems are found, steps must be taken immediately to correct the fault so that water quality is maintained. This usually means making repairs to or cleaning out the tank. The procedure for cleaning a water tank is covered in Section 6.2.
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5.2 Testing for contaminated waterWater sampling and testing drinking water supplies in communities is undertaken by either the water supplier or the EHO from the local authority. Who does this job depends upon which of the two agencies has responsibility for providing the water supply. EHPs should make themselves known to these agencies so that they can assist in sampling programs. However, some communities may not have a regular sampling program.
If the results of the tests show there are germs in the water supply, steps will have to be taken to remove the germs and their source. For example, if the water bore is found to contain germs, the source of the germs will have to be found and fixed if possible. Where this cannot be done, the water in the tank will have to be more strongly chlorinated.
The EHO can make sure that EHPs follow the correct sampling procedure.
The EHP must talk with the EHO or the water supplier before doing any water sampling.
They will authorise any water sampling so that the community will not be charged for the cost of the test/s. If the EHP is to assist in water sampling programs, he/she should check with the EHO or water supplier before taking samples to make sure that all the necessary procedures are being followed, such as the correct way to send the sample/s to the laboratory for testing.
Routine water testsThere are two kinds of tests which may be routinely carried out on a community water supply:
The test for germsColiform bacteria is one of the most important germs that is looked for in water, in particular one type of coliform called E. coli (Escherichia coli).
Coliforms indicate faecal pollution. Faecal coliforms, including E. coli, indicate human faecal pollution.
This test is complicated and is done at professional laboratories.
The test for the chlorine level in the tankThis test is done to make sure there is enough chlorine in the water to produce sufficient free residual chlorine. If testing shows the correct free residual chlorine level, the water should be free of germs.
Other water testsAnother test can be done to find out what chemicals there are in the water. This can include testing for salt and hardness or other chemical contaminants.
Tests for some parasites in a water supply can also be done. Special samples of the water similar to those taken for germs must be submitted to a laboratory where the water will be examined. If such tests are required the EHP must contact the local EHO or the EHP supervisor before sampling.
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Taking a water sampleTo test the water supply for germs the water sample is taken in a special water sample bottle. Each bottle has its own label and comes in a sealed plastic bag. Make sure the cap is screwed on properly to protect the sample from contamination.
Any chlorine in the water is neutralised as soon as it enters the bottle. Neutralising means using a chemical action to combine the chlorine with another substance so that the chlorine is no longer free to act on germs while it is being transported to the laboratory. The substance in the bottle which neutralises the chlorine in the water is sodium thiosulphate.
Neutralising the chlorine in this way gives a true indication of the drinking quality of the water at the moment of sampling. If the chlorine is not neutralised it will continue to kill the germs in the sample before it gets to the laboratory. The test would then show a water supply that is potable even though the sample may have contained germs when it was taken.
Fig. 6.30: A water sample bottle.
Several things must be remembered when taking water samples to test for germs:
- The water samples will have to be sent to an approved laboratory for testing
- The water samples must be kept on ice while they are transported
- The water samples should be at the testing laboratories within 6 hours of being collected. However, water samples can be accepted for up to 24 hours after the time of collection. EHPs or others collecting samples should contact their testing laboratories for guidelines on transit times for samples.
Before the EHP takes any water samples he/she must be properly prepared to do the job. This means:
- obtaining the necessary equipment. These include:
- bottles, forms, eskies and freezer bricks. These can be obtained from the professional laboratories
- a gas or methylated spirit burner if sampling from a tap. A methylated spirit burner can be a piece of cottonwool attached to the end of a length of wire and soaked in methylated spirits.
- contacting a professional laboratory for sampling kits
- organising the quickest possible transport of samples to the laboratory. There may be a charge for transporting samples
- remembering to label the bottles prior to taking the water sample. Once the bottle is wet it is difficult to write on the label. Also remember to fill out the sample submission form and have the correct address put on the esky.
Water samples may need to be taken from any one of three different situations:
- Running water from a tap
- Flowing water such as a river or stream
- Still water such as a tank, dam or billabong
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Water sampling from a tap
- Run water from the tap for one minute.
- Turn off the tap and sterilise it by flaming it for 30 seconds with a flame from a gas burner or methylated spirits burner.
- Run the water again for 20-30 seconds.
- Hold the bottle by the base, remove the cap and then take the water sample.
- Immediately recap the bottle and place the bottle in its plastic bag.
- Place the sample in the esky with a freezer brick. The completed sample submission form can be placed in an envelope in the esky.
Water sampling from flowing water
- Remove the bottle from its plastic bag, holding the bottle near the bottom.
- Remove the cap from the bottle.
- Hold the bottle upside down and lower it into the water to about elbow depth.
- Turn the bottle so that the top is slightly higher than the bottom and the lip of the bottle is facing into the flow of water. By facing into the flow of water, germs from the person's hand or arm are taken away from the sampling area. Fill the bottle with water.
- Remove the bottle from the water and complete the procedure as for water from a tap.
Fig. 6.31: Water sample from tap.
Fig. 6.32: Sampling flowing water.
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Sampling still waterThe procedure is basically the same as for running water. The only difference is when the bottle is turned ready to fill, the bottle should be gently pushed forwards to create an artificial flow while it is being filled. The flow of water takes any germs from the person's hand and arm away from the sampling area.
Fig. 6.33: Sampling still water.
There may be a time when an EHP finds it necessary to submit water samples from a swimming pool for testing. This type of water sampling requires a special number of samples to be taken and special transport arrangements. If this type of sampling needs to be done it is important to contact the local EHO to find out the correct procedure.
Sampling water for chemicalsSometimes the community water supply is tested for chemicals or minerals, such as salts and metals which may have dissolved in it. In this case, it is not necessary to be so careful about not getting germs into the sample bottle. Get the sampling bottles from the laboratories and sample according to these procedures:
- Mark the bottle with source, identification, number and date.
- Run water for one minute.
- Take the sample.
- Seal the bottle and fill in the form giving sample details. Sometimes there is no form to fill in and when this happens a letter explaining the sample must be provided.
- Send off the sample and letter or completed form. This sample undergoes different tests to those for germs and, therefore, goes to a different laboratory. As there are several laboratories which do these tests, arrangements will need to be made with the laboratory before sampling.
- the laboratory to which such samples should be sent
- the transport method
- any costs for testing and transport
Testing for chlorineThe water in a community tank should be regularly tested for the amount of free residual chlorine. If it is not high enough germs in the water may not be killed and the water may not have its chlorine safety buffer against further contamination.
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The chlorine level in water is usually tested with a chlorine test kit. The most common is a Lovibond Comparitor or a photometer although sometimes a less accurate swimming pool water test kit can be used. Both kits can also be used to test pH (the acidity or alkalinity level) of the water.
Fig. 6.34: Chlorine level testing kits.
The Lovibond Comparitor has two chambers in the centre for placing the samples of water. However, the swimming pool kit provides results for both chlorine and pH at the same time while the Lovibond requires two steps and a change in test disc. The Lovibond is the more accurate of the two kits.
With either kit, drops of solution or tablets are added to the water samples in the test chambers in accordance with the instructions provided.
Always remember to rinse the sampling chambers with some of the water to be tested before taking the water sample.
The chlorine level in the water can be found by matching the colour in the chlorine chamber to the standard colours alongside it for the swimming pool kit, or on the colour disc for the Lovibond Comparitor. The Comparitor has more chlorine levels but the discs must be changed to read the pH.
The photometer is different from the Lovibond Comparitor. Instead of comparing the colours manually, the photometer tells you how much residual chlorine is in the water.
Drops of solution or tablets are added to the water samples in a small tube. The tube is then shaken and inserted into the photometer for a reading.
The recommended concentration of free residual chlorine in drinking water is 0.2 to 0.6 parts of chlorine per million parts of water (0.2 to 0.6 ppm or mg/L). On the Lovibond Comparitor the result will be shown as 0.2, 0.4, or 0.6. This test kit will also have readings of 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0.