Water testing - what's it all about?

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There are many reasons people have to do a water test. These range from tests for drinking water quality, suitability as input to food or industrial processing or if you are a farmer, suitability for irrigation and stock.

Not only is water monitored or tested at its source to find its suitability or if it needs treatment - called input water, it is often tested after use to make sure it complies with discharge standards or to find out if it is suitable for reuse. Farmers often take water from different sources eg rainwater, surface water or ground water. These may be very different and each requires testing. If water is stored then the stored water itself should be monitored to ensure quality. Even within a house the plumbing can add unwanted metals to water.

Australians are increasingly concerned with protecting water resources. For example looking for the first signs of eutrophication or degradation has become important. Critical tests for water quality include carbon dioxide, pH, oxygenation (as dissolved oxygen or using ORP to measure oxidizing potential), total aerobic bacteria, turbidity, fresh or reactive organic matter and dissolved organics as UV absorption. Testing shows whether the water is degrading or is under stress.

Unfortunately many rural communities and households have to deal with poor quality water for drinking and domestic use. Testing key water quality factors will identify many problems. Better source water management and preliminary treatments are always the best options followed by targeted filters.

What do we test in water at Apps Laboratories?

Out approach is to start by testing 'quality' factors. For example factors like pH, carbon dioxide and oxidizing potential are often indicators of deep seated problems which show up as bad tastes and smells, dirty looking water or water that contains unwanted chemicals or metals.

Irrigators are specially interested in dissolved solids and salts so we test for conductivity and all major ions like sodium, chloride, bicarbonate, aluminium, calcium and magnesium. A useful measure is one similar to sodium adsorption ratio in soils. If sodium is out of balance with calcium and magnesium then this test will give an early warning that good nutrients may be displaced and the soil structure may be affected if that water is used for irrigation without adequate leaching. Water that is either very alkaline or acidic can also affect nutrient availability in the soil.

Corrosion can be a significant problem on farms and in homes. To determine if this could be problem we measure pH, REDOX potential, total salts, alkalinity and hardness. The result is an index the Langelier Index that shows if the water is tending to be corrosive or scaling.

Food and beverage manufacturers are interested in input water quality. Overall water quality factors are important but chlorination products like free and combined chlorine need to be monitored. Different types of salts and hardness can affect tastes especially in brewing.

Most filters and water treatment have 'working limits' of salts and other chemicals. For example if you want to install a reverse osmosis unit then the hardness has to be below certain limits. Critical factors for monitoring the effectiveness of filters include total salts, UV absorbtion and aerobic plate count.

Fish farmers should check water quality in dams and fish tanks. This is important at all stages. Input water, conditions within the tanks or dams and output / pre filter water all need monitoring. Like aquarists they often monitor pH and salts in tank water. They also take care not to use water which contains chlorine. New aquariums need to be monitored closely to make sure ammonia and nitrites are kept at bay. Aquaculturists measure or monitor a wide range of factors including turbidity, dissolved oxygen, pH, conductivity, nitrites, ammonia, REDOX, phosphate, copper, hardness and alkalinity.

Household water supplies in rural areas are monitored for the basic water quality indicators dissolved organics index, turbidity, oxidizing potential, carbon dioxide and pH. Guidelines for bacterial quality that includes levels of E coli, coliforms and total aerobic bacteria are found in the Australian Drinking Water Guidelines. Convenient test kits are available for testing these groups at home or in the lab.

To do an assessment of environmental water quality or health we measure turbidity, nitrates, phosphates, ammonia and reactive silica. Organic matter loading is often measured indirectly by ammonia, nitrites, carbon dioxide and UV absorption. Depleted dissolved oxygen can indicate pollution from organic matter. REDOX potential and pH are a good way to predict what chemical reactions (which affect water quality) are likely to be significant. For further information on REDOX and many other factors see the terminology page and our online notes What do your water test results mean? At Apps Laboratories we often get out the microscope and look at the algae in the water. This gives us extra clues about whether the water is healthy or not because the types of algae present can indicate stressed or polluted conditions.

Some sample reports for water test are available in PDF format for you to download. Click here to go to the downloads page. You will need Acrobat Reader to view the files available there.

A dam on a farm in East Gippsland. Note that the water is very dirty. This may be partly due sheep in the paddock which have access to the dam. The underlying clay itself is the type of clay which mixes and forms colloids in the water. Once any water gets coloured by colloidal clays like this filtering becomes difficult. In one method, a chemical can be added to flocculate the clays and then the water has to be settled and then filtered. It is mostly cheaper and simpler to protect catchments and dams by maintaining vegetation cover. Colloids block out light so they upset many of the natural processes in the water which overall tend to keep the water healthy. High colloids are sometimes caused by irrigation water with a sodium inbalance. Rice growers in some areas in Australia have trouble establishing seedlings because of turbidity caused by increased salts.

Which tests can people do themselves?

First some tests are better done 'on the spot'. For example chlorine in drinking water will change before it gets to the lab so it's better to use a simple chlorine test kit or test strips. Others like dissolved oxygen are also best done without delay. Oxygen and Chlorine can be measured with 'simple to use' chemical tests which require only minimal preparation. test strips are available for a range of factors including phosphate, nitrate, nitrite, alkalinity, hardness, pH, copper, iron, chloride and ammonia,

Recently Apps Laboratories introduced a range of bacteria test kits called Coliscan Easygel which can be used at home to test for coliforms, E coli and total aerobic bacteria.

There are test meters available for pH, REDOX and conductivity and these are very convenient and easy to use.

A lab like Apps Laboratories can periodically test your water but there is some advantage of owning a test meter, test strips or test kits. Test instruments are cost effective if there are many samples to test or regular testing needs to be done. Testing your own water gives more insight into seasonal changes and variation between samples.

What meters are available? Conductivity / TDS meters are widely used and give a good overview of dissolved salts in water. This is important for irrigators and horticulturists. The next most widely used are pH meters. pH is an important indicator of water quality and largely determines its overall characteristics.

Dissolved oxygen meters are handy for monitoring dissolved oxygen and hence health in fish dams and water treatment facilities.

REDOX or ORP meters have been used in aquariums for a long time but now they are being applied to water quality management.


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