There are a lot of 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 - 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.
People in rural areas of Australia are increasingly concerned with protecting water resources. For example looking for the first signs of eutrophication or development of blue green algae has become important. Here nutrient levels, CO2 and Oxygen should be monitored. Testing shows whether the water is degrading or is under stress.
What do we test in water?
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.
Corrosion can be a significant problem on farms. To work out if this could be problem we measure acidity, REDOX potential, iron and hardness, then work out an index to show if the water is tending to be corrosive.
Hydroponics growers monitor hydroponics solution to keep the balance of nutrients right. They are interested in pH, soluble salts, chlorides and all the major and minor plant nutrients. They also need to know what is in the 'make up' water so they can get their formulas right.
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.
Fish farmers like to 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 are often monitored for metals such as zinc, copper and iron. If contamination from human waste is suspected then tests which indicate the presence of intestinal bacteria are available.
To do an assessment of water quality or health we measure turbidity, nitrates, phosphates, ammonia if we are really concerned, and reactive silica. Ideally we like to measure organic matter but this is difficult to measure directly in water. There is a test called biochemical oxygen demand which is a good indicator for organic matter loading. Likewise dissolved oxygen can indicate the degree of pollution from organic matter but should be measured on a fresh sample. We measure REDOX potential because this is a good way to predict what chemical reactions (which affect water quality) are likely to be significant. For further on REDOX see the terminology page. 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 some algae 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 it is no good just filtering it. A chemical needs to be added to flocculate the clays and then the water has to be settled and then filtered. By the way, colloids like in the photo block out a lot of light so they upset all the natural processes in the water which overall tend to keep the water healthy.
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 strip. Others like dissolved oxygen are also best done on the spot. Oxygen and Chlorine can be measured with 'simple to use' chemical tests which require only minimal mixing.
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, total count and Aeromonas (Membrane filter kits only) bacteria.
There are test meters available for pH, REDOX and conductivity and these
are very convenient and easy to use.
The great advantage of owning a test meter is that you can test over a
wider area or in different samples. You can also conveniently test at
different times to monitor changes - for example through the seasons.
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.