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Frequently Asked Questions

What is Water Quality?

1. What is the definition of ‘Water Quality?’

Water quality is defined as water which is safe, drinkable and appealing to all life on earth. It should contain no chemical or radioactive substance that is harmful to the health of any life. It should be free of disease-causing organisms and stable in terms of corrosion or scaling. Polluted water is water that is not safe and not healthy for people and animals to drink or to wash in. Polluted water is particularly dangerous to water plants and animals. Polluted water is also particularly dangerous to people who get their water directly from a river or dam. In South Africa the scarce fresh water is decreasing in quality because of an increase in pollution and the destruction of river catchments, caused by urbanisation, deforestation, damming of rivers, destruction of wetlands, industry, mining, agriculture, energy use, and accidental water pollution. As the human population increases, there is an increase in pollution and catchment destruction.

2. Why is it important to test the quality of water?

Water knows no boundaries and as it flows it links communities together through their many uses of this resource. The quality of a stream or river is often a good indication of the way of life within a community through which is flows. It is an indicator of the socio-economic conditions and environmental awareness and attitude of its users. Everything that happens in a catchment area is reflected in the quality of the water that flows through it, because the results of human activity and lifestyle ultimately end up in rivers, through runoff.

All life in the water is dependent on the interaction within the river itself and in the surrounding catchment. These processes can either maintain a healthy ecosystem or disrupt ecological processes and degrade the water supply. Rivers and streams owe their existence to the nature of catchments and the relationship between rainfall and evaporation. Rivers are open systems where the exchange of material and energy within the environment occurs all the time. It is difficult to treat rivers as ecosystems because they are important pathways for the flow of energy and the circulation of nutrients across the boundaries of habitats.

3. What is the pH of water and why do we test it?

pH, which reflects the acidity or alkalinity of water, is an important measure of pollution.

When you measure pH you will be measuring the concentration of hydronium (H30+) and hydroxide (OH-) ions in the water. The concentration of these ions is reported using pH units. pH is measured on a pH scale from 0 to 14.


If the sample measured has more hydrogen ions, it has a pH of less than 7 and is regarded as acid, which has a sour taste. If there are more hydroxyl ions the pH is greater than 7 and it is regarded as alkaline, which has a soapy taste and texture. Thus, pH is a measure of the acidity or alkalinity of the sample.

Water that is very acidic (high concentrations of H3O+ ions) or very basic (high concentrations of OH- ions) is unsafe to use around the home; can be dangerous if you swim in it; will kill aquatic plants and animals. Water solutions that are very acidic (like battery acid) and solutions that are very basic (like drain cleaner) are very dangerous and can burn you badly. You should be very careful when you use strong acids.

Neutral water has equal and very low concentrations of the two ions.

Rainwater is naturally slightly acidic but the acidity of water in a catchment is determined by the particular kinds of rocks and minerals, biological activity and nutrient cycling, which occurs there. Limestone is alkaline but basalt is very slightly acid. Air pollution (nitrates and sulphur dioxides) from vehicles and thermal power stations causes acid rain, a serious threat to aquatic ecosystems, particularly in Mpumalanga. The acid rain in Mpumalanga appears to have caused a 0.1 pH change in all its rivers. Another important place where hydronium ions come from is acid rain. Coal-fires, coal-fired power stations and motorcars release acidic gases into the air. When rain dissolves these gases it forms acids. These acids wash into the river and make the river water acidic. Sewage and industrial effluent discharged into rivers can also affect their pH balance. The pH of healthy rivers is usually neutral (7) or ranging between 6.5 and 8.5. Many “black” rivers in South Western Cape can have a natural pH of 4 – 5. A lot of rotting dead leaves and plants in a river will make the water acidic. Some rivers in the Cape flow through wild forests. These rivers collect dead leaves from the trees in the forest and become acidic. The water in these rivers looks like black tea.

Water that is very acidic or basic can usually dissolve metals (eg. metal water pipes). The dissolved metals form ions.

Water with high concentrations of metal ions can be poisonous. Strongly acidic or basic water will burn your eyes and even your skin if you swim in it. Water with high concentrations of hydronium and hydroxide ions is also poisonous to the animal and plant life in the water.

Factory waste can have very high concentrations of hydroxide ions or hydronium ions. Water from mines, especially coal or gold mines, can also have high concentrations of hydronium ions. Mines and factories should treat their waste to remove the hydroxide ions or hydronium ions before they pump it into a river or dam. Sewage and industrial waste also affects the pH of river water.

Very acidic or basic water is unsafe to drink. However, high concentrations of hydronium and hydroxide ions in water are not necessarily toxic by themselves. Coke has a pH of between 2 and 3, and gastric juice is also very acidic. The problem is that acidic water tends to dissolve metals like zinc, lead and copper. The metal ions in solution can be toxic. Also, ammonium ions (NH4+), which are not poisonous, can be deprotonated in basic conditions, to form ammonia (NH3), which is poisonous. Acidic water can dissolve water pipes. Common sources of acidic or alkaline pollution include acid rain and improperly treated factory and mine effluent.

The pH for drinking water is between 7.8 and 8.4. Rand Water’s water pH is 8.0 – 8.4.

4. What are Nitrates and why do we test for them?

Nitrate is the name of an ion with the formula of NO3-.

Water with a high concentration of nitrates is poisonous to humans. This is because the nitrate ions are changed into nitrite ions when they get into a person’s blood. A baby that drinks water with a concentration of nitrate ions about 10 mg/l might get blue baby syndrome.

The nitrogen in nitrate ions is an important nutrient (food) for aquatic plants and blue-green algae. High concentrations of nitrate ions in the water may cause large numbers of aquatic plants and blue-green algae to grow in the water. This is called eutrophication. Some species of blue-green algae produce poisons and make the water green and ugly to look at. When aquatic plants die you get large numbers of bacteria decomposing them. These bacteria use up the oxygen in the water. Without oxygen many aquatic animals will die.

Nitrate enrichment through sewage contamination and fertiliser run-off is not as critical as it is with phosphates because aquatic ecosystems are not as sensitive to increases in nitrate levels. Nitrate ions and ammonia (NH3) are an important part of fertilisers (plant food). Nitrogen normally occurs in a form that plants cannot use (i.e. nitrogen gas), however, it may be used in the decomposition of dead water plants and by blue-green algae which can convert nitrogen in the air into ammonia and nitrates that plants can use.

Nitrate ions also come from urine. Urine contains urea. When the urea gets into the water it can be changed into nitrate ions. Nitrates and ammonia are used in some industrial processes and may be pumped as waste from factories into river or dam water.

How do nitrate ions get into our rivers and dams? The farmers spread fertilizers on their fields to grow crops better. The rain may wash the fertilizers into the rivers and dams. Urine can get into the rivers and dams from leaking sewerage pipes, badly built pit toilets, animal wastes, or even from people who use the bank of the river as a toilet. Industries are required by law to remove nitrates and ammonia from their waste before they pump it into rivers and dams but, unfortunately the law is usually not implemented.

5. What are Phosphates and why do we test for them?

Phosphorus is an essential element for life, both as a nutrient for plant life and as a key element in the metabolic processes of all living things. The normal low phosphate (PO4) level in water inhibits the growth of plants but a small increase of phosphates can result in a rapid increase in plant growth such as blue-green algae, especially in dams. This process, called eutrophication, could be increased by human activities. If there are too many plants in the water and they die lots of bacteria will break down (decompose) the dead plants. These bacteria can use up the oxygen dissolved in the water. Animals like fish and insects can’t live in water where there is little or no dissolved oxygen. For example, fish will suffocate and bacteria will die. Usually the oxygen is only used up in slow flowing rivers, or in dams where the water is standing still. In fast flowing rivers new oxygen is mixed into the water all the time. Fast flowing rivers can carry orthophosphates into dams where they will cause eutrophication problems.

An increase in phosphorus can come from domestic effluent (especially soapy water), farm and lawn fertilisers, industrial effluent, sewerage pipe leaks and the destruction of wetlands. Wetlands are natural swamps where phosphate sediments are formed and used in the vigorous growth of the diverse and specially adapted vegetation of this particular ecosystem.

6. What is meant by Dissolved Oxygen Content in water and why do we test for it?

Rivers with consistently high levels of dissolved oxygen (DO) are usually regarded as healthy and stable eco-systems capable of supporting many different kinds of water life. Much of the oxygen comes from the atmosphere through rain, tumbling water in fast-flowing streams and photosynthesis. In some dams the levels of dissolved oxygen may rise during the day due to photosynthesis but drop again during the night due to plant respiration. Large dissolved oxygen fluctuations may be found in rivers and dams choked with invasive water plants. Effluent and agricultural chemical (especially fertilizers) enrich the water and stimulate the growth of algae and other plants causing fluctuations in the dissolved oxygen levels in the water. Sewerage effluent also promotes large populations of aerobic bacteria which use oxygen as they decompose organic matter. Water temperature also affects dissolved oxygen levels as oxygen dissolves more easily in cold water.

A change in the concentration of dissolved oxygen can have a major impact on the aquatic ecosystem. Rivers with a constant DO level above 90% are usually regarded as healthy. A value lower than 80% usually indicates large quantities of material in the river that are absorbing a large amount of oxygen, most commonly organic waste. It is also possible to get a saturation exceeding 100% if the current is fast flowing, which is called super saturation. This may result in an increase of blue-green algae which could become a problem in the aquatic ecosystem.

Many organisms are dependant on the presence of DO or respiration. Various organisms, such as fish, larvae of stoneflies, caddisflies and mayflies, are affected by low concentrations of dissolved oxygen, especially if it occurs over a long period of time. This can result in changes in behaviour, blood chemistry, growth rate and food intake.

7. Why is it important to test the Temperature of water?

Temperature is an important parameter to take into account when measuring water quality.
Before one checks the temperature of water it is important to take note of the following:

  • The temperature of the water must be taken at the site without removing the water from the river. Removing the water in a sample bottle will immediately alter the temperature and therefore give you an inaccurate reading.
  • When taking multiple temperature samples, the thermometer must be held at a constant depth. It is recommended that this is 10cm below the surface of the water.
  • Normal background temperature of the water body (taking into account the time of day and time of year) must be noted as a comparison to interpret the result.
  • When testing the temperature of the water

Temperature can be regarded, like pH, as an indicator test, a test that is done up-front to establish whether there is any major problem with the water body.

Temperature can be taken at two sites along a river in order to establish whether there is a pollution problem. A marked difference in temperature at the two sites that experience the same conditions will often indicate that pollution has entered the river.

The temperature of the water in a river can be altered by many things. Temperature can increase if any foreign material is added to the water body, especially effluent from industries or mismanaged sewerage works. Storm water containing various forms of pollution can also alter the temperature, as well as soil from soil erosion.

Aquatic life such as insect larvae, fish, frogs and other living organisms need a certain temperature that does not fluctuate greatly in order to survive. Any major changes in water temperature will drastically affect their ability to function and will have a detrimental effect on the eco-system.

8. What is E. coli and why do we test for it?

River or dam water that is of good microbiological quality has few disease-causing microbes (bacteria, viruses, parasites such as protozoa) in it. Many of these disease-causing microbes come from human faeces in the water.

It would be impossible to test the water for all the disease-causing bacteria, viruses and parasites that might be found in it. Instead we test the water for special indicator organisms. These indicator organisms tell us:

  • That the water might be polluted with human and other animal faeces.
  • If there are animal faeces in the water then there might be disease-causing bacteria, viruses or parasites present. These germs or viruses can cause diseases like typhoid, dysentery and gastro-enteritis. Thousands of people die each year from these diseases.

Faecal coliform bacteria (faecal coliforms - FC) are a group of bacteria many of which are found within human beings and other warm blooded animals. Total Faecal Coliforms present in the water are an indication that harmful, disease-causing organisms are present in the water, due to faecal pollution, however, not all faecal coliforms originate from human or other mammals intestines. Therefore, we also test for E.coli a specific indicator for faecal contamination in the water. If this is present then there are definitely pathogenic organisms in the water and it is unsafe to drink. E. coli is a type of total coliform bacteria but, they only live in the intestine of humans and other warm blooded animals. These bacteria are important because they help digest food.

These bacteria can enter the water directly because of poor sanitation; the dung and droppings of animals; runoff from streets and stormwater drains; and sewage disposal in rivers. Faecal coliform bacteria occur together with pathogenic (disease-causing) organisms, which cause human illness. If the faecal coliform bacteria count in a river is high due to sewage contamination it is thus probable that pathogenic organisms also occur in large numbers and can be passed on to people who drink the river water. Human diseases like typhoid, hepatitis, cholera, gastroenteritis, dysentery and ear and skin infections can be contracted from river water with a high faecal coliform bacteria count.

9. What is Turbidity and why do we test for it?

Most river and dam water is full of small grains of soil and algae. The grains of soil and algae hang in the water. We say that they are in suspension. These suspended grains make the water look cloudy or even muddy. We call this cloudiness or muddiness, turbidity.

Water that is very turbid carries many thousands of grains of soil and algae. Bacteria and viruses stick to these grains. This means that water, which is very turbid, may be unsafe to drink. Another problem is that plants need sunlight to grow (for photosynthesis). Water that is very turbid stops sunlight from entering the water. This means that plants will stop growing in that water. The grains in very turbid water can block the gills of aquatic animals. Animals that hunt will have difficulty finding their prey in very turbid water, which can lead to growth under development. High turbidity water can lead to a loss of plant and animal diversity.

If there is a lot of soil erosion in a catchment area then a lot of soil will get washed into the river making it turbid. Builders can dump building material and earth into a river making it more turbid. Industrial waste and even sewerage leaks can also make the river turbid. Lastly, a lot of microscopic algae in the water will make river and dam water turbid. Some rivers are naturally turbid. When a river is in flood the water becomes very muddy and turbid. Usually this muddiness only lasts for a few days. Some rivers are also very muddy and turbid all the time eg. The Orange River. The plants and animals that live in the Orange River are adapted to living in very muddy water.

10. What is Electrical Conductivity and why do we test for it?

Conductivity is a measurement of the ability of the water to conduct electricity.

The amount of material dissolved in water is a major determinant of water quality, and can be measured in three ways: total dissolved solids, salinity (saltiness) or conductivity. Conductivity is an electrical measure of the amount of solids dissolved in a solution, i.e. chemical salts and minerals, present in the water (e.g. calcium bicarbonate, nitrogen species, phosphates, sulphates, chlorides, iron and other metals). It is measured in milli-Siemens per metre (mS/m) using a conductivity metre. The ability of water to carry an electrical current depends on the presence of ions, their total concentration, mobility, valence, relative concentrations and the temperature measurement. The greater the concentration of ions in the water, the greater its ability to conduct electricity. Conductivity measurements are principally used as an indication of the dissolved mineral content in water and may be related to total dissolved solids by using a factor of 6.5, i.e. electrical conductivity (mS/m) x 6.5 = total dissolved solids (mg/l).

Water in our rivers and dams usually contain low concentrations of ions. If the concentration of ions increases because of pollution, its conductivity increases, the water will begin to taste salty and can become unsafe to drink. Water with a high concentration of ions can kill plants if it is used to water them. This type of water can dissolve (corrode) water pipes or even block the pipes if the ions come out of solution. Most of the plants and animals living in the water will suffer if that water is suddenly polluted by a high concentration of ions.

Where do these dissolved ions come from that cause high conductivity? Fertilizers may be washed from a field into a river or dam. Factories and mines can also pump wastewater with a high conductivity into rivers and dams. Some natural water, like ground water, dissolved salts from the rocks around it. This water may also have a high concentration of ions in it, even if it hasn’t been polluted by humans. Rivers near the sea may also have a high conductivity because seawater has high concentrations of ions.

What does electrical conductivity indicate?

  • The EC of distilled water is low as opposed to seawater, with a high EC.
  • The EC (measured in milli Siemens per meter) of water indicates whether the water is fresh or saline.
  • Rain Water has an EC of less than 1mS/m.
  • EC indicates where the water originates from e.g. if water travelled over granite, it has an EC of around 5 Ms/m. Water that travelled over sedimentary rocks usually has a much higher EC, ranging from 30 to 170 Ms/m.
  • Climate can increase the EC, by concentrating the salts during droughts.
  • One can determine the approximate total dissolved solids (TDS) value of water by multiplying the EC with 6.5 i.e. TDS = EC X 6.5

What problems can electrical conductivity cause?

The following health problems can occur where the EC exceeds 370 mS/m.

  • Disturbance of the water and salt balance in children.
  • Increase the blood pressure of heart patients and renal patients.
  • Laxative effect when sulphate concentration is high.

Aesthetic problems of water with an EC as high as 150 mS/m, are that it tastes salty and water with an EC higher than 300 mS/m, fails to quench your thirst. Sensitive groups are children under the age of one year, people on salt restricted diets, such as heart and kidney patients and individuals with chronic diarrhoea.

How can electrical conductivity be treated

  • The water pH can be increased with the additional alkaline reagents, such as lime, sodium hydroxide or sodium carbonates
  • The water pH can be decreased with the addition of acidic reagents, such as sulphuric or hydrochloric acid or it can be done by the addition of carbon dioxide, which forms carbonic acid when it combines with water.

Rand Water uses an extensive purification process to keep the conductivity within SANS 241 standard (less than 150Ms/m) to quench your thirst.

11. What is Residual Chlorine and why do we test for it?

Chlorine is a chemical that is used to disinfect water prior to it being discharged into the distribution system. It is used to ensure water quality is maintained from the water source to the point of consumption. When chlorine is fed into the water, it reacts with any iron, manganese, or hydrogen sulphide that may be present. If any chlorine remains (residual), it will then react with organic materials, including bacteria.

In order to ensure that water is sufficiently treated through the whole distribution system, an excess of chlorine is usually added. This amount is usually adjusted to make sure there is enough chlorine available to completely react with all organics present. The chlorine will decrease in concentration with distance from the source, until it reaches the point where the chlorine level can become ineffective as a disinfectant. Bacteria growth will occur in distribution systems when very low levels of chlorine are encountered. Therefore, it is important to make sure there is enough chlorine to efficiently disinfect even at the far ends of the distribution system. Chlorination can kill many pathogenic (disease causing) micro organisms such as E.coli, but others, like Cryptosporidium and Giardia, are very resistant to chlorine and require other measures to properly remove them.

There are some important chlorination trends found in drinking water treatment:

  • As chlorination increases, the time required to disinfect decreases.
  • Chlorination is more effective as the temperature increases.
  • Chlorination is less effective as pH increases (becomes more alkaline).
  • Chlorination is less effective in turbid water.


12. What are the health risks associated with low residual chlorine?

Studies have shown that when residual chlorine levels drop below recommendations, several water quality problems can occur. With regard to public health, bacteria and selected viruses, called bacteriophage, are able to multiply in water that is not properly disinfected and, depending on the species, could potentially cause waterborne illnesses.

It is important to note that, although chlorination has been the most common method of disinfection for over 100 years, there have been recent studies that have shown that chlorine in water can react with otherwise innocent organic material in drinking water and form chemicals called Trihalomethanes (THMs), such as Chloroform. THMs have been shown to be potentially carcinogenic (Cancer causing) and are, therefore, carefully monitored in water systems that are routinely chlorinated. While recommendations only state minimum residual chlorine levels, it is important that a careful balance is maintained in drinking water. There needs to be enough chlorine to make sure everything is properly disinfected. However, an extreme excess of chlorine is not necessary and may lead to high levels of THMs and the adverse health risks described previously.


13. What do I do if my water does not meet residual chlorine recommendations?

In municipal water systems, the drinking water is chlorinated prior to being distributed and chlorine residuals should be measured at the far end of the distribution line. This ensures that the house located furthest from the plant still receives water that is adequately disinfected. If your water does not have appropriate chlorine residual levels, contact your local treatment facility and have them conduct further tests to make sure enough disinfectant is added to the water at the plant. For homes that get their water from wells, either commercial disinfectants or diluted household bleach may be used to adequately treat drinking water.

Usually, gaseous chlorine is added to the water at large treatment facilities. However, this form of chlorine is too dangerous to be used for home use and other disinfectants such as those mentioned above are recommended. Contact a local water treatment authority to determine the recommended levels for your well system.


14. What do we mean when we talk about the 'Hardness' of water?

Perhaps you have on occasions noticed mineral deposits on cooking pots, or rings of insoluble soap scum in your bath tub. These are not signs of poor housekeeping, but are rather signs of hard water. Hard water is water that contains cations with a charge of +2, especially Ca2+ and Mg2+. These ions do not pose any health threat, but they can engage in reactions that leave insoluble mineral deposits. These deposits can make hard water unsuitable for many uses, and so a variety of means have been developed to "soften" hard water; i.e., remove the calcium and magnesium ions.

Sources of Hardness Minerals in your water

  • Water is a good solvent and picks up impurities very easily. When water is combined with carbon dioxide to form very weak carbonic acid, an even better solvent results. As water moves through soil and rock, it dissolves very small amounts of minerals and holds them in solution. The degree of hardness becomes greater as the calcium and magnesium content increases and is related to the concentration of multivalent cations in the water.
  • The hardness of your drinking water around South Africa varies depending on the rocks and soils of the area that the water comes from, and the treatment process used.

Potential Health Effects

  • Hard water is not a health hazard. In fact, the National Research Council (National Academy of Sciences) states that hard drinking water generally contributes a small amount towards total calcium and magnesium human dietary needs. They further state that in some instances, where dissolved calcium and magnesium are very high, water can be a major contributor of calcium and magnesium to the diet.
  • Rand Water has not established drinking water guidelines for hardness because there are no known negative health effects associated with calcium and magnesium minerals in your drinking water.

Indications of hard water

  • Excessive hardness in water interferes with almost every cleaning task from laundering and dishwashing to bathing and personal grooming. Dealing with hard water problems in the home can be a nuisance. The amount of hardness minerals in water affects the amount of soap and detergents necessary for cleaning. Soaps used in hard water combine with the minerals to form a sticky soap curd. Some synthetic detergents are less effective in hard water as the active ingredients are partially inactivated by hardness, even though it stays dissolved. Bathing with soap in hard water leaves a film of sticky soap curd on the skin. The film prevents removal of soil and bacteria.
  • Excessive hardness in water may also change the taste of water, especially for brewing tea and coffee.
  • Hard water also contributes to inefficient and costly operation of water using appliances. Heated hard water forms a scale of calcium and magnesium minerals that can contribute to the inefficient operation or failure of water –using appliances. Pipes can become clogged with scale that reduces water flow and ultimately requires pipe replacement.


Hardness of water is classified as follows:
Hardness Range (mg/l CaCO3)
Description of Hardness


Moderately Soft

Slightly hard

Moderately hard


Very Hard


Total hardness should be limited to between 50-100mg/l, where possible.

Soft Water

Soft water is great for laundry, bathing, steam irons, and auto batteries, but definitely not for anything else. A soft water is aggressive at leaching metals and has been linked to heart diseases. If you are contemplating installing a softener (Home Treatment Device). There are serious questions you should ask: Who will test the effectiveness of the softener? How often will these tests be run?

How will your drinking water quality be affected?

Rand Water does not test any home water treatment devices, including softeners, and does not recommend the use of particular devices.

15. What is the hardness of Rand Water's tap water?

Water in Rand Water’s area of supply ranges from 60 to 110 mg/l, thus we have a moderately soft to slightly hard water.

16. What is meant by Heterotrophic Plate Count?

Heterotrophs are broadly defined as microorganisms that require organic carbon for growth. They include bacteria, yeasts and moulds. A variety of simple culture- based tests are intended to recover a wide range of microorganisms from water are collectively referred to as “heterotrophic plate count” or “HPC”.

Only a small portion of the metabolically active microoganisms present in water may grow and be detected under any given set of HPC test conditions, and the population recovered will differ significantly according to the method used. The actual organisms recovered in HPC testing can also vary widely between locations, between seasons and between consecutive samples at a single location.

Microorganisms recovered through HPC tests generally include those that are part of the natural (typically non-harzardous) microbiota of water in some instances, they may also include organisms derived from diverse pollutant sources.

Do microorganisms grow in water?

Microorganisms will normally grow in water and on surfaces in contact with water as biofilms. Growth following drinking water treatment is normally referred to as “regrowth”. Elevated HPC’s occur especially in stagnant parts of piped distribution systems, in domestic plumbing, in bottled water and plumbed-in-devices, such as softners, carbon filters and vending machines. The principal determinants of regrowth are temperature, availability of nutrients and lack of residual disinfectant. Nutrients may derive from the water body or materials in contact with water.

Rand Water purifies the water by means of a conventional purification process, maintaining HPC at acceptable level that comply with SANS 241 drinking water quality specifications. Your tap water will satisfy your daily requirements.

17. What are the South African Water Quality Guidelines for different uses of water?

The South African Water Quality Guidelines are used as a basis for developing materials to inform water users about the physical, chemical, biological and aesthetic properties of water. It consists of the water quality criteria, the Target Water Quality Range (TWQR), and supporting information, such as the occurrence of the constituent in the aquatic environment, its effects on water uses, how these effects can be mitigated and possible treatment options.

The TWQR for a particular water use is defined as the range of concentrations or levels at which the presence of the constituent would have no known adverse or anticipated effects on the fitness on the water assuming long-term continuous use, and for safeguarding the health of aquatic ecosystems. All the different TWQR for all the different water use sectors are dealt with in South African Water Quality Guidelines volumes one to seven.

Volume 1: South African Water Quality Guidelines - Domestic Water Use

Domestic water refers to water that is used in domestic environment and also refers to all uses water can be put to in this environment. These include water for drinking, food and beverage preparation, hot water systems, bathing and personal hygiene, laundry and gardening.

Domestic water users can experience a range of impacts like health, aesthetic and economic impacts as a results of changes in water quality. Water quality problems are associated with the presence of constituents and the interactions between them. The constituents like cadmium, chromium (VI), lead, mercury and vanadium can have either acute and/or irreversible effects on human health, even at low concentrations. As a precautionary measure, it is advisable not to use, for potable purpose, water containing these constituents, at concentrations above the TWQR.

Volume 2: South African Water Quality Guidelines - Recreational Water Use

Recreational water refers to all inland water which is used for recreational purposes. These include full contact recreation (swimming), intermediate-contact recreation (waterskiing and canoeing) and non-contact recreation like picnicking and hiking alongside water bodies. Recreational water users may experience a range of impacts as a result of changes in water quality. These include: health, aesthetic, economic impacts and human safety.

Volume 3: South African Water Quality Guidelines - Industrial Water Use

Industries are defined as systems of water-using processes, in which fitness for use of the water is assessed in terms of the following norms:

  • its potential for causing damage to equipments (e.g. corrosion and abrasion).
  • problems it may cause in the manufacturing process (e.g. precipitates and colour changes).
  • impairment of product quality (e.g. taste and discolouration).
  • complexity of waste handling as a result of using water of the quality available.

Volume 4: South African Water Quality Guidelines - Agricultural Water Use: Irrigation

Irrigation water in these guidelines refers to water which is used to supply the water requirements of crops and plants which are not provided by rain, and refers to all uses water may be put to in this environment. This include water for:

  • the production of commercial crops
  • irrigation water application and distribution systems
  • home gardening
  • the production of commercial floricultural crops
  • potted plants.

Irrigation water users may experience a range of impacts as a result of changes in water quality. These may be categorised as follows:

  • reduced crop yield as a result of increased salinity or the presence of constituents that are toxic to plants
  • impaired crop quality; this may result in inferior products or pose health to consumers
  • impairment of soil suitability as a result of the degradation of soil properties and accumulation of undesirable constituents or toxic constituents
  • damage to irrigation equipment (corrosion or encrustation).

Volume 5: South African Water Quality Guidelines - Agricultural Water Use: Livestock Watering

The use of water for livestock production depends on several factors, such as the type of production system in use (intensive or extensive), the type of livestock and the type of livestock products. The potable quality of water for livestock may be defined according to the palatability of the water which would affect intake and hence production, as well as its degree of contamination with pathogenic micro-organisms, hydrocarbons, pesticides and salts such as nitrates, sulphates, fluoride and the salts of heavy metals.

There are different impacts that may be experienced as a result of changes in water quality. These include:

  • livestock consumption (toxicological and palatability effects)
  • livestock distribution systems (economic impacts on the effects of scaling, corrosion or deposition of sediments in the distributing system)
  • livestock product quality (consumer health hazards and product quality problems).

Volume 6: South African Water Quality Guidelines - Agricultural Water Use: Aquaculture

Aquaculture is aquatic agriculture and includes the husbandry, management, nutrition, genetics and controlled propagation of all aquatic organisms for use by humans.

Aquaculture can be divided into several sectors:

  • cage culture in dams or natural lakes
  • extensive farming in small earthen farm dams
  • extensive and semi-extensive fish farming in purpose designed fish ponds
  • intensive farming in raceways and tanks.

The greatest threat to freshwater aquaculture is industrial pollution of rivers, the effects of afforestation and deforestation on the water quality and quantity, the poor use of agricultural and riparian land, and of herbicides and pesticides.

Volume 7: South African Water Quality Guidelines - Aquatic Ecosystems

Aquatic ecosystems in these guidelines refer to the abiotic and biotic components, habitats and ecological processes contained within rivers and their riparian zones, reservoirs, lakes and wetlands and their vegetation. Since the aquatic ecosystems serve as the resource base, they must be effectively protected and managed to ensure that water resources remain fit for agricultural, domestic, recreational and industrial uses on a sustainable basis. For the aquatic ecosystems guidelines, the TWQR is not a water quality criterion as it is for other water uses, but rather a management objective that has been derived from quantitative and qualitative criteria.

Volume 8: South African Water Quality Guidelines - Field Guide

All the different TWQR for all the different water use sectors dealt with in volumes one to seven are compiled in Volume 8. This volume serves as a quick and easy reference for comparison of the TWQRs for different water use sectors to determine the fitness of use for water and can always be used as a field guide. In all cases when using the Field Guide the user must refer back to the specific guideline for a particular water use sector and constituent as provided in a comprehensive guidelines, in order to obtain more detailed information to assess the fitness for use of water.