Reading your Drinking Water Analysis Report may seem like a daunting task but we are always here to help. The new SANS241:2015 Drinking Water Standards were published in March 2015.
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The water we use for drinking, washing, and preparing food, comes from rainwater, surface water (rivers, dams etc.) and groundwater sources (springs and borehole water). The amount of fresh water available is limited.
Water quality describes water’s suitability for use, concerning its chemical, physical and microbial properties, for drinking, irrigation, bathing, and effluent.
Safe water should contain no chemical or radioactive substances, be free from disease-causing organisms and be non-corrosion and scaling forming.
Water quality is measured by;
the concentration of dissolved oxygen
bacterium levels
salinity (amount of salt)
turbidity (amount of material suspended)
the concentration of microscopic algae
presence of pesticides, herbicides, heavy metals and other contaminants
Various analyses determine water quality and the suitability for the intended purpose, i.e. drinking, swimming, effluent, irrigation, bathing etc.
Poor water quality can pose health risks to all organisms, including flora and fauna.
Note: the suitability of water for gardening purposes depends on a number of other factors, such as climate and soil quality.
Properties of Water Quality
Chemical Water Quality: refers to the concentration of dissolved substances such as salts, metals and organic chemicals. Many chemical substances are essential for daily intake, but high concentrations make water unpleasant and cause illness.
Physical Water Quality: refers to water properties determined by physical methods such as conductivity, pH and turbidity. These qualities mainly affect the taste, odour and appearance (aseptic) of the water.
Microbiological Water Quality: refers to the presence of organisms that cannot be seen by the naked eye, such as viruses, protozoa and bacteria (pathogens). Many of these are associated with water-borne diseases. Microbial indicators indicate a potential risk for faecal pollution and infectious diseases, as it is costly and difficult to detect pathogens in water. Microbial indicators include Total Coliforms, E.coli, Faecal Coliforms and Heterotrophic Plate Counts.
Why is it important to test your water quality?
Water is the link between various communities and resources. What happens in catchment areas is reflected in the water quality throughout the entire system.
The results of human activities in industry, construction, lifestyle and agriculture ultimately end up in the nearby rivers through run-off. If pollution occurs upstream, it runs downstream and eventually into our oceans.
Water quality is dependent on the interaction within the river and its surrounding catchment area. The processes within the catchment area can either maintain a healthy ecosystem or disrupt it and degrade the water supply. Affecting water quality downstream and potentially, if severe enough, groundwater systems and our oceans as well.
Group A: includes general indicators that should be tested frequently as they are indicators of potential problems
Electrical Conductivity (EC): an indicator of Total Dissolved Salts (TDS), also establishes if the water is drinkable and capable of quenching thirst.
Faecal coliforms: indicating the possible presence of disease-causing organisms.
Total Coliforms, E.coli and HPC: indicate the general hygiene of the water
pH: has a marked effect on taste and indicates possible corrosive properties.
Turbidity: affects the appearance, affecting the aesthetic acceptability of water.
Free Chlorine (residual): is the measure of the effectiveness of the disinfection of water. Residual chlorine is the concentration of chlorine remaining at least 30 minutes after disinfection. (Only found in treated/Municipal water)
Group B: substances commonly present at concentrations that may lead to health problems and should be determined before being supplied.
Arsenic (As): predominantly present in mining areas
Nitrate + Nitrite: predominant in groundwater samples, particularly in agricultural areas
Fluoride (F): predominant in hot arid areas
Sulphate (SO4): predominantly common in mining areas
Chloride (Cl): predominant in hot arid areas
Total Coliforms: provides indication of disease-causing organisms, indicator of disinfection effectiveness.
Group C: substances that occur less frequently at concentrations of health concern and should be treated in areas where soft water of low pH is used.
Cadmium (Cd): occurs along with zinc in acidic waters, where it may have been dissolved from appliances
Copper (Cu): effects the colour of the water, normally occurs when copper piping is used to carry water with a low pH
Group D: substances may commonly be present at concentrations of aesthetic and economic concern in domestic water sources
Calcium (Ca): can cause scaling and reduces the lathering of soap
Sodium (Na): effects the taste of water, resulting in a bitter taste at higher concentrations
Iron (Fe): affects the taste of water, and can also cause a discolouration (reddish brown)/
Manganese (Mn): common cause of the black or brown discolouration of fixtures and stains in laundry. Predominantly found in mining areas
Magnesium (Mg): effects the taste of water, it is bitter at high concentrations. Adds to the effects of calcium
Potassium (K): effects the taste of water, resulting in a bitter taste at higher concentrations
Zinc (Zn): effects the taste of water. Caused by acidic water dissolving the zinc from galvanised pipes or appliances.
Total Hardness: the combination of Ca and Mg
Water that is not safe for consumption or irrigation is polluted. Water pollution occurs when water is not fit for use as a result of human activities. These include intensive irrigation, mining activities, industries and dense human settlements.
In South Africa, clean water is a scarce commodity. Our water quality is decreasing due to increased pollution, destruction of river catchments, urbanisation, deforestation, damning, destruction of wetlands, industry, mining, agriculture, energy use and accidental water pollution. As our population increases, there is an increase in pollution and catchment destruction.
Who uses water?
domestic users: drinking, food preparation, washing, bathing and gardening
recreational users: swimming and fishing
industrial users: power generation, process water
agricultural users: watering crops and livestock farming
Excessive levels of nitrates in water may cause aquatic eutrophication. The Nitrogen (N) present in nitrate ions is a source of aquatic plants and blue-green algae. High levels of nitrates may result in increased growth of aquatic plants and algae, making the water “green”. Some species of blue-green algae produce poisons.
The Nitrogen (N) present in nitrate ions is a food source for aquatic plants and blue-green algae. High concentrations of nitrates in water may cause increased growth of aquatic plants and algae, resulting in eutrophication. This is excessive growth of blue-green algae making water green. Some species produce poisons and make water green. Once these aquatic plants die, large numbers of decomposing bacteria result. These bacteria use up the oxygen in the water causing aquatic species (fish and plants) to die.
Nitrate supplementation through sewage contamination and fertilizer run-off is not as critical as it is with Phosphates (PO43-) as aquatic species are not as sensitive to increased levels. Nitrate and ammonia (NH3) are important components of most fertilizers. Nitrogen normally occurs in a form that plants cannot use, however, it may be used in the decomposition of dead water plants and by blue-green algae which can convert nitrogen gas in the air into ammonia and nitrates that plants use. Nitrate ions are also a result of urea contamination (urine).
The Langelier Saturation Index (LSI) is a crucial tool used in water chemistry to assess the equilibrium state of water concerning calcium carbonate (CaCO₃) saturation. The LSI helps determine whether water will tend to dissolve or precipitate calcium carbonate, which can affect scaling and corrosion in water systems.
Formula
The LSI is calculated using the following formula:
LSI=pH−pHs\text{LSI} = pH - pH_s LSI=pH−pHs
Where:
pH is the actual pH of the water.
pH_s is the pH at which water is saturated with calcium carbonate, which is calculated based on temperature, total dissolved solids (TDS), and alkalinity.
Interpretation of LSI Values
LSI < 0: The water is undersaturated with calcium carbonate, meaning it is likely to dissolve calcium carbonate and may lead to corrosion in pipes and fixtures.
LSI = 0: The water is in equilibrium, meaning it is neither corrosive nor scaling.
LSI > 0: The water is supersaturated with calcium carbonate, which can lead to scaling and deposit formation on surfaces and pipes.
Relationship to Hardness
Calcium and Magnesium Content: Water hardness is primarily caused by the presence of dissolved calcium and magnesium ions. High levels of hardness contribute to the potential for scaling, particularly in systems with elevated pH levels. When water is hard and saturated with calcium carbonate, it can lead to the precipitation of scale, especially in hot water systems.
Corrosion and Scaling: The LSI can indicate the tendency of hard water to cause scaling or corrosion. For example, hard water with an LSI greater than 0 may precipitate calcium carbonate, leading to scale buildup. Conversely, if hard water has an LSI less than 0, it may corrode pipes and fixtures instead.
Treatment Implications: Understanding both hardness and the LSI is crucial for water treatment. If water is hard and has a high LSI, treatment might focus on preventing scale formation. If it is hard and has a low LSI, treatment may aim to mitigate corrosion.