Problems
This page identifies typical water quality problems, their causes and their potential impact on consumer health.
Inspecting a sewage treatment plant outlet
Pathogens
Pathogens are micro-organisms with the potential to cause human disease. Pathogens may be present if faecal matter enters the water supply, either from agricultural activities or overflows from sewerage systems or septic tanks. Pathogens can also be introduced into water by recontamination in the pipes or reservoirs of the distribution system. Pathogens can cause health problems ranging from mild gastroenteritis to severe and sometimes fatal diarrhoea, dysentery, hepatitis, and fever.
Nutrients, cyanobacteria, and organic and inorganic chemicals
Nutrients, particularly nitrogen and phosphorus, from urban activities and fertilisers can increase the growth of cyanobacteria in water.
Cyanobacteria (or blue-green algae) generally grows in warm, still water in sunlight and makes water look green. Some cyanobacteria produce toxins that are harmful to people and animals.
Metals can enter water by leaching from mineral deposits, mine tailings, processing industry discharges, and fertilisers. They can also come from the corrosion of metal pipelines (eg copper and lead).
Pesticides, herbicides and insecticides mostly come from agricultural industries such as horticulture, cropping, forestry, feed lots, and intensive grazing. They can also come form weed spraying along water courses. Industrial chemicals, fuels and organic compounds can come from industry wastewater discharges and spills, and leakage from fuel storage tanks. Some small-scale and informal industries have minimal controls over discharges which can lead to problems.
Exposure to cyanobacterial toxins, and organic and inorganic chemicals can have acute (usually from a short-term or sudden exposure) or chronic (from long-term exposure) effects, and the nature, severity and incidence of health problems will generally increase as dose or exposure increases. The Australian Drinking Water Guidelines (NHMRC 2004) have useful fact sheets on the source and health effects of chemical contaminants and toxins. For more information you can also refer to the World Health Organization (WHO) website at www.who.int and the World Health Organisation Guidelines for Drinking Water Quality.
Aesthetic parameters
Aesthetic parameters generally affect the taste, odour, appearance or 'feel' of the water. While slightly high salt content or colour may make the water unpalatable, that does not necessarily mean that it is unsafe to drink.
Aesthetic parameters include turbidity, colour, salt (total dissolved solids or electrical conductivity), temperature, pH, hardness, alkalinity, and some metals, such as iron and aluminium.
Aesthetic parameters come from a wide range of sources, for example:
- high levels of turbidity can come from soil erosion within the catchments, particularly after rain
- colour can come from vegetation and naturally present iron and manganese
- salt can come from soil salinisation.
Collecting water samples from a sewage treatment plant outlet
Some aesthetic parameters can affect how well water can be treated, such as:
- turbidity may make disinfection less effective
- colour (caused by organic matter) may result in higher concentration of disinfection by-products such as trihalomethanes.
Reference: Australian Drinking Water Guidelines (NHMRC 2004) and Safe Water Guide for the Australian Aid Program 2005 - A Framework and Guidance for Managing Water Quality, AusAid (2005). You can download the full document from www.ausaid.gov.au.
