Water is the most essential ingredient of human life. Our bodies consist of 66% water, and we drink around 2 liters every day!

Yet not everybody in the world has access to good quality water. Some shocking statistics indicate just how much of an issue unsafe water is all over the world: around 1.1 billion people do not have access to safe drinking water! Overall an estimated 900 million people suffer and approximately 1.8 million die from water-related diarrhoeal illnesses each year – the vast majority of which is concentrated on children in developing countries.

About water quality and health risks

In short, drinking water can be called safe if it does not pose a significant health risk to people. There are many standards that determine exactly what properties water must have in order not to constitute a health risk. The international World Health Organisation has published guidelines on water quality and in South Africa the standard SANS 241:2006 defines when drinking water can be called safe.

Generally speaking the properties of water can be divided into three categories:

  1. Physical characteristics describe things such as the temperature of water, the amount of solid materials suspended in it, and the turbidity – a measure of the clarity of water.
  2. Chemical properties of water relate to the various substances that can be present in water, describing things such as the pH, hardness, and toxicity of water.
  3. Biological constituents of water include plants, algae, worms, bacteria, viruses and protozoa.

The most common and widespread health risk is posed by the biological, or microbial, contamination of water. The greatest threats are infectious diseases caused by pathogenic microbes; bacteria, viruses and parasites. Unacceptable levels of various chemicals in water can sometimes be dangerous too, but more often these are long-term risks.

Common biological contaminants of water are algae that can cause problems by blocking treatment systems, causing objectionable taste and odour, or in the case of blue-green algae (or cyanobacteria) the production of harmful toxins. Worms (or helminths) also pose a significant health risk in unsafe water. They can cause serious diseases such as helminthiasis (caused by hookworms) and bilharzia (caused by flatworms).

The greatest health risks associated with drinking water are caused by pathogenic microbes; bacteria, viruses and protozoa. Certain bacteria in drinking water can cause well-known infectious diseases such as typhoid, cholera and dysentery. Waterborne viruses have been related to dangerous infections such as Polyomyelitis (commonly known as polio), and Hepatitis A and E. The most important protozoan pathogens that are linked to drinking water are Cryptosporidium and Giardia; the cysts of these parasites are very small, difficult to detect, highly infectious and resistant to chlorine.

Waterborne infectious diseases are transmitted primarily through contamination of the water sources with excreta of humans and animals who are either active cases or carriers of the disease. Infection through consumption of contaminated water is called the faecal-oral route (see figure below). For pathogens transmitted by the faecal-oral route, drinking-water is only one vehicle of transmission. Contamination of food, hands, utensils, clothing and carriers can also play a role. Therefore it is important to maintain effective barriers against faecal-oral contamination. The primary barrier lies between the infected excreta of a host and the various transmission mediums. This barrier can be raised by ensuring safe disposal of excreta, good sanitation and hygiene.
Secondary barriers exist between the initial transmission medium and food or drinking water, and between any infected materials, items or carriers and a new host. These barriers can also be strengthened by good sanitation and hygiene as well as disinfection of food and drinking water.

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UV technology

Ultraviolet (UV) disinfection works by passing high-intensity UV radiation through water. UV radiation destroys microbes by inactivating their genetic materials (RNA or DNA).

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Water treatment

Numerous techniques, processes and products are available for treating water. All these systems use combinations of technologies and processes that are suitable for the type of raw water that is being treated.

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