General Chemicals

Outbreaks of water-related diseases due to harmful chemical or biological contaminants continue to occur mostly in developing counties. Few outbreaks occured even in developed/industrialized counties. Based on the United Nations 2015 World Water Development Report, about 750 million people are still in lack accesses to 'improved water supply' nowadays.

The widespread use of asbestos cement pipes in distribution systems has raised numerous concerns. A study carried out in the UK found that some drinking waters can contain up to 1 million asbestos fibers per liter, with more than 95% of these being less than 2 μm in length (WRC, 1984).
Few countries continue to install asbestos cement pipes, mainly because of the inhalation risks associated with working with the dry material. The use of new asbestos cement pipes has been banned in the UK since 2000, because of its health and safety risk.

Nitrate is the final stage of oxidation of ammonia and the mineralization of nitrogen from organic matter. Most of this oxidation in soil and water is achieved by nitrifying bacteria and can only occur in a well oxygenated environment. The same bacteria are active in percolating filters at sewage treatment works, resulting in large amounts of nitrate being discharged in sewage effluents. The use of nitrogenous fertilizers on the land can also give rise to increased nitrate concentrations in both surface and underground waters. Waters containing high nitrate concentrations are thought to be

Turbidity

Turbidity affects the aesthetic quality of the water supplied. Consumers will notice significant changes when sediments are disturbed. Excessive dissolved air in tap water can cause consumer concerns over apparent turbidity even though there is no risk to health. In such situations, the water appears milky when in a glass but gradually clears from the bottom upwards.

Cyanide and cyanide complexes are only found in waters polluted by effluents from industrial or mining processes which uses cyanide. Most cyanides are biodegradable and should be removed by chemical treatment before an effluent is discharged into a receiving water. Chlorination to a free chlorine residual under neutral or alkaline conditions effectively decomposes any remaining cyanide that may be present in raw water.