IMPURITIES

When water supply from natural or subterrainium sources fails to meet potable standards it may contain one or several unwanted agents listed as follows.

Iron

occurs widely in nature and is found in many natural and treated waters. Iron is an objectionable constituent in both domestic and industrial water supplies. The presence of Iron affects the taste of beverages and causes unsightly staining of laundered clothes, plumbing, swimming pool surfaces and the like. The formation of insoluble iron deposits is troublesome in many industrial applications and in agricultural water uses such as drip feed irrigation. In industry iron salts occur through corrosion of plant and equipment, and from industrial processes. Iron can be tested for by using a reagent containing alkaline thioglycollate. Iron is also detectable sight as a rusty sludge or in lower degrees by both smell and taste.

Manganese

containing minerals occur widely and manganese salts are commonly found in many natural waters. Manganese is an objectionable constituent in water used for domestic purposes or industrial applications. In domestic situations Manganese will cause brown or black staining to laundry or plumbing even in very low concentrations. In process applications such as paper manufacturing or textile finishing similar staining can occur. Manganese salts may impart an astringent taste to drinking water supplies, and in swimming pool applications can give an aesthetically displeasing brown colouration to the water. Manganese along with calcium and magnesium contributes to the hardness in water and can be tested for by using an oxidising agent then reaction agents wioth a catalyst and inhibitor.

Ammonia

occurs as a breakdown product of nitrogenous material in natural waters. It is also found in domestic effluents and certain industrial waste waters. Ammonia is harmful to aquatic life and ammonia levels must be carefully controlled in water used for fish farming and aquariums. Ammonia is tested for using alkaline salicylate and reagents.

Nitrates

are normally present in natural, drinking and waste waters. Nitrates enter water supplies from breakdown of natural vegetation, the use of chemical fertilisers in modern agriculture and from the oxidation of compounds in sewage effluents and industrial waste. Nitrates are tested for by reducing it to nitrite and a diazonium reaction.

Turbidity

is caused by the scattering of light by suspended matter such as clay, silt, finely divided organic and inorganic matter. Often turbidity is a result of less usual occurrences such as flooding and screen failure.