Ammonia in the environment originates from metabolic, agricultural and industrial processes and from disinfection with chloramine.
Bromide is commonly found in nature along with sodium chloride, owing to their similar physical and chemical properties, but in smaller quantities. Bromide can be involved in the reaction between chlorine and naturally occurring organic matter in drinking-water, forming brominated and mixed chloro-bromo by-products, such as trihalomethanes (THMs) and halogenated acetic acids (HAAs)
Chloride in drinking-water originates from natural sources, sewage and industrial effluents, urban run-off containing de-icing salt and saline intrusion.
Chlorine is produced in large amounts and widely used both industrially and domestically as an important disinfectant and bleach. It is the most commonly used disinfectant and oxidant in drinking water treatment.
Chlorine dioxide is used as a disinfectant and for odour and taste control in water.
Naturally occurring ﬂuoride concentrations in drinking water depend on the type of soil and rock through which the water drains. It is present in most brands of toothpaste, and it is often added to drinking water supplies.
Concentrations above 1.5 mg/L may disturb tooth mineralisation in children up to about 6 to 8 years, leading to dental ﬂuorosis, a mottling of the teeth. Skeletal ﬂuorosis, characterised by hypermineralisation and thus brittle bones, has occurred in association with high ﬂuoride concentrations in drinking water.
Hydrogen peroxide is used as an oxidant in the treatment of drinking water (often in conjunction with ozone) to oxidise metals or organics, reduce tastes and odours, or act as an algicide, disinfectant or biocide.
Nitrate is formed from the oxidation of organic wastes such as manure, by the action of nitrogen-fixing bacteria in soils, or from lightning strikes through air. Nitrates are also manufactured for use in explosives and inorganic fertilisers.
Nitrite is relatively unstable and can be formed by the reduction of nitrate in poorly oxygenated waters. It is rapidly oxidised to nitrate and is seldom present in well oxygenated or chlorinated supplies.
The major biological effect of nitrite in humans is its involvement in the oxidation of normal haemoglobin to methaemoglobin, which is unable to transport oxygen to the tissues.
Ozone is used as a disinfectant in water treatment plants. It is a very strong biocide and oxidising agent, and is effective in reducing colour, taste and odour, and oxidising iron and manganese.
Phosphates usually enter water from land runoff, human and animal excreta, decaying vegetation and industrial processes and detergents.
Sulphate occurs naturally in a number of minerals, and is used commercially in the manufacture of numerous products including chemicals, dyes, glass, paper, soaps, textiles, fungicides and insecticides.
Most sulphate salts are very soluble and cannot be removed from drinking water by conventional water treatment processes.
Sulphites are used as a food preservative or enhancer. They may come in various forms, such as sulphur dioxide (which is not a sulphite, but a closely related chemical oxide), sodium or potassium bisulphite and sodium or potassium metabisulphite.
Sulphites are counted among the top nine food allergens, causing breathing difficulty within minutes and sometimes sneezing, swelling of the throat, hives, and migraine.