Contaminants may be naturally occurring or man-made. Examples of chemical contaminants include pesticides, metals like lead, toxins produced by bacteria, and human or animal drugs. In most cases contaminants can be removed with specific and efficient drinking water systems. Biological contaminants are referred to as microbes or microbiological contaminants. Examples of biological or microbial contaminants include bacteria, viruses, protozoan, and parasites. The most effective treatment for microbiological contaminants is filtration and ultraviolet sterilization.
Discoloured water is an indicator of poor quality and can be caused by a variety or combination of contaminants. Tannins, Iron, Manganese, and Sulfur are the most common causing yellow, brown, rusty, to black coloured water.
Tannins are a product of decaying vegetation and will generally impart a tea colour to the water. Tannins in water can sometimes be mistaken for iron discolouration, so it is very important that it be properly identified for successful removal. (link for solutions)
Iron, when in its oxidized state, can impart a light yellow to dark brown discolouration in water. It can also be present in water in a dissolved form (clear water iron) which is not visible to the naked eye. Any concentration over 0.3 ppm (parts per million) will cause staining. When exposed to dissolved oxygen in the water, it will change to an undissolved state or precipitate (Ferric iron), and will impart colour to the water. Most deep wells have lower amounts of dissolved oxygen and thus the iron remains in a dissolved state. If well water sits for too long, without being recycled, the clear water iron can oxidize and turn to rust. Cottagers quite often experience this problem as they are not there often enough to recycle the well through normal everyday use. (link to solutions)
Iron bacteria is a natural part of our environment and can also impart colour to water by digesting iron. Iron bacteria sometimes appear as an oil-like or rainbow-coloured sheen on the surface of water. More importantly, it produces a gelatinous slime that can plug screens on well pumps, reducing well yield, and can also clog pipes and fixtures. (link for solutions)
Manganese in water reacts similar to iron and can impart a dark hue to water depending on how much is present. (Link to solution)
Sulfur can impart a light to dark black discolouration in water when present in higher concentrations however is more notable for its characteristic ” Rotten Egg “ odour. (Link to solution)
Hardness in water consists of calcium and/or magnesium and is the most prominent contaminant(s) that significantly affects longevity and performance of all water-using appliances in the home. Approximately 99% of the water in our homes is used for bathing, laundry and cleaning. We use it in our dishwashers, laundry machines, hot water heaters, other water-heating appliances such as coffee makers, water kettles and all of our plumbing and water fixtures. While hardness is not obvious because it is dissolved in water, it leaves tell tale signs such as white deposits on dishes and glassware, on the inside of dishwashers, around faucets and in tubs and on shower doors and stalls. Studies have shown that hard water scale can shorten the life of water-using appliances and fixtures by up to six years and can significantly increase energy costs.
Iron is another common contaminant that can be found in many ground-water wells and can cause characteristic yellow/brown stains in toilets, tubs, sinks, dishwashers, and most water using appliances. It’s presence in water will also stain laundry and is especially noticeable on white laundry items. Amounts as little as 0.3 parts per million will cause stains. Its presence in water is sometimes obvious as it can impart colour to water when it is in an oxidized (rust) form. Iron can also be present in a dissolved form which doesn’t impart colour to water, but can stain just as readily. Water with higher levels of Iron generally exhibits what can be best described as a “tinny or metallic odour”. Iron bacteria is sometimes present in water contaminated with iron. While it can also cause stains, there are more serious problems related to its geletanous characteristic and resulting ability to clog well-pump screens, and plumbing .
Municipal and community water supplies to the general public are strictly regulated and are generally considered to be safe for consumption. Specific processes are used to clean and disinfect the water before it is delivered to the end user. Chlorine is a residual disinfectant that is commonly used to kill viruses and bacteria. Many people find the resulting odour in the water to be offensive and do not like the taste. Some municipal and community water supplies may also exhibit hard water characteristics. The smell and taste associated with chlorinated water can be easily filtered and any hardness can be removed by softening.
Sulfur (hydrogen sulfide) is characterized by its offensive “rotten egg odour” . Quite often it is a result of decaying vegetation in swampy areas that may feed an aquifer. It is a very pungent gas and very small amounts can be offensive. Sulfur reducing bacteria are the primary producers of large amounts of hydrogen sulfide. It can cause scale buildup in water pipes and is corrosive to metals such as iron steel, copper and brass. It will tarnish silverware and will cause copper and brass to turn black. Hydrogen sulfide is not considered to be a health risk at concentrations found in most wells, but can be at very high concentrations which rarely exist in well water. Sulfur is generally a nuisance contaminant which in addition to its scaling ability and corrosiveness, can impart a bitter taste to water and foods prepared with it.