Turbidity – An Indicator of Drinking Water ContaminantsWater turbidity is the level of cloudiness of water that affects water clarity. Turbidity arises from suspended matter in the water column that refract light, thus reducing the ability of the water to allow light to penetrate. This reduces the clarity of the water, giving it a cloudy appearance.
Health Implications of Turbidity in Drinking WaterTurbidity is generally considered an aesthetic water problem, and as such it is not included on the list of drinking water contaminants. However, it is a good indicator of the presence of drinking water contaminants, including pathogens that can affect human health, such as Giardia and Cryptosporidium, which cause gastrointestinal upsets. Turbidity arises when organic or inorganic matter, such as clay, silt, minerals, debris, and plant or animal matter are suspended in the water column. These particulates provide both shelter and a source of food to microbes, enabling them to survive and even flourish. Water with a high turbidity reduces the effect of disinfection treatments, such as chlorine, for the eradication of water born bacteria and protozoa. Consequently, it is essential that turbidity levels are kept low if water is to be disinfected to remove drinking water contaminants effectively.
Turbidity spikes from both filtered and unfiltered water treatment facilities have been associated with epidemic outbreaks in the past, and while turbidity cannot be conclusively blamed for these outbreaks, it represents a good indicator that disease causing micro-organisms may be present and that extra precautionary measures should be taken.
Other Problems Associated with Water TurbidityTurbidity arising from inorganic minerals held in suspension can be abrasive, leading to eroded plumbing, pipes and fittings plumbing. Turbidity arising from organic matter held in suspension can stain sanitary-ware and laundry.
Measuring TurbidityWater turbidity is measured with an electronic turbidity meter, or a transparency tube, to measure light penetration in water. In deep water situations, a secchi disk can also be used to determine water clarity. Turbidity is measured in nephelolometric turbidity units (NTU), the NTU recorded will increase with increased turbidity. The drinking water standard for turbidity as set by the US Environmental Protection Agency (EPA) is 1 NTU, but higher turbidity levels will typically not be noticeable until a reading of 5 NTU is recorded.
Water Purification Methods to Reduce TurbidityTurbidity in drinking water can be reduced by filtering out the suspended particles using a variety of water purification filtering methods.
Mechanical filters offer a very effective method of trapping the particles held in suspension on a fine screen, as water flows through. Tank filters support a variety of filtration media, including sand, or other granular material, and are useful for removing turbidity from the entire water supply as the water leaves the tank.
Cartridge filters are another option for removing drinking water contaminants, and will remove suspended particulate matter, ranging from tiny particles through to larger size particles depending on the pore size of the filter cartridge. Cartridges are usually disposable, and are simply replaced when they get clogged up. Cartridge filters can tend to restrict water flow, especially when they become clogged. Cartridge filters are fitted to individual taps to remove particles and purify water as it pass through the filter.
Activated carbon can be used in combination with tank or cartridge filters to adsorb organic compounds and other drinking water contaminants that give water an unpleasant odor or taste.
Reverse osmosis units are also effective for removing turbidity to provide a clear supply of drinking water. The water is forced across a semi-permeable membrane that allows water to penetrate, but not particles or dissolved impurities, which are removed from the water stream. While large units are available to treat the entire water supply, these are usually far to expensive to be viable. Individual units fitted to a tap that is used to supply water for drinking or cooking offer an extremely efficient water purification method of removing turbidity and other drinking water contaminants from water to provide clean, purified water for household use.
Hermanson, R.E. Turbidity, Color, Odor and Taste in Domestic Water. Clean Water for Washington, Washington State University Extension.http://watersystemscouncil.org/infoSheets.php