Dissolved Solids and how they affect your Drinking WaterTotal dissolved solids (TDS) is the total amount of organic matter and inorganic salts, metals and minerals that are held in solution in drinking water. Total dissolved solids is a term used to define matter held in solution that is able to pass through a filter with a two micrometer pore size; larger size particulate matter held in suspension is referred to as total suspended solids (TSS). Some dissolved solids that are typically found in drinking water include inorganic salts, such as calcium, magnesium, potassium, sodium, bicarbonates, chlorides, sulphates and nitrates, plus small amounts of dissolved organic matter.
Effects of Total Dissolved Solids in Drinking WaterTotal dissolved solids (TDS) are not considered to pose a direct health threat to humans, and consequently they are regarded as secondary drinking water contaminants by the US Environmental Protection Agency (EPA). Some total dissolved solids can corrode pipes and can cause scaling on water pipes and household equipment, which can reduce the life of these appliances. Total dissolved solids can affect the taste of drinking water when they occur in high concentrations. However, very low concentrations of dissolved salts can give water a very bland taste, making it less palatable. According to the World Health Organization, water tastes best when the level of total dissolved solids is less than 300mg/L, but still tastes good when total dissolved solids range from 300-600mg/L. The palatability deteriorates as the level of total dissolved solids increases, with water having a poor taste at levels above 900mg/L, and being unpalatable when the level of dissolved solids is greater than 1200mg/L. Due to the above aesthetic reasons, the EPA has set the standard for total dissolved solids in drinking water to 500mg/L.
While total dissolved solids are not considered a health hazard directly, high levels of total dissolved solids may indicate the presence of dissolved ions listed as primary drinking water contaminants that could pose a risk to human health in high concentrations (e.g. fluoride, lead, arsenic, copper, aluminum, etc.). Therefore if your drinking water has high levels of total dissolved solids it is advisable to have it tested to determine the constituents so that any potential health hazards can be addressed.
Sources of Total Dissolved Solids in Drinking WaterTotal dissolved solids occurring as drinking water contaminants can originate from several sources, including natural sources and anthropogenic sources. Natural sources include input from mineral springs, salt and carbonate deposits, and from sea water flowing into freshwater sources. Anthropogenic sources include storm water run-off from urban areas, sewage and agricultural run-off, industrial wastewater discharges, and from chemicals used in treating drinking water. Salts used in de-icing roads and to prevent skidding can also be washed into waterways and increase the total dissolved solids load. Drinking water contaminants may also consist of dissolved solids that accumulate in water due to corrosion of plumbing (e.g. lead or copper pipes and fittings).
Water Purification Methods to Reduce TDS Drinking Water ContaminantsThe method of water purification used to remove TDS drinking water contaminants will depend on whether they are made up predominantly of cations such as calcium, magnesium, and iron, or whether the TDS drinking water contaminants are associated with high levels of anions such as sodium, potassium, etc. For treatment of the former (cations) the addition of a water softener may be sufficient to eliminate the problem. While this may not remove total dissolved solids from the water, it may reduce some of the problems associated with water hardness (e.g. scaling). For treatment of the latter (anions) a reverse osmosis filtration system or water distillation unit would be recommended to remove total dissolved solids present as drinking water contaminants.
Ultimately, you will need to have your water tested to determine the concentrations of total dissolved solids, and if concentration levels are high, further tests will need to be conducted to ascertain what drinking water contaminants make up the total dissolved solids in order to select the appropriate water purification option. It must be noted that even if the concentration of total dissolved solids is low, this water may have corrosive properties that can result in toxic drinking water contaminants such as lead and copper entering the water if pipes and fittings are corroded. Furthermore, trace metals of a toxic nature may still be present in water with a low TDS in sufficient levels to pose a risk to human health.
Oram, B. “Total Dissolved Solids”. Water Research Center. Web, 4 Dec. 2011.
World Health Organization. “Total dissolved solids in Drinking-water.” WHO/SDE/WSH/03.04/16. 2003. Web, 4 Dec. 2011.