Dissolved Solids and Water Purification
To make drinking water palatable, the level of dissolved substances (TDS) can’t be too high, but it also can’t be too low
Water quality metrics are needed to ensure that surface and groundwater – common sources of water for human consumption – are free from contaminants and pollutants.
The level of dissolved solids, also commonly referred to as total dissolved solids (TDS), is a way of measuring the level of organic and inorganic substances in water.
This measure refers to any type of solid dissolved in water that is filterable. As explained by the Boulder Area Sustainability Information Network:
In the United States, TDS is considered a “secondary maximum contaminant level.” That is, most dissolved substances do not threaten health, but they may prompt consumers to stop drinking or using water despite it being safe. Total dissolved solids can affect the water’s color, odor, and taste. The Environmental Protection Agency has a secondary drinking water standard for TDS of no more than 500 mg/L.
Excessive amounts of some of the compounds dissolved in water can cause corrosion or other problems in water-distribution systems. A prime example is scaling, which damages pipes, water heaters, and appliances.
Dissolved Solids in Industrial Settings
Conductivity is an important water quality metric in industrial applications where water with a low specific conductance is needed for manufacturing. Specific conductivity is a measurement of the ions present in water. For example, if there is a high amount of salt dissolved in water, this affects water’s conductivity.
Dissolved solids can also be a problem in the manufacture of items that require a certain level of purity, such as pharmaceuticals, or food and beverage items.
High amounts of salt can also render water unsuitable for agricultural irrigation. Whether the source is seawater or brackish groundwater, Fluence’s NIROBOX™ line has a solution to bring TDS down to levels suitable for environmental release, crop or landscape irrigation, industrial processes, and, of course, drinking.
Finding the Right Level
Chemicals and other materials that contribute to total dissolved solids can be measured individually. They can come from natural sources, such as minerals or silts that occur through leaching or runoff. Others may be the product of human use – such as with pollutants in sewage or urban and agricultural run-off, wastewater discharges, or salts used to de-ice roads.
Most drinking water, according to the EPA, contains an average of between 200 and 300 mg/L of TDS. Water with TDS of more than 500 mg/L is not recommended for human consumption. High amounts of TDS in drinking water supplies can make it taste off, or odd.
The World Health Organization reports that in tasting panels, water with less than 300 mg/L of TDS tastes “excellent,” while “good” water has a TDS content ranging from 300 to 600 mg/L. Water containing more than 1,200 mg/L of total dissolved solids was deemed unacceptable. The agency also reports that water containing “extremely low concentrations of TDS may also be unacceptable because of its flat, insipid taste.”