Total Dissolved Solids, also known as TDS, are inorganic compounds found in water, such as salts, heavy metals, and some traces of organic compounds dissolved in water.
Excluding the organic matters that are sometimes naturally present in water and the environment, some of these compounds or substances can be essential in life. But, it can be harmful when taken more than the desired amount needed by the body.
The total dissolved solids present in water are among the leading causes of turbidity and sediments in drinking water. When left unfiltered, total dissolved solids can be the cause of various diseases.
Total dissolved solids (TDS) measure the combined total of organic and inorganic substances contained in a liquid. This includes anything present in water other than the pure H20 molecules. These solids are primarily minerals, salts, and organic matter that can be a general indicator of water quality.
What are Total Dissolved Solids in Water?
Water is called a universal solvent because it’s able to dissolve and absorb molecules from many different substances.
TDS is defined as the combined content of all inorganic and organic substances contained in a liquid that are present in a molecular, ionized or microgranular suspended form.
In other words, it’s all of the minerals, salts, and organic particles in the water that you can’t see.
Not all of these organic compounds are harmful, and many are naturally present in our environment. Some of these minerals include potassium, calcium, magnesium, chlorides, bicarbonates, and sulfates.
However, they can be harmful if you take in more than your body needs, or if heavy metals such as iron are present.
TDS in our water supplies can come from:
- natural water sources
- urban run-off
- industrial wastewater
- chemicals during water treatment
- pipes and pipe fittings
- agricultural run-off
- road de-icing salts
The TDS in Drinking Water
The TDS in drinking water comes from natural water sources, sewage, urban run-off, industrial wastewater and chemicals used in the water treatment process, and the hardware or piping used to distribute water. Higher TDS was brought by natural environment features like salt deposits, mineral springs, seawater intrusion, and carbonate deposits in the US.
Other sources may include anti-skid materials, salts used for road de-icing, stormwater, agricultural runoff, water treatment chemicals, and point/non-point wastewater discharges.
In general, the total dissolved solids concentration is the total cations (positively charged) and anions (negatively charged) ions in the water. Thus, the total dissolved solids test gives a qualitative measure of the number of dissolved ions but does not tell us nature or ion relationships.
In addition, the test does not provide us insight into the specific water quality issues, such as Elevated Hardness (mineral content in water), Salty Taste, or Corrosiveness (also called aggressive water, which is how water dissolves with other materials).
Therefore, the total dissolved solids test is used as an indicator test to determine the general quality of the water. The sources of total dissolved solids can include all of the dissolved cations and anions. Still, the following table can be used to generalize the relationship of TDS to water quality problems.