About TDS

Total Dissolved Solids (TDS) refers to the total amount of inorganic and organic materials dissolved in a particular volume of water. These materials can include minerals, salts, and metals. TDS is often measured in parts per million (ppm) or milligrams per liter (mg/L). High TDS levels can affect the taste, odor, and appearance of water, and may also indicate the presence of other contaminants.

 

What are TDS?

  • TDS represents the total amount of dissolved substances in water, excluding pure water (H2O). 
  • These dissolved substances include both inorganic and organic matter. 
  • Inorganic salts, such as calcium, magnesium, sodium, potassium, and anions like carbonate, bicarbonate, chloride, and sulfate, are major contributors to TDS. 
  • Organic matter, such as dissolved plant and animal material, also contributes to TDS. 

 

Why measure TDS?

  • Water Quality:

TDS is a key indicator of water quality and can help assess the overall purity and hardness of a water source.

  • Taste and Odor:

High TDS levels can make water taste salty, bitter, or metallic. 

  • Potential Health Effects:

While TDS itself is not usually a direct health hazard, high levels may indicate the presence of other harmful contaminants. 

  • Industrial and Environmental Monitoring:

TDS is important for monitoring water quality in industrial processes and in natural water systems. 

 

How is TDS measured?

  • Conductivity Meter:

TDS can be estimated using a conductivity meter, which measures the water's ability to conduct an electrical current. Dissolved ions in the water increase conductivity. 

  • Laboratory Analysis:

A more precise measurement can be obtained by filtering a water sample, evaporating the water, and weighing the remaining residue. 


What are acceptable TDS levels?

  • The World Health Organization (WHO) suggests that drinking water with a TDS level below 300 mg/L is excellent, between 300 and 600 mg/L is good, between 600 and 900 mg/L is fair, and between 900 and 1200 mg/L is poor, according to the WHO.
  • The US EPA recommends a secondary maximum contaminant level (SMCL) of 500 mg/L for TDS in drinking water, according to the EPA.