The concentration of total dissolved solids (TDS) in drinking water should not…

Concept

Total dissolved solids (TDS) is the combined concentration of dissolved salts, minerals, and small amounts of organic matter in water.

Drinking-water standards distinguish the normal acceptable limit from a higher permissible limit allowed only when no alternative source exists.

Application

For the drinking-water standard used in this UGC NET item, the acceptable upper limit for TDS is 500 mg/L. Therefore, under the normal acceptability criterion, the concentration should not exceed 500 mg/L.

Cross-check and contrast

The threshold 500 mg/L equals 0.500 g of dissolved material per litre. The 2000 mg/L value sometimes quoted in Indian standards is the exceptional permissible limit when no alternative source exists, not the normal acceptable limit asked here.

• 400 mg/L equals 0.400 g/L and is a concentration below the stated standard ceiling; it is not the ceiling itself.

• 300 mg/L equals 0.300 g/L and is likewise a lower concentration, not the maximum acceptable threshold.

• 200 mg/L equals 0.200 g/L and is the smallest offered concentration, not the standard upper limit.

Thus, the concentration should not exceed 500 mg/L.