Criteria for drinking water quality recommended by WHO includes – a)  Colour < 15 TCUb)  pH 6.5–8.5c)  Chloride 200–600 mg/1d)  Turbidity <5 NTUe) Zinc < 4 mg/1
Guidelines of for drinking water

Colour < 15 true colour units (TCU)
Turbidity < 1 nephlometric turbidity units (NTU) (has been changed in 22nd /e of Park) 
Hardness < 100 — 300 mg/litre calcium ion
pH: 6.5 — 8.5
Total dissolved solids (TDS) < 600 mg/litre
Chloride    200 - 600 mg/L
 H2S < 0.05 mg/L
Iron < 0.3 mg/L
Sodium < 200 mg/L
Sulphate < 250 mg/L
Zinc < 4 nag/L
NH3 < 1.50 mg/L
Fluorine < 1.5 ppm (0.5 — 0.8 ppm: Optimum level)
Nitrates < 50 mg/litre
Nitrites < 3 mg/litre
Gross alpha radiological activity < 0.1 Bq/litre
Gross beta radiological activity < 1.0 Bq/litre
Zero pathogenic microorganisms
Zero infectious viruses
Absence of pathogenic protozoa and infective stages of helminthes
Dissolved O2 has indirect effect, level is not specified.
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