Table 1.

Water quality standards by BIS, UNECE and WHO.

Parameters	Class
	IS 2296:1992					UNECE 199427					WHO
	A	B	C	D	E	I	II	III	IV	V
DO (%) un-stratified water	–	–	–	–	–	90–70	70–50	50–30	30–10	< 10	–
DO (mg/l)	≥ 6	≥ 5	≥ 4	≥ 4	–	> 7	7–6	6–4	4–3	< 3	5
BOD (mg/l)	≤ 2	≤ 3	≤ 4	–	–	–	–	–	–	–	–
COD (mg/l)	–	–	–	–	–	< 3	3–10	10–20	20–30	> 30	10
TDS (mg/l)	≤ 500	–	≤ 1500	–	≤ 2100	–	–	–	–	–	500
Total alkalinity (mg/l)	200	–	–	–	–	> 200	200–100	100–20	20–10	< 10	200
Total coliform (MPN/100 ml) max	50	500	5000	–	–	–	–	–	–	–	0