Table 2.

Statistical measures and evaluation of physico-chemical, heavy metals and biological parameters during COVID-19 before and after lockdown period against WHO, USEPA and BIS standards.

Parameters	Unit	Pre-lockdown			Lockdown			World Health Organization (2017)	USEPA (2009)	BIS (2012)	% of samples exceed the World Health Organization (2017) Limits		Decreased Variation	Decreased Variation in %
		Min	Max	Mean	Min	Max	Mean				Pre-lockdown	Lockdown
pH	–	7.40	8.20	7.78	7.10	8.2	7.63	6.5–8.5	6.5–8.5	6.5–8.5	–	–	0.16	1.99
EC	μs/cm	550	3568	1448.55	421	2899	1129.30	1500		–	45	25	319.25	22.04
TDS	mg/l	456	3215	1718.10	425	1956	1203.40	1000	500	500	75	55	514.7	29.96
DO	mg/l	1.26	9.26	5.07	1.11	6.89	4.01	–	–	–	–	–	1.06	20.90
BOD	mg/l	2.30	9.50	5.50	1.50	9.6	4.80	–	–	–	–	–	0.70	12.70
Turbidity	NTU	1.56	9.65	4.97	1.21	6.62	3.39	–	–	1	–	–	1.59	31.90
No3	mg/l	35.0	72.00	52.95	12.0	56	38.35	50	–	45	50	15	14.6	27.57
As	mg/l	0.01	0.10	0.06	0.001	0.098	0.05	0.01	–	0.01	100	100	0.014	23.20
Cr	mg/l	0.01	0.08	0.05	0.01	0.07	0.04	0.05	0.1	0.01	40	15	0.009	20.88
Fe	mg/l	0.12	0.46	0.29	0.10	0.32	0.22	0.3	0.3	0.3	45	5	0.070	24.48
Cu	mg/l	0.12	0.30	0.22	0.11	0.30	0.20	2	1.3	1	–	–	0.017	7.81
Zn	mg/l	0.57	1.00	0.83	0.52	0.999	0.76	–	5	15	–	–	0.063	7.60
Cd	mg/l	0.00	0.002	0.00	0.00	0.001	0	0.003	0.005	0.01	–	–	0.001	41.67
Pb	mg/l	0.006	0.019	0.012	0.004	0.009	0.007	0.01	0.015	0.05	65	–	0.005	40.98
Total coliform bacteria	MPN/ml/l	6.20	189	94.76	1.20	95	58.91	–	–	–	–	–	35.85	37.83
Faecal coliform bacteria	MPN/ml/l	8.90	195	97.10	4	85	42.92	–	–	–	–	–	54.18	55.80
Escherichia coli	MPN/ml/l	0	77	37.75	0	62	30.45	–	–	–	–	–	7.3	19.34
Faecal streptococci	CFU/ml/l	0	10	4.25	0	10	2.95	–	–	–	–	–	1.3	30.59