Table 2 shows the conversion of the groundwater quality standard from the concentration to the special weights. It can be seen from Table 2 that a water sample with less than 0.47643 will be classed into Grade I, which is considered as clean and excellent for drinking. If the concentrations of very few parameters exceed the limits, those water samples are classified as Grade II. Likewise, water samples classified as Grade III mean they are slightly polluted with a few values exceeding the standards. Similarly, water samples in Grade IV mean moderately contaminated with at least two parameters exceeding the criteria. Grade V means the water is seriously polluted as almost all the parameters are far beyond the standard values.

Table 2

Statistics summary of the improved Nemerow pollution indices in GB/T 14848-93

Groundwater parameters .	Grade I .	Grade II .	Grade III .	Grade IV .	Grade V .
TH (mg/L)	≤150	≤300	≤450	≤550	>550
COD (mg/L)	≤1.0	≤2.0	≤3.0	≤10	>10
TDS (mg/L)	≤300	≤500	≤1,000	≤2,000	>2,000
Cl− (mg/L)	≤50	≤150	≤250	≤350	>350
(mg/L)	≤50	≤150	≤250	≤350	>350
(mg/L)	≤2.0	≤5.0	≤20	≤30	>30
(mg/L)	≤0.001	≤0.01	≤0.02	≤0.1	>0.1
F− (mg/L)	≤1.0	≤1.0	≤1.0	≤2.0	>2.0
	≤0.476	≤0.702	≤1	≤3.198	>3.198
Water class	Excellent	Good	Fair	Poor	Very poor

Groundwater parameters .	Grade I .	Grade II .	Grade III .	Grade IV .	Grade V .
TH (mg/L)	≤150	≤300	≤450	≤550	>550
COD (mg/L)	≤1.0	≤2.0	≤3.0	≤10	>10
TDS (mg/L)	≤300	≤500	≤1,000	≤2,000	>2,000
Cl− (mg/L)	≤50	≤150	≤250	≤350	>350
(mg/L)	≤50	≤150	≤250	≤350	>350
(mg/L)	≤2.0	≤5.0	≤20	≤30	>30
(mg/L)	≤0.001	≤0.01	≤0.02	≤0.1	>0.1
F− (mg/L)	≤1.0	≤1.0	≤1.0	≤2.0	>2.0
	≤0.476	≤0.702	≤1	≤3.198	>3.198
Water class	Excellent	Good	Fair	Poor	Very poor

TH, Total hardness; COD, Chemical oxygen demand; TDS, Total dissolved solids; ⁠, Improved Nemerow pollution index.

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