Table 1 Initial parameters of tannery wastewater
Parameters | Raw effluent collected | Maximum tolerance limits for industrial effluents discharged (mg/l) | |
|---|---|---|---|
Into inland surface water | Into public sewers | ||
Physical parameters | Â | ||
 Colour | Blackish colour | Colourless | – |
 Odour | Disagreeable smell | Odourless | Unobjectionable |
 pH | 7.43 | 5.5–9.0 | 5.5–9.0 |
Chemical parameters | Â | ||
 Electrical conductivity (EC) (mS/cm) | 27.3 | 0.288 | – |
 Biochemical oxygen demand (BOD) (mg/l) | 1250 | 30 | 350 |
 Chemical oxygen demand (COD) (mg/l) | 4210 | 250 | – |
 Total dissolved solids (TDS) (mg/l) | 15,900 | 2100 | 2100 |
 Total solids (TS) (mg/l) | 31,740 | 2200 | – |
 Total hardness (TH) (mg/l) | 923 | 600 | 300 |
 Turbidity (NTU) | 453 | 10 | 5 |
 Sodium (mg/l) | 5000 | – | 60 |
 Chromium (Cr) (mg/l) | 1055 | 0.1 | 2.0 |
 Lead (Pb) (mg/l) | 0.43 | 0.1 | 1.0 |