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The effect of filtration on GW characteristics is presented in Table 5 (see option 1). The mean raw GW pH was changed from 7.51 to 7.38, 7.19, and 7.24 in CF, SF1 and SF2 effluent, respectively. Similarly, mean alkalinity was also changed from 187 mg/L to 171, 154, 140 mg/L in CF, SF1 and SF2 effluent, respectively. Soap was a major contributor to the alkalinity. As the suspended solids (soap particles) were trapped in the reactor CF, SF1 and SF2 progressively, alkalinity was reduced. A drop in pH and alkalinity in SF1 and SF2 effluents may also be due to the release of H+ ions during the nitrification process.

Table 5

Mean raw and treated GW characteristics observed in each treatment option

 Option 1 (TSF)
Option 2 (Alum treatment)
Option 3 (PAC treatment)
Option 4 (FeCl3 treatment)
ParameterRawTreatedaRawTreatedbRawTreatedcRawTreatedd
pH 7.51 7.24 7.51 7.44 7.66 7.37 7.57 7.54 
Turbidity, NTU 83.4 4.5 89.6 0.9 83.8 0.6 77.7 2.3 
Electrical conductivity, μS/cm 488 465 454 495 497 520 500 523 
Total suspended solids, mg/L 92 15 83 94 92 
Oil and grease, mg/L 35 30 31 31 
BOD5, mg/L 106 28 95 11 113 105 15 
Boron, mg/L 0.071 0.010 0.063 0.010 0.079 0.010 0.07 0.010 
Sodium adsorption ratio 2.36 2.00 1.55 1.50 3.10 2.35 2.45 2.15 
Fecal coliforms, MPN/100 mL 1.97 × 105 < 2 2.50 × 105 < 2 1.40 × 105 < 2 2.60 × 105 < 2 
 Option 1 (TSF)
Option 2 (Alum treatment)
Option 3 (PAC treatment)
Option 4 (FeCl3 treatment)
ParameterRawTreatedaRawTreatedbRawTreatedcRawTreatedd
pH 7.51 7.24 7.51 7.44 7.66 7.37 7.57 7.54 
Turbidity, NTU 83.4 4.5 89.6 0.9 83.8 0.6 77.7 2.3 
Electrical conductivity, μS/cm 488 465 454 495 497 520 500 523 
Total suspended solids, mg/L 92 15 83 94 92 
Oil and grease, mg/L 35 30 31 31 
BOD5, mg/L 106 28 95 11 113 105 15 
Boron, mg/L 0.071 0.010 0.063 0.010 0.079 0.010 0.07 0.010 
Sodium adsorption ratio 2.36 2.00 1.55 1.50 3.10 2.35 2.45 2.15 
Fecal coliforms, MPN/100 mL 1.97 × 105 < 2 2.50 × 105 < 2 1.40 × 105 < 2 2.60 × 105 < 2 

aFinal effluent from option-1.

bfinal effluent from option-2.

cfinal effluent from option-3.

dfinal effluent from option-4; TSF, two-stage sand filtration.

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