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Filtration was carried out in continuous mode. Every week the GWCT was completely emptied by operating outlet valves kept at the bottom for draining purposes. This was necessary to avoid the accumulation of solids and contaminants in the GWCT. Characteristics of the raw and coarse filtered GW are given in Table 3.

Table 3

Characteristics of raw and coarse filtered greywater

Raw greywater
CF effluent
ParameternMin–maxAvg ± SDMin–maxAvg ± SD
pH 85 6.62–8.13 7.49 ± 0.30 6.4–8.34 7.52 ± 0.29 
Turbidity, NTU 85 5.7–190.0 80.3 ± 30.5 3.1–98.1 39.2 ± 16.2 
Temperature, °C 85 22.2–30.4 28 ± 2.9 21.6–30.7 26 ± 2.9 
EC25, μS/cm 85 269–646 489 ± 83 265–637 482 ± 84 
Total dissolved solids (TDS), mg/L 77 184–396 304 ± 53 182–406 299 ± 53 
TSS, mg/L 77 24–215 88 ± 30 14–176 70 ± 24 
Oil and grease (O&G), mg/L 59 4–80 33 ± 13 3–58 23 ± 9 
Alkalinity, mg/L 79 152–260 187 ± 15 144–248 171 ± 16 
BOD5, mg/L 63 30–306 102 ± 49 15–290 87 ± 43 
COD, mg/L 58 68–596 243 ± 101 44–556 224 ± 95 
Total coliforms (TC), MPN/100 mL 15 3.10 × 105–4.90 × 107 1.88 × 107 ± 9.86 × 106 2.10 × 105–2.10 × 107 7.90 × 106 ± 7.00 × 106 
Fecal coliforms (FC), MPN/100 mL 15 1.20 × 104–8.40 × 105 2.83 × 105 ± 3.46 × E5 9.30 × 103–7.20 × 105 1.90 × 105 ± 3.20 × 105 
E. coli, CFU/100 mL 15 3.00 × 102–2.10 × 103 9.71 × 102 ± 5.24 × 102 4.00 × 102–1.70 × 102 9.10 × 102 ± 4.60 × 102 
Sodium adsorption ratio (SAR) 1.40–3.60 2.30 ± 0.37 – – 
Boron, mg/L 0.05–0.10 0.07 ± 0.01 – – 
Arsenic, mg/L < 0.01 < 0.01 – – 
Ammonia nitrogen (NH3-N), mg/L 61 0.50–3.90 2.00 ± 0.93 0.30–3.36 1.69 ± 0.81 
Phosphates (PO4-P), mg/L 42 0.20–1.90 0.95 ± 0.24 0.10–1.80 0.87 ± 0.23 
Raw greywater
CF effluent
ParameternMin–maxAvg ± SDMin–maxAvg ± SD
pH 85 6.62–8.13 7.49 ± 0.30 6.4–8.34 7.52 ± 0.29 
Turbidity, NTU 85 5.7–190.0 80.3 ± 30.5 3.1–98.1 39.2 ± 16.2 
Temperature, °C 85 22.2–30.4 28 ± 2.9 21.6–30.7 26 ± 2.9 
EC25, μS/cm 85 269–646 489 ± 83 265–637 482 ± 84 
Total dissolved solids (TDS), mg/L 77 184–396 304 ± 53 182–406 299 ± 53 
TSS, mg/L 77 24–215 88 ± 30 14–176 70 ± 24 
Oil and grease (O&G), mg/L 59 4–80 33 ± 13 3–58 23 ± 9 
Alkalinity, mg/L 79 152–260 187 ± 15 144–248 171 ± 16 
BOD5, mg/L 63 30–306 102 ± 49 15–290 87 ± 43 
COD, mg/L 58 68–596 243 ± 101 44–556 224 ± 95 
Total coliforms (TC), MPN/100 mL 15 3.10 × 105–4.90 × 107 1.88 × 107 ± 9.86 × 106 2.10 × 105–2.10 × 107 7.90 × 106 ± 7.00 × 106 
Fecal coliforms (FC), MPN/100 mL 15 1.20 × 104–8.40 × 105 2.83 × 105 ± 3.46 × E5 9.30 × 103–7.20 × 105 1.90 × 105 ± 3.20 × 105 
E. coli, CFU/100 mL 15 3.00 × 102–2.10 × 103 9.71 × 102 ± 5.24 × 102 4.00 × 102–1.70 × 102 9.10 × 102 ± 4.60 × 102 
Sodium adsorption ratio (SAR) 1.40–3.60 2.30 ± 0.37 – – 
Boron, mg/L 0.05–0.10 0.07 ± 0.01 – – 
Arsenic, mg/L < 0.01 < 0.01 – – 
Ammonia nitrogen (NH3-N), mg/L 61 0.50–3.90 2.00 ± 0.93 0.30–3.36 1.69 ± 0.81 
Phosphates (PO4-P), mg/L 42 0.20–1.90 0.95 ± 0.24 0.10–1.80 0.87 ± 0.23 

n, number of samples; Avg, arithmetic average; SD, standard deviation; CF, coarse sand filter.

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