Comparative study between chemical coagulation/precipitation (C/P) versus coagulation/dissolved air flotation (C/DAF) for pre-treatment of personal care products (PCPs) wastewater Original Research Article

For pretreatment of wastewater discharged from personnel care products (PCPs) factory, two treatment schemes were investigated. The 1st step in both schemes was chemical coagulation followed by precipitation in the 1st scheme and dissolved air flotation in the 2nd one. Ferric chloride (FeCl3·6H2O), alum (Al2(SO4)3·18H2O) and ferrous sulfate (FeSO4·6H2O) were used as coagulants. Lime (CaO) was used as coagulant aid and for pH adjustment. For C/P, the three coagulants investigated were found to be more or less similar in their performance. Maximum CODtotal removal obtained by ferric chloride, ferrous sulfate and alum was 75.8 ± 9.7, 77.5 ± 9.6 and 76.7 ± 9.9%, respectively. Corresponding BOD5 total removal values were 78 ± 15.8, 78.7 ± 15.6 and 74.1 ± 19.3%, respectively. However, the optimum dose of ferric chloride and alum was 600 and 700 mg/l while that of ferrous sulfate was 850 mg/l. Alum produced a voluminous sludge, but with the least solids content. Ferric chloride produced compact sludge with a good settleability as reflected by the low sludge volume index (SVI) of 76.3 ± 28.8 ml/gTSS.