COAGULATION-FLOCCULATION TREATABILITY STUDY OF BILGE AND BARGE WASTEWATER APPLYING FERRIC CHLORIDE AND CATIONIC POLYMERS

This paper presents the results of an experimental investigation about the performance of a laboratory-scale dissolved air flotation (DAF) unit for treating bilge and tank cleaning wastewaters. The wastewaters contained moderate organic and suspended solids content. Chemical oxygen demand (COD) and total suspended solids variations were in the ranges of 599 to 816 mg/L and 108 to 252 mg/l, respectively. The wastewater had an average salinity of 9 g/L and pH of 6.9. Conventional bench-scale tests were performed to study the treatability of the wastewater by coagulation-flocculation with ferric chloride (FeCl3) and a series of cationic acrylamid polymers. The ferric chloride test showed that at a dosage of 100 mg/L, approximately 67% of the COD and TSS were removed. The best performing polymer, Callaway 4823LS, was a high-molecular weight, low charge density cationic acrylamid polymer. The removal rates achieved with 25 to 100 mg/L of ferric chloride and Callaway 4823LS at doses 0.2 to 5.0 mg/L were 74 to 83% for COD, 61 to 79% for TSS, and 49 to 83% for turbidity.