Application of combination of coagulation-flocculation and membrane separation processes for tofu industrial wastewater treatment

Tofu is one of the popular foods consumed by Indonesians, however in the making process produced much wastewater, which is usually directly discharged into the river. This study aims to evaluate the effectiveness of coagulation-flocculation and membrane processes to treat the tofu wastewater in order to meet the government regulation for discharged wastewater. The coagulant agent used was alum, while the membrane process involved ultrafiltration (UF) and reverse osmosis (RO) processes. Experimental results showed that the effectiveness of coagulation increased with the addition of a coagulant dose until the optimal dose is reached at 300 ppm. The similar phenomena with Trans Membrane Pressure (TMP) in the UF process which showed an increase in effectiveness to 1 bar, and the rejection rate decreased as TMP across the UF membrane increased. The lowest concentrations of TSS, turbidity, TDS, COD and BOD in the final product of processed water after RO process were 0 mg/L, 0 FAU, 3.0 mg/L, 9.8 mg/L and 16 mg/L, respectively, which are far below the government regulation so that it can be disposed directly into the river.