Effects of trans-membrane-pressure on tofu industry wastewater treatment through ultrafiltration and reverse osmosis processes

Wastewater from the tofu industry is one of the causes of water pollution. It requires effective treatment since exceeds the requirements of national standards. The previous study, which only used ultrafiltration process in the membrane separation still contain chemical oxygen demand (COD) higher than the standard set by the government. This study therefore, aimed to treat tofu wastewater through a combination of coagulation-flocculation and ultrafiltration (UF) and reverse osmosis (RO) processes in order to meet the discharged water based on the government regulation. It was expected that the produced water would meet the National Environmental Quality Standard before released into the environment. Alum was used as coagulant with doses of 100 ppm to 800 ppm. The wastewater feed has a pH, total dissolved solids (TDS), total suspended solids (TSS), turbidity and chemical oxygen demand in the ranges of 3.8 - 4, 850 - 880 mg /L, 380 - 420 mg /L, 450-530 FAU and 5600 - 6600 mg /L, respectively, which are far beyond the requirement of the National Environmental Quality Standard. Experimental results show the effectiveness of coagulation-flocculation increased with the addition of coagulation dose until an optimum level was obtained at 300 ppm. All the parameters observed except COD of produced water from the UF process met the national standard. The COD of produced water from the UF process was further reduced in the RO process resulting in a far below the maximum content allowed in government regulations.