An economic approach of palm oil mill effluent tertiary treatment using ferrous sulphate

Abstract

Study was conducted to use ferrous sulphate as coagulant to reduce the biological load for tertiary treatment in palm oil mill effluent treatment to meet the discharge quality requirement of BOD-20 and BOD-50 ppm. Various levels of ferrous sulphate dosages, from 100 to 2000 ppm, were tested using jar-test technique to determine the optimum dosage of ferrous sulphate that will meet the discharge quality requirement. Treated effluent with BOD level below 100 ppm was used as feed water for the treatment. The trace metal analysis was also conducted to determine if there were any traces of heavy metal that will produce hazardous activated sludge from the coagulation process. It was found that the required ferrous sulphate dosage to meet BOD-50 requirement was at 750 ppm, while BOD-20 requirement was achieved when the ferrous sulphate dosage was at 1,750 ppm and did not produce hazardous activated sludge. Though the SS level was still higher than the discharge limit, the SS level could be further reduced when the sedimentation process was further increased to 4-6 hours and followed by sand filtration. The ferum content for both the supernatant and sludge were also within permissible limit, below 100 pm and 250 ppm, respectively. Based on these laboratory findings, the anticipated capital investment and operating costs of physicochemical tertiary treatment was much lower than when using the biological tertiary treatment to meet the desired BOD-20 and BOD-50 ppm requirement. The proposed physicochemical tertiary plant will consist of chemical preparation and dosing system, The anticipated sedimentation tank and sand filter, against more complex aerobic suspended and submerged attached growth biological treatment processes system. operating cost was less than RM0.50 per ton of POME compared to the biological tertiary plant cost that typically costs more than RM1.00 per ton of POME.