Post-treatment of Anaerobically Digested Palm Oil Mill Effluent by Polymeric Flocculant-Assisted Coagulation

Typically, palm oil mill industries use conventional anaerobic ponds for treatment of palm oil mill effluent (POME). But, this method alone cannot produce effluent discharge to an allowable limits set by the authorities. This study aimed to investigate further treatment of anaerobically digested POME (COD = 682 +/- 14 mgL(-1), TSS = 29 +/- 7 mgL(-1) and turbidity = 106 +/- 3 NTU) by coagulation-flocculation process. Alum, an industrial-accepted coagulant and OC 100 and PC 100W as two industrial-based polymeric flocculants were used in coagulation-flocculation process. Results indicate coagulation process in its optimum conditions (pH = 6, alum dosage = 1800 mgL(-1), rapid mixing = 5 min, and slow mixing = 20 min) reduces the COD, TSS and turbidity by 59%, 80% and 86%, respectively. Flocculants OC 100 and PC 100W caused further reduction of TSS (85-88%) and turbidity (97-98%). By application of post treatment, the POME characteristics reached to an acceptable discharge level enforced by Malaysian department of environment (DOE).