The treatment of palm oil mill effluent, POME is an important issue for the minimization of water pollution. The coagulation-flocculation process using Moringa oleifera seeds after oil extraction as natural coagulant is reported for POME treatment in the present study. The important process parameters pH, settling time, M. oleifera (after oil extraction) dosage and flocculant (NALCO 775 1) dosage were optimized using design of experiments (DOE). A full factorial composite experimental design and response surface methodology (RSM) were used to obtain the optimum values of the parameters. The suspended solids of the raw POME were reduced from 17.927 mg/L to 181 mg/L and % recovery of the sludge as 87% was obtained at an optimum pH 5, settling time 114 min, M. oleifera dosage of 3469 mg/L and 6736 mgL of flocculant (NALCO 7751) dosage in the present study. (C) 2007 Elsevier B.V. All rights reserved.