Centrifugation effect on olive mill wastewater treatment by coagulation-flocculation using Ca(OH)2-pectin system

Abstract The aim of this research was the study of the centrifugation effect on olive mill wastewater (OMW) treatment by coagulation-flocculation using the Ca(OH)2-pectin system. To separate the treated OMW from the residual sludge, two methods were used: gravity decantation and centrifugation. Efficiency of the treatment was evaluated following the evolution of the OMW treated volumes and the reduction rates of dry matter (DM) and phenolic compounds (PC) and other parameters related to residual toxicity. Compared to gravity decantation, centrifugal separation significantly enhances the treatment of the OMW studied. Additionally, this separation method reduces considerably the treatment duration compared to gravity decantation i.e. 10 minutes instead of 4 hours. The lime-pectin system improved OMW purification. Optimal doses of lime and pectin were respectively 10 g/l and 0.2 g/l. Under these conditions, centrifugal separation allowed to obtain a volume of treated OMW about 78.2% of the raw effluent volume and reduced the rates of DM by 38% and of PC by 79%. The COD was also reduced by 60.0%. These results show that the resulting sludge may be used for production of fertilizers or land augmentation, thus avoiding costly disposal.