Palm oil mill effluent (POME) treatment using electrocoagulation and adsorption

Palm oil production involves multi-stage processes which release large volume of palm oil mill effluent (POME). Due to its high polluting environmental impact, POME must be treated prior to discharge. Integrated electrocoagulation (EC)-adsorption (AD) process has shown great potential to remove various organic and inorganic pollutants from wastewater. Up to date, no study has been found yet on POME treatment using integrated EC-AD process. Therefore, this study aims to investigate the feasibility of integrated EC-AD process as an alternative treatment for POME. In this study, EC was run simultaneously with AD to treat POME. The integrated EC-AD process achieved the highest removal of total suspended solid (TSS), chemical oxygen demand (COD), colour and total organic carbon (TOC) as compared to EC and AD stand-alone processes. The integrated EC-AD process successfully reduced 74-98% of TSS, 33-93% of COD, 85-99% of colour and 82-100% of TOC from POME at various POME initial concentrations ranging from 20% to 100%. The adsorption equilibrium of TSS was best fitted by the Langmuir isotherm whereas the adsorption of COD, colour and TOC were better interpreted by the Freundlich isotherm. This implied that the coconut shell-based activated carbon (CSAC) used in this study had both homogeneous and heterogeneous surfaces. The adsorption kinetics of TSS, COD, colour and TOC onto CSAC were fitted well by both pseudo-second-order (PSO) and Elovich kinetic models, which indicated that the adsorption process was mainly controlled by chemical sorption. The intra-particle diffusion (IPD) model plots showed that the adsorption was controlled by both IPD and film diffusion. Boyd plots further confirmed that the adsorption process was controlled by film diffusion. On the other hand, for EC, the adsorption equilibrium of TSS, colour and TOC onto aluminum (Al) hydroxide complexes were best fitted by the Freundlich isotherm whereas the adsorption of TSS was better interpreted by the Langmuir isotherm. This implied that the Al hydroxide complexes had both homogeneous and heterogeneous surfaces. The adsorption kinetics of TSS, COD, colour and TOC onto Al hydroxide complexes showed that the adsorption process for EC was mainly controlled by chemical sorption. Overall, the integrated EC-AD process has demonstrated great potential for POME treatment, and could be recommended as an alternative treatment method for wastewater