W.L. Ang

CAKE FILTRATION FOR SUSPENDED SOLIDS REMOVAL IN DIGESTATE FROM ANAEROBIC DIGESTED PALM OIL MILL EFFLUENT (POME)

Oil palm industry contributes significantly to the economic growth in Malaysia. At the same time, it generates a huge amount of palm oil mill effluent (POME) which contains valuable resources for energy, water and nutrients recovery. Currently, it has been used as feed for anaerobic biogas reactor to produce methane, a renewable energy source. The effluent discharged from the anaerobic digester, known as digestate, still contains abundant water and nutrients for recovery. However, the presence of suspended solids in digestate hinders the downstream water and nutrients recovery processes. Cake filtration process that has been successfully employed in water industry to remove suspended solids appears to be an attractive option for the removal of suspended solids in digestate. This paper investigates the performance of cake filtration process in removing suspended solids in digestate. Various types of filter aid such as perlite, diatomaceous earth (DE), bleaching earth (BE), powdered activated carbon (PAC), and boiler ash (BA) are used in this study. The amount of filter aid used as precoat and body feed was also varied (with ratio 1:1 from 1.0 g to 3.0 g) in the process. The effectiveness of cake filtration process was evaluated based on the quality of filtered digestate and the filtration flux. Overall, the particle size and size distribution of filter aids have huge influence on the cake filtration process. Turbidity removal above 90 % can be achieved regardless the type and amount of filter aids used. Due to the presence of plenty fine pores (as shown by FESEM image) on perlite particles and its narrow particle size distribution, the permeation of water was the highest flux (1 ml/cm2.min) and retention of suspended solids also was among the highest compared to other filter aids. This study shows that cake filtration process has the potential to be used to remove suspended solids in digestate so that the nutrient and water can be recovered in the following downstream process.