The development of the palm oil industry has induced the generation of palm oil mill effluent (POME) together with its waste activated sludge (WAS) in recent years. This study aims to discover new opportunities in treating POME WAS that has high organic content with low degradability but having potential in converting waste into energy. The optimized electrochemical oxidation (EO) of pre-treated WAS was applied prior to anaerobic digestion (AD) to improve the POME WAS digestibility (by assessing its solids minimization and biogas production) under mesophilic conditions at 30 ± 0.5 °C and solids retention time of 15 days. The enhancement in sludge minimization was verified, with 1.6-fold over the control at steady-state. Promising results were obtained with a total chemical oxygen demand (COD) removal of 68.8% with 11.47 mL CH4/g CODadded in pre-treat digester, compared with 37.1% and 3.9 mL CH4/g CODadded in control digester. It is also worth noting that the specific energy (SE) obtained for this EO pre-treated AD system is 2505 kJ/kg TS with about 94% increment in methane production. It is evident that this system was applicable on POME WAS in ameliorating solids minimization as well as enhancing biogas production.

Waste activated sludge (WAS) is formed by a diverse microorganisms, organic and inorganic compounds merged and mixed together in an extracellular polymeric substances (EPS) network. EPS is a complex high-molecular weight macromolecules in WAS that happens to be one of the common analysis to determine the efficiency of treatment. Therefore, different extraction methods has been applied in order to achieve better EPS extraction yield. This paper serves as a base to review the commonly used chemical extraction methods to extract EPS components. The mechanisms, conditions and efficiencies of each of the chemical extraction methods were discussed and compared accordingly. The possible use of different chemical extraction methods for different type of activated sludge were summarized.