An Effective Two-Steps Polyacrylamide-Microalgae System for Flocculation and Bioremediation of Palm Oil Mill Effluent

Abstract

The use of microalgae for effluent treatment has been extensively studied in the past decade. Such system has a dual benefit of preventing pollutants from entering the waterbody while simultaneously produces valuable biomass. However, agricultural wastewater especially palm mill oil effluent (POME), contains a significant amount of suspended solids that may interfere with the growth process of the microalgae. The present study explored strategies to reduce POME turbidity for enhanced bioremediation efficiency. polyacrylamide (PAM) was used as pre-treatment of the POME prior to treatment using microalgae. The optimization result shows that PAM at concentration of 24 ppm able to reduce 46.5% of the turbidity. The pre-treated POME was then used for microalgae cultivation for subsequent nutrient removal. Improved condition of the POME has resulted in higher growth rate of three native microalgae, Chlorella Sorokiniana (UKM3), Chlamydomonas, sp. (UKM6) and Scenedesmus sp. (UKM9) with specific growth rate, μ of 0.29 day-1, 0.25 day−1 and 0.23 day-1 respectively. After 20 days of cultivation, more than 82.3% of biochemical oxygen demand (BOD) was successfully removed by UKM6. While highest chemical oxygen demand (COD) removal achieved was 56.7% by UKM9. The combined process also proved effective at removing 59.1%, 70.0% and 96.2% of TN, PO43− and NH3-N respectively. Therefore, the proposed two-stage treatment method could offer a promising alternative to conventional POME treatment technologies and increase the effectiveness of microalgae for bioremediation.