Removal of COD and total nitrogen from palm oil mill effluent in flat-photobioreactor using immobilised microalgae Chlorella sp.

Abstract

Untreated palm oil mill effluent (POME) contains organic materials, tannin compounds and high in soluble solids that can damage the environment when discharged into inland waterways and cultivated lawns. Organic materials of the POME can be processed into an algae cultivation medium due to its mineral contents. In this study, Chlorella sp. was used to remove COD and total nitrogen in POME. Chlorella sp. has microscopic size, low specific gravity and, it is difficult to separate in wastewater. Chlorella sp. cells were trapped in the calcium alginate matrix to form a bead with a diameter of 3-4 mm. To obtain the highest removal efficiency of COD and the total nitrogen, different concentration of Na-alginate (4%, 6%, and 8%) were used to optimize the beads preparation at different contact times (1, 3, 5, and 7 days). Based on the results, the beads made from 8% Na-alginate concentration were able to eliminate, 11-62.46% total nitrogen efficiently, and 23-63.1% COD efficiently on the seventh day. This showed that higher Na-alginate concentration has higher removal efficiency.