Opportunities and Challenges of Microalgal Cultivation on Wastewater, with Special Focus on Palm Oil Mill Effluent and the Production of High Value Compounds

South East Asia dominates the production of palm oil worldwide. During the traditional wet processing, palm oil mill effluent (POME) wastewater is generated which poses serious environmental problems. Wastewater treatment using microalgae was initiated recently because of the advantages to lower nutrient content efficiently while the biomass can be utilized as bulk biomass or value added product. In the present review the utilization of wastewater for microalgal cultivation is discussed with particular attention to the feasibility of utilizing POME as microalgal growth medium. Whereas much recent research was focused on the production of bulk biomass, the potential for the production of value-added compounds has not often been addressed. Various strategies of obtaining high-value products are discussed. These include cultivation systems, algal species selection as well as and their growth strategies (autotrophic, heterotrophic, mixotrophic). In addition, potential problems associated with microalgal cultivation on POME will be evaluated. Finally, the concept of using stepwise strategies to obtain high value added product will be proposed.