CO 2 fixation capability of Chlorella sp. and its use in treating agricultural wastewater

Abstract

Palm oil mill effluent (POME) is a highly polluted agro-industrial wastewater. The CO 2 in industrial flue gas requires treatment before it can be discharged into the environment. Utilizing microalgae as the agent to treat wastewater and industrial flue gas is a waste-to-wealth approach. The resulting biomass can be commercialized in the form of valuable products. Chlorella sp. is a microalgal species that can tolerate the pollutant load and has been proven to be a suitable species for CO 2 fixation. In this study, Chlorella sp. was cultivated in POME with the aim of reducing the pollutants in the POME and simultaneously capturing CO 2 . The optimization of the operational conditions of this microalgae-based treatment system was carried out using the response surface methodology (RSM) face centered-central composite design (FC-CCD). Operational factors include the air concentration of CO 2 (10–25% v/v), the inlet gas flow rate of 500–2000 mL min −1 , and initial inoculum concentration (10–30% v/v) of Chlorella sp. cultivated in POME. The target deliverables include the maximum amount of CO 2 fixed by Chlorella sp. and the total nitrogen (TN) reduction as indicators of pollutant reduction by this treatment system. We found that a limited supply of CO 2 caused growth limitation, while excess CO 2 resulted in acid production that triggered microalgae growth inhibition. The optimum operational conditions were 10% v/v CO 2 , 1670 mL min −1 aeration rate, and 24.8% v/v inoculum concentration, predicted to simultaneously fix CO 2 at 0.12 g of CO 2 L −1  day −1 and reduce 80.9% TN, respectively.