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CO2 fixation capability of Chlorella sp. and its use in treating agricultural wastewater
- Hariz, Harizah Bajunaid, Takriff, Mohd Sobri, Ba-Abbad, Muneer M., Mohd Yasin, Nazlina Haiza, Mohd Hakim, Noor Irma Nazashida
- Journal of applied phycology 2018 v.30 no.6 pp. 3017-3027
- Chlorella, aeration, air, biomass, carbon dioxide, carbon dioxide fixation, flue gas, inoculum, microalgae, oil mill effluents, pollution control, pollution load, response surface methodology, total nitrogen, wastewater
- Palm oil mill effluent (POME) is a highly polluted agro-industrial wastewater. The CO₂ 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 CO₂ fixation. In this study, Chlorella sp. was cultivated in POME with the aim of reducing the pollutants in the POME and simultaneously capturing CO₂. 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 CO₂ (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 CO₂ 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 CO₂ caused growth limitation, while excess CO₂ resulted in acid production that triggered microalgae growth inhibition. The optimum operational conditions were 10% v/v CO₂, 1670 mL min⁻¹ aeration rate, and 24.8% v/v inoculum concentration, predicted to simultaneously fix CO₂ at 0.12 g of CO₂ L⁻¹ day⁻¹ and reduce 80.9% TN, respectively.