Utilization of native Chlorella strain in laboratory-scale raceway reactor for synthetic wastewater treatment: A study in batch and continuous modes with multi-substrate modeling

Abstract

Despite of the possibility to include microalgae in civil wastewater treatment process, the practice is still not common due to the lack of available instruments to implement it. In this study, a straightforward comprehensive approach for dealing with microalgal wastewater treatment involving an original kinetic model is proposed. A first set of batch cultures of a native strain of Chlorella was firstly carried out to obtain the kinetic parameters: maximum growth factor (μmax) and half-saturation constant (Ks), for each limiting nutrient. Maximum growth factor values of 0.0279 for PO43−, 0.0319 h−1 for NH4+, 0.0352 h−1 for glucose, and 0.0263 h−1 for the overall medium were found. Regarding the Ks, values of 1.08 mg L−1, 27.70 mg L−1, 1.34 mg L−1, were found for PO43−, NH4+ and glucose respectively, and a value of 2.8 % of the total nutrients for the overall medium. These parameters were used to set a multi-substrate kinetic model able to predict the growth in batch and in continuous operation within a laboratory scale raceway reactor. The removal capabilities of the microalgae for each addressed pollutant were evaluated in a batch system and in a continuous system at dilution rates of 0.0025, 0.005, 0.01 and 0.015 h−1. This comprehensive approach represents a significant step towards addressing the continuous treatment of wastewater utilizing microalgae.