Microalgae-based bioremediation of wastewaters - Influencing parameters and mathematical growth modelling

Microalgae have been increasingly recognized as relevant for bioremediation purposes, particularly for wastewater polishing. The implementation of microalgae systems requires efforts on the development of strategies to achieve a cost-effective process. Kinetic models are essential to understand microalgae growth, and for a large-scale implementation and operation under the desired standards. This work aims to assess the influence of wastewater composition, and selected external factors (temperature and photoperiod) on Chlorella vulgaris growth and bioremediation ability. Kinetic models (Monod, Schnute, Logistic, Richards and Gompertz) were used and critically compared to describe the microalga growth under the different operating conditions. The concentration of nitrate was found to be critical for growth under a controlled pH, regardless the presence of micronutrients. A mixotrophic growth, even under low concentrations of glucose, allowed C. vulgaris to be more resilient to variations in temperature and photoperiod, without affecting the bioremediation effectiveness. The microalga shown a low growth ability in acidic wastewaters with ammonium as a nitrogen source. The Monod, Logistic and Gompertz models perfectly fitted the microalga growth. Final results provide a set of conditions and associated kinetic parameters of relevance for C. vulgaris bioremediation as well as highlights the role of the microalga for wastewater polishing.