Culture of four microalgal strains for bioenergy production and nutrient removal in the meliorative municipal wastewater

Abstract

ABSTRACTMicroalgae have been considered as the most promising sources of alternative bioenergy. For the purpose of saving costs, the present work focused on the potential use of microalgae in the meliorative municipal wastewater, which contains 90% municipal wastewater and 10% dairy wash wastewater. Four microalgal species, Palmellococcus miniatus, Neochloris oleoabundans, Scenedesmus quadricanda #507, and Chlorella zofingiensis, were cultured in pure municipal wastewater and meliorative municipal wastewater, respectively, for 5 days. Their biomass accumulation and removal rates of nitrogen and phosphate were measured. Results showed that the growth rates of Neochloris oleoabundans, Palmellococcus miniatus, and Chlorella zofingiensis in meliorative municipal wastewater (>0.8 g·L–1·d–1) were significantly higher than that in municipal wastewater (2.6 g·L–1·d–1), while there was no significant difference between the growth rates of Scenedesmus quadricanda #507 in meliorative municipal wastewater and in municipal wastewater. Neochloris oleoabundans exhibited the highest growth rate (0.86 g·L–1·d–1) and relatively high nutrient removal capacity. Scenedesmus quadricanda #507 had the highest P removal rate of over 94%. The four species have a similar N removal rate at about 90%. The results showed that the highest average removal rate of N and P were about 23.1 mg·L–1·d–1 and 7.1 mg·L–1·d–1. Furthermore, the content of lipid or carbohydrates increased and a different profile of fatty acids were found compared to those in municipal wastewater. Cellular components changes of microalgae in meliorative municipal wastewater were favorable as raw materials for bioethanol and biodiesel production. Cultivation with meliorative municipal wastewater is a win-win culture mode that facilitates the biomass production, lipid and carbohydrate accumulation, and wastewater purification.