Effect of wastewater-borne bacteria on algal growth and nutrients removal in wastewater-based algae cultivation system

•Municipal wastewater-based algae cultivation system was used in this study.•Mutual compound relationship between algae and centrate-borne bacteria was found.•Low initial algal concentration was more favorable for bacterial growth.•The initial algal inoculum of 0.1g/L was optimal to obtain maximal algal biomass.•There was a synergistic effect of algae and bacteria for nutrition removal. Centrate, a type of nutrient-rich municipal wastewater was used to determine the effect of wastewater-borne bacteria on algal growth and nutrients removal efficiency in this study. The characteristics of algal and bacterial growth profiles, wastewater nutrient removal and effect of initial algal inoculums were systematically examined. The results showed that initial algal concentration had apparent effect on bacterial growth, and the presence of bacteria had a significant influence on algal growth pattern, suggesting symbiotic relationship between algae and bacteria at the initial stage of algae cultivation. The maximum algal biomass of 2.01g/L with 0.1g/L initial algal inoculums concentration can be obtained during algae cultivation in raw centrate medium. The synergistic effect of centrate-borne bacteria and microalgae on algae growth and nutrient removal performance at initial fast growth stage has great potential to be applied to pilot-scale wastewater-based algae wastewater system cultivated in continuous or semi-continuous mode.