Chlorella pyrenoidosa-mediated removal of pathogenic bacteria from municipal wastewater – Multivariate process optimization and application in the real sewage

Abstract

The use of microalgae for pathogen removal from wastewater has been recently brought to the limelight. However, the optimized conditions for microalgae-mediated pathogen removal (MAPR) have not been established yet. The present work is the first attempt to employ a multivariate optimization approach, the Taguchi method, for MAPR optimization. Interestingly, Chlorella pyrenoidosa demonstrated high Escherichia coli removal rates (90.1–99.9 %) from low, medium, and high-strength synthetic municipal wastewater. Process optimization revealed that 12,000 lux illumination and 37 °C were optimal conditions to achieve maximum E. coli removal from high-strength wastewater (600 mg L−1 biochemical oxygen demand). Results indicated that the interplay between C. pyrenoidosa and E. coli is most probably governed by photooxidation since increased illumination was associated with a 93 % reduction in the removal time. Furthermore, a substantial decline in the pathogen load (92 % decline in total bacteria count) was observed in real sewage through C. pyrenoidosa cultivation at optimized conditions. Additionally, 98 % Enterobacteriaceae removal and 96 % Salmonella sp. removal were also observed from real sewage in presence of C. pyrenoidosa. Hence, MAPR results demonstrated the robustness of C. pyrenoidosa for pathogen removal from wastewater. Overall, the present study established a set of optimized conditions that could be exploited for mechanistic investigation or scale-up studies for real-world applications.