Evaluation of domestic wastewater treatment using microalgal-bacterial processes: effect of CO2 addition on pathogen removal

Abstract

Microalgal-bacterial processes represent a sustainable and cost-effective biotechnology able to promote efficient wastewater treatment, including natural pathogen removal (disinfection), as well as being able to perform CO2 uptake and biogas upgrading. In this context, the influence of CO2 supply from a synthetic gas mixture (30% v/v CO2) on the removal of pathogens (Pseudomonas, enterococci, and Escherichia coli) and total coliforms during secondary domestic wastewater treatment by a microalgal-bacterial symbiosis in a 180-L high-rate algal pond (HRAP) was investigated. The supply of CO2 in the HRAP positively influenced the Pseudomonas aeruginosa removal, with the removal efficiency increasing from 97.4% (1.6 log) to 99.6% (2.5 log) without and with CO2 supply, respectively. Likewise, the total coliform removal efficiency rose from 88.7% (1.1 log) to 99.4% (2.8 log). On the other hand, the effect of CO2 supply on enterococci (99.7% and 2.6 log) and Escherichia coli (98.6% and 2.2 log) removal was negligible.