A Critical Study on Development of Nature-Based Sustainable Passive Technologies for Treating and Disinfecting Municipal Wastewater

In this era, disinfection and efficient effluent treatment are of critical importance. In this study, various types of constructed wetlands (CWs) followed by the biological slow sand filter (BSSF) were used on a larger scale than in the lab to treat and disinfect real municipal wastewater efficiently. As secondary wastewater treatment technologies, CWs with gravels (CW-G), free water surface (FWS-CWs), and CWs integrated microbial fuel cell (MFC) with granular graphite (CW-MFC-GG) were planted with Canna indica. In addition, tertiary treatment technology, BSSF for disinfection, was implemented. The combination of CW-MFC-GG-BSSF achieved the highest total coliform removal with a final concentration of 172 CFU/100 mL and 68.26% removal, whereas CW-G-BSSF and CW-MFC-GG-BSSF removed faecal coliform to an effluent concentration of 0 CFU/100 mL. In addition, faecal coliform E. coli was not detected in CW-G-BSSF and CW-MFC-GG-BSSF. In terms of treatment performance, CW-G-BSSF and CW-MFC-GG-BSSF attained low effluent COD concentrations in mg/L, respectively, with influent COD of 61.63 8.56 mg/L, as well as phosphate concentrations of 0.42 0.02 mg/L and 0.68 0.06 mg/L with influent phosphate concentration of 3. Consequently, the final effluent from both CW-G-BSSF and CW-MFC-GG-BSSF satisfies the discharge standards established by the Indian regulatory authority for both treatment and disinfection. CW-MFC-GG also demonstrated a power density of 85.71 mA/m3 and a current density of 25.71 mW/m3 in 48 hours at an internal resistance of 700. Therefore, CW-G and CW-MFC-GG followed by BSSF could be a promising approach for improved disinfection and wastewater treatment.