Efficiency evaluation of solar photolysis and solar photocatalysis processes used for the wastewater disinfection

ABSTRACT

The wastewater reuse, especially for irrigation, requires a safer microbial quality. However, the tertiary treatment is often nonexistent, especially in developing countries where, unfortunately, wastewater treatment needs to be more systematic. Solar water disinfection processes could be appropriate treatments for improving the microbial quality of the wastewater reuse. This study evaluates the effectiveness of both solar photolysis and solar photocatalysis processes in disinfecting secondary-treated wastewater recovered from an activated sludge wastewater treatment plant where the disinfection treatment is not applied. The best parameters of the solar disinfection processes were determined. The experiments were conducted in a bench test composed of 4 flat-bottom flasks with a volume of 2 L each. Then, the disinfection efficiency of both processes was evaluated by a comparative study where 250 Wh/m² of UV radiation was cumulated. The disinfection efficiency of studied pathogenic (1) total coliforms, (2) fecal coliforms, (3) streptococci, (4) staphylococci, (5) sulfite-reducing spores, and (6) fungi ranged from 0.86-Log to 3.35-Log reduction. At last, an innovative static plan photoreactor of 50 L allowed reproducing the positive effect of the solar wastewater disinfection. After 8 h of solar exposure duration and a cumulative UV radiation of 360 Wh/m², results showed a complete disinfection of all studied pathogenic below the limit detection of the microbial analysis, except of sulfate-reducing spores.

Keywords:

• Secondary-treated wastewater
• Photolysis
• SODIS
• Photocatalysis
• Photoreactors
• Solar disinfection efficiency

Acknowledgments

This study was supported by the Solar Equipment Development Unit (UDES) and the National Sanitation Office (ONA). The authors wish to thank Mr Toufik Medjiah from the Tipasa wastewater treatment plant also Mrs Sarah Djelti, Miss Sarah Mahidine and Mr M-L Yousfi from the Development Unit of Solar Equipments.