Evaluation of synergy and bacterial regrowth in photocatalytic ozonation disinfection of municipal wastewater

• Published in: The Science of the total environment Vol. 601-602; pp. 626 - 635
• Main Authors: Mecha, Achisa C., Onyango, Maurice S., Ochieng, Aoyi, Momba, Maggy N.B.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.12.2017
• Subjects: Bacteria; Disinfection; Municipal wastewater; Photocatalytic ozonation; Titanium dioxide; Ultraviolet and solar light; Bacteria; Disinfection; Photocatalytic ozonation; Titanium dioxide; Municipal wastewater; Ultraviolet and solar light
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.05.204

The use of solar and ultraviolet titanium dioxide photocatalytic ozonation processes to inactivate waterborne pathogens (Escherichia coli, Salmonella species, Shigella species and Vibrio cholerae) in synthetic water and secondary municipal wastewater effluent is presented. The performance indicators were bacterial inactivation efficiency, post-disinfection regrowth and synergy effects (collaboration) between ozonation and photocatalysis (photocatalytic ozonation). Photocatalytic ozonation effectively inactivated the target bacteria and positive synergistic interactions were observed, leading to synergy indices (SI) of up to 1.86 indicating a performance much higher than that of ozonation and photocatalysis individually (SI≤1, no synergy; SI>1 shows synergy between the two processes). Furthermore, there was a substantial reduction in contact time required for complete bacterial inactivation by 50–75% compared to the individual unit processes of ozonation and photocatalysis. Moreover, no post-treatment bacterial regrowth after 24 and 48h in the dark was observed. Therefore, the combined processes overcame the limitations of the individual unit processes in terms of the suppression of bacterial reactivation and regrowth owing to the fact that bacterial cells were irreparably damaged. The treated wastewater satisfied the bacteriological requirements in treated wastewater for South Africa. [Display omitted] •Disinfection of synthetic and real municipal wastewater was studied.•Ozonation, photocatalysis and photocatalytic ozonation were used.•Synergy indices of up to 1.86 were obtained during photocatalytic ozonation.•Disinfection time was reduced by 50–75% using photocatalytic ozonation.•There was no bacterial regrowth after UV and solar photocatalytic ozonation.