Combined sewer overflow treatment: Assessing chemical pre-treatment and microsieve-based filtration in enhancing the performance of UV disinfection

Tiziana Venditto; Kyriakos Manoli; Ajay K Ray; Siva Sarathy

doi:10.1016/j.scitotenv.2021.150725

Combined sewer overflow treatment: Assessing chemical pre-treatment and microsieve-based filtration in enhancing the performance of UV disinfection

Sci Total Environ. 2022 Feb 10;807(Pt 1):150725. doi: 10.1016/j.scitotenv.2021.150725. Epub 2021 Oct 5.

Authors

Tiziana Venditto¹, Kyriakos Manoli², Ajay K Ray³, Siva Sarathy⁴

Affiliations

¹ Department of Chemical and Biochemical Engineering, University of Western Ontario, London, ON N6A 5B9, Canada. Electronic address: tvenditt@uwo.ca.
² Nireas-International Water Research Center and Department of Civil and Environmental Engineering, University of Cyprus, P.O. Box 20537, CY-1678 Nicosia, Cyprus.
³ Department of Chemical and Biochemical Engineering, University of Western Ontario, London, ON N6A 5B9, Canada.
⁴ Department of Chemical and Biochemical Engineering, University of Western Ontario, London, ON N6A 5B9, Canada; Trojan Technologies, London, ON N5V4T7, Canada.

PMID: 34624287
DOI: 10.1016/j.scitotenv.2021.150725

Abstract

Disinfection of combined sewer overflow (CSO) is necessary to reduce the amount of microorganisms discharged into surface waters. In this study, an efficient and cost-competitive treatment for CSO, employing UV disinfection, was developed. High suspended solids content in CSO poses a significant challenge for UV disinfection so laboratory experiments were carried out to asses the effect of chemical pre-treatment followed by micro-sieve filtration on the reduction of total suspended solids (TSS) and the increase of UV transmittance (UVT). The efficiency of UV, with and without pre-treatment, was investigated and a microbial inactivation model was developed to describe the fecal coliforms (FC) inactivation kinetics. Finally, the environmental impacts of the proposed treatment were simulated at the large-scale by stormwater management model (SWMM), and the cost of the proposed treatment train was evaluated and compared with current CSO treatment strategies. Experimental results showed that UV alone achieved 3.6-log reduction of FC at a UV fluence of 80 mJ/cm², while a 4-log reduction of FC was achieved at a much lower UV fluence of 10 mJ/cm², when the UV disinfection was preceded by chemical pre-treatment and microsieving filtration using a 32 μm mesh. Under these conditions, the TSS removal achieved was 73%, and the UVT increased from 14% to 32%.The SWMM showed that the proposed CSO treatment achieved a reduction in TSS by one order of magnitude and a decrease in number of FC from 1.05 × 10¹⁴ to 1.24 × 10¹⁰ CFU. The cost analysis performed herein suggests that the proposed treatment train is competitive to current CSO treatment strategies in terms of cost-effectiveness. The study demonstrates the potential of the innovative CSO treatment scheme to quickly and effectively treat a large amount of wastewater flow thus providing municipalities with a low footprint treatment unit for CSO.

Keywords: Combined sewer overflow; Filtration; Inactivation kinetic model; Stormwater management model; UV disinfection.

MeSH terms

Cities
Disinfection*
Filtration
Kinetics
Sewage
Wastewater*

Substances

Sewage
Waste Water