Combined sewer overflows: A critical review on best practice and innovative solutions to mitigate impacts on environment and human health

Abstract

Combined sewer overflows (CSOs) are of major environmental concern for impacted surface waterbodies. In the last decades, major storm events have become increasingly regular in some areas, and meteorological scenarios predict a further rise in their frequency. Consequently, control and treatment of CSOs with respect to best practice examples, innovative treatment solutions and management of sewer systems is an inevitable necessity. As a result, the number of publications concerning quality, quantity and type of treatments has recently increased. This review therefore aims to provide a critical overview on the effects, control and treatment of CSOs in terms of impact on the environment and public health, strict measures addressed by regulations, and the various treatment alternatives including natural and compact treatments.Drawing together the previous studies, an innovative treatment and control guideline is also proposed for the better management practices.

A review of combined sewer overflows as a source of wastewater-derived emerging contaminants in the environment and their management

“…However, capacity can be exceeded during periods of heavy rainfall or snowmelt. In such instances, a relief mechanism incorporated into the sewer system known as a CSO allows excess flows to be directed to a nearby watercourse without treatment (Botturi et al 2020) (Fig. 1).…”

“…A further option for the treatment of emerging contaminants in CSOs is by technological compact treatments (Botturi et al 2020). For example, Botturi et al (2020) describe the installation of a pilot scale modular system adopting rotating belt filtration, granular activated carbon (GAC) filtration and UV disinfection. Although such processes have been studied for the removal of emerging contaminants previously (e.g.…”

“…Therefore, the removal of suspended particulates prior to adsorption or chemical treatment of CSOs is needed. The belt filtration processes utilised by Botturi et al (2020) sieves CSOs through a 350 μm mesh prior to GAC and UV treatment. In another study, Jung et al (2015) investigated the adsorption of naproxen and paracetamol to activated biochar under synthetically prepared CSO wastewater.…”

“…Incomplete removal of emerging contaminants is observed during treatment by conventional WTPs as they were not designed for this purpose. A further notable source of emerging contaminants which has received comparatively less attention is combined sewer overflows (CSOs) (Phillips et al 2012;Munro et al 2019;Botturi et al 2020;Brunsch et al 2020;Mutzner et al 2020). In such systems, untreated wastewater can be released directly to the environment during periods of heavy rainfall.…”

The Impacts of Climate Change and Porous Pavements on Combined Sewer Overflows: A Case Study of the City of Buffalo, New York, USA

“…A very common type of sewer system in old urban areas is the combined sewer system (CSS), a network of pipes that collects both stormwater and wastewater and expels excess untreated water volumes into nearby water bodies. These discharges, known as combined sewer overflows (CSOs), transport washed-off atmospheric and urban surface pollutants along with the debris buildup in the CSS during dry weather periods and cause multiple adverse effects (e.g., WMO and GWP, 2008;Botturi et al, 2020).…”