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

Bruce Petrie

doi:10.1007/s11356-021-14103-1

Abstract

Emerging contaminants such as pharmaceuticals, illicit drugs and personal care products can be released to the environment in untreated wastewater/stormwater mixtures following storm events. The frequency and intensity of combined sewer overflows (CSOs) has increased in some areas due to increasing urbanisation and climate change. Therefore, this review provides an up-to-date overview on CSOs as an environmental source of emerging contaminants. Other than compounds with high removal, those chiral species subject to enantioselective changes (i.e. degradation or inversion) during wastewater treatment can be effective markers of CSO discharge in the environment. A proposed framework for the selection of emerging contaminants as markers of CSOs is outlined. Studies have demonstrated that CSOs can be the main source of emerging contaminants with high removal efficiency during wastewater treatment (e.g. > 90%). However, the impact of CSOs on the environment is location specific and requires decision-making on their appropriate management at catchment level. This process would be aided by further studies on CSOs which incorporate the monitoring of emerging contaminants and their effects in the environment with those more routinely monitored pollutants (e.g. pathogens and priority substances). Mitigation and treatment strategies for emerging contaminants in CSOs are also discussed.

Highlights

Wastewater-derived emerging contaminants such as over-thecounter and prescription pharmaceuticals, illicit drugs, personal care product ingredients and food-related compounds are ubiquitous in surface waters globally (Ellis 2006; Zuccato et al 2008; Lange et al 2012; Hughes et al 2013)
An additional concern is the presence of emerging contaminants as complex mixtures in the environment which could result in synergistic effects (Schnell et al 2009)
Considerable toxicity was observed for a mixture of nonsteroidal anti-inflammatory drugs (NSAIDs) at the same concentration where little effect was observed for the compounds individually (Cleuvers 2004)

Summary

Introduction

Wastewater-derived emerging contaminants such as over-thecounter and prescription pharmaceuticals, illicit drugs, personal care product ingredients and food-related compounds are ubiquitous in surface waters globally (Ellis 2006; Zuccato et al 2008; Lange et al 2012; Hughes et al 2013). 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. At a WTP in Stuttgart, Germany, the variability of the mean emerging contaminant concentration across seven CSO events was about one order of magnitude (Launay et al 2016). They accounted for 40–90% of released emerging contaminant loads with > 90% WTP removal (Phillips et al 2012) (Table 2). Chèvre et al (2013) noted that the concentrations of some compounds to be exceeded in the contribution of CSOs alone can result in predicted-no-effect- environment

Findings

Monthly over

Conclusion