Assessing the environmental and economic efficacy of two integrated constructed wetlands at mitigating eutrophication risk from sewage effluent

Richard J Cooper,Terry Thomas,Elizabeth Hawkins,Jonah Tosney,Jake Locke

doi:10.1111/wej.12605

Richard J Cooper, Terry Thomas + Show 3 more

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https://doi.org/10.1111/wej.12605

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Abstract

AbstractThe nutrient removal efficiency of two integrated constructed wetlands (ICWs) installed at commercial wastewater treatment plants (WWTPs) in Norfolk, UK, is assessed – the River Ingol ICW (1 year old) and the River Mun ICW (5 years old). Analysing water samples collected across the ICWs between February and September 2019, significant reductions in both effluent nutrient concentration and load were recorded. At the River Mun ICW, mean nitrate and phosphate concentrations were reduced by ~63% across the wetland, whilst nutrient loadings were reduced by ~57%. At the River Ingol ICW, mean nitrate and phosphate concentrations were reduced by ~30%, whilst nutrient loadings were reduced by ~70%. Economically, the total capital cost of both ICWs was comparable at £31‐39 per person served. Overall, this study demonstrates ICWs can significantly reduce the eutrophication risk associated with WWTP discharges and can do so whilst providing a cost‐effective alternative to conventional tertiary wastewater treatment.

Highlights

Nutrient enriched sewage effluent discharged from wastewater treatment plants (WWTPs) is a major global driver of freshwater eutrophication (Neal et al, 2005; Jarvie et al, 2006; Bowes et al, 2012; Roberts and Cooper, 2018)
3.1 Nitrogen Dynamics At the River Mun integrated constructed wetlands (ICWs), mean nitrate concentrations were significantly (p
The reduced nutrient removal efficiency relative to the River Mun ICW can be explained by the lack of well-developed plant-microbial interactions within the wetland during the first full growing season (Kayranli et al, 2010b; Ceschin et al, 2019), with macrophyte surface coverage ranging from ~50% in cell 1 to

Summary

Introduction

Nutrient enriched sewage effluent discharged from wastewater treatment plants (WWTPs) is a major global driver of freshwater eutrophication (Neal et al, 2005; Jarvie et al, 2006; Bowes et al, 2012; Roberts and Cooper, 2018). Whilst tertiary treatment can be highly effective, the technology can be expensive and its application is generally limited to larger WWTPs discharging into more environmentally sensitive waterbodies (Sedlak, 2018). In this regard, integrated constructed wetlands (ICWs) have the potential to provide an alternative, cost-effective, natural treatment for sewage effluent (Babatunde et al, 2008; Kayranli et al, 2010a; Chang et al, 2012). With the additional aim of enhancing biodiversity and ‘integrating’ into the local environment, ICWs are designed to be environmentally sustainable, robust and largely self-managing, making them a cost-effective pollution mitigation option (Scholz et al, 2007a)

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