July 21, 2022 by Mike Gardner

Assessing the impact of wastewater treatment works effluent on downstream water quality_II

Mike Gardner and three colleagues from the UKWIR Chemicals Investigation Programme (CIP) have recently published a paper – summarising river quality obtained by this nationwide monitoring programme over the last ten years. The paper is available under open access here.

This paper is based on long-term monitoring data of river water contaminant concentrations at over 600 sites in England and Wales. Samples were taken at approximately fortnightly intervals over two years at locations upstream and downstream of sewage effluent discharges. The changes in concentrations between the upstream and downstream sites are interpreted in the context of their statistical significance and in relation to riverine statutory water quality criteria. Results show that, contrary to what is often assumed, instances of poor compliance with riverine water quality standards tend to be associated with contamination at the river catchment scale rather that at a local level. This has implications for the selection of approaches to remedial action that are likely to be successful in achieving environmental goals.

An evaluation is also presented of the benefits of regulation of concentrations of trace metals in terms of the bioavailable fraction present in the river, rather than as total or dissolved concentration values.