Proceedings

To date, sewage treatment works (STW) have been permitted on the concentration of phosphorus in final effluent at individual sites, rather than the overall load of phosphorus entering a watercourse. With the Environment Agency’s agreement, Wessex Water devised an alternative catchment-wide approach. For this trial, 24 STWs in the Bristol Avon catchment have been included in a catchmentwide permit. Each STW has been assigned a ‘stretch target’ for phosphorus load reduction expressed in tonnes per year with an annual reduction target of 46.6 tonnes for the whole catchment (this is in addition to existing load reductions). Investment under this trial is £20M lower than the traditional approach (capital investment at all sites). Without catchment permitting, there would have been significantly less phosphorus removal in the catchment during 2015-20. A three year monitoring period started in January 2017 to provide data on the impact of carrying out improvement work under this regime. The results and observations of the first six months will be presented.