Friday 27 Sep 2019Ultraviolet Disinfection of Stormwater to achieve Bathing Waters Directive/Shellfish Waters Directive compliance

Josh Flower - Pell Frischmann

Harrison 170 14:30-15:30


The conventional approach to meeting bacteriological limits in designated Bathing waters/Shellfish waters has historically been to manage/limit spills from Combined Sewer Overflows (CSO's). Providing additional conventional treatment capacity at Sewage Treatment Works within a particular catchment is inherently inefficient as the works would be over-sized for the majority of inflow scenarios. The provision of storm storage has for many years been the cost effective method of reducing CSO spills and therefore meeting bacteriological limits. However, for some large urban coastal catchments (Such as Plymouth and Exeter) the storm storage (and associated pumping) required is prohibitively expensive. An alternative approach has been permitted by the Environment Agency to provide UV disinfection to CSO discharges. During this talk, I will discuss the broad strategic benefits of this approach and some of the challenges associated with the direct UV treatment of crude sewage.


Having graduated from the University of Exeter in 2015 with an MEng- Civil and Environmental Engineering, Josh started working as a Graduate Civil Engineer with Pell Frischmann. Within the 4 years he has worked at PF he has been involved with a wide variety of wastewater projects, primarily focusing on South West Water and Wessex Water non-infrastructure schemes with a 7 month secondment to Mumbai in part to assist with a nationally significant environmental project (Mithi River foul water interception).

The provision of UV disinfection on the settled storm discharge from Countess Wear STW in Exeter was the first project I managed and is being used by the Environment Agency as the pilot scheme to develop the national approach to permitting stormwater disinfection systems.

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