An innovative use of UV technology to achieve Bathing Water Compliance

The Cog Moors Wastewater Treatment Works (WwTW) is located to the West of Cardiff in the Barry catchment and is an activated sludge plant serving a 208,000PE across a large geographical catchment including the West of Cardiff. In order to meet compliance with the directive and as key part of the overall catchment solution the first UV plant in the UK designed to treat storm flows has been installed and commissioned at the works before the 2009 bathing season. The innovative use of this technology has resulted in significant whole life costs and sustainability savings over the traditional approach.
Cog Moors WwTW Storm UV Treatment

It comprises an inlet works with flows subjected to two dimensional 6mm equivalent screening and storm overflow via 10 no rectangular storage settlement tanks (total

16800m 3).
The flows discharged from the storm tanks gravitate to the combined final effluent (FE)/storm pumping station. The flow to treatment then passes through grit removal and then to the primary settlement stage. The settled sewage is then pumped forward to the secondary treatment process which comprises an activated sludge plant followed by final settlement. The treated Effluent then gravitates to the combined Final Effluent / Storm pumping station where it is discharged to sea via a long sea outfall.
The storm UV plant at Cog Moors is designed to treat all storm flows up to 2.38m3/s that are discharged after the filling of the storm tanks during the bathing season. The storm flows then gravitate from the discharge weirs at the end of the storm tanks and flows are diverted into the UV plant, by breaking into the existing storm return flume, before returning flows downstream where it continues to the pumping station for discharge via the long sea outfall.
The Team
As part of the Dwr Cymru Asset Management Alliance (AMA) the South East Team (SET) which comprises of Dwr Cymru Welsh Water and its strategic construction partners, Imtech Process Ltd and Morgan Est together with cost consultants Chandler KBS and EC Harris are responsible for the design and construction of a £190 million investment programme to resolve unsatisfactory combined sewer overflows (uCSO’s), key flooding and growth issues during Asset Management Plan 4 (AMP4) during the period 2005-2010. As part of the Amp 4 delivery, under the Bathing Water directive, there are drivers on compliance at the EU designated bathing waters at Barry (Jackson Bay, Whitmore Bay and Cold Knap).
The storm UV system is the first commercially successful, medium-pressure UV lamp system that is specifically designed for handling high volume and low quality wastewater and incorporates an automatic chemical / mechanical cleaning technology.
Carbon Footprint and Economic Analysis
The use of UV disinfection on continuous discharges has resulted in a perception that all UV disinfection systems consume large amounts of energy and therefore, have high associated operating costs and are not ‘green’. They were also considered difficult to maintain and operate. However these perceptions are not necessarily applicable when using UV to disinfect intermittent discharges. In order to deal with these perceptions a Carbon Footprint and Economic analysis comparison of storm water treatment options at Cog Moors WWTW was carried out.

All information on this page is published and owned by and is used with courtesy. All images used on this page Courtesy of Dŵr Cymru Welsh Water.