Proceedings

Dŵr Cymru Welsh Water and our Capital  Alliance use both standard storm storage treatment options and our novel Rainscape approach of retro-fitting sustainable drainage in order to deal with significant flows to our networks following heavy rainfall.  This very high runoff can lead to frequently operating combined sewer overflows (CSO), flooding and significant flows arriving at our waste water treatment works (WWTW) that can continue for an extended period of time even after the rainfall ceases.  However in some instances these may not deliver the outcomes required (such as CSO spill reductions) in an cost effective manner.  Up until now passing all the flows forward for treatment has been technically infeasible because standard secondary treatment uses biological processes that do not cope with the amount of variation in flows in a combined sewer network during heavy rainfall.

The DCWW Alliance has been able to circumvent this issue in an affordable manner by identifying and collaboratively trialing new technologies to increase the hydraulic capacity of our WWTWs which are both new & innovative to the UK,.  This will allow us to exceed the current maximum treated flows (Peak flow equivalent treatment (PFET)) and enhance our treatment processes at two of our treatment works in order to reduce the  frequency with which their storm tanks at the will have to operate.  When combined with RainScape, conventional storage and smart network approaches this will  give DCWW the most cost effective and flexible solution for delivering our outcomes in those catchments.