Retrofit self-cleansing screens enable three Storm King® hydrodynamic vortex separators to meet the 6 mm in two direction screening requirement. 

Situation

At Dalgety Bay, just north of Edinburgh in Scotland, storm flows in excess of the sewer capacity are diverted to three Storm King® overflow hydrodynamic vortex separators for treatment prior to discharge to the Firth of Forth. 

These hydrodynamic vortex separators remove floatables, Total Suspended Solids (TSS), BOD and other materials, preventing them from reaching the environment.

Problem

The Scottish Environment Protection Agency (SEPA) set a new standard that requires screening with a 6 mm screen in two directions. The three Storm King®  units had been designed to meet the previous performance specification, equivalent to that provided by a 12 mm bar screen, so the overflows needed improvement to meet the new requirement.

Solution

SEPA engaged Waterway Consultancy, who reviewed a number of solutions and determined that the best solution would be to retrofit an improvement to the existing system. The consultancy and Hydro International were able to come up with a retrofit solution for three self-cleansing screens.  

Outcome

The retrofit of the three self-cleansing screens only required the three existing Storm King® overflows to undergo minor construction modifications, keeping costs and disruption to a minimum.   

The self-cleansing screens meet the new standard of 6 mm in two direction screening required, in addition to the removal of sediments and associated BOD provided by the Storm King® hydrodynamic vortex separators.

The selection of new, higher specification self-cleansing screens meant that we were able to retrofit at minimum cost and without a lot of work or disruption," said Brian Sutherland of Waterway Consultancy. "The existing Storm King® chambers only required minor construction modifications, which was of great benefit to the client.