As a result of population growth and environmental regulations our client had to increase the sewage treatment capacity at the Sewage Treatment Works in Chipping Norton.

The existing sludge treatment capacity was 46l/s and the project sought to increase this to 73l/s by (amongst other things) increasing the capacity of the inlet screens.

The inlet works on site is connected from 3 separate mains that outfall to a flow distribution chamber to manage the flows through the screens.

The contract was procured using the Thames Water Geographic Framework and the Primary supplier was selected to submit a proposal.

Due to the increase in flows required to be screened the Contractor initially proposed to replace the two existing ROTAMAT screens with three new escalator screens. This arrangement needed significant civils work to enable the new screens to be integrated into the works and did not benchmark well alongside similar schemes.

Through the benchmarking exercise we were able to identify that the major factor driving the need to increase treatment capacity was storm water flows to the works. After reviewing the requirements with the client we were able to establish that it would be acceptable for the storm flows to bypass the inlet screens reducing the scope and significantly reducing the costs of construction.