What is the purpose of the Proposed Development?
The Proposed Development comprises the relocation of the Cambridge Waste Water Treatment Plant (WWTP) from its existing site on land adjoining the north eastern side of the city of Cambridge, to a new location. The relocation enables the delivery of South Cambridgeshire District and Cambridge City Councils’ Area Action Plan for a new low-carbon city district in North East Cambridge, which could create 8,350 homes and 15,000 jobs over the next 20 years.
The purpose of the proposed WWTP will be to treat all waste water and wet sludge from the Cambridge catchment, plus that from the proposed growth indicated in the Local Plan to 2041, with ability to expand beyond to deal with further growth, all within the footprint of the proposed new facility.
As part of its statutory function, Anglian Water operates the existing Cambridge WWTP. The existing Cambridge WWTP receives waste water from the Cambridge catchment either directly from the connected sewerage network or tankered to the plant from homes and businesses that are not connected. This waste water is then treated and the treated effluent discharged through an outfall to the nearby River Cam. The existing Cambridge WWTP is an integrated WWTP, as would be the Proposed Development. Integrated WWTP incorporate a sludge treatment function, in the form of a Sludge Treatment Centre (STC), which treats the sludge derived from the waste water from the catchment, and the “wet sludge” produced by other satellite plants which do not have integrated STC.
The Waterbeach new town development will comprise some 11,000 new homes along with associated business, retail, community and leisure uses when built out. Waste water from Waterbeach will be treated by the proposed WWTP once operational. However, the rate of development at Waterbeach New Town may require a new pipeline (rising main) to be built from Waterbeach to the existing Cambridge WWTP to allow treatment of waste water in advance of the proposed WWTP becoming operational. In that case, either a later connection would be made to the proposed WWTP from a point on the pipeline route, or flows diverted from the existing Cambridge WWTP via the transfer tunnel. The PEIR assumes a worst-case scenario of all Waterbeach waste water being transferred to the existing Cambridge WWTP and on to the proposed WWTP.
How has the proposed WWTP been sized?
The design capacity of the proposed WWTP will be approximately 548,000 population equivalent. The waste water treatment element (i.e. the Water Recycling Centre not including the STC) has an overall design capacity of 270,000 to 300,000 population equivalent. The STC will be designed to treat sludge produced at the proposed WWTP plus imported liquid sludges arriving by road. The STC is designed to treat a total amount of up to 16,000 Tonnes Dry Solids (TDS) per year for both indigenous and imported sludge.
There is flexibility and capacity within the operational footprint of the proposed WWTP to allow for future expansion ensuring the Proposed Development can accommodate growth to at least 2080. These elements are likely to be modular process tanks and units with associated equipment within the footprint of the operational WWTP and not require works to transfer infrastructure outside of this area. At present it is anticipated that impacts arising from a phased construction of these elements would fall within the realistic worst case scenarios assessed.