The contract involves demolishing the existing treatment works, which date from 1966, and building new treatment units, tanks, pumping stations and storage facilities in its place.
The first phase of the work, starting this month, is construction of temporary works to treat wastewater before all elements of the existing site are demolished. Once this is complete, estimated to be in mid 2015, work will then start on the construction of the new treatment plant.
The contracting joint venture operates under the name 4Delivery.
The project is expected to be complete in 2019.