Mogden Sludge Dewatering Works

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Over a period of many years liquid sludge was processed at Perry Oaks, both by air-drying and in latter years by deep lagoon storage prior to disposal to agricultural land.

Clearance of liquid sludge was accelerated during the 1990’s and temporary centrifuges were installed to mechanically dewater all sludge received from Mogden.

Decommissioning of the Perry Oaks site and setting up a residual operating area on a smaller part of the site has allowed the major area to be released for T5 development. Sludge dewatering operations continue on a small area of Perry Oaks until the new facilities at Iver South are complete.

This has meant that construction at Terminal 5 could be started on the remainder of the site and sludge processing can remain in operation during construction of replacement facilities at Iver South and before final decommissioning.

Relocation scheme The new works will comprise liquid sludge storage, sludge dewatering using centrifuge plant, and a large area for sludge cake storage.

Enabling works for the scheme are extensive. These include uprating and extending the existing twin sludge mains from Mogden to Iver South, transfer of Iver South STW flows, provision of a new access to the site, together with upgrade and extension to the sludge stream at Mogden to ensure compatibility with the facilities at Iver South.

One of the key initial tasks was the preparation of the Iver South site for development. This has included:

* improving access off the A4 with junction improvement and widening the existing service road;
* construction of a bridge over the Colnebrook river and extending the existing access road into the new site;
* diversion of all sewage flows to a new pumping station with pipelines to an adjacent catchment;
* new power and water supplies;
* isolation of surrounding groundwater and flood water usinga bentonite/cement cut-off wall;
* satisfying all planning conditions, technical, procedural andand environmental.