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Monday 22 December 2008Optimising discharges to save costs
Work is underway on Sizewell’s Direct Discharge of Effluent project, which aims to save £500k per year for the NDA through reductions to the site’s energy and maintenance costs.
The savings will come from the running of one remaining cooling water (CW) pump – still used to carry out authorised discharges to sea. The project team aims to install two much smaller pipes within an existing outfall tunnel which is situated off the coast at Sizewell – one for treated sewage, the other for active effluent.
The new system is designed to discharge under optimum conditions using tidal flow, allowing the power guzzling CW pump to be removed from service. The smaller pipes will also help prevent the build-up of effluent, allowing the site to comply with its discharge consent for fully treated sewage.
Alan Walker and Jeremy Sharp are managing the project, and contract firm Red 7 Marine has been brought in to provide specialist marine services.
“The installation of the pipe involves running a heave line through the tunnel, from the site to the outfall structure,” Alan says, “The idea is then to attach the new pipe to the heave line and pull it back to shore.”
It was intended that a Remote Operated Vehicle would deploy the heave line, however, when the line got tangled up, that operation was aborted. The team came up with an alternative solution involving a drogue parachute which was attached to the end of the heave line and the CW pump turned on. The flow of water successfully propelled the parachute through the tunnel where it could be safely secured at the other end.
The project is progressing well however, high winds and swell have made it difficult for the divers to get out to Sea when planned. Alan says: “We’ve had to play it by ear and take opportunities for diving when the weather allows, however, we did anticipate some delays when we were establishing the schedule, so our target date for completion hasn’t been affected.”
