The Flag Fen effluent recycling plant was commissioned in 2000 to treat sewage works final effluent through microfiltration and reverse osmosis, providing high purity de-min plant feedwater to the nearby Peterborough Power Station.
Until late 2000 the Centrica-owned Peterborough gas turbine power station used mains water in its demineralisation plant for boiler-feed water production. Although this is a widely used process, there are significant financial and environmental costs associated with the use of mains water for this purpose and the chemical regeneration of de-min resins, rinse water, waste chemical and wastewater disposal.
Alpheus approached the power station with a proposal to supply high purity water via an innovative membrane process, utilising sewage works final effluent as its raw water source.
Following successful site trials, a 10-year build, own and operate (BOO) contract was signed for the Flag Fen Water Reuse Plant.
Replacing the previous mains water supply, the water significantly improved the performance of the de-min plant and purity of steam generation, whilst reducing chemical, power and effluent discharge costs.
The recycling plant takes up to 1,600m3/d of the sewage works final effluent (approximately 2% of the total flow) for a nominal charge and, after treatment, up to 1200m3/d of high purity water is pumped 1.5km to the power station's water storage tank.
Wastewater from the recycling plant is discharged back to the sewage treatment works inlet at a commercial trade effluent charge rate, although the reverse osmosis concentrate is directed to the sewage works final effluent outlet channel to the River Nene.
At the time of commissioning, the plant was one of only two membrane effluent recycling plants in the world.
The water quality supplied to the power station has provided improved and more predictable plant performance. Significant savings have been achieved in the de-min plant operating costs and chemical waste disposal costs.
Health and safety benefits have also been achieved by reducing the handling of highly corrosive chemicals and traffic on site. Environmental and social benefits include a major reduction in the use of mains water, fewer chemicals discharged to the sewer and less heavy goods traffic to and from the site.