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A salty tale

Viewpoint - Giving the green light to Britain's rst desalination plant was a good decision but also a missed opportunity.

Last week's granting of planning permission for the proposed new Beckton desalination plant has been greeted with relief not just by the water resource planners at Thames Water Utilities but by many in the water industry.

This decision sends an important signal that the government recognises that demand side efciency measures - that it is rightly pressing the industry to drive through - will be insufficient on their own to meet the supply/ demand de it we face. Major new water resource schemes such as the Beckton Desalination scheme are going to be a fact of life, particularly in the waterscarce south east.

A much debated issue at the public inquiry was whether an ef uent reuse solution could be a viable alternative to the desalination plant. This debate has been raging globally in water-starved areas as resource planners look to exploit sea water desalination and/or effluent reuse.

Swaying the choice at Beckton was the fact that it's a brackish water desalination plant, not a sea water plant. This allowed Thames Water to take advantage of the low salinity estuarine waters to operate reverse osmosis process at pressures not significantly higher than the pressures required to purify efuent reuse using reverse osmosis. The osmostic pressures required for the brackish Beckton source waters are less than a third of the pressures for a sea water desalination plant.

However, the inquiry inspector criticised the planning application for missing the opportunity to develop a simultaneous twin track evaluation of desalination with effluent reuse.

A dual approach would have addressed some of the key issues needing resolving relating to ef uent reuse. Uppermost among these issues is the public perception problem. The 'yuck' factor is seen as a major risk to the implementation of an efuent reuse scheme.

Water companies need to frame reuse schemes in realistic time frames and scope projects to comply within a public health and regulatory framework that currently does not exist. Without these boundaries water companies will continue to place unnecessary time and cost risks to effluent reuse solutions despite the fact that they offer a more sustainable solution. This was a missed opportunity.

To address the sustainability concern, Thames Water felt compelled to offer a revised agreement to operate the desalination plant from 100% renewable energy rather than 10% as offered in the original planning submission. Thames Water proposes to convert a recently decommissioned gas turbine plant to operate on bio-diesel fuel. Use of the bio-diesel is estimated to reduce the carbon footprint in operation by around two thirds.

This trend to offset the high carbon footprint of power-hungry desalination schemes by offering renewable energies looks likely to continue.

Looking ahead I hope that some of the novel tidal and wave generators will offer yet more carbon-efcient solutions.

I hope this decision will give Water utility resource planners the con dence to promote desalination and reuse schemes for inclusion in their water resource plans when they are completed later this year.

David Eddy is global water manager at consultant MWH.

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