Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | OCTOBER 2016 | 17 Project focus Wastewater Treatment Catchment permitting for Wessex spells flexible approach Project focus ● Wessex Water and EA develop catchment permit approach for phosphorus ● 24 treatment sites in Bristol Avon catchment included ● Improvement work under new permits set to start in January 2017 A n innovative approach to the regulation of phosphorus developed by the Environment Agency and Wessex Water is about to be put into action in the Bristol Avon catchment. The system of catchment permitting – which sees multiple sewage treatment works subject to collective phosphorus reduction targets - has been formulated over the last two years since the principle of the approach was included in Wessex Water's business plan for AMP6. Improvement work under the new permits will get underway in January 2017 and be monitored closely over the subsequent three years. Only a quarter of the Bristol Avon catchment – which covers the area east and south of Bristol and includes Royal Wootton Bassett, Chippenham, Bath and Frome – is currently classified as having good ecological status under the Water Framework Directive. Phosphorus in the watercourse is one of the key reasons for this, with discharges from sewage treatment works being a significant contributor. However, with Wessex Water having 66 sewage treatment works in the catchment and its larger sites already achieving good limits of 2mg/l P or lower, it became clear that capital investment at many further sites was difficult to justify on cost-benefit grounds. "We have been in dialogue with the agency about this for several years – well before PR14 – ever since it became clear that the costs Only a quarter of the Bristol Avon catchment has good ecological status under the WFD James Brockett EDITOR WATER & WASTEWATER TREATMENT ● Phosphorus is the leading issue for compliance to the Water Framework Directive (WFD) to which water companies are a significant contributor ● capex solutions, typically ferric dosing, are expensive and also entail high running costs, so are not economic when applied to multiple smaller sites ● opex interventions, such as optimising existing processes, can achieve results but involve more risk so require a flexible approach • Drivers