Yorkshire Water awards £4m nitrate removal contract

Skipton, UK  - Yorkshire Water has awarded a Nitrate Removal Scheme contract in excess of £4 million to North Yorkshire-based civil engineering company, Mott MacDonald Bentley (MMB) - a joint venture between JN Bentley and Mott MacDonald.

Following a tender process MMB has appointed Skipton-based ACWA Services as M&E subcontractor to design, supply, install and commission its Nitreat technology for the removal of nitrate from drinking water. The plant, which is to be installed at Yorkshire Water’s Keldgate WTW is due for commissioning by the end of 2009 and will be the largest of its kind in the UK water industry.

The Keldgate WTW, which draws groundwater from natural borehole supplies, is located in a rural farming area which is identified as one of Defra’s Nitrate Vulnerable Zones. Tests have indicated that the level of nitrate in the water supply has been increasing steadily for some time and whilst current levels are acceptable, without intervention, by 2025 it could reach levels of 63mg/litre - much higher than the Prescribed Concentration Value (PVC) of 50mg/litre

Under the contract, MMB is to ensure that the main civil engineering part of the contract, which includes groundworks, buildings and access roads, is constructed to a design that is environmentally sympathetic to Keldgate’s rural surroundings.

According to Peter Ripley, managing director of ACWA Services, the company’s nitrate removal systems are already operating successfully in the Thames Water and Anglian Water regions. In addition to removing nitrates, these installations also provide a number of operational advantages.

“The system makes more effective use of resin, provides low levels of waste and eliminates process downtime for regeneration, whilst maintaining consistent effluent characteristics. Site performance tests have proved the effectiveness of the system to produce waste volumes of less than 0.5% of total works output, which is a significant advantage of the process design,” said Ripley.

The counter-current Nitreat ion exchange system is claimed to be an improvement on conventional ‘batch’ systems, as exhausted ion resin is continuously taken off-line, backwashed, regenerated, rinsed and returned to absorption, with all phases of the cycle occurring concurrently.

The works capacity at Keldgate is 90 million litres per day and the design will allow up to 33 million litres of it to pass through the nitrate removal system. After reducing nitrate levels to fewer than five parts per million, the treated water will be blended back into the main flow to produce water for public consumption at 42mg/litre – well within the limits for drinking water quality and future proofing the system against anticipated rises in nitrate levels.

With lower volumes of waste, lower power consumption and the demonstrated ability to provide more consistent high quality treated water, the ACWA process will satisfy MMB’s environmental and quality considerations and through value engineering carried out on previous projects, will provide the optimum and most cost-effective solution for Yorkshire Water.