November 2007

Award for Nitreat™, innovative nitrate removal technology

At the end of October 2007, Mike Smith, Executive Contracts Director at ACWA Services Limited, together with colleagues from Anglian Water Plc, Biwater Treatment Ltd and Puritech Ltd received an award from the Institute of Chemical Engineers in recognition of the successful application of 'NITREAT™' - a novel form of ion exchange for the removal of nitrate from drinking water.

The prestigious IChemE Awards annually encourage, celebrate and reward innovation and excellence. The Awards recognise and promote organisations that make an outstanding contribution to safety, the environment, sustainable development and other aspects of the chemical and bioprocess industries.

The EU limits the nitrate content of drinking water to 50mg/l to avoid blue baby syndrome.

Anglian Water Services identified 14 water supplies at risk of developing concentrations of nitrate in excess of 50mg/l. Anglian's Innovation and Supply Chain departments assessed available treatment options against a number of performance requirements:

• Efficient use of water resource, including minimisation and disposal of any waste stream produced and impact on the environment.
• Value for money: Business benefits regarding capital and operational costs.
• Site footprint
• Operability including security of supply, flexibility to handle variations in raw water concentrations and robustness against possible future tightening of standards.

Based on this review, the 'NITREAT™' process developed by ACWA, was selected and has now been installed at six sites in the Anglian Region. A further four are now under construction due for completion in 2008 and three more are in the programme. Stringent performance tests carried out on completion have proved that the design parameters implemented by ACWA produce treated water with nitrate levels consistently below 5mg/l which is blended back with raw water to achieve a set point of 45 mg/l as nitrate, well within the requirements of Drinking Water Inspectorate Regulations. A further, demonstrated benefit of this technology is the reduction of waste stream to 0.5% of the throughput, considerably lower than alternative systems.

At the heart of the 'NITREAT™' system, is an innovative multi-port valve originally developed for use in industrial processes by Puritech, but adopted by ACWA Services who developed the application engineering of the valve for use in the water industry to improve nitrate removal by ion exchange.

The unique, patented design of multi-port valve, directs the flows to and from 20 columns, 14 of which are producing low nitrate water into supply whilst the remaining 6 are in backwash or regeneration mode. The multi-port valve indexes round all the ion exchange columns incrementally on a set time period, typically 2 hours, and ensures the appropriate columns have the correct flows whether that is the low nitrate water into supply or the addition of the correct strength of brine for regeneration. The design of the valve eliminates any possibility of cross contamination between flows. The use of a multiple column approach ensures the dilution effect from thirteen columns and allows complete exhaustion of the resin from the fourteenth column before regeneration without compromising treated water quality.

ACWA, respected in the water industry for its track record in innovation, is not resting on its laurels. The multi-port valve is being further developed to cope with higher pressure. Following demonstration of reliability, single duty designs have been developed as an alternative to duty/standby. The ion exchange technology is being further developed for applications such as removal of hardness, colour, pesticides and endocrine disruptors.