Thames Water taps Hydro sand filtration technology

London - Thames Water is investing in tertiary sand filtration technology from Hydro International as part of its improvement programmes at seven wastewater treatment works to meet improved discharge standards for ammonia levels.

The utility is installing the first 18 DynaSand Oxy vertical sand filters for ammonia reduction at WWT plants in Oxfordshire, Wiltshire and Berkshire as part of its £multi-billion AMP 5 capital investment programme.

The filters, selected by Black and Veatch, will enable Thames Water to augment the tertiary treatment process at the sites to meet the Environment Agency’s latest water-quality requirements.

The units are the first to be ordered for Thames Water projects after Hydro’s appointment as a preferred suppliers for nitrifying continuous flow sand filtration equipment as part of a three-year framework agreement for AMP 5.

The first 18 units will be installed at Marlborough and East Shefford in Wiltshire, Marsh Gibbon in Oxfordshire and Washwater in Berkshire during 2012 with the remaining units being installed in 2013.

The DynaSand Oxy filters remove suspended solids and denitrify in a single stage before discharge into the receiving water courses.

“The units help meet Environment Agency consents at the sites,” said Paul Nolan, procurement manager for Black & Veatch at Reading, which is the appointed programme delivery manager. “The sand filter technology selected provides a commercial solution for the client to achieve the required process performance.”

Hydro is one of two framework suppliers for filtration equipment - CF Sand filters and NCF Sand filters, throughout the Thames Water region.

The framework agreement covers the supply of DynaSand filters used for tertiary and final treatment of sewage effluent, removal of suspended solids or ‘polishing’, as well as the supply of DynaSand® Oxy filters for ammonia reduction.

The vertical sand filter operates continuously, using an internal washing process to eliminate the need for water storage tanks, backwash pumps and water collection.

In the DynaSand Oxy process, ammonia is converted into nitrate by autotrophic nitrifying bacteria as the water flows upwards through the filter bed. The bacteria form a layer on the surfaces of the filter grains and the resultant nitrates remain dissolved in the water.