Dŵr Cymru Welsh Water is to install Veolia tertiary treatment technology at Connahs Quay WwTw. The project is part of a £1.65-million upgrade being carried out by Imtech Water, Waste and Energy – one of the utility's AMP5 partners.

This new contract, which follows similar installations at a number of other Dŵr Cymru Welsh Water wastewater treatment works, will see two Hydrotech HSF2212/11-1F Discfilter units being installed.  

The upgrade, due for completion in July 2013, will accommodate growth and improve final effluent quality at the 20,000 population equivalent works.

Each of the Discfilters will treat 113l/s of final effluent to a suspended solids standard of 15mg/l 95%ile. The contract includes design, supply, and installation of the two filters, which will be fabricated in 316 stainless steel and GRP and fitted with self-cleaning backwash spray nozzles. The advanced nozzles will provide further operational robustness and reduce operator intervention.  

The Hydrotech Discfilter uses a series of rotating segmented discs that support 10 micron polyester filter fabric panels. As the wastewater flows through the disc segment, suspended solids including biomass flocs and precipitated phosphates are captured on the fabric and removed from the effluent.  

When required, backwashing of the fabric is initiated automatically on headloss, with the dirty backwash water being returned to the head of works. Low backwash water volumes, typically only 1 – 3% of throughput, low power consumption and minimum maintenance are among the selling points for the Hydrotech Discfilter.

The units are also providing tertiary treatment at Dŵr Cymru Welsh Water’s Churton, Farndon and Mold wastewater treatment works, treating 10, 14.6 and 92 l/s respectively – in addition to installations at Thames Water, Scottish Water, Yorkshire Water, Anglian Water, Severn Trent and United Utilities.