Auto-desludging at Queensferry STW

At Welsh Water's Queensferry Sewage Treatment Works in Clwyd near the Welsh/English border, two Watson-Marlow Bredel SPX80 heavy duty hose pumps were installed in January 2000 in an automatic primary tank desludging system.

As originally designed there were no pumps used at Queensferry, the system operated on timer controlled opening and closing of automatically actuated valves. Now, David Holthöfer manager for the site, expresses himself delighted with the marked improvement in overall system performance since the SPX80 pumps were fitted, as well as with the pumps' all-round reliability.

Operating under time switch control, the pumps run at 23 rev/min delivering 16,100 l/h of 3 % to 5% density sludge. Discharge pressure is approximately 5 bar. The pumps are installed close to the two primary sludge tanks in the open and without protective covers. Pump motors are 7.5 kW, fitted with heaters and thermistors.

Watson-Marlow Bredel hose pumps are operating at a number of other sites managed by David Holthöfer - some have been in service for around twenty years - but the pumps at Queensferry STW are the first of the SPX close coupled series to be installed in the area. As well as faster hose changing, the SPX design offers enhanced corrosion resistance, overload protection and simpler maintenance.

Produced for flow rates up to 80 m³/h and pressures up to 16 bar, Watson-Marlow Bredel hose pumps with their composite, braided nylon reinforced hose element are extensively used for handling sewage sludge and on many similar applications involving viscous, fibrous and abrasive material.