Customer requirements

United Utilities is the UK’s largest listed water company. They own, operate and maintain utility assets, including water, wastewater, electricity and gas. They’re a FTSE 100 company with a turnover of £2 billion and see themselves as stewards of the natural resources in the North West of England, in the UK and across the world.

At the Cowm water treatment plant at their Watergrove Water Treatment Works, at Wardle near Rochdale; United Utilities needed to add Powdered Activated Carbon (PAC) to the water drawn from the Cown reservoir to neutralise a naturally occurring material known as Geosmin, which literally translates as ‘earth smell’. It is an organic compound produced by microbes and algae which gives untreated water a harmless yet undesirable earthy taste and aroma.

The Bulk Bag Discharger

As an approved supplier to United Utilities, Spiroflow Ltd were well placed to bid for the Powdered Activated Carbon (PAC) dosing system required. The dosing system comprises the following equipment: a ‘Spiroflow’ Bulk Bag Discharger, with integral lifting hoist on a runway beam for the easy loading of bags of PAC into the discharger, a Flexible Screw Conveyor to transfer PAC from the discharger up to a volumetric metering feeder with buffer hopper above, from here it is transferred to a second buffer hopper, which maintains a constant head of material above a ‘Transvac’ venturi ejector. It is in this educator that PAC is drawn under vacuum from the second buffer hopper and metered proportionately into a by-pass water stream to form a slurry that then re-enters, and is mixed, with the main water flow into the water treatment works and subsequently the distribution system that serves homes and businesses in the Rochdale area.

Spiroflow solutions

Procurement of the dosing system was through GCA - an alliance of main contractors comprising Galliford Try and its joint venture partners Costain and Atkins. Our bid was successful on price and according to Darren Glover of GCA, “The equipment is very good. We had an initial teething problem caused by unexpected clumps of PAC which Spiroflow quickly remedied by fitting a vibrator to the collection hopper. The system has worked well ever since”.

The Flexible Screw Conveyor + the Ejector dosing equipment