Recycling & Waste Management
The growing requirement to minimise use of natural resources is also a major driving force in the inclusion of the water treatment phase which reduces the requirement for fresh water to feed the washing plant by more than 90%.
The first stage of the water treatment process involves the introduction of the AquaCycle A400 thickener. This unit is provided with a fully automatic polyelectrolyte dosing unit and AquaStore water storage system. The waste water from the processing plant is sent to the AquaCycle unit through a gravity feed from the discharge point at the top of the Evowash cyclone. The first dose of polyelectrolyte is given in a de- aeration chamber at the side of the thickener tank. This slows the flow of material into the tank ensuring effective settling. Polyelectrolyte has the effect of forcing the minus 63 micron particles to join together and fall to the bottom of the tank where the integrated scraper mechanism conditions the sludge to ensure it maintains an even consistency. The clean water overflows the top of the tank via the peripheral weir and the water is then sent to the AquaStore for recirculation around the washing plant. When the sludge is ready to be discharged a signal is sent to the PLC controls which engage the sludge pump. The conditioned sludge from the AquaCycle is then sent to a concrete buffer tank.
It is the final stage of the water treatment process which allows maximum water recycling and minimal waste from the washing plant. A GHT 1500 filter press installed on walls is employed. From the buffer tank the sludge is pumped to the press. Once the press has been filled the sludge is subjected to
15 bar pressure. Once the press cycle has been completed the drip tray opens and the press releases the filter cakes into the bay beneath. As a result of the introduction of the water recycling system at Grundy and Co the only waste material produced is the filter cakes from the press. The recycling plant for Grundy and Co represents the beginning of a new era for the recycling of construction, demolition and excavation waste materials according to CDE. “Our recycling systems have been proven over many years in the leading market for recycling sand and aggregates in the world” explains Terry Ashby, general manager for CDE in the UK. “This success is as a result of the commitment to continuous development of the systems to ensure they continue to offer the best technological solution. The systems are proven to deliver – not only in terms of final product quality but the return on investment model is hard to ignore.” This view is supported by Tom Powell at Grundy and Co. “A lot of people thought we were mad committing to this substantial investment at the time we did given the situation that the construction industry found itself in,” explains Tom. “We have always tried to keep driving the business forward and this was the next step. By waiting for the upturn we ran the risk of missing the boat and we felt that the timing was right for a decision to allow us to be in a position to take advantage of the very real opportunities for washed recycled sand and aggregates.”
For more information contact CDE on tel: +44 28 8676 7900 or visit:
www.cdeglobal.com
www.solidsandbulk.co.uk
November 2010 • Solids & Bulk Handling 53
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