Military solution for UK tank cleaning

An innovative application of technology, more frequently seen clearing landmines in Bosnia than sewage sludge in Yorkshire, is improving safety at a major treatment works near Leeds in the UK. A specially built remote-control Bobcat has removed the need for an operator to be placed in a potentially risky environment.

In February 2003, Yorkshire Water invited UK construction company Gleeson and the US water and wastewater specialist MWH to find a safer and more cost-effective way to clean out storm tanks at Knostrop Wastewater Treatment Works, a facility serving the entire city of Leeds. Previously, the ten tanks, each the size of a football pitch and with a capacity of 138,000m3, had been cleaned manually by an operator driving a modified dumper.

Philip Worrall of MWH explains, “The manual procedure for pushing sewage sludge presents hazards as the operator of the machine is inside the tank. In the event of an accident, it would take considerable time to safely rescue the operator from such a large tank. The only way to increase safety was to remove the operator from the storm tank altogether.

“We explored the possibility of remote-control technologies and found that Merseyside Fire Brigade used a system that might work with substantial modification, as did the army for clearing land mines. This convinced us that the technology was up to the task.”

Although other automated solutions exist to remove sewage sludge following a storm, they are prohibitively expensive for tanks of this size: total project cost for fitting scour pumps at Knostrop was estimated at ¬1.3 million while the remote Bobcat solution costs ¬334,000.

Manufacturers of appropriate plant vehicles and remote-control devices were contacted, and a detailed functional design specification for the vehicle was created, including a series of modifications to make it suitable for operation in up to 600mm of raw settled sludge. The result, a Bobcat 753 skid-steer loader with proprietary remote-control technology by Joysticks Ltd, can be operated either remotely or manually.

A range of fittings for the front of the vehicle mean that, in addition to clearing sewage sludge from the 3m deep concrete tanks, it can be used for a variety of other tasks around the site. As well as enhancing safety, the remote-control Bobcat is labour-saving: the new system is operated entirely from outside the tank and eliminates the need for an additional operator.

Other Yorkshire Water sites have already expressed interest in using the equipment, while the technology may be suitable for use at sites across the UK and internationally.

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