Land and Water Services: Rapid Sludge Dewatering (UK)

As part of their quest to find innovative treatment and re-use solutions for difficult and wet waste materials Land and Water Services Ltd (LAWS) has been using Geotube®Technologies for the accelerated, onsite, dewatering of difficult sludges for Anglian Water Services Pic.

On a live contract at Pitsford Water Treatment Works, LAWS technology, combined with innovative, low impact dredging techniques, has seen a substantial reduction in the over-all quantities of difficult materials for disposal.

Dredging Operations

Dredging works can be conducted with the water remaining in the water body, which negates the need for expensive dewatering, fish rescue and habitat protection measures, the “Status Quo” is maintained throughout the operation. For larger contracts LAWS road transportable cutter-suction dredger can be deployed, with a 10″ suction head, this unit can achieve high dredge outputs in water depths from 600mm to 6m.

On smaller projects one of LAWS versatile, amphibious tool carriers can be equipped with a 4″ capacity boom mounted, scroll feed, suction pump; and on sites where bankside access is acceptable a dipper mounted, high capacity sludge pump can be fitted to any of LAW’s 52 long reach excavators.

Rapid Dewatering

The sludge mixtures are delivered via pipeline directly to the Geotube® containment system. Constant monitoring of the input feed pipes enables the dedicated process engineer to adjust and inject the correct mix of polymers and coagulants to the pump mix immediately prior to it entering the bag.

Once inside the bag the sludge and flocculent mix cases the rapid binding of the free sludge particles, liberating clean water. The clean water is then ejected from the micro-pores of the TencateGeotubes® and returned to the water-body, leaving high concentrates of the sludge within the Geotubes®.

Whilst up to 99% of the particulates are retained within the bags, the bulk of the water is liberated instantly. After the final cycle of filling and dewatering, the solids remain in the bag and continue to increase in density due to desiccation as residual water vapour escapes through the fabric. The result being that when the bag is finally opened the sludge concentration has significantly increased leaving a dry “soil” to be excavated for recycling or controlled disposal.

Versatile Configuration

Geotubes® can be configured to suit individual sites with minimal space and/or differing sludge make-up using expert technical and installation teams. The Geotubes® are arranged on a temporarily lined surface such that any clean waters that are released from the bags can be swiftly returned to the water-body under gravity. Where appropriate, drinking water quality polymers are used to ensure that no negative impacts are reflected back to the originating water-body.

At PitsfordWTW LAWS successfully completed the dredging and recovery of more than 2,500m3 of fine particle sediments, resulting in a final retained volume in the dewatered bags of less than 400m3.

Steve Massey, Land and Water’s Divisional Business Manager commented on the use of this technology and the scope of application: “This method delivers a solution to Clients where they can dramatically reduce the quantity of sludge for disposal with minimal impact to the environment in a quick and safe manner.”

Bio solids Recycling and Environmental Compliance Manager for Anglian Water Services, Gary Cunliffe comments: “Using the Geotube technology will enable us to separate solids from liquid at site, and provide savings on haulage, and disposal costs and drastically reduce the carbon footprint of lagoon sludge dewatering.”

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Press Release, August 12, 2013