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ONE-DAY WONDER

Last year's landfill legislation meant options other than dig and dump had to be found. Necessity is the mother of invention, and in this case resulted in a new mobile batching plant.

The cost of sending contaminated materials to landfi ll has soared since the banning of mixed disposal of hazardous, non-hazardous and inert waste in July last year.

This problem was compounded by the dramatic reduction in the number of UK landfi ll sites able to accept hazardous waste to only 11.

Coupled with the need to pretreat waste before landfill disposal, this created an opportunity for innovative onsite solutions and and ground improvement contractor Con-Form claims to have come up with one.

Quality assurance and marketing manager Simon Harding says ConForm has developed a system that allows potential waste materials to be treated using an effective and affordable technique.

The company wanted a process that allowed reuse of these materials for ground improvement projects and helped change the mentality of traditional dig and dump.

Managing director Andy Armstrong says the key was developing specialist batching plant that can be up and running in a fraction of the time of conventional equipment - a typical static batching plant, including formation of foundations for the plant and silo if needed, can take as long as three weeks to set up.

Con-Form designed a mobile batching plant that could be operational within one working day of its arrival on site. Its trailer-based design, which the company believes is unique, minimises erection and dismantling work and features a low-level silo and water tank.

At the same time, the company applied for a waste management licence from the Environment Agency to allow the plant to treat both contaminated and non-contaminated materials classified as waste.

Con-Form says this means it can provide onsite stabil ation and solidification of waste materials that previously may not have been viable to treat, or might have been treated and sent to landfill instead of being used for construction.

The plant can handle both imported and site-won materials, from granular hardcore to silty slurries, meaning it can produce products such as bentonite-enriched soils and pavement quality concrete. It can also solidify inert and hazardous wastes.

The process is computer controlled to minimise human error, with the materials constantly weighed and moisture checked to ensure a uniform final product.

Harding says the batching plant can process up to 300m 3/h, depending on the constituent materials being processed, with a projected annual capacity of more than 1Mt.

He estimates that eliminating the need to take materials offsite, and thus the need to import clean aggregate in their place, could save about 250,000 lorry movements in the UK a year with consequent benefits for the environment.

The new system made its debut in April at the Malcolm Construction Services Merkland Quay Recycling Centre, Glasgow. Here, it is being used to modify more than 50,000t of belt fi nes produced from Malcolm's crushing operations, which in their natural state had limited commercial application.

Backhoes load the material into the hoppers while the pre-blended binders are stored in an adjacent integral silo. Fines and binders are continuously fed into the mixer at a controlled rate with water automatically added where necessary.

The resulting material is discharged directly into a waiting vehicle for transportation to site, an extensive brownfield redevelopment on the south side of Glasgow. Here, site workers place, compact and test it to confi rm a 15% CBR for the non-frost-susceptible material.

The batch plant work is scheduled to complete within 10 weeks of its April start.

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