WRAP: successful test of glass filtration media

Yorkshire Water says it is encouraged by results of trials investigating the potential of Recycled Glass Filtration Media (RGFM) as an alternative to traditional sand.
The successful trial at the wat…

Yorkshire Water says it is encouraged by results of trials investigating the potential of Recycled Glass Filtration Media (RGFM) as an alternative to traditional sand. The successful trial at the water utility“s sewage works near Malton in northern England was funded by WRAP (the Waste & Resources Action Programme) and undertaken by consultants Aqua Enviro. Receiving wastewater from 10,000 people in the town and its surrounding area, the Malton site must comply with stringent Environment Agency standards for removing suspended solids from its effluent, before this goes into the River Derwent. Suspended solids harm the environment by de-oxygenating the water and affecting river flow to the detriment of fish and other aquatic life. It is desirable to reduce these to preserve the quality of the receiving watercourse. The trials showed that RGFM filter was able to remove up to 70% of solids. Andrew Calvert, Yorkshire Water research and development optimisation manager, explained: “Our tests, carried out between November 2004 and June this year, demonstrated RGFM is a suitable alternative to utilising sand and as or more slightly more effective in removing suspended solids”. “Unlike sand, the recycled glass showed no tendency to clog up, or “blind“, when faced with high loadings of suspended material and could help remedy this problem”. “Performance on backwashing – pumping clean water backwards through the filters, flushing them clean of sludge – matched or bettered that of sand”. An initial pilot trial at the Malton plant compared the various types of RGFM available, which are all manufactured to BSI PAS 102 specifications, with sand. The medium grade of material proved the most similar. The full trial including this material took place in a test rig, set up alongside the existing filtration system at the works, so day-to-day efficiency was not impaired. The rig used 3-12mm glass bead as a bedding material, with 600kg of recycled glass sand laid on top. Samples of the influent were tested alongside the treated effluent, to ensure performance levels were assessed accurately. The effluent was checked for removal rates of suspended solids, sediment and chemical oxygen demand. Commenting on the overall results, Mr Calvert said: “The trial results show recycled glass is a highly suitable medium for tertiary solids removal and we will now use it at our sites”. The tests are part of a wider initiative by WRAP, a UK Government-established, not-for-profit company promoting sustainable waste management, to encourage the use of materials made from recycled glass across a variety of industry sectors. These include brick and tile manufacture, grit blasting and sports turf. WRAP“S campaign is intended to move the UK towards its target under the European Union packaging directive, which says that by 2008 60% of used glass must be recycled. The UK currently recycles 42%. Bronnie Allen, Materials Development Manager (Glass) with WRAP, said: “We“re delighted with the feedback from the Yorkshire Water tests, which appear to validate findings from trials we are financing at other sites. These indicate RGFM is viable commercially and offers performance benefits over traditional filtration materials”.