Croda Chemicals Europe has been encouraged by the interim results of trials investigating the potential of Recycled Glass Filtration Media (RGFM) as an alternative to traditional sand, at its site in …
Croda Chemicals Europe has been encouraged by the interim results of trials investigating the potential of Recycled Glass Filtration Media (RGFM) as an alternative to traditional sand, at its site in Rawcliffe Bridge, near Goole in northern England. Croda“s trial is being funded by WRAP (the UK Waste & Resources Action Programme). It is part of a wider initiative by the 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. The results of the Croda trial show the glass-based material is set to cut suspended solids in the site“s wastewater by up to 80%. Suspended solids have a negative effect on the environment by de-oxygenating 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. Croda“s Rawcliffe Bridge site specialises in lanolin and derivatives. Products include surfactants for cosmetic creams and lotions, speciality lipids for dietary supplements and fatty acid amides. Tim Uppard, Process Engineering Section Head at the Rawcliffe Bridge site, which has a capacity of 50,000 tonnes a year, explained: “Environment Agency consents due to take effect in 2006 require the maximum level of suspended solids in our effluent be reduced to 50mg/l, compared to our average before the trial began in September of 250mg/l”. “The agency tightly controls the amount of suspended solids treated water discharges can contain and organisations exceeding their limits can face hefty fines”. “We were therefore keen to find the most suitable tertiary treatment to achieve compliance. We also wanted to find a way of reusing a proportion of its process water, as part of our continuing environmental improvement programme”. “It looks like RGFM is coming up trumps on both counts. We“ve been very impressed by the initial trial results and are now looking forward to taking the project to the next stage, at which the material will be put through its paces 24 hours a day”. The high level of suspended solids in Croda“s effluent meant the treatment system tested at its site by consultancy Aqua Enviro had two phases. An initial pilot trial used three identical two-stage filter systems, filled with different grades of RGFM and Active Filtration Media, made from a highly processed grade of recycled glass, to decide the ideal combination for removing solids. This confirmed the plant should use medium grade material to remove most of the solids and the finer type at a polishing stage to take out as many of those in suspension as possible. During the large-scale trial, samples of effluent from both filters were analysed to determine removal rates of suspended solids and chemical oxygen demand. A fully automated rig imitated the operation of a complete system and allowed analysts to decide the filtration cycle and backwashing arrangements (the process involving clean water being pumped backwards through the filters to flush them clean of sludge) maximising removal rates. Mr Uppard said: “Initial results of the trials have not only shown a drop in suspended solid levels of about four-fifths, they also indicate the RGFM filters coped excellently with major peaks in solids loading”. “If these standards can be maintained, we will not only meet Environment Agency demands but also cut operating costs, through reduced cleaning and maintenance bills, and have lower capital outlay in the future, as we will need smaller and less sophisticated membrane systems”. The test two-month trial involving 24-hour running was concluded in November 2005. WRAP“S campaign is intended to move the UK towards its target under the European Union packaging directive which says 60% of used glass must be recycled by 2008. The recycling rate currently stands at 42%. Bronnie Allen, materials development manager (glass) with WRAP, said: “We“re delighted with the initial feedback from Croda, which appears to support the findings of other WRAP funded trials. The trials indicate RGFM, which is manufactured to BSI PAS 102 specifications, is both viable commercially and offers performance benefits, compared to traditional filtration materials”.