New technology for sludge management reduces waste to landfill by 80%

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Courtesy of CDEnviro

The first batch of results from a new sludge management and waste reduction system at Severn Trent's Coleshill Sewage Treatment Works in Birmingham, England show a consistent 80% reduction in waste to landfill volumes. The DMax system has specifically been developed by CDE Ireland Ltd to process a variety of wastes as detailed below. This list is not exhaustive and represents the material for which the plant was initially constructed: Inlet Grit (predominant material); Wet Well waste; Gully waste; Waste from drain cleaning services; Waste from pond emptying services.

Through our contacts with some of the major water utility companies and contractors to the industry which have been developed over many years we became aware of an issue that required action in relation to the above waste streams. Existing practice was to dispose of this waste to landfill at substantial cost and environmental impact.

We set about developing the DMax system to address this issue and to help the water utility companies to significantly reduce their waste to landfill volumes while also recovering materials from within these waste streams for further use. The process is an adaptation of the turnkey classification, washing and dewatering technologies that we have applied to the global quarrying and mining industries since 1992.

The Process

The processing operation begins with material being delivered to a feed hopper and being transferred to our AggMax attrition system. At this point material is given a thorough clean and the first stage of the classification process occurs. The first stage involves the removal of the material with no commercial value and no potential for future use. In this case this is rag and organic material. This material is delivered to a high frequency screen at the rear of the AggMax unit where is it dewatered and stockpiled into a bay beneath the screen. This represents the material now destined for landfill. An analysis of the quantity of material that this represents as a proportion of the total feed can be seen in the table showing plant performance later in this report.

Meanwhile, the oversize mineral material is discharged onto a high frequency dewatering screen at the head of the AggMax unit where it is given a final rinse and discharged into a skip or to a stockpile. This material is subsequently transferred to construction and demolition waste processors free of charge where further classification into various product sizes takes place and the clean, dry aggregate material is then sold to the recycled aggregates market.

The minus 5mm material and waste water from the AggMax is pumped to a specially modified GritMax classification and dewatering plant. The screen of the GritMax unit contains special innovations in screening media to ensure the effective transfer of material along the screen, reducing the occurrences of blinding of the screen and maximising plant efficiency. The feed to the GritMax is washed, classified and dewatered on one compact unit and discharged to a separate bay or stockpile beneath the GritMax unit. The waste water containing the minus 75 micron material is subsequently returned to the sewage treatment plant for further processing.

As a result of a license being secured from The Environment Agency the dewatered grit product can be used on civils projects being undertaken by the water utility company operating the plant, ensuring maximum material recovery.

The Benefits

A plant such as the one detailed above was installed and commissioned for Severn Trent Water at their Coleshill Sewage Treatment Works in Birmingham in February 2009 and data produced by Severn Trent shows a significant reduction in landfill volumes as detailed below:

Month 1 - March 2009
Material Processed - 1309 tons
Msterial to landfill - 271 tons
Landfill Reduction - 79%

Month 2 - April 2009
Material Processed - 974 tons
Msterial to landfill - 194 tons
Landfill Reduction - 80%

Month 3 - May 2009
Material Processed - 493 tons
Materials to landfill - 96 tons
Landfill reduction - 81%

As a result of the successes being enjoyed as demonstrated by the figures above, Severn Trent also introduced reed bed material to the plant to test the possibility of recycling and recovery of materials for further use from this waste stream. It is important to note here that the plant was not originally set up to process this material. This point is central to any analysis of the success of this technology.

The DMax system is not an ‘off the shelf’ plant that comes in a few model ranges. Each plant is customised to the specific requirements of the individual project in question. This ensures maximum material recovery and maximum diversion of waste from landfill on each installation.

The results achieved during the reed bed material trial were even more impressive than those detailed above. The data from the tests on the reed bed material are detailed below:

Severn Trent Reed Bed Material: Test processing through DMax plant.

Month - May 2009
Material Processed - 375 tons
Msterial to landfill - 0 tons
Landfill Reduction - 100%

The following materials were recovered during the reed bed material trial:

Reed Media (+10mm) 216 tons (58% of total feed)
Reed 16 tons (4%)
Pea Gravel (-10mm) 27 tons (7%)
Peat 8 tons (2%)
Waste water $ -75 micron material 108 tons (29%)

Future Benefits

This is the first plant of its kind in the water utility industry in the UK and we believe in the world. As the first customers to show a willingness to trial this technology, Severn Trent have shown themselves to be industry leaders in terms of their commitment to addressing the waste created in the various water treatment processes with which they are involved.

It is largely thanks to their forward thinking attitude and their commitment to working with us to ensure this technology delivered the required results we have been able to bring this new system to market in the UK. We firmly believe that the potential offered by the development of this new technology in terms of the potential reduction in waste to landfill volumes in enormous and can be applied on a global scale.

Within the UK alone the plant detailed previously is only processing a small proportion of the waste produced by Severn Trent. If we take into account all of the water utility companies in the UK alone, this DMax system has the potential to divert hundreds of thousands of tons from waste from landfill and recover large volumes of recycled grit and aggregates for further use over the next few years.

These are conservative estimates for the UK market and with application of the system throughout Europe and beyond where similar problems are being experienced, the potential rises to millions of tons diverted from landfill and recovered for further use.

In addition to the huge environmental benefit this technology brings there is also the very significant issue of the massive cost savings that will be enjoyed as a result of the introduction of the DMax system. With landfill costs rising and forecast to continue to do so in the coming years the DMax system offers water utility companies a route to achieving considerable reductions in costs and increasing operational efficiencies.

One of the most significant efficiency savings being enjoyed by Severn Trent as a result of the introduction of the DMax system relates to the number of transport movements required. As a result of the recycling and material recovery being undertaken by the plant, Severn Trent have reduced their transport movements associated with the transport of inlet grit alone by 50%. This has led to significant cost reductions for the company and has also had a major impact on reducing the carbon footprint of Severn Trent.

This is proof that implementing effective waste management and recycling systems is a means of ensuring continued business growth and development in partnership with reducing the environmental impact of our operations. This is a powerful message that acts as a counter argument against those who argue that growing regulation of waste disposal is simply an additional cost for businesses to bear.

The introduction of the DMax system through the installation at Severn Trent’s Coleshill site is an example of the development of new technology which offers significant environmental benefits as can be seen in the numbers quoted previously.

Further details on this project and how this technology can be applied to your application can be obtained by contacting CDE via their web site at or by email at

A full case study of this project is avaikable for download from the CDE Enviro web site downloads area at

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Watch CDE project videos on their YouTube TV channel at

View and download project images at CDE's online image library at

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