The Wildfowl and Wetlands Trust (WWT) in Slimbridge, Gloucester, has played host to the first fully operational trial of an advanced filtration media (AFM) system. The experimental works are part of a trial funded by the Waste and Resources Action Programme (WRAP) to develop and promote the use of recycled glass.
The trial plant, constructed by Water Development Services and operated over a three-month period for WRAP, used Bürkert Fluid Control Systems’ valve technology, and has proved so successful that the system has been adapted for continuing use at Slimbridge.
The visitors’ centre has more than 60 ponds within landscaped grounds of around 20 hectares, with more than 3,000 captive waterfowl. The ponds are fed in series by the Gloucester canal water, some of which is pumped from the River Severn.
The trial proved that recycled glass could be used as a superior replacement for sand, and that the clarity and quality of the water was improved through the
use of AFM.
AFM uses crushed recycled glass instead of sand, which is known to deteriorate and be costly to maintain. AFM can be used in a similar way to a standard sand filtration media. However, the properties of AFM mean that the filtration system can perform tasks that could not be considered using sand. Sand filtration can provide very high quality water, but when the process is used
to treat waste water, biofouling and coagulation in the filter can cause serious operational problems. These problems are solved by using AFM.
Bürkert played a key role in the trial and development of AFM, providing the solenoid valves that control the flow of water through the system. According to project manager Christopher Dean, Bürkert was chosen because of its innovation and sophistication, and the valves are “vital to the operation”.
Without the valves, the trial would not have been able to take place and the development of AFM would probably have taken considerably longer. The valves allowed the trial to run effectively and with positive results. The system reduced suspended solids by at least 75% and more often by 90%, while for sand the reduction was between 50% and 94%.
The unit was located next to the Chilean Flamingo House and used on the dirty water in the adjacent pond. The trial plant was equipped with two filters operating in parallel: one using recycled glass media and the other using traditional silica sand.
From the outset, both the sand and glass media fil-ters performed well and reduced the suspended solids and chemical oxygen demand by more than 90%.
However, within three months the sand filter perfor-mance started to deteriorate by bio-fouling while the glass media filter continued to operate efficiently.