July marked a milestone for wastewater treatment in the UK, with the installation of 10 OxyMem membrane aerated biofilm reactor (MABR) modules from DuPont Water Solutions at Severn Trent’s Redditch Spernal site in Worcestershire, which has become the largest MABR in the UK.

Excess biosolids from satellite plants

The plant processes wastewater from the surrounding catchment area as well as excess biosolids from satellite plants. Consideration for future population growth and tighter ammonia consents led Severn Trent to look for improved process efficiencies.

Rather than expanding the plant, Severn Trent opted for an upgrade by converting it to an IFAS (integrated fixed film activated sludge) MABR system. DuPont OxyMem MABR modules were simply lowered into the existing anoxic zone on site, over a two-day period, to boost nitrification capacity of the current process.

The advanced technology offers simultaneous COD and ammonia removal, with nitrification rates two to three times greater than MBBR technology at the design temperatures.

This full-scale installation follows an extensive 12-month pilot trial at Severn Trent’s Minworth site on the northeastern outskirts of Birmingham.

Energy consumption

There, the OxyMem system proved its value, producing sludge at just 0.13 kg TSS/kg COD applied compared to the typical 0.3 - 0.4 kg of TSS/kg COD applied for activated sludge. Energy consumption was low and the aeration efficiency was 4.5 kg O2/kWh, two to three times more efficient than conventional technologies.

Justin Silver, innovation project manager said: “Severn Trent is excited at the potential for MABR technology as a cost-effective way to retrofit and upgrade activated sludge plants to meet tightening effluent standards and to cater for population growth.”

A major advantage of upgrading with DuPont OxyMem MABR modules is due to their 'plug and play' nature, as the units can be easily lifted and lowered into place without the need to interrupt the process.

Additionally, Severn Trent can install the modules which is particularly important during the current health crisis that has led to certain restrictions for external personnel to enter the site.

“The modularity of this self-contained solution means not only can it be easily dropped into place, but it is also scalable should needs change,” said John McConomy, commercial director, DuPont’s OxyMem product line.

“Severn Trent have put their trust into our system after it proved itself in trials. They are leading the way in the market in terms of low-impact, sustainable wastewater treatment that enhances and protects the investment in existing infrastructure.”