Severn Trent Continues to Invest in CoMag® Systems

Evoqua to supply another major waste water treatment works


  • Algal blooms and poor river ecosystems are triggered by high levels of phosphorus in the river.
  • The UK Environment Agency’s National Environment Programme is imposing low phosphorus limits to combat the blooms and restore water bodies to “good” status.
  • This impacts many municipal wastewater treatment plants, including Hartshill, Nuneaton.


Evoqua Water Technologies has been selected by Severn Trent to supply its innovative ballasted clarification technology, the CoMag® system, at yet another major wastewater treatment works. This new contract at Hartshill (near Nuneaton) follows the successful implementation of the CoMag system, which reduces levels of phosphorus entering the watercourse, at the Severn Trent sites of Finham (near Coventry) and Cannock. This is in addition to several other municipal water companies that have adopted the technology.

Controlling and reducing phosphorus, which comes from a number of sources, such as treated wastewater and agriculture, is vital to protect our environment and its inhabitants across the globe. Left untreated, its presence contributes to algal blooms, ultimately reducing oxygen in the water, and significantly impacting the aquatic environment. This is an issue which is on the rise as populations, and therefore the flow of domestic wastewater increases.


The CoMag process will be installed by MWH Treatment who chose the CoMag system as the most suitable technology for these projects, which need to achieve extremely low phosphorus levels (< 0.2 mg/l T-P) and handle large throughputs.

At Hartshill, the use of Design for Manufacturing Assembly (DfMA) has been selected, which is easily utilised with a CoMag system and will result in significantly reduced installation time.

The CoMag system is a unique technology that uses magnetite – fully inert iron ore particles – to enhance the clarification process, settling chemical floc up to ten times faster than conventional clarification. This enables the resulting clarifier to be up to 90% smaller than its alternatives. Importantly for Severn Trent, the innovative technology continuously recovers most of the magnetite, which will support the plant’s sustainability requirements and budget.

" We are always looking for innovative solutions to enhance and improve our wastewater treatment process. Following the previous installation at our Cannock and Finham sites, we are confident that the CoMag system will play a key role in helping to refine and improve our treatment process at Hartshill, which will in turn lead to a cleaner and healthier natural environment. "

Lily Harvey, Project Manager, Severn Trent

Simon Radford, UK Sales Manager of Evoqua’s Wastewater Treatment division, added, “These next contracts with Severn Trent are particularly significant as it demonstrates that Severn Trent is extremely satisfied with the CoMag® systems that are already in operation. In the case of Hartshill, we have developed our CoMag system offering with a DfMA approach which enables minimal construction time on site. The CoMag system is making significant reductions to the level of phosphorus in waterways across the country and supporting plants as they prepare for projected population increases. Importantly, as well as operationally effective and sustainable, our solution comes in significantly lower on whole life costs than market alternatives.”

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