Installation of high rate multi-media filtration technology at Severn Trent’s Newent and Ledbury WWTWs to satisfy new phosphorus discharge consents that came into force on 31st March has ensured both plants are operating below regulatory permit levels for phosphorus as set by the Environment Agency.

Both projects were delivered by Severn Trent’s nominated Tier 1 capital delivery partner, CiM6 (a partnership between Costain and Stantec).

In both cases Bluewater Bio Ltd, who supplied the high rate multi-media filtration technology FilterClear, provided a fully automated Tertiary Solids Removal (TSR) plant.

Ledbury WwTW is a medium sized activated sludge works serving the market town of Ledbury, Herefordshire. The works consists of two crude oxidation ditches operating in enhanced biological phosphorus removal (EBPR) mode.

Photo:Fully automated 4v2800 FilterClear TSR plant installed at Ledbury STW

To further polish the EBPR effluent, ferric sulphate dosing was added upstream of Bluewater Bio’s FilterClear model 4v2800 tertiary solids removal plant. The system is capable of treating up to 132 L/s of flow and is comfortably achieving the performance guarantee of less than 0.24 mg/L phosphorus.

Newent WWTW is a medium sized trickling filter works with a population equivalent (P.E.) of 17,500. Ferric sulphate dosing was added at the primary settlement stage and into the feed to a new FilterClear 4v2340 tertiary solids removal plant to achieve a new phosphorus limit of less than 0.64 mg/L. Now completed, the FilterClear tertiary solids removal plant is treating up to 78 L/s, with the treated flow discharging into a nearby tributary of the River Severn.

FilterClear is a high-rate multimedia filtration technology, capable of treating flows ranging from 2 L/s to in excess of 1,000 L/s. Since successfully demonstrating that the technology can achieve total phosphorus concentrations of less than 0.1 mg/l in the national CIP2 trials, FilterClear has been successfully implemented at multiple sites for Severn Trent and other water companies.

Richard Price, Framework Operations Director at Costain, commented:

“Both projects successfully achieved the new regulatory permit on 31st March 2020 and have been operating below permit levels since that date. We have been impressed with the hard work, flexibility and commitment of the team at Bluewater Bio and look forward to working with BwB in the future in delivering more FilterClear schemes for Severn Trent.”