The success of a 12-week trial of a filtration technology at a UK wastewater treatment plant shows that the modified system, first developed for the aquatic market, can help sites meet challenging phosphorus consents, explains the group behind it.
The Flocell XFM40 modular filtration system was installed at a rural water utility wastewater treatment plant (WwTP) in England and has demonstrated a reduction in phosphorus levels to as low as 0.04 mg/litre.
The collaboration between WCS Environmental Engineering (WCSEE), aquatic filtration specialist Evolution Aqua, and a UK water company has set a precedent for targeted phosphorus removal at WwTPs with persistent consent challenges.
Pressure test
The WwTP was experiencing ongoing challenges in meeting a new expected phosphorus consent of 0.25mg/l in AMP8 – the five-year regulatory asset management plan period starting April 2025. This made it an ideal location to trial the solution.
The site has processing capacity for a population equivalent of 3,200 with 29l/s of wastewater. One Flocell XFM40 unit comprising eight modular filters, capable of flows of up to 40l/s, was delivered to site in a 12m (40ft) container and installed in the summer of 2024.
The model was specifically chosen by the utility as the capacity of the unit matched the flow rates at the facility and the containerised unit could run at different flow rates for robust testing during the trial.
After 12 weeks the trial was a clear success, with the Flocell XFM40 helping the WwTP to achieve phosphorus removal levels as low as 0.04 mg/l, significantly exceeding the target of 0.25 mg/litre.
Flocell is a business division of Evolution Aqua, and the group partnered water treatment specialist WCSEE to modify the Flocell XFM technology, which was originally developed for application in koi carp ponds filtration, to the WwTP market.
The WCSEE team, which has decades of experience working with UK utilities in wastewater treatment, undertook in-depth particle size and thermogravimetric total suspended solids (TSS) analysis during the trial by obtaining over 1,000 individual samples.
WCSEE and Evolution Aqua were on site throughout the trial and worked closely with utility managers to run the new plant. Onsite operators were trained to run the system in less than half-an-hour, with the labour requirement to run and maintain the system assessed as about 30 minutes every 1-2 weeks.
Technology provenance
The Flocell XFM modular filtration system is a proven technology in the aquatic sector and has been deployed for over two decades. Evolution Aqua is building on that expertise in partnership with WCSEE to expand impact in the wastewater treatment market.
The Flocell XFM is a modular range of filtration systems for tertiary solids and phosphorus removal. The open-cell media is designed to efficiently reduce tertiary solids and soft, difficult-to-manage, flocs retaining particulates without increasing pressure within the filter or reducing flow. The units can be operated under pumped or gravity flow and can be used inline or on a ‘dialysis’ flow mode.
The performance of the Flocell XFM40 during the trial has been proven to achieve phosphorus removal levels consistent with the expectations of environmental regulation in AMP8.
Andrew Baird, technical director at WCSEE said, “It’s been highly rewarding working in partnership with Evolution Aqua to modify their technology for the wastewater sector and to be entrusted with a trial of such importance.
“Helping the utility not only meet, but exceed its phosphorus consent, is further proof that the technology can be a trusted addition to many wastewater treatment plants, especially smaller sites in rural areas.”
The principles behind it
Flocell’s modular filtration systems use air to clean the filters, rather than a traditional backwash cycle. The low-energy blowers agitate the media pack, removing contained solids during the short cleaning cycle.
Using air also reduces energy consumption and substantially reduces the volume of backwash water required for cleaning, making the Flocell XFM filtration systems over 99.9% water efficient.
Only the volume of the filter is discharged when cleaning with prolonged periods of operation possible due to a high retention capacity and no physical moving parts with low maintenance requirements.
More importantly, as the solid content of the backwash is very high, at 1,800mg/l, meaning this can go directly to onsite sludge storage or returned for co-settlement to the head of the works with incoming effluent, without adding significantly to the hydraulic load and requiring infrequent removal.
Gavin Haywood, director at Evolution Aqua said, “Working on this site with WCSEE, and in collaboration with a very supportive major UK water utility, has enabled the very impressive operational capabilities of the Flocell XFM modular filtration system to be fully validated, even under stress conditions.
“Achieving these results, while maintaining over 99.9% water use efficiency, removes the need for backwash tanks and associated infrastructure and maintains operational hydraulic loading in a small and compact footprint which requires only a level base, reducing concrete usage that can be delivered to site and brought online within a few hours of deployment.”
Phosphorus challenges
Wastewater utilities face ongoing challenges in identifying suitable phosphorus solutions in an environment of budgetary constraints and ever tightening discharge consents. Population growth, including in rural and semi-rural areas, means an increase in the volume of pollutants entering wastewater treatment systems.
High levels of phosphorus entering water bodies can cause eutrophication, leading to algal blooms, oxygen depletion, and loss of aquatic life, so it is crucial that WwTPs are able to address and eliminate this problem at the tertiary stage of treatment.
WCSEE’s experienced technicians work closely with clients before, during, and post installation to further enhance Flocell XFM modular filtration system functionality and can tailor and scale the technology to individual site requirements.
Baird said, “By working in close collaboration with the utility and Evolution Aqua we have been able to deliver the best value for the client, as well as ensuring the treatment site meets its stringent phosphorus consent.
“Given the rising expectation of water company customers and the government’s environmental ambitions, we look forward to working with our existing and future clients to roll out this market leading, highly effective, tertiary treatment filtration technology.”
