Trial of an innovative phosphorus removal technology at a Sussex wastewater treatment plant (WwTP) has led to the purchase of two Flocell XFM20 filtration units by UK utility Southern Water.
Wastewater treatment specialist WCS Environmental Engineering (WCSEE), now Marlowe Environmental Services (MES), initially hired out the equipment for use at Storrington WwTP in June 2025. Following a successful trial period, Southern Water took the decision to approve the units for permanent ongoing use.
The two Flocell XFM20 units, comprising four modular filters, can process flows up to 40l/s collectively. Installed and delivered in a 6m container with no requirement for additional civil engineering, the system is enhancing existing tertiary treatment, enabling Storrington WwTP to consistently achieve its 0.5 mg/litre phosphorus consent, with a peak flow of 47l/s, serving a population equivalent of approximately 8,000.
The Environment Act 2021 mandates an 80% reduction in phosphorus from treated wastewater by 2038, with interim targets for water companies to invest in upgrades. Water companies in England and Wales face ongoing challenges to meet the stringent phosphorus permits, some as low as 0.25mg/litre.
For Storrington WwTP managers this meant identifying a robust, space-efficient, solution capable of enhancing current treatment performance without extensive civils and on a short lead time, while ensuring site compliance to meet a permit of 15mg/l biological oxygen demand (BOD), 20mg/l total suspended solids, 0.5mg/l phosphorus, 4mg/l iron, and 10mg/l ammonia.
Connor Sandalls, senior processing engineer at Southern Water, said: “I discovered Flocell XFM at the European Wastewater Management Conference in 2024 and immediately saw the potential for implementation at several Southern Water WwTPs.
“Following the hire which began in June 2025, the two Flocell XFM20 units have been approved as one of a range of treatment options for Southern Water to use at appropriate wastewater treatment works. The engagement and collaboration have been fundamental to the success of the hire period.”
Southern Water purchases phosphorus filtration technology
