Phosphorus reduction technology successfully trialled by United Utilities

A water efficient, low energy phosphorus reduction technology from wastewater treatment specialist WCS Environmental Engineering (WCSEE) and sustainable filtration specialist Flocell has been trialled by United Utilities to help deliver tightened phosphorus removal consents at one of their wastewater treatment works.

Water companies in England and Wales are experiencing ongoing challenges in meeting new and expected phosphorus permits, some as low as of 0.25mg/l. To help meet tightening permit limits, United Utilities has recently purchased one Flocell XFM 40 modular filtration system unit comprising eight modular filters, capable of flows of up to 40l/s.

The decision follows a successful 12-week trial at one of the company’s rural wastewater treatment works (WwTW) which demonstrated capability to meet phosphorus concentrations less than 0.25 mg/l when combined with chemical dosing. During the trial, the team undertook in-depth particle size distribution analysis and total suspended solids (TSS) analysis on over 1,000 individual samples.

Callum Grundy, Principal Innovation Engineer, at United Utilities said: “Following the trial, we have established the Flocell system as one of a range of treatment options we have available for use on our appropriate wastewater treatment works.

“We were looking for a filtration technology that could be deployed to help meet low phosphorus concentrations without the impacts of backwash returns. This was found in the Flocell XFM 40 system, which was trialled successfully over a 12-week period.

“The engagement and collaboration we had with WCSEE and Flocell was fundamental to the success of the trial. We are now looking forward to exploring its potential further and are really pleased to be supporting the local economy here in the Northwest, with the technology being manufactured in Wigan.”

Precedent setting

Flocell is a business division of Evolution Aqua Group and partnered with WCSEE to modify the Flocell XFM technology to the WwTP market - which was originally developed for application in koi carp ponds filtration.

The Flocell XFM Modular Filtration System is a proven technology in the aquatic sector and has been deployed for over two decades. Flocell is building on that expertise in collaboration 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.

Andrew Baird, technical director at WCSEE said, “It is great to collaborate with United Utilities and to see the process through from initial enquiry, testing, to purchase and installation. WCSEE has been delivering projects for the utility over many years and the company is proud to be trusted to deliver tight phosphorus consents at Appleby and at other WwTWs with this contract win.”

Dr Adam Guest, Senior Process Engineer at United Utilities, who advised during the Appleby trial, said: “The simplicity and robustness of the Flocell XFM system means it can be set up to be operational very quickly with limited commissioning requirements.

“The introduction of tertiary solids removal systems to help meet tight phosphorus drivers, can result in significant volumes of backwash water being returned to the inlet works. This can lead to hydraulic challenges on many sites, particularly on some of our smaller, rural WwTWs.

“The ability of the system to operate for extended periods without backwash, and the limited backwash volume, make it ideal for small WwTW. In dialysis mode there is no requirement for complex flow control system, which also adds to the simplicity of installation.”

Water efficient

Flocell’s modular filtration systems use air to clean the filters. The low-energy blowers agitate the media pack, removing contained solids during the short cleaning cycle.

With no moving parts, the XFM system significantly reduces energy consumption and unlike other technologies, requires no process water to operate, substantially reducing the volume of backwash water required for cleaning.

Only the volume of the filter is discharged when cleaning with prolonged periods of operation possible due to a high retention capacity and low maintenance requirements. This makes Flocell XFM filtration systems over 99.9% water efficient.  

More importantly, the solids content of the backwash is very high, at 1,800mg/l, which means the throughput can go directly to onsite sludge storage or be returned to the head of the works for co-settlement with incoming effluent, without adding significantly to the hydraulic load.

Gavin Haywood, director at Evolution Aqua said, “Working on this site with WCSEE and in collaboration with United Utilities 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.”

Delivered to site in a 12m container, the flexible Flocell XFM system can be installed onsite on a flat surface, with no need for associated civil engineering works. It can be commissioned within one hour.

If the flow rates change onsite, multiple units can be connected in series or run independently on multi-pass, to treat significantly higher flows, which will ensure environmental permits can be met quickly and efficiently.