Uffington Waste Water Treatment Works (WwTW), operated by Thames Water, serves a population of 700-800 in a rural location. The WwTW comprised a primary settlement tank, filter bed and humus tank. Due to its age and servicing an increasing population, the works required chemical coagulant dosing to improve load removal through precipitation, settlement and filtration.

The site began to breach consents occasionally and Thames Water was aware that discharge limits for the WwTW were likely to become stricter in the short-term. This could require the whole site to be upgraded. The cost of chemical dosing was also disproportionately high compared to the size of the site. Average flows were 174m3/day with a maximum of 347m3/day; average loadings to the works are 45kg/d BOD and 6kg/d ammonia.

The BOD discharge was nearing consent; the solids and ammonia had already breached it.

ARM Ltd provided Thames Water with a long-term solution: an Aerated Saturated Vertical Flow reedbed to operate as a tertiary final polishing system. The vertical flow orientation decreased the size of the required bed whilst the aeration provided enhanced microbial treatment to bring the BOD, suspended solids and ammonia site discharges into consent. Two beds were installed, measuring 550m2.

The Forced Bed Aeration™ solution saved Thames Water the capital costs of replacement or refurbishment of the works whilst providing them with a long-term low-maintenance, low-carbon solution which places emissions back within consents.