Vertical flow reedbeds
Kingstone and Madley Waste Water Treatment Works, operated by Welsh Water, was constructed in the late 1940's and has been modified on several occasions over the years to accommodate the increasing population in the area.
In the late 1980's four parallel horizontal flow passive reedbeds were added to the system to provide a tertiary polish to the effluent prior to discharge to the local watercourse. These have performed well and are still in operation with discharge consent levels generally being maintained, though there has been some loss of treatment capacity due to age and increased loading rates resulting in the short circuiting of flow across the reedbed surface.
Further predicted increases in local population and tightening discharge consents led to a review of the treatment process across the whole works to ensure compliant treatment of the additional loads. As a result a full site refurbishment and filter replacement was planned. Welsh Water was keen to employ existing assets were possible and, therefore, asked ARM Ltd to provide proposals for a reedbed refurbishment and upgrade.
The average daily flow to the reedbeds is 332m3 with a peak flow of 16.6 l/sec.
Following a site review ARM Ltd determined that with the use of Forced Bed Aeration™ (FBA™) only two of the four existing horizontal flow beds (approximately 1500m2 total) would be required to treat the post refurbishment design load to the required consent levels. The chosen beds were in a very poor condition and would require complete refurbishment themselves including liner replacement, new media, distribution / collection system, duty / standby blowers and conversion from horizontal flow to saturated vertical flow operation.
The new system was designed based on the upstream process consisting of a primary settlement tank, refurbished trickling filters and humus tank.
Effluent from the existing system is now fed into a newly built direction chamber which feeds into the retrofitted reedbeds.
Delivered within just four months ARM Ltd was also able to keep the site fully operational which was vital for the uninterrupted treatment of wastewater.
The new FBA™ treatment reedbed provides Welsh Water with a robust, secure, high performance, tertiary treatment capability at the Kingstone and Madley site providing long term compliance.
Because only two of the beds were used the remaining two beds offer additional passive treatment if required and potential for significant additional capacity if refurbished.