Landfill leachate and sludge treatment
Vertical flow reedbeds
Essex and Suffolk Water
The asset management strategy for Essex and Suffolk Water identified a need for a new process for sludge handling at Hanningfield Water Treatment Works. Supplied with raw water from Hanningfield Reservoir (354 Ha), Hanningfield WTW produces 150 million litres of potable water a day. As part of the water treatment process, 2 to 4 million litres of ferric (iron) sludge per day is generated primarily from the de-sludging of the Pulsator clarifiers. The sludge is primarily a mineral sludge with seasonally fluctuating levels of algae and suspended solids.
Previously, sludge waste at Hanningfield WTW had been pumped to sludge lagoons at Hanningfield Reservoir, but with the reservoirs nearing the end of their serviceable life, a new sludge handling system was required.
ARM Ltd, in partnership with Orbicon, conducted a trial to assess the efficiency of sludge reedbeds in the treatment of the ferric sludge being generated at Hanningfield. A test system consisting of six basins was built at the site, with each basin measuring 20m2 and planted with Phragmites australis. The test basins had a design comparable to a full-scale plant.
The results of the trial confirmed that the sludge treatment in the reedbed systems offered many advantages compared with mechanical treatment options. Key observations included:
As a result of the trial, a full-scale reedbed system was ordered, with a process area of 42,500m2 across 16 basins.