Two large escalator screens with 6 mm perforation are installed at the inlet of the Chelmsford wastewater treatment plant with each screen arranged to discharge the screenings into a common launder channel. The launder water and the screenings were originally discharged into a macerator tank located at the end of the launder channel. A pair of macerator pumps forwarded the macerated solids and the water to a pair of washer dewaterers from where the dewatered solids were discharged into a skip located alongside the units in an odour controlled container. Basically the existing screenings handling plant were D-shaped screens with a screw compactor on the discharge side.
The operators experienced wear problems of the macerator pumps due to presence of grit, but their major problem was that the washer dewaterers were not able to process the amount of solids fed to them during peak times.
Anglian Water decided to replace their screenings handling system with a pair of super-launder wash-presses HUBER WAP/SL size 6, though this involved some modification of the existing launder channel system. Each WAP/SL unit is designed to intensively wash, dewater and compact up to 4 m³/h wet screenings. However, at peak times the units automatically alter their operating cycle such that each can handle 6 m³/h.
Since Anglian Water has replaced their existing screenings handling system with our super-launder wash-presses WAP/SL, they have made significant savings in operating and maintenance costs. The operators are happy because our units work far more reliably than their prior system.
Because Anglian Water has been so content with our WAP/SL super-launder wash-presses, we have supplied units of various sizes for replacement of failing screenings handling systems to other Anglian Water plants, e.g. Southend, Rochford, Wickford and Burnham on Crouch and many others. We also supply our units to other UK water companies and have over 100 units installed. It appears that our WAP/SL has become the accepted state-of-the-art screenings wash-press in the United Kingdom.
By Dale Foster, Regional Manager for Huber Technology, UK