Weaverbrook Circular Tank Scraper
Weaverbrook Circular Tank Scrapers: Overview
Sludge thickening carried out in circular tanks can be categorised into 3 main areas
1) Storm Tanks
These take excess flow during periods of high rainfall and are typically used as buffer tanks to hold the excess effluent until the storm has passed, and the contents of the tank can then be fed into the normal system. The tanks may often have no weirs or diffusion drum or scum removal. The heavier solids do however settle out and so these tanks are provided with bridge scrapers.
2) Primary Tanks
These are the normal first stage of treatment (after coarse/fine screening to remove tramp materials and oversized solids). There is normally no attempt at scum removal at this stage but much depends on the incoming flow make-up and it therefore may be necessary to remove excessive scum at this point to reduce the scum load on the final stage scrapers.
3) Final/Humus Tanks
Usually the last process unit(s) between the main treatment chain and the discharge point to watercourse or sea outfall. Scum removal is usually applied at this stage, as is weir/launder cleaning, to prevent large congestions of algae etc breaking away and distorting instantaneous sampling results.
A further application is the use of Picket Fence Thickeners for sludge consolidation prior to pressing or centrifugal dewatering.