In circular tanks; the flow pattern is radial. To supply a radial flow; the wastewater can be entered to the tank from the center or around the periphery of the tank. Peripheral driven rotating scrapers removes the settled sludge by echelon or logarithmic spiral shaped scraper blades in the central located sludge collection pit.
Also suction system can be widely used in the conditions where excavation costs dictate a flat or very shallow bottom and in applications where very hot climates or other process limitations forcing a short retention period, in order to prevent denitrification and septical conditions for settled solids. In this design the settled sludge is evacuated by pipes.
Surface skimmer device is used for removal of scum and other floating materials. Scum sump and scum pump configurations are also available.
Medya