Sludge withdrawal mechanism for wasting and returning settled sludge from secondary clarifier with granular sludge

A method of separating settled sludge from a clarifier, comprising:

• introducing a mixed liquor comprising an activated sludge into the clarifier;
• allowing the mixed liquor to settle an effective amount of the activated sludge forming a clarified zone comprising an effluent, a disperse sludge zone comprising flocculant sludge, and a settled sludge zone comprising settled sludge;
• providing a composition sensor fluidly connected to a waste conduit of the clarifier and operably connected to a controller;
• determining a relative concentration of the flocculant sludge and the settled sludge in the waste conduit based on measurements obtained by the composition sensor;
• withdrawing at least some of the flocculant sludge from the disperse sludge zone and directing the withdrawn flocculant sludge to waste, wherein withdrawing the at least some of the flocculant sludge comprises directing an upper header along the disperse sludge zone to collect the at least some of the flocculant sludge;
• controlling, via the controller, a height of the upper header responsive to the measurements obtained by the composition sensor to collect at least some of the flocculant sludge, and
• withdrawing at least some of the settled sludge from the settled sludge zone and directing the withdrawn settled sludge to an upstream treatment operation.