Which method primarily assists in the removal of sludge in suspended growth processes?

The method that primarily assists in the removal of sludge in suspended growth processes is gravity settling. In wastewater treatment systems that use suspended growth processes, such as activated sludge systems, microorganisms are allowed to grow in suspension within the treatment tank. After a certain retention time, the mixed liquor containing both the treated wastewater and the suspended microorganisms is directed to a secondary clarifier or settling tank.

In this clarifier, gravity settling plays a crucial role by allowing the heavier sludge particles, which contain activated biomass, to settle to the bottom under the influence of gravity. This process results in the formation of a distinct sludge layer, which can then be either recycled back to the aeration tank to maintain the desired concentration of microorganisms or removed from the system as waste sludge for further treatment or disposal.

Other methods mentioned, like filtering, are more effective in solid-liquid separation processes but do not specifically facilitate the primary removal of the bulk sludge in this context. Chemical treatment might be utilized for specific pollutants or to flocculate solids, while incineration is typically associated with final sludge disposal rather than the primary separation process within suspended growth systems.