Activated sludge description?

Activated sludge description?

• A. Fixed-film biological treatment
• B. Chemical precipitation
• C. Membrane filtration
• D. Suspended-growth biological treatment system

Answer: (D)

Activated sludge describes a suspended-growth biological treatment system. In this approach, microorganisms are kept freely in the wastewater, with air or oxygen continually mixed in to supply the microbes and to keep the biomass in suspension. The microorganisms form flocs that biologically oxidize organic matter and nutrients as the wastewater moves through an aeration zone. After sufficient treatment, the mixed liquor passes to a secondary clarifier where the biomass settles out as sludge. Part of that sludge is recycled back to the aeration tank to maintain microbial population, while excess sludge is removed. This contrasts with fixed-film systems, where microbes grow on a surface rather than floating freely, and with chemical precipitation or membrane filtration, which rely on non-biological processes or physical separation rather than suspended biological activity.

Activated sludge describes a suspended-growth biological treatment system. In this approach, microorganisms are kept freely in the wastewater, with air or oxygen continually mixed in to supply the microbes and to keep the biomass in suspension. The microorganisms form flocs that biologically oxidize organic matter and nutrients as the wastewater moves through an aeration zone. After sufficient treatment, the mixed liquor passes to a secondary clarifier where the biomass settles out as sludge. Part of that sludge is recycled back to the aeration tank to maintain microbial population, while excess sludge is removed. This contrasts with fixed-film systems, where microbes grow on a surface rather than floating freely, and with chemical precipitation or membrane filtration, which rely on non-biological processes or physical separation rather than suspended biological activity.