Bioremediation Both aerobic and anaerobic euglenozoans are sufficient component of activated sludge in aeration tanks. The activated sludge process is a type of biological
wastewater treatment process for treating
sewage or
industrial wastewaters using
aeration and a biological
floc composed of bacteria and
protozoa. It uses air (or
oxygen) and
microorganisms to
biologically oxidize organic pollutants, producing a waste sludge (or
floc) containing the oxidized material. The general arrangement of an activated sludge process for removing carbonaceous pollution includes the following items: An aeration tank where air (or oxygen) is injected in the mixed liquor. This is followed by a settling tank (usually referred to as “final clarifier” or “secondary settling tank”) to allow the biological flocs (the sludge blanket) to settle, thus separating the biological sludge from the clear treated water. Part of the waste sludge is recycled to the aeration tank and the remaining waste sludge is removed for further treatment and ultimate disposal.
Plant types include package plants, oxidation ditch, deep shaft/vertical treatment, surface-aerated basins,
sequencing batch reactors (SBRs). Aeration methods include diffused aeration, surface aerators (cones) or, rarely, pure oxygen aeration.
Sludge bulking can occur which makes activated sludge difficult to settle and frequently has an adverse impact on final effluent quality. Treating sludge bulking and managing the plant to avoid a recurrence requires skilled management and may require full-time staffing of a works to allow immediate intervention. A new development of the activated sludge process is the
Nereda process which produces a granular sludge that settles very well.