An SBR
system does not require an RAS system, as both
aeration and settling occur in the same tank. This
prevents any sludge from being lost during the react
step and eliminates the need to return sludge from
the clarifier to the aeration chamber (Metcalf and
Eddy, 1991).
Oxidation ditches
An oxidation ditch, a modified form of the
activated sludge process, is an aerated, long term,
complete mix process. Many systems are designed
to operate as extended aeration systems. Typical
oxidation ditch treatment systems consist of a single
or multi-channel configuration within a ring, oval,
or horseshoe-shaped basin. Horizontally or
vertically mounted aerators provide aeration,
circulation, and oxygen transfer in the ditch.