The SBR process operates on a fill and draw batch system wherein the reactor acts as a biological reactor and settling tank at various stages of the treatment cycle. Wastewater may be accumulated in a batch and then delivered to a reaction tank(s), which contains activated sludge. The batch is subject to biological treatment for a prescribed period with both anoxic and aerobic cycles possible. At the end of the reaction period, the batch is allowed to settle, after which the clarified effluent is decanted from the top of the tank. The sludge remains in the tank to provide the biological population for the subsequent cycle. Excess biomass is pumped on a regular basis to a sludge holding tank for digestion and disposal.
The SBR acts as the equivalent of several components in the conventional activated sludge treatment process, as follows:
1. Aeration Tank: the SBR acts as an aeration tank during the reaction stage where the
activated sludge is mixed with the influent under aerated conditions.
2. Secondary Clarifier: the SBR Tank acts as a secondary clarifier during the settling and
decanting stages where the mixed liquor is allowed to settle under quiescent conditions, and
the overflow is discharged to the next stage of treatment.
3. Sludge Return System: the activated sludge, following settling in the SBR, is mixed with the
influent similar to the sludge return system, except that the feed is transferred to the sludge
rather than the sludge being transferred to the front end of the plant.
The SBR process is an activated sludge process, which, as the name implies, treats wastewater batches through a timed sequence of operations within a reactor tank(s). All aspects of the wastewater treatment sequence are readily controlled by a PLC (programmable logic controller), and the plant can be remotely monitored through a graphical computer interface.
• True batch mode of operation,
• Nutrient removal capabilities,
• Solids excluding decanters,
• Production of high quality effluents of near tertiary quality,
• Complete process train including sludge inventory control,
• Minimal operating costs,
• Computer interface technologies and advanced monitoring instrumentation capability,
• The influent and effluent are never directly hydraulically connected so that process short-
circuiting and washout of sludge is very unlikely and high effluent qualities can be consistently
• The settling cycle provides ideal flocculation opportunity for the solids and therefore results in
better clarifying of the effluent before discharge.
• The settling cycle is isolated and quiescent so is not disturbed by velocity currents due to flow
entering and leaving in an uncontrolled manner -- resulting in more efficient use of the clarifier
and better effluent quality.
• The process results in better conditions for the culture of biological growth, which allows
improved, more intuitive, operator control of the sludge inventory and sludge properties.