Sequential Batch Reactor

The Sequential Batch Reactor (SBR) process is a sequential suspended growth (Activated sludge) process in which all major steps occur in the same tank in sequential order the complete five phases take place in single reactor thus reducing overall plant footprint. By this process we can achieve enhanced removal of nitrogen, phosphorus and ammonia, in addition to removing TSS and BOD.

The Five stages of SBR are

  • FILL: Waste water fills the tank, mixing with biomass that settles during the previous cycle.
  • REACT: Aeration is provided into the tank to aid biological growth and facilitate waste reduction.
  • SETTLE: Mixing and Aeration stop during this stage to allow solids to settle.
  • DRAW: Clarified effluent is discharged.
  • IDLE: Sludge can be removed during this stage.


  • Lower installed cost that "conventional" methods.
  • Consistent high - quality , low nutrient level effluent.
  • Tolerates wide variation in flow and organic load
  • No clarifier required
  • Better control over filamentous growth and settling problems.
  • Nutrient removal without chemicals - nitrification, de-nitrification and phosphate removal
  • Simple sludge process management.
  • Less equipment to service and maintain
  • Existing plants can also be converted to SBR process
  • Less operator attention than "Conventional" process
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