Sequencing Batch Reactor (SBR) system is a variation of the activated-sludge process for treatment of waste water. SBR reactors treat wastewater such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches. Oxygen is bubbled through the mixture of wastewater and activated sludge to reduce the organic matter (measured as biochemical oxygen demand (BOD) and chemical oxygen demand (COD). The treated effluent may be suitable for discharge to surface waters or possibly for use on land.

Process steps of SBR in one basin

It differs from activated-sludge plants because the SBR combines all of the treatment steps and processes into a single tank, thus reducing the footprint, whereas conventional facilities rely on multiple basins.

SBR helps introduce various process flexibilities and alternatives in process controls and design so as to better achieve the latest effluent discharge standards. With its design flexibility and better process control the SBR process has been widely used not only to treat domestic wastewater, but also for biological treatment of industrial wastewater containing difficult-to-treat organic chemicals.

Basins of SBR reactors

Improvements in equipment and technology, like aeration devices, piping design and computer control system, have made SBR an efficient solution over the conventional activated-sludge system. The system is very practical for a number of reasons:

  • Required low area as well as man power operation
  • With effective automated system, it will save more than 60% of the operating expenses than a conventional activated sludge process.
  • Able to achieve high effluent quality in a very short aeration time.
  • Biochemical oxygen demand (BOD) levels of less than 5 mg/L can be achieved consistently.
  • Minimizing sludge handling requirements downstream of SBR


  • Municipal wastewater
  • Effluent of anaerobic treatment process
  • Hotel/resorts
  • Foods and drinks industry
  • Any other type of wastewater with high degradable COD fraction