Sequential Batch Reactor (SBR) Sewage Treatment Plant

A Sequential Batch Reactor (SBR) is a type of wastewater treatment system used for the biological treatment of
wastewater, particularly in processes like sewage treatment, nutrient removal. The SBR process allows for batch
processing in a single reactor, where the wastewater is treated in sequential phases.
In the SBR process, the treatment occurs in distinct phases and in a batch manner rather than a continuous flow.
This gives the system flexibility to operate effectively even when wastewater characteristics change over time.
Basic Phases of the SBR Process:
1. Fill Phase (Influent Phase):
o The wastewater is introduced into the reactor during this phase.
o The fill phase typically lasts a few hours, and during this time, the influent is mixed with activated
sludge (microorganisms) present in the reactor.

2. React Phase (Aeration Phase):
o The wastewater is aerated in this phase to allow microorganisms to degrade organic matter, such
as ammonia and carbon, and to promote the growth of the microbial community.
o Oxygen is supplied to the reactor, which supports the aerobic microorganisms that break down
organic pollutants.
o Nitrification (conversion of ammonia to nitrate) typically occurs in this phase.
3. Settle Phase:
o After aeration, the air supply is turned off, and the mixed liquor (water containing microorganisms
and pollutants) is allowed to settle.
o The microorganisms, including the activated sludge, settle to the bottom, forming a sludge blanket.
o The treated water (supernatant) can then be decanted or removed from the top.
4. Decant Phase:
o The supernatant (treated effluent) is removed from the top of the reactor after the sludge has
settled.
o The supernatant is discharged in filter feed tank and further pumped through filtration units. .
5. Idle Phase (Optional):
o A resting or idle phase may be included for system maintenance or to allow for additional
clarification of the effluent.

The Sequential Batch Reactor (SBR) process in a Sewage Treatment Plant (STP) operates in batch cycles, allowing
the treatment of wastewater through phases like filling, aeration, settling, and decanting. It provides flexibility, high
treatment efficiency, and is particularly useful for handling variations in wastewater flow and composition.