Page 13 - Simplified Wastewater Treatment Fundamentals\SBR

Sequential Batch Reactors (SBR)

SBR Sequence cont.

Settling – This third sequence of treatment stops aeration and allows the mixed

liquor to settle within the same tank space. The SBR tank turns into a clarifier.

Decanting – The settled mixed liquor forms a blanket on the bottom of the tank

creating a clear upper layer, or supernatant. SBR’s are equipped with movable

discharge weirs, allowing the clear layer to be decanted as effluent. As the tank

level drops, the movable weirs adjust to the lowering level.

Idle - Under low flow conditions an SBR tank can idle after the end of a treated

batch until enough wastewater is available to be pumped to and fill the SBR Tank.

Mixing, Aeration, Settling and Decanting is considered one cycle or batch. Each

cycle or batch can take as long as 4 hours.