Sequencing Batch Reactors In Wastewater Treatment Plants

Activated sludge systems use suspended natural biological and bacterial growth to remove contaminants by absorption and subsequent breakdown. Sequencing batch reactors (SBR) are a special form of activated sludge treatment in which all of the treatment processes take place in the reactor and clarifiers are not required. This process treats the wastewater in batch mode and each batch is sequenced through a series of treatment stages. 

Sequencing batch reactors or sequential batch reactors treat wastewater such as sewage in batches. Oxygen is bubbled through the wastewater to reduce both biochemical and chemical oxygen demand. In turn, this makes the effluent suitable for discharge to surface waters or use on land. 

HOFFMAN & LAMSON blowers are the premier provider of engineered solutions for sequencing batch reactors across a wide range of applications. Our blowers deliver quality, reliability, value, and performance to serve many wastewater applications including, sequencing batch reactors. 

Sequencing Batch Reactor Process

While there are several configurations of sequencing batch reactors, the process is similar for all. The basic installation consists of at least two identically equipped tanks with a common inlet, which can alternate the flow between them. The tanks have a “flow-through” system with raw wastewater (influent) coming in at one end and treated water (effluent) flowing out the other. While one tank is in settle/decant mode the other is aerating and filling.

Sequencing Batch Reactors in Wastewater Treatment

Sequencing Batch Reactor Treatment Stages

    1. Filling - The sequencing batch reactor tank is filled with the influent in a rapid, controlled manner to maintain suitable food-to-microorganism ratios. This function is similar to a selector, which encourages the growth of microorganisms that have better settling characteristics. Mixing is provided by mechanical means (no air). This stage is also called the anoxic stage. 
    2. Reaction - This stage promotes the utilization of biochemical oxygen demand and ammonia, where applicable by microorganisms. The length of the aeration period depends on the strength of the wastewater and the degree of nitrification (conversion of ammonia to a less toxic form of nitrate or nitrite) required by the treatment. Aeration of the mixed liquor is performed by the use of fixed or floating mechanical pumps or by the injection of air through fine bubble diffusers fixed to the floor of the tank. 
    3. Settling - Aeration is stopped and the sludge settles, leaving clear, treated effluent above the sludge blanket. 
    4. Decanting -The “clean” process effluent is removed from the tank through the decanter, without disturbing the settled sludge. 
    5. Idling - The sequencing batch reactor tank is idle until it is time to commence a new cycle. 

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