Sequencing Batch Reactors (SBRs)
Download the ADI-SBR brochure.
Sequencing Batch Reactors, or SBRs, are an advanced form of activated sludge technology whereby all process reactions and sedimentation/clarification take place in the same reactor vessel. The unit of time, rather than space, is used to separate process reaction events – that is, a process controller/computer is used to coordinate the sequencing of events/environments in a single tank to treat wastewater in batches. The result is that no separate unit vessels, clarifiers or return sludge pumps are required. This saves on land, labor and maintenance costs.
The SBR removes organic material and suspended solids, like conventional activated sludge systems, plus it can also be used to biologically remove nutrients – nitrogen and phosphorus.
How does an SBR work?
Different environments are created in the SBR by controlling process equipments such as aerators, mixers, pumps and decanters during a cycle. By linking a programmable logic controller (PLC), the process is easily monitored and controlled on-site by plant personnel. The timing and sequencing of events in an SBR cycle depend on the influent wastewater characteristics and the treatment objectives.
Typically there are four cycle events:
- FILL – The influent wastewater is distributed into the sludge blanket. The FILL event can take place under mixed or unmixed and aerated or un-aerated conditions.
- REACT – The REACT event includes mixing and aeration. Aerated conditions serve to oxidize organic carbon, nitrify ammonia and promote uptake of phosphorus in the sludge. Un-aerated conditions promote denitrification and phosphorus removal.
- SETTLE – The SETTLE event is when all mixing and aeration is turned off and the mixed liquor solids settle, allowing a clear supernatant to form in the upper part of the reactor.
- DECANT – The DECANT event occurs after a substantial depth of supernatant has formed. Automatic valves open and supernatant is drawn off the upper portion of the tank. Sludge wasting can occur during this time as well, as the settled sludge bed will have attained a maximum solids concentration.
The possible variations and combinations of events within the single reactor allow for the removal of organic carbon, suspended solids, ammonia, total nitrogen and total phosphorus. The most important and fundamental advantage of the system is flexibility.
The ADI-SBR has a number of benefits over more conventional activated sludge systems, including:
- Lower capital and operating costs
- Greater ability to meet effluent limitations (organic and nutrient)
- Better resistance to sludge bulking
- No need for external clarifiers
- Easily adaptable to nutrient removal
- Greater system flexibility and control
- Less land required and less equipment to maintain
- Can retrofit existing tanks, basins, ponds and convert to SBR
ADI-SBR technology has been proven on wastewaters from a wide variety of industries, including:
- Pharmaceutical
- Pulp and paper
- Corn wet-milling
- Dairy processing
- Chemicals production
- Food processing
- Meat processing
- Yeast
- Potato processing
- Fish processing
- Bakery
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