SEQUENCING BATCH REACTORS (SBR)

(Water Quality) A wastewater treatment technique consisting of an activated sludge system which operates sequentially in time rather than in space, that is, all steps of the process take place, one after the other, in the same tank instead of moving to a second tank for the continuation of the treatment. The typical SBR operation involves filling a tank with raw wastewater or primary effluent, aerating the wastewater to convert the organics into a microbial mass, providing a period for settling, discharging the treated effluent, and a period identified as "idle" that represents the time after discharging the tank and before refilling. Typically, a multiple tank system is required, allowing incoming flow to be switched to one tank while the other is going through the aeration, clarification, discharge, and idle functions. A key element of the SBR process is that a tank is never completely emptied, but rather a portion of settled solids is left in the tank for the next cycle. The retention of sludge within the tank establishes a population of microorganisms uniquely suited to treating the waste.