1. Description and working principle The BioAugmentation Batch Enhanced (BABE®) process is comprised of a single batch reactor. Side stream waters high in ammonia content and return activated sludge (RAS) from the main biological treatment process are combined (STOWA 2006) with previously settled sludge in the batch reactor. The RAS is used to augment the bacteria in the settled sludge. By utilizing a batch reactor, the long residence times necessary to grow both the nitrifying and denitrifying bacteria are possible. There are five phases to the BABE® process: 1) filling, 2)mixing and aeration 3)mixing 4)settling, and 5) settling and decant (STOWA 2006).