BCs are more resistant to process upsets for two reasons. First, the microorganisms are attached to the media and are not washed out of the system by high flows. Since the microorganisms are attached to the media, recovery from toxic discharge upsets is much more rapid. Second, there are more kilograms of microorganisms in an RBC plant than an activated sludge plant. The more microorganisms in a system, the better able it is to withstand increased organic loads and toxic discharges.