soluble organic sources of biochemical oxygen demand (BoD) can be removed by any viable microbial process, aerobic, anaerobic or anoxic. However, aerobic processes are typically used as the principal means of BOD reduction of domestic wastewater because the aerobic microbial reactions are fast, typically 10 times faster than anaerobic microbial reactionA. Therefore, aerobic reactors can be built relatively small and open to the atmosphere, yielding the most economic means of BOD reduction.