Efficient wastewater treatment relies on high rates of bacterial metabolic activity - cell growth and maintenance. This research has developed and applied methods to reliably and simply measure the cells metabolic state and maintenance using [NADH] fluorimetry. These measures, alongside those of in situ DNA and protein synthesis, describe how bacteria allocate energy to create more (undesirable) or less (desirable) biomass through respiration. This research success can be applied to better understanding the microbial processes that control water quality of both natural and engineered environments.