A rapid, direct measurement of bacterial growth rate in anaerobic wastewater treatment

Reliable design and operation of biological wastewater treatment systems demand robust models of biological degradation processes. However, methods to directly measure key bacterial growth kinetics have not been readily available. Those methods that are available rely on the classic measurement of aerobic respiration using oxygen uptake take rates. This paper shows how the thymidine assay can be used as a rapid and direct measurement of bacterial specific growth rates (mu) in situ for an anaerobic treatment process, independent of aerobic respiration. A filtration-based assay is applied and evaluated a dispersed-phase high-rate anaerobic treatment process, with results obtained in less than an hour. The chemical oxygen demand (COD) biomass in the reactor was 0.52 kg COD m(-3) and the specific growth rate of these anaerobic bacteria was 0.8 +/- 0.2 d(-1). It took the bacterial populations 21.6 hours to double. This is an important advancement from existing methods that use aerobic respiration as a pseudo measurement of bacterial specific growth rates. The method allows rapid and direct measures of microbial growth rates for anaerobic treatment processes.