Biomass Activity Tests PDF Print


Pulse-Flow respirometers can be used to assess biomass activity for aerobic and anaerobic reactions. In aerobic tests, cultures are combined with nutrients, trace minerals, and an organic substrate – such as acetic acid or ethanol. The maximum oxygen uptake rate reflects the amount of active biomass in the test culture. Examples are shown below:

Aerobic Biomass Activity

In the case illustrated here, a culture having a VSS concentration of 2,000 mg/L was exposed to 300 mg/L of acetate COD. The active biomass concentration was determined from kinetic modeling to be 320 mg/L so that the VSS in the test culture was the 16 % active acetate-utilizing microorganisms.

Anaerobic Biomass Activity

In anaerobic tests, the active biomass is indicated by the maximum specific methane production (SMP) rate in the presence of high concentrations of acetic acid, ethanol or other organic substrates.

In this example, the maximum SMP for Sample #1 was 1.4 g CODCH4/g VSS/day. The maximum SMP for 100% active acetoclastic methanogens is 6 g COD/g VSS-d. Therefore, the test culture contained 23% active methanogens.