Determination of Biodegradation Kenetics by Respirometry
Intrinsic kinetic tests involve adding relatively high concentrations of organic substrate to small concentration of acclimated microorganisms so that the COD/VSS ratio typically is greater than 10. Kinetic parameters are then determined by non-linear modeling using well-known relationships between biological growth and oxygen uptake. Examples are shown below:
In this example, 700 mg/L of glycerin COD was added to a test culture containing 45 mg/L of active biomass. Modeling showed the following kinetic parameters: Yield coefficient, Yg = 0.42 mg VSS/mg COD removed; specific substrate conversion rate, qm = 0.35 mg COD/mg VSS/hr; specific growth rate, μmax = 0.10 g VSS/g VSS-hr.
Extant kinetic tests involve adding relatively low concentrations of organic substrate to large concentrations of biomass so that the COD/VSS ratio usually is less than 0.1. Extant kinetic parameters are then determined by using non-linear modeling techniques. Examples are shown below:
This example shows the results of dosing an anaerobic culture with three concentrations of an industrial cleaning agent followed by respirometric measurement of methane production. The threshold toxic concentration was less than 80 mg/L of product and 800 mg/L produced a 50% decrease in methane production rate.