EXTRAPOLATION OF BIODEGRADABILITY TEST DATA BY USE OF GROWTH KINETIC-PARAMETERS

Formulas for extrapolation of test data on biodegradability to percent age removal in treatment plants and biological half-life time in surfa ce water are derived from growth kinetics. A pseudo-first-order rate c onstant can be used provided that substance properties and microbial d ensity in the environment are assessed independently. For comparison o f kinetics at different concentration levels an extrapolation factor c an be used that is based on the ratio between maximum growth rate and sludge age in a treatment plant. The specific microbial density is est imated on the basis of proportional growth on all degradable substance s in a state of equilibrium after adaptation. As a consequence the per centage removal can be predicted on the basis of sludge age and influe nt concentration in combination with the substance properties. The for mulas predict that the combination of sewage treatment and surface wat er gives an almost equal biological half-life time for all readily bio degradable substances in the surface water. The predicted removal perc entages and biological half-life times are in agreement with observati ons. (C) 1994 Academic Press, Inc.