Transient chlorine profiles within a biofilm during treatment with a flowing solution of approximately 2.5 mg/L of free chlorine.  The biofilm-bulk fluid interface was at distance zero; biofilm is represented by negative distances and the chlorine solution by positive distances.  These five profiles constitute a time series spanning 75 minutes.  There was slow advance in the penetration of chlorine over this period.  Chlorine penetrated only about 100 microns into the biofilm in this experiment.  See de Beer et al., 1994.