AWWA QTC98285

This paper examines the mechanisms of the resistance of biofilm in the presence of different chlorine species. The impact of chlorine and monochloramine on bacterial viability in the biofilm is addressed and the composition of the exopolymer before and after the application of different doses of both disinfectants is characterized. The biofilm was grown on glass beads in four stainless-steel reactors fed with yeast-extracts-enriched tap water. After a biomass steady state was reached in the reactors, chlorine was applied to reactors 2 (1 mg/L and 3 (2.5 mg/L); reactor 4 was chloraminated at a dosage of 3 mg/L monochloramine and no disinfectant was applied to reactor 1 (control). The active biomass in the biofilm was measured using four different methods adapted from the following references: the potential exoproteolytic activity; the radioactive glucose respiration; the BacLight staining; and, the phospholipids analysis. The three former techniques are based on bacterial activity while the phospholipids analysis is performed after extraction and digestion of the biomass. The BacLight technique allows the dead/live counts under epifluorescence microscopy. Carbohydrates and amino acids in the biofilm are analysed using chromatographic techniques after digestion of the exopolymer. A pulsed amperometric detector determines carbohydrates, and amino acids are detected after derivatization by o-phtaldialdehyde.