Combining industrial biocides with polarization. Biofilms were grown (8.5 ml of the SPW medium) in vials of stainless steel in the DBA instrument as described for Fig. 2. The vials were emptied and refilled (20.5 ml) with SPW containing (0 ppm, 5 ppm, 25 ppm, or 50 ppm) of the indicated biocide (technical product). Biocides with concentrations of 5–25 ppm were combined with polarization. The technical products contained the effective substance 2-dibromo-2-cyanoacetamide (20%), bromochloro-5,5-dimethylhydantoin (99% w/w), or peracetic acid (15% peracetic acid with 13–16% H₂O₂ w/w). The columns indicate the total amount of biofilm found per vial 48 h later (45°C, 87 rpm). The columns show averages of two independent experiments with the error bars