Peroxygen disinfection of pseudomonas aeruginosa biofilms on stainless steel discs

Abstract

The disinfection of Pseudomonas aeruginosa biofilms on stainless steel (AISI 304) by a formulation of peracetic acid and hydrogen peroxide [Proxitane®5] has been studied using a laboratory scale rig incorporating a modified Robbins device. The influence of disinfectant temperature, flow rate and concentration has been characterised and comparisons made between biofilms established under static and nutrient flow conditions. Disinfection was enhanced with increased concentration of disinfectant (1–25 ppm peracetic acid, PAA) at all flow rates tested. The greatest reduction in viable cell number occurred at the highest temperature tested (50°C). At 30°C, the transition from laminar to turbulent flow (at 0.768 ms‐1) was accompanied by a 99.7% increase in disinfection at 15 ppm PAA. This effect was not attributable to dislodgement of cells by increased fluid mechanical shear alone. Increased flow velocity (0 to 0.993 m s‐1) and moderate (10°C) increments in temperature enhanced disinfection effectiveness in the Proxitane®5 concentration range corresponding to 5 ppm PAA to 25 ppm PAA. An insight into biofilm disinfection has been gained and the results are relevant to industrial Clean‐in‐Place processes.