Foam flow cleaning, an effective and environmentally friendly method for controlling the hygiene of closed surfaces contaminated with biofilms

This work investigates the capacity of a foam flow to clean stainless-steel surfaces contaminated by bacterial biofilms. Three bacterial strains ( Escherichia coli SS2, Bacillus cereus 98/4, and Pseudomonas fluorescens Pf1) were grown for 24 h in a horizontal position. Wet foam (liquid fraction of 0.5) using Sodium Dodecyl Sulfate (SDS) at 0.15 % W/W circulated through square stainless-steel ducts at different flow rates. By increasing the wall shear stress, a cleaning efficiency was observed of up to a 2.1 and 1.4 log reduction in the surface contamination for both of the two highly adherent biofilms tested, namely B. cereus and P. fluorescens compared to E. coli biofilms being totally removed. Whatever the bacterial strain and the flow condition, foam flow was more efficient in detaching biofilm than the related SDS solution without foam. A Life Cycle Assessment study was performed to investigate the environmental impacts of the foam cleaning. Significant environmental impact benefits were observed, with a drastic reduction in water and energy consumption when compared to different no-foam in place cleaning conditions (SDS or NaOH at 60 °C).