Effectiveness of <i>E. coli</i> Biofilm on Mortar to Inhibit Biodegradation by Biogenic Acidification

Abstract

Effectiveness of E. coli DH5α biofilm growth on mortar surfaces to inhibit microbiologically-influenced deterioration is investigated. Unlike traditional chemical deterioration processes through direct acid addition, biodegradation is realistically simulated through biogenic acidification using two species of sulfur-oxidizing bacteria (SOB). Calcium leach-out analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) suggest that E. coli DH5α biofilm prevents or controls microbiologically-induced mortar deterioration. The pH of the solution in the reactor containing E. coli biofilm-covered mortar did not decrease as the SOB was not able to grow. However, the growth of SOB in the control reactor with mortar increased the sulfate concentration to 6,350 mg/L and the calcium leach-out to 69&nbsp;ppm. SEM and XRD analyses showed the presence of gypsum on control mortar without E. coli biofilm; however, there was no sign of gypsum on the biofilm-covered mortar surface. Fluorescence in situ hybridization analysis shows that SOB did not attach to the surface of biofilm-covered mortar and the E. coli biofilm was still present after biogenic acidification.