A Novel Zeolite Coating for Protection of Concrete Sewers from Biological Sulfuric Acid Attack

Abstract

Microbial growth inhibition and resistance to biological deterioration of concrete specimens coated with silver-loaded zeolite was evaluated by measuring the time course of bacterial growth, biological sulfur oxidation, and sulfate production using Acidithiobacillus thiooxidans as a corrosive agent. Live bacterial cells declined from an initial inoculum concentration of 1.1 × 104 cell ml-1 to zero in 10 days, during which only 0.5–1% of the initial sulfur concentration of 10 g l-1 was biologically oxidized, corresponding to sulfate production rates of 35–42 mg SO 4 2 − g − 1 S − 1 . Leaching coefficients of calcium and silicon in the specimens coated with silver-loaded zeolite of 1.6 × 10 − 4 to 4.6 × 10 − 2 cm 2 d − 1 respectively, were only 0.8% and 1% of the uncoated specimens.