Microbial catalyzed acid production in Los Angeles County sewers

Abstract

Corrosion of concrete sewer crowns will cost the County Sanitation Districts of Los Angeles County approximately $150 million for repairs to their deteriorating sewage system. Other parts of the country are experiencing similar problems. Crown corrosion is induced by microbial oxidation of reduced sulfur to sulfuric acid, which attacks the concrete. Bacteria, of the genus Thiobacillus are generally responsible for catalyzing these reactions. Thiobacillicollected from sewers were used to establish stoichiometry and biochemical aspects of sulfide oxidation. Metals inhibition was studied among the same cultures. Thiobacilli collected from extremely corroded sewers possess a greater tolerance for metals than those from lightly corroded areas. Acidophilic isolates grow at greater rates and oxidize sulfide more efficiently than non-acidophiles. Chemical inhibitor studies indicated that S(-II) oxidation is tightly linked to respiration by T. thiooxidans. It is doubtful that initial steps in bacterially catalyzed S(-II) oxidation are linked to oxidative phosphorylation.