Microbial Ecology of Crown Corrosion in Sewers

Abstract

The sulfuric acid that causes corrosion of sewer crowns is generated by a complex microbial ecosystem. Several species capable of oxidizing sulfur compounds colonize exposed concrete. A microbial succession occurs that is ultimately dominated by Thiobacillus thiooxidans. Heterophilic symbionts consume inhibitory waste products. Characteristics of this system were investigated. Surface pH and corrosion rates of new concrete in an experimental chamber exposed to sewer gases were monitored. After an initial period in which pH varied sharply over periods of hours, days, or weeks, corrosion‐inducing microorganisms were well established. The corroding surfaces were flushed intermittently with sewage to determine whether this might serve as a control method. Heavy and frequent flushing will be necessary to significantly reduce corrosion rates.