Nicholas Critchley, Savcor
Concrete waste water structures can deteriorate at a rapid pace when measureable concentrations of hydrogen sulphide gas are present in a local environment. Hydrogen sulphide is formed in sewerage systems when sulphates are reduced by anaerobic bacteria. Whilst not a corrosive agent in itself, through adsorption onto moist exposed surfaces of the concrete it can then undergo oxidation into a weak sulphuric acid solution which over time attacks the concrete. The cement paste is eroded which causes loss of the cover layer. As our communities have become more sensitive to the odours of sewerage transfer, treatment and storage structures have been enclosed to restrict the release of odours.
Containment and the subsequent increase concentration of H2S gas within these structures has in turn caused accelerated deterioration of the concrete. To protect against these damaging effects engineers have turned to high quality coatings and linings and chemical resistant mortars.