IFAT 2018

••• 10••• Innovationen Combating sulphuric acid corrosion Researchers from TU Graz and the University of Graz develop new solution for wastewater plants Toxic gases released during bio- genic processes, such as hydrogen sulphide, also pose a significant health risk, causing a range of symptoms from irritation to res- piratory failure and death. Writ- ing in the journal Water Research, an interdisciplinary group of re- searchers from TU Graz and the University of Graz has outlined strategies aimed at preventing what is termed microbial induced concrete corrosion (MICC). Microbial induced acid corrosion in wastewater treatment facilities results from a sequence of biogen- ic sulphate reduction reactions, followed by reoxidation. Initially, sulphate in pressure pipelines or standing wastewater is reduced by bacteria under anaerobic – or oxygen-free – conditions, forming hydrogen sulphide. This pungent, highly poisonous gas escapes in- to the sewer air and diffuses into sewer pipes and manholes. There reoxidation by autotrophic bacte- ria takes place on concrete walls that do not even come into con- tact with wastewater. These microorganisms produce sulphuric acid which reacts with concrete construction elements. As Günther Koraimann of the In- stitute of Molecular Biosciences at the University of Graz, who has studied these processes in detail, explains: “This leads to the vigor- ous formation of a biofilm on the surface of the concrete, a reduc- tion of the pH value to below two, in other words highly acidic, and extensive formation of new min- erals, mainly in the form of gyp- sum. The combination of these processes results in the rapid de- struction of the concrete.” The Graz-based scientists worked on a holistic solution using an inter- disciplinary research approach. In-depth research into the micro- structural and microbiological processes was followed by the de- velopment of new MICC-resistant materials in close collaboration with the Institute of Construc- tion and Building Materials at TU Darmstadt. In this context, geo- polymer concrete proved to be particularly well suited to with- stand acid corrosion. Microbial induced concrete corrosion (MICC) causes massive damage to wastewater plants. Resear- chers from Graz present a new solution against the sulphuric acid attack. Photo: TU Graz Continued from page 1