title: Biogenic acids produced on epoxy linings installed in sewer crown and tidal zones.
abstract: In this study the biogenic acids generated by microbes on the surface of Bisphenol A epoxy mortar coupons were investigated for up to 30 months. The epoxy coupons were installed in six sewers in three city locations, Sydney, Melbourne and Perth. Coupons were installed in both the crown and the tidal zones of the sewers to capture the effect of location within the pipe on acid production. The coupons were retrieved approximately every 6 months to provide a dynamic analysis of the biogenic acid production. Our results reveal the colonisation of epoxy mortar by the more aggressive acidophilic bacteria occurred within six months to two years of their installation in the sewer pipes. Biogenic acid generation appear to occur homogeneously from the tidal zone to the crown of the sewer pipes. The reduction in the surface pH of the epoxy lining was supported by the successive growth of microbes beginning with fungi followed be neutrophilic and heterotrophic bacteria and finally by the acidophilic bacteria and the corresponding accumulation of organic and sulphuric acids attributed to these organisms. This study also revealed the potential inhibiting effects on the microbes induced by the accumulation of metabolic products on the epoxy surface. The accumulation of organic acids and H2S coincided with the growth and metabolism inhibition of fungi and acidophilic bacteria. These results provide insights into the microbial interaction and biogenic acids production that contribute to lining degradation and corrosion of concrete in sewer pipes.
authors.affiliation: School of Chemical and Biomolecular Engineering, The University of Sydney, NSW 2006, Australia. Electronic address: marjorie.valix@sydney.edu.au.
authors.forename: M
authors.initials: M
authors.lastname: Valix
authors.affiliation: School of Chemical and Biomolecular Engineering, The University of Sydney, NSW 2006, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Shanmugarajah
mesh_terms: D000143:Acids / Q000737:chemistry* / Q000378:metabolism; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism; D002264:Carboxylic Acids / Q000737:chemistry / Q000378:metabolism; D003252:Construction Materials; D003343:Corrosion; D004852:Epoxy Compounds / Q000737:chemistry* / Q000378:metabolism; D005658:Fungi / Q000254:growth & development / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009930:Organic Chemicals / Q000737:chemistry* / Q000378:metabolism; D012498:Sanitary Engineering / Q000379:methods; D012722:Sewage / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry / Q000378:metabolism; D013499:Surface Properties; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: D000143:Acids; D002264:Carboxylic Acids; D004852:Epoxy Compounds; D009930:Organic Chemicals; D012722:Sewage; D013464:Sulfuric Acids; D006862:Hydrogen Sulfide
keywords: Epoxy-A; H(2)S; Organic acids; Sewer corrosion; Sulphuric acid; pH