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Wang D.,National Research Council Canada | Cullimore R.,Droycon Bioconcepts Inc. | Hu Y.,National Research Council Canada | Chowdhury R.,National Research Council Canada
International Biodeterioration and Biodegradation | Year: 2011

Various types of microorganisms have been found to inhabit the inner surfaces of asbestos cement (AC) pipe and their activities can cause significant structural damage. They cause a patina to form on the inside surface of AC pipes as a distinctively continuous coating, commonly 2-5 mm in thickness and generally pigmented as yellow, orange, brown or black depending on the metallic cations that have been incorporated into the surface of biofilm (bioaccumulation). Four sublayers can be identified in the patina, from the outer sublayer that directly interacts with the conveyed drinking water to the inner sublayer that is in proximity of the intact cement matrix. The microbes in the outer sublayer are composed mainly of inactive biomass that separates the aerobic environment of the flowing water from the anaerobic conditions inside the patina. The bacteriological community structure shifts from mixed heterotrophic bacteria (HAB), iron-related bacteria (IRB) and slime-forming bacteria (SLYM) in the outer layer, to a more diverse community with IRB, acid-producing bacteria (APB) and SLYM and HAB in the middle sublayer, and further to the SLYM dominated in the inner sublayer. By directly interacting with cementitious materials, including generating organic acids, IRB and APB play important roles in the leaching of free lime and the dissolution of calcium (Ca)-bearing hydrated components of AC pipes, creating porous structure and reducing the pipe strength. Scanning electron microscopy with an energy dispersive X-ray has revealed that bacterial activity on the internal AC pipe wall had resulted in a significant loss of hydrated cement matrix, which can cause pipe failure when stresses imposed on the pipe exceed the remaining pipe strength. © 2011. Source


Wang D.,NRC Institute for Research in Construction | Cullimore D.R.,Droycon Bioconcepts Inc.
Journal of Environmental Sciences | Year: 2010

Asbestos cement (AC) pipes were commonly installed in the drinking water distribution systems from the mid 1920s to the late 1980s. In recent years, an increase in the number of water main breaks has occurred in the AC portions of some pipe networks, which can be partially attributed to the corrosion of the aged pipes. This study evaluated the potential role that microorganisms may have played in the degeneration and failure of AC pipes. In this study, a fresh AC pipe section was collected from the distribution network of the City of Regina, Canada and examined for microbiological activities and growth on inside surfaces of pipe sample. Black slime bacterial growths were found to be attached to inner pipe surfaces and a distinctively fibrous internal coating (patina) with iron oxides was formed over the time. The microbial populations inside the patina and the black slime were tested with BART(tm) testers. Heterotrophic aerobic bacteria (HAB) and slime forming bacteria (SLYM) dominated in both the black growths and inside the patina. Iron related bacteria, denitrification bacteria and sulfate reducing bacteria were also commonly present. Microbial challenge assays were conducted by submerging the cut segments of the AC pipe into selected bacterial cultures for a period of 10 days under both aerobic and anaerobic environments. Weight changes were determined and the surface morphology was examined for each of the assayed pipe segments. Results indicated that acid producing bacteria, SLYM and HAB could facilitate the pipe weight loss under anaerobic environments. © 2010 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Source


Nelson K.Y.,University of Regina | Razban B.,University of Regina | McMartin D.W.,University of Regina | Cullimore D.R.,Droycon Bioconcepts Inc. | And 2 more authors.
Bioelectrochemistry | Year: 2010

A new methodology is presented here as an effective, preliminary technique for the identification of indigenous aerobic and facultatively anaerobic bacterial communities found within microbial fuel cells (MFCs). The dual-phased method, named Rapid Agitation Static Incubation-Microbial Identification, or RASI-MIDI, is comprised of rapidly agitating the sample within a SLYM-BART tester followed by stationary incubation which produces a biomass that is subjected to extraction of methyl ester fatty acids. These distinctive fatty acid profiles represent a bacterial community fingerprint unique to the MFC, and are stored in a library for analysis. A total of 84 samples were analyzed for bacterial community structures from seven different groups of MFCs, with each MFC group comprised of a different bacterial community. Results showed that comparisons of replicate MFCs comprising the same bacterial communities generated high similarity index (SI) numbers (SI values ranging from 0.77 to 0.97), indicating highly correlated fatty acid profiles. In contrast, comparisons of MFCs having known dissimilar community structures did not consistently generate SI values in the analysis considered to be a significant match. It was found that this protocol described herein uniquely and accurately produced MFC fatty acid profiles contained in bacterial communities and thus provides a potential method for routinely studying MFC bacterial community fingerprints. © 2009 Elsevier B.V. All rights reserved. Source


Razban B.,University of Regina | Nelson K.Y.,University of Regina | McMartin D.W.,University of Regina | Cullimore D.R.,Droycon Bioconcepts Inc. | And 2 more authors.
Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering | Year: 2012

An analytical method to produce profiles of bacterial biomass fatty acid methyl esters (FAME) was developed employing rapid agitation followed by static incubation (RASI) using selective media of wastewater microbial communities. The results were compiled to produce a unique library for comparison and performance analysis at a Wastewater Treatment Plant (WWTP). A total of 146 samples from the aerated WWTP, comprising 73 samples of each secondary and tertiary effluent, were included analyzed. For comparison purposes, all samples were evaluated via a similarity index (SI) with secondary effluents producing an SI of 0.88 with 2.7% variation and tertiary samples producing an SI 0.86 with 5.0% variation. The results also highlighted significant differences between the fatty acid profiles of the tertiary and secondary effluents indicating considerable shifts in the bacterial community profile between these treatment phases. The WWTP performance results using this method were highly replicable and reproducible indicating that the protocol has potential as a performance-monitoring tool for aerated WWTPs. The results quickly and accurately reflect shifts in dominant bacterial communities that result when processes operations and performance change. © 2012 Copyright Taylor and Francis Group, LLC. Source


Razban B.,Droycon Bioconcepts Inc. | Chen W.,University of Regina | Wang D.,National Research Council Canada | McMartin D.,University of Regina | Cullimore R.,Droycon Bioconcepts Inc.
NACE - International Corrosion Conference Series | Year: 2010

Asbestos reinforced concrete (ARC) pipes were commonly used for drinking water distribution networks in North American, primarily from middle1940s to early 1980s. In the City of Regina, Canada approximately 68% of all water mains are ARC pipes, to a total length of 535 km. In this preliminary research it was found that bacteriological activities within the internal surface coating (patina) as well as within the concrete could induce bio-deterioration, which eventually leads to pipe failures. Identification of the bacterial consortia was performed using the S43048 protocols for the chromatographic detection of the C5 to C20 fatty acids methyl esters (FAME). Using proprietary library software, high similarity indexes were statistically generated, confirming the ubiquitous nature of the bacterial community (consortium) within the patina (a distinctively fibrous internal coating) of various pipe samples. Bacteriological activities caused deterioration to the ARC pipes was primarily related to acid producing bacteria. These bacteria are fermentative in the reductive environments, generating sufficient fatty acids that would reduce the pH into the acidic range of 3.5 to 5.5 and could cause structural failures in the concrete. © 2010 by NACE International. Source

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