Microbiological and molecular evaluation of an alluvial water well field and fouling-related phenomena

An important source of water for the city of North Battleford, Saskatchewan is groundwater extracted from wells installed adjacent to the North Saskatchewan River. Unfortunately, these wells undergo fairly rapid deterioration (3-4 years) leading to reduced well capacity and water quality. The reasons for this deterioration are poorly understood. The studies in this thesis have tried to quantify the prevalence, activity and diversity of microbial populations in the aquifer and to explain the possible outcomes of microbial interaction with the environment which might lead to biofouling of the wells. A panel of conventional cultural, microscopic, metabolic and molecular techniques were utilized to analyze water, sediment and biofilm samples collected from various locations in the aquifer. The studies indicated that the aquifer was anoxic and harboured abundant concentrations of iron and manganese very close to the well and also presence of diverse groups of organisms including Fe-, Mn-, S-oxidizing bacteria as well as Fe-, Mn-, nitrite- and sulphate-reducing bacteria. A two year spatio-temporal study indicated that the biofilm growth significantly increased within the 1-2 m zone from the well and were also associated with a rapid reduction in specific capacity of the well. PCR, qPCR, and DGGE analyses indicated that the microbial community composition and diversity varied with space and time with greatest changes detected within the zone proximal to the well. Sequence data indicated that the major bacterial species prevalent in the aquifer belonged to Sulfuricurvum spp., Rhodobacter spp., Methylobacter spp., Acidovorax spp., and Geobacter spp. The studies demonstrated that water extraction influenced microbial community diversity, activity and composition, the effect of which did not extend beyond 1-2 m well radius. The application of impressed current did not demonstrate any anti-fouling effect, but rather favoured the growth of biofilm around the well and the accumulation of insoluble precipitates leading to accelerated deterioration of the well. Overall, the microbial community diversity, activity and composition in the study aquifer changed with respect to time and space, and water extraction. These changes altered the biogeochemical processes in the aquifer, especially within the zone closest to the wells leading to clogging and well deterioration

Methodological approaches for studying the microbial ecology of drinking water distribution systems

The study of the microbial ecology of drinking water distribution systems (DWDS) has traditionally been based on culturing organisms from bulk water samples. The development and application of molecular methods has supplied new tools for examining the microbial diversity and activity of environmental samples, yielding new insights into the microbial community and its diversity within these engineered ecosystems. In this review, the currently available methods and emerging approaches for characterising microbial communities, including both planktonic and biofilm ways of life, are critically evaluated. The study of biofilms is considered particularly important as it plays a critical role in the processes and interactions occurring at the pipe wall and bulk water interface. The advantages, limitations and usefulness of methods that can be used to detect and assess microbial abundance, community composition and function are discussed in a DWDS context. This review will assist hydraulic engineers and microbial ecologists in choosing the most appropriate tools to assess drinking water microbiology and related aspects

Bacterial diversity and production of sulfide in microcosms containing uncompacted bentonites

CITATION: Grigoryan, A. A., et al. 2018. Bacterial diversity and production of sulfide in microcosms containing uncompacted bentonites. Heliyon, 4(8):e00722, doi:10.1016/j.heliyon.2018.e00722.The original publication is available at https://www.sciencedirect.comAims: This study examined the diversity and sulfide-producing activity of microorganisms in microcosms containing commercial clay products (e.g., MX-80, Canaprill and National Standard) similar to materials which are currently considered for use in the design specifications for deep geologic repositories (DGR) for spent nuclear fuel. Methods and results: In anoxic microcosms incubated for minimum of 60 days with 10 g l-¹ NaCl, sulfide production varied with temperature, electron donor and bentonite type. Maximum specific sulfide production rates of 0.189 d-¹, 0.549 d-¹ and 0.157 d-¹ occurred in lactate-fed MX-80, Canaprill and National Standard microcosms, respectively. In microcosms with 50 g l-¹ NaCl, sulfide production was inhibited. Denaturing gradient gel electrophoresis (DGGE) profiling of microcosms revealed the presence of bacterial classes Clostridia, Bacilli, Gammaproteobacteria, Deltaproteobacteria, Actinobacteria, Sphingobacteriia and Erysipelotrichia. Spore-forming and non-spore-forming bacteria were confirmed in microcosms using high-throughput 16S rRNA gene sequencing. Sulfate-reducing bacteria of the genus Desulfosporosinus predominated in MX-80 microcosms; whereas, Desulfotomaculum and Desulfovibrio genera contributed to sulfate-reduction in National Standard and Canaprill microcosms. Conclusions: Commercial clays microcosms harbour a sparse bacterial population dominated by spore-forming microorganisms. Detected sulfate- and sulfur-reducing bacteria presumably contributed to sulfide accumulation in the different microcosm systems. Significance and impact of study The use of carbon-supplemented, clay-in-water microcosms offered insights into the bacterial diversity present in as-received clays, along with the types of metabolic and sulfidogenic reactions that might occur in regions of a DGR (e.g., interfaces between the bulk clay and host rock, cracks, fissures, etc.) that fail to attain target parameters necessary to inhibit microbial growth and activity.https://www.sciencedirect.com/science/article/pii/S2405844018314658?via%3DihubPublisher's versio