The microbial diversity of a deep saline aquifer used for geothermal heat storage in the North German Basin was investigated. Genetic fingerprinting analyses revealed distinct microbial communities in fluids produced from the cold and warm side of the aquifer. Direct cell counting and quantification of 16S rRNA genes and dissimilatory sulfite reductase (dsrA) genes by real-time PCR proved different population sizes in fluids, showing higher abundance of bacteria and sulfate reducing bacteria (SRB) in cold fluids compared with warm fluids. The operation-dependent temperature increase at the warm well probably enhanced organic matter availability, favoring the growth of fermentative bacteria and SRB in the topside facility after the reduction of fluid temperature. In the cold well, SRB predominated and probably accounted for corrosion damage to the submersible well pump, and iron sulfide precipitates in the near wellbore area and topside facility filters. This corresponded to lower sulfate content in fluids produced from the cold well as well as higher content of hydrogen gas that was probably released from corrosion, and maybe favored growth of hydrogenotrophic SRB. This study reflects the high influence of microbial populations for geothermal plant operation, because microbiologically induced precipitative and corrosive processes adversely affect plant reliability.2
In this study, the operation of a cold store, located in 30-60 m depth in the North German Basin, was investigated by direct counting of bacteria and genetic fingerprinting analysis. Quantification of microbes accounted for 1 to 10 x 10 5 cells per ml fluid with minor differences in the microbial community composition between well and process fluids. The detected microorganisms belong to versatile phyla Proteobacteria and Flavobacteria. In addition to routine plant operation, a phase of plant malfunction caused by filter clogging was monitored. Increased abundance of sulphur-oxidizing bacteria indicated a change in the supply of electron acceptors, however, no changes in the availability of electron acceptors like nitrate or oxygen were detected. Sulphur-and iron-oxidizing bacteria played essential roles for the filter lifetimes at the topside facility and the injectivity of the wells due to the formation of biofilms and induced mineral precipitations. In particular, sulphur-oxidizing Thiothrix generated filamentous biofilms were involved in the filter clogging.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.