Abstract
Drinking water plumbing systems appear to be a unique environment for microorganisms as they contain few nutrients but a high mineral concentration. Interactions between mineral content and bacteria, such as microbial calcium carbonate precipitation (MCP) however, has not yet attracted too much attention in drinking water sector. This study aims to carefully examine MCP behavior of two drinking water bacteria species, which may potentially link scaling and biofouling processes in drinking water distribution systems. Evidence from cell density evolution, chemical parameters, and microscopy suggest that drinking water isolates can mediate CaCO3 precipitation through previously overlooked MCP mechanisms like ammonification or biosorption. The results also illustrate the active control of bacteria on the MCP process, as the calcium starts to concentrate onto cell surfaces only after reaching a certain cell density, even though the cell surfaces are shown to be the ideal location for the CaCO3 nucleation.
Highlights
Microbial calcium carbonate precipitation (MCP) is an omnipresent phenomenon that has been extensively studied in various contexts, ranging from natural processes such as sediment lithification to engi neering applications like concrete restoration (Boquet et al, 1973; Dhami et al, 2013; Dupraz and Visscher, 2005; Hammes et al, 2003)
CaCO3 precipitation generally results from a pH increase and CO2 pro duction mediated by different microbial metabolisms
Seven drinking water isolates belonging to two species, Sphingobium limneticum and Micrococcus luteus (Supple mentary Figure S1), have shown CaCO3 precipitating behavior and were studied in detail
Summary
Microbial calcium carbonate precipitation (MCP) is an omnipresent phenomenon that has been extensively studied in various contexts, ranging from natural processes such as sediment lithification to engi neering applications like concrete restoration (Boquet et al, 1973; Dhami et al, 2013; Dupraz and Visscher, 2005; Hammes et al, 2003). Despite the extensive investigation of MCP in concrete engi neering and geological recycling (Zhu and Dittrich, 2016), the important role of calcium carbonate formation in biofilm has never been discussed in the context of a drinking water environment. It has, been found to be important for different sources of drinking water supplies including ground water and surface water (Fujita et al, 2000; Liu et al, 2017; Meier et al, 2017; Obst et al, 2006). A good un derstanding of the MCP process in drinking water may provide an important insight for numerous serious problems associated with both biofilm formation and scaling issues including pipe corrosion, water discoloration, regrowth of opportunistic pathogens, etc.(Hafid et al, 2015; Prest et al, 2016; Vaz-Moreira et al, 2011)
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