Microscale investigations of temperature-dependent microbially induced carbonate precipitation (MICP) in the temperature range 4-50 degrees C

Microbially induced carbonate precipitation (MICP) involves a series of bio-geochemical reactions whereby microbes alter the surrounding aqueous environment and induce calcium carbonate precipitation. MICP has a broad range of applications, including in situ soil stabilization. However, the reliability of this process is dependent on a number of environmental conditions. In particular, bacterial growth, urease activity and precipitation kinetics all depend on temperature. Batch test and microfluidic chip experiments were performed in this study to investigate the effects of temperature on bacterial density and activity and the MICP processes occurring at different temperatures (4-50 degrees C). Spatial and temporal variations in the formation and development of calcium carbonate precipitates, including their amount, type, growth rate, formation and deformation characteristics, were monitored. Results show that different types of calcium carbonate precipitates with varying sizes and quantities were produced by varying the temperature. Low temperature (4 degrees C) did not reduce urease activity, but limited the final amount of cementation; low temperature reduced bacterial growth and attachment ratio, as well as calcium carbonate precipitation rate. High-temperature (50 degrees C) conditions significantly reduced urease activity within a short period of time, while a repeated injection of bacteria before every two injections of cementation solution increased the final amount of cementation. The findings made from this paper provide insight into how MICP processes vary across a range of temperatures and could be valuable for optimizing the MICP process for different applications.