Efficiency and Characteristics of MICP in Environments with Elevated Salinity, Diminished Oxygen, and Lowered Temperature: A Microfluidics Investigation

TL;DR

This study investigates how high salinity, low oxygen, and cold temperatures affect Microbially Induced Carbonate Precipitation (MICP) using microfluidic techniques, revealing environmental impacts on bacterial activity, crystal formation, and permeability reduction.

Contribution

It provides novel insights into the effects of challenging marine environmental conditions on MICP mechanisms and performance, using advanced microfluidic and spectroscopic methods.

Findings

Cold temperatures hinder bacterial growth significantly.

High salinity reduces calcium carbonate crystal quantity by 20.2%.

Low oxygen increases crystal diameter by 20.3% but decreases quantity by 50.9%.

Abstract

Microbially Induced Carbonate Precipitation (MICP) shows promise for enhancing soil strength, but environmental factors significantly affect its mechanisms. The feasibility of MICP in challenging conditions, such as the soil around piles in shallow seabeds during winter,characterized by high salinity, low oxygen, and cold temperatures,remains uncertain due to limited research. To address this gap, we employed microfluidic techniques and advanced measurement tools, including Raman spectroscopy and SEM, to assess how these conditions influence bacterial growth, calcium carbonate crystallization, and porous medium permeability through MICP.Our findings indicate that cold temperatures notably hinder bacterial growth, while high salinity and low oxygen also play critical roles, particularly reducing bacterial attachment. In seawater environments, high salinity and cold temperatures significantly affect calcium carbonate crystal shape and type; low oxygen has a lesser impact. Specifically, high salinity reduces crystal quantity by 20.2% with minimal effect on diameter, while low oxygen increases diameter by 20.3% but decreases quantity by 50.9%. Cold temperatures decrease diameter by 36.9% without much effect on quantity.After six injections of the cementation solution, MICP treated samples showed a chemical transformation efficiency of 20.6% compared to DI water, primarily due to cold temperatures (contributing 40.1%). An exponential decline in permeability with increasing calcium carbonate content was observed, leading to the categorization of calcium carbonate generation into fast and slow decay types. This study provides insights for optimizing mineralization in marine conditions and emphasizes how environmental factors impact MICP performance, presenting challenges for engineering applications.