Experimental Study on Coastal Sediment Reinforcement by Induced Carbonate Precipitation by Different Enzyme Sources

Abstract

Coastal erosion is increasing worldwide due to the increasing frequency of extreme natural phenomena and excessive human exploitation. In this study, a small model experiment was conducted to investigate the solidification effects of three enzyme sources—soybean urease, freshwater Bacillus pasteurella, and seawater domesticated Bacillus pasteurella—on coastal sediments and their impacts in a seawater environment. The solidifying effect of different enzyme sources was determined by measuring the mechanical properties and corrosion resistance of the cured specimen model. The influence of solidified seawater in a seawater environment was obtained by measuring the changes in the pH value, calcium ion concentration, and ammonia nitrogen content of solidified seawater. The results show that different enzyme sources have a certain strengthening effect on coastal sediments. The mechanical properties of coastal sediments can be enhanced by increasing the amount of enzyme solution or level of solidification and can effectively resist simulated flow erosion. Comparing the reinforcement effects of different enzyme sources, it can be seen. It was observed that Bacillus pasteurella acclimated in seawater had better reinforcement effects than Bacillus pasteurella fresh water, and Bacillus pasteurella fresh water had better reinforcement effects than soybean urease. In the seawater measurement tests, the solidification of coastal sediments using different enzyme sources led to a decrease in the seawater pH value, and the acidification of seawater dissolved the generated calcium carbonate, increased the concentration of calcium ions in seawater, and produced ammonia nitrogen as a byproduct in the seawater. It was observed that, compared with the other two enzyme source solutions, the seawater-domesticated Bacillus pasteurella can better adapt to the high-salt environment of seawater, microbial metabolism is not inhibited, urea decomposition ability is improved, and calcium carbonate production is higher, which can effectively improve the engineering characteristics of coastal sediments and play a positive role in coastal protection and development.