Biocementation of Sri Lankan Beach Sand Using Locally Isolated Bacteria: A Baseline Study on the Effect of Segregated Culture Media

Abstract

Bioengineering has paved the way into multidiscipline as a more sustainable and eco-friendly solution to numerous problems. Among them, microbial induced carbonate precipitation (MICP) is a newly emerging microbiological soil/sand stabilization method, where microbial urease is employed for calcium carbonate precipitation throughout the soil matrix by urea hydrolysis which leads to soil strength and stiffness enhancement. This paper investigates avenues for strengthening loose beach sand from Sri Lanka by MICP through a series of laboratory experiments. A bacterial strain belonging to Sporosarcina sp., a native ureolytic bacterium was isolated from Sri Lankan soil, and urease activity and induction of calcium carbonate precipitation were quantified. The isolated bacteria showed a stable growth over the test period of 7 days and a maximum urease activity of 2.1 µmol of hydrolyzed urea/min.mL after 48 hours of cultivation. A major part of the study was focused on determining the effect of centrifuged cell pellets resuspended in distilled water and fresh culture medium (NH4-YE medium) on the effectiveness of MICP. The small-scale column solidification tests revealed that although urease activity is considerably higher for cell pellets suspended in distilled water, the strength improvement on column top by intact cell culture injection is about 5 times higher than that from cell pellets. Further, different size and types of calcium carbonate crystals were examined in MICP tests done for intact culture liquid and centrifuged cell suspensions. However, detailed analysis of biocementation by the selected isolate is highly recommended as future work.

Bioremediation of Coal Contaminated Soil as the Road Foundations Layer

“…Mechanical repairs can use soil-fiber [3] to replace soil materials that do not meet standards, while chemically can be done with the addition of lime [4]. But the newest method that can be done is bio-chemical which is more environmentally friendly or known as microbial induced carbonate precipitation (MICP) which can increase soil strength [5] and increase slope stability [6]. The results of previous research indicate that coal contaminated soil can be used as a material for civil engineering construction but stabilization efforts are needed to improve the mechanical characteristics of the soil so that it can be utilized.…”

“…These species have good adaptability to the environment compared to other bacteria [14]. Also, urea can be used as a source of energy by respiration, in which CO2 is converted into CO 3 2 in an alkaline environment, thereby metabolizing and depositing calcium carbonate [5]. Besides, calcium carbonate could be produced by Bacillus and Sporosarcina more fastly and with a high yield.…”