Increased Microbially Induced Calcium Carbonate Precipitation (MICP) Efficiency in Multiple Treatment Sand Biocementation Processes by Augmentation of Cementation Medium with Ammonium Chloride

Abstract

The cementation medium for ureolytic microbially induced calcium carbonate precipitation (MICP) typically consists of urea and a calcium source. While some studies have augmented this basic medium, the effects of adding substrates such as ammonium chloride are unclear. The studies detailed in this paper sought to quantify the effect of the ammonium chloride augmentation of cementation medium (CM) on the process of MICP. An aqueous MICP study was initially carried out to study the effects of adding ammonium chloride to the urea–calcium cementation medium. This batch test also explored the effect of varying the concentration of calcium chloride dihydrate (calcium source) in the CM. A subsequent sand column study was undertaken, whereby multiple treatments of CM were injected over several days to produce a biocement. Six columns were prepared using F65 sand bioaugmented with Sporosarcina pasteurii, half of which were injected with the basic medium only and half with the augmented medium for treatment two onwards. Effluent displaced from columns was tested using ion chromatography and Nesslerisation to determine the calcium and ammonium ion concentrations, respectively, and hence the treatment efficiency. Conductivity and pH testing of effluent gave insights into the bacterial urease activity. The addition of 0.187 M ammonium chloride to the CM resulted in approximately 100% chemical conversion efficiency within columns, based on calcium ion measurements, compared to only 57% and 33% efficiency for treatments three and four, respectively, when using the urea–calcium medium. Columns treated with the CM containing ammonium chloride had unconfined compressive strengths which were 1.8 times higher on average than columns treated with the urea–calcium medium only.

Synergistic biocementation: harnessing Comamonas and Bacillus ureolytic bacteria for enhanced sand stabilization

“…This result underscores the efficacy of cementation between sand particles. Notably, similar findings have been reported in previous studies where individual bacteria were employed to improve permeability in the sand (Liu et al 2020 ; Namdar-Khojasteh et al 2022 ; Spencer et al 2023 ; Ugur et al 2024 ). The B2 & B11-30 °C combination yielded the best permeability result with 1.54 × 10 − 6 m/s compared to all the other bacterial samples.…”

“…Calcite precipitation was assessed using X-ray diffraction (XRD) analysis to identify mineral phases and scanning electron microscopy (SEM) to visualize crystal morphology and distribution. Multiple studies have used these methods to provide insights into the effectiveness of bacterial strains in promoting sand cementation and calcium carbonate precipitation (Spencer et al 2023 ; Zeitouny et al 2023 ). The ability of the bacterial strains to perform in sand was assessed at two different temperatures, 14 ± 0.6 °C and 30 °C.…”

Non‐ureolytic microbially induced carbonate precipitation: Investigating a cleaner biogeotechnical engineering pathway for soil mechanical improvement

“…Thus, in order to perform a comparison between different techniques, different studies with relatively similar soil types and compaction levels were used, whose results are presented in Table 5. As can be seen, ureolytic MICP technique [50] has resulted in an almost similar UCS range. Spencer et al [50] enhanced ureolytic MICP performance by adding ammonium chloride to increase the urease reaction efficiency, which has augmented the unconfined compressive strength.…”

“…Spencer et al. [50] enhanced ureolytic MICP performance by adding ammonium chloride to increase the urease reaction efficiency, which has augmented the unconfined compressive strength. However, both ureolytic MICP and its augmented version suffer from production of ammonium ions, which are absent in the non‐ureolytic MICP.…”

“…Thus, in order to perform a comparison between different techniques, different studies with relatively similar soil types and compaction levels were used, whose results are presented in Table 5. As can be seen, ureolytic MICP technique [50] has resulted in an almost similar UCS range. Spencer et al.…”