Polymer-assisted enzyme induced carbonate precipitation for non-ammonia emission soil stabilization

Abstract

Biocementation using enzyme induced carbonate precipitation (EICP) process has become an innovative method for soil improvement. One of the major limitations in scaling-up of biocement treatment is the emission of gaseous ammonia during the urea hydrolysis, which is environmentally hazardous. In order to eliminate this shortcoming, this paper presents a series of experiments performed to evaluate a novel approach for preventing the ammonia byproducts in the EICP process via the use of polyacrylic acid (PAA). Through the adjustment of the pH to acidic, PAA not only promotes the enzyme activity, but also averts the conversion of ammonium to gaseous ammonia and its release, thus preventing any harm to the environment. The sand samples were treated with cementation solution and assessed for improvement in strength. Calcium carbonate content measurements and X-ray powder diffraction analysis identified the calcite crystals precipitated in the soil pores. Scanning electron microscopy analysis clearly showed that calcium carbonate was precipitated connecting soil particles, thus providing a uniaxial compressive strength (UCS) of up to 1.65 MPa. Overall, the inhibition in the speciation of gaseous ammonia shows the great potential of PAA for large-scale promotion of biocement.

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

“…The ammonium ions can enter surface and ground water, and unless they are not produced in large volumes or removed and remediated, they can bring about environmental concerns [39]. In recent years, the conversion of ammonium ions to other products and microbial precipitation of struvite (magnesium ammonium phosphate) instead of calcite [40] as well as adjusting pH by means of polyacrylic acid to inhibit the conversion of ammonium ions to gaseous ammonia have been considered [41]. However, all such solutions do not lead to the total removal of produced ammonium ions, and the risk of ground water pollution still exists in soil improvement projects involving large soil volumes.…”

Evaluation of engineering properties of clayey sand bio-mediated with terrazyme enzyme

“…A number of studies have provided evidence on the positive impact of introducing specific enzymes into soil (Thomas et al, 2018;Hoang et al, 2019;Renjith et al, 2020;Yan et al, 2022). Some examples of bio-enzymes available in the commercial market include Permazyme (Peng et al, 2011), Renolith (Singh and Garg, 2015), Fujibeton (Rajoria and Kaur, 2014), and Terrazyme (Saini and Vaishnava, 2015).…”