Search Results (3)

Microbially induced carbonate precipitation (MICP) technology is an environmentally friendly technique that can contribute to tailings consolidation and ecosystem restoration. Our study found that local MICP bacteria, Lysinibacillus fusiformis, could remediate copper tailings pollution at different slope positions (K1, K2, and K3) in arid areas. We analyzed the effect of MICP treatment on the slag from macro- to microscopic levels with a dissolution test, soil physical and chemical tests, wind tunnel testing experiments, and scanning electron microscopy (SEM). The results demonstrated that the MICP bacteria, L. fusiformis, effectively remodeled the slag structure, thereby preventing the diffusion of tailing slag caused by wind erosion. This structural remodeling resulted in a significant increase in slag strength (maximum strength: 2707 KPa) and an increased content of CaCO₃. Furthermore, it led to a significant reduction in total salinity content (36.4–43.6%), pH (4.1–4.4%), and improvement in nutritional status (total potassium content (16–31.4%) and the available phosphorus content (2.1–2.3 times) of the tailings slag (p < 0.05). There was also a 15% increase in urease and catalase activity in K1, a 7% increase in invertase activity in K3 (p < 0.05), and a significant increase in carbon and nitrogen microbial biomass in K1, K2, and K3 (p < 0.05). Full article

Beachrocks are a window to the past environmental, geological, sedimentological and morphological conditions that were dominant in the coastal zone during their formation. Furthermore, beachrocks have the ability to reduce coastal erosion impact on sandy beaches. This study focuses on the beachrock formation mechanism through the comparison of cement characteristics, mineral chemistry and sedimentology of beachrock occurrences from two different geological and geographical localities: Diolkos, Corinth, Greece and Sumuide, Okinawa, Japan. In addition, in order to investigate a potential soft engineering method to protect coasts from erosion, artificial beachrock samples were created in vitro using sand samples and ureolytic bacteria from both areas under accelerating conditions. For Okinawa artificial beachrock experiments, the bacteria Pararhodobacter sp. was used, and for Diolkos, it was the bacteria Micrococcus yunnainensis sp. For the natural beachrocks, a multi-analytical approach was accomplished with the use of microscopic investigation, a scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction and X-ray fluorescence. Correlations were made between natural and artificial beachrocks. Results have shown that Diolkos beachrock was formed in the upper part of the intertidal zone, consisting of detrital material originating from the local bedrock, while Sumuide beachrock formed in the low intertidal–upper subtidal zone, consisting of coral sand and foraminifera fragments. For the artificial beachrocks, three samples were created using the microbial-induced carbonate precipitation (MICP) method, one from Diolkos (Corinth, Greece) and two from Sumuide (Okinawa, Japan). Diolkos artificial beachrock was better consolidated in comparison to Sumuide. Our investigation has shown that bacterial density was the key factor for the creation of the artificial beachrocks, while the samples’ granulometry played a secondary role in the process. The laboratory artificial beachrocks show encouraging results for a new soft engineering method to encounter beach erosion while keeping an ecofriendly character by saving energy, material resources and gas emissions. Artificial beachrocks can share the same properties of a natural beachrock and can contribute positively to marine biodiversity as a natural rocky habitat. Full article

Microbial Induced Carbonate Precipitation (MICP) via urea hydrolysis is an emerging sustainable technology that provides solutions for numerous environmental and engineering problems in a vast range of disciplines. Attention has now been given to the implementation of this technique to reinforce loose sand bodies in-situ in nearshore areas and improve their resistance against erosion from wave action without interfering with its hydraulics. A current study has focused on isolating a local ureolytic bacterium and assessed its feasibility for MICP as a preliminary step towards stabilizing loose beach sand in Sri Lanka. The results indicated that a strain belonging to Sporosarcina sp. isolated from inland soil demonstrated a satisfactory level of enzymatic activity at 25 °C and moderately alkaline conditions, making it a suitable candidate for target application. Elementary scale sand solidification test results showed that treated sand achieved an approximate strength of 15 MPa as determined by needle penetration device after a period of 14 days under optimum conditions. Further, Scanning Electron Microscopy (SEM) imagery revealed that variables such as grain size distribution, bacteria population, reactant concentrations and presence of other cations like Mg²⁺ has serious implications on the size and morphology of precipitated crystals and thus the homogeneity of the strength improvement. Full article