The disposal of tailings in a safe and environmentally friendly manner has always been a challenging issue. The microbially induced carbonate precipitation (MICP) technique is used to stabilise tailings sands. MICP is an innovative soil stabilisation technology. However, its field application in tailings sands is limited due to the poor adaptability of non-native urease-producing bacteria (UPB) in different natural environments. In this study, the ultraviolet (UV) mutagenesis technology was used to improve the performance of indigenous UPB, sourced from a hot and humid area of China. Mechanical property tests and microscopic inspections were conducted to assess the feasibility and the effectiveness of the technology. The roles played by the UV-induced UPB in the processes of nucleation and crystal growth were revealed by scanning electron microscopy imaging. The impacts of elements contained in the tailings sands on the morphology of calcium carbonate crystals were studied with Raman spectroscopy and energy-dispersive X-ray spectroscopy. The precipitation pattern of calcium carbonate and the strength enhancement mechanism of bio-cemented tailings were analysed in detail. The stabilisation method of tailings sands described in this paper provides a new cost-effective approach to mitigating the environmental issues and safety risks associated with the storage of tailings.

Despite its proven high toxicity, unsymmetrical dimethylhydrazine (UDMH) continues to be used in rocket technology and some other areas of human activity. In this work, the ability of plant-bacterial consortia to reduce the genotoxicity of UDMH and its incomplete oxidation products was investigated. Genotoxicity was assessed using a specific lux-biosensor, Escherichia coli MG1655 pAlkA-lux, which emits stronger light when cellular DNA is alkylated. For microbiological biodegradation, the Bacillus subtilis KK1112 strain was isolated from the soil via a two-stage selection process for resistance to high UDMH concentrations exceeding 5000 MAC. This strain's ability to biodegrade UDMH was demonstrated, as treatment of UDMH-polluted medium with KK1112 resulted in reduced DNA alkylation. A synergistic reduction in the DNA-alkylating potency of UDMH oxidation products was studied under the combined application of bacteria KK1112 and plant seedlings: Bromus inermis Leyss, Medicago varia Mart. and Phleum pratense L. The greatest effect was achieved when bacteria were used in combination with B. inermis. KK1112 cells accelerated seedling development and mitigated UDMH-induced growth inhibition. The findings suggest that the consortium of KK1112 and B. inermis has a great potential for remediation of UDMH-polluted soils in arid climatic zones.