Use of new bacterial strain in solidification and stabilisation of municipal solid waste incineration fly ash

The use of microbially induced carbonate precipitation (MICP) is known to be effective in the solidification and stabilisation of fly ash that results as a by-product of municipal solid waste incineration. In the search for more adaptable and applicable bacteria for MICP fly ash treatment, five species of bacteria were isolated from nursery soil. The biochemical characteristics of the five bacteria were tested to assess their adaptation to the environment of fly ash. The geotechnical properties and heavy metal leaching concentrations of the fly ash treated by the five bacteria were also tested to evaluate solidification and stabilisation effects. Results were compared with the commonly used bacteria Bacillus pasteurii. The Ensifer adhaerens strain outperformed other strains, including B. pasteurii, in environmental adaptation, particle solidification and heavy metal stabilisation of fly ash. Further MICP treatment tests under different bacterial concentrations, curing conditions and fly ash void ratios were carried out on this strain to investigate the influence of various factors on MICP efficiency. Both the MICP and the pozzolanic solidifying properties played important roles in the solidification and stabilisation mechanisms, where the best solidification effect occurred at a bacterial concentration of 14.92 × 10⁷ cells/ml and a fly ash void ratio of 0.724.