Properties of Solid Waste-based Solidified Sludge Improved by Microbially Induced Calcium Carbonate Precipitation Technology

Abstract

We examined the enhancing effects of different dosages of product of Centrifugation of Bacterial Liquid (product of CBL) on the performance of slag-fGD gypsum-cement-bentonite-sludge system using MICP technology. We analyzed the multifaceted performance of the solidified sludge from macroscopic and microscopic perspectives. The experimental results reveal that the increase in product of CBL dosage results in positive impacts on the solidified sludge, including higher side compressive strength, lower leachate heavy metal concentration, and improved crack repair rates. At a 0.4% product of CBL doping concentration, the strength of the solidified sludge is enhanced by 26.6% at 3 d, 61.2% at 7 d, and 13.9% at 28 d when compared to the unmodified solidified sludge. After 28 days, the concentrations of Zn and Cu ions reduce by 58% and 18%, respectively, and the crack repair rate is 58.4%. These results demonstrate that the increase in heavy metal concentration in the leachate leads to an increase in the strength of the solidified sludge. The strengthening procedure heavily relies on the mineralisation reaction of Bacillus pasteurii, which produces a substantial amount of CaCO₃ to cement the particles and fill the pores initially. The modified solidifying sludge exhibits a self-repairing effect and an enhanced multifaceted performance as a result of oxygen being restored after crack formation and reactivation of Bacillus pasteurii. Such conditions facilitate the body’s recovery.

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Wuhan University of Technology and Springer-Verlag GmbH Germany, Part of Springer Nature