Abstract
This paper presents a method to solidify/stabilize the municipal solid waste incineration (MSWI) fly ash by originally employing the microbial induced carbonate precipitation (MICP) technique. In this method, the rich endogenous calcium in the MSWI fly ash was utilized to induce calcite precipitation, which is different from the operation of adding extra calcium source in previous researches. The fly ash sample had a CaO content of 44.5%, and its leaching concentrations of Zn, Cr and Pb exceed the limits of the identification standard for hazardous wastes in China. The optical density at 600 nm (OD600) of the bacterial solution was about 1.0 after the processes of bacterial activation and reproduction. The prepared fly ash sample was well mixed with bacterial solution at an ash-liquid ratio of 1 kg: 0.3 L and cured at a temperature of 20 °C and a humidity of ≥95% for 7 days. After treatment, the heavy metal leachability significantly reduced to meet the standard for pollution control of landfill site, and the unconfined compressive strength increased approximately 40%. The precipitated carbonates were verified by SEM-EDS analysis and quantified by measurement of carbonate content via acid-dissolving method. The results shone a light on the possibility of using MICP technique as a useful and efficient tool to stabilize the MSWI fly ash before being reused or properly stored in landfills.•The MICP method is efficient to reduce the heavy metal leachability and increase the compressive strength of MSWI fly ash.•The endogenous calcium in MSWI fly ash was utilized to induce calcite precipitation.•The heavy metals in MSWI fly ash were well immobilized by the formation of carbonates.
Highlights
The municipal solid waste incineration (MSWI) fly ash is a kind of porous material and rich in inorganic substances such as heavy metals, calcium, etc
This method originally employs the Microbial induced carbonate precipitation (MICP) technique to stabilize the MSWI fly ash, i.e., reduce the heavy metal leachability and enhance the compression strength. This method utilizes the rich calcium embodied in the MSWI fly ash, which is different from the operations adopted by the previous researches, i.e., adding extra calcium source
The MSWI fly ash sample was dried at the temperature of 70 C, and mixed with the above bacterial solution at solid-liquid ratio of 1:0.3
Summary
The municipal solid waste incineration (MSWI) fly ash is a kind of porous material and rich in inorganic substances such as heavy metals, calcium, etc. The solution contained urease-producing bacteria, calcium chloride, urea, nutrient, etc., was added into the soil column to form calcium carbonate that binds the soil particles together, improving the engineering properties of soils [7,8,9,10]. This method originally employs the MICP technique to stabilize the MSWI fly ash, i.e., reduce the heavy metal leachability and enhance the compression strength. This method utilizes the rich calcium embodied in the MSWI fly ash, which is different from the operations adopted by the previous researches, i.e., adding extra calcium source
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