Abstract
The sand columns inoculated with the indigenous microorganism (Aspergillus niger) were used to investigate the effect of bioclogging during the radioactive effluent percolation. The hydraulic gradient, volumetric flow rate, and uranyl ions concentration were monitored over time. The sand columns were operated with continuous radioactive effluent of uranium tailings reservoir. After 68 days, the hydraulic conductivity of the sand columns decreased more than 72%, and the adsorption rate of uranyl ions by Aspergillus niger reached more than 90%. Environmental scanning electron microscope imaging confirmed the biofilm covering the surface of sand particles and connecting sand particles together, which resulted in a reduction of hydraulic conductivity. The results indicated that the propagation of Aspergillus niger can clog the seepage channel and effectively adsorb the uranyl ions of radioactive effluent in the porous media, which provides a suitable measure for controlling the migration of radioactive effluent of uranium tailings reservoir into the subsurface environment.
Highlights
With the increasing demand of nuclear fuel, hundreds of uranium tailings reservoirs were built to store the radioactive nuclear wastes which were produced during the mineral extraction
To research the bioclogging mechanism in sand columns, SEM was employed to observe the sand samples after the experiment. e scanning electron micrographs are presented in Figure 6, and it can be observed that the sand samples inoculated with Aspergillus niger have formed the bio lm which covered the surface of sand particles, connected the sand particles together, and resulted in the decrease of hydraulic conductivity
Aspergillus niger was inoculated into the sand columns to investigate the e ect of bioclogging and the adsorption rate of uranyl ion under the radioactive e uent percolation, and the following conclusions were obtained: (1) In this experiment, ve indigenous microorganisms were cultivated, and Aspergillus niger was chosen for the strongest reproductive capacity
Summary
With the increasing demand of nuclear fuel, hundreds of uranium tailings reservoirs were built to store the radioactive nuclear wastes which were produced during the mineral extraction. E bioclogging technology has the advantages of detecting and sealing the sources of leakage automatically by inoculating the microorganism and nutrient into porous media, which can reduce the permeability of porous medium and adsorb pollutants by growth, reproduction, and death of microorganisms [7,8,9,10,11,12]. E sand columns inoculated with Aspergillus niger were employed in this study to investigate the effects of bioclogging under constant percolation (radioactive effluent). is paper aims to explain the phenomena and mechanisms of bioclogging during the process of percolation and to provide experimental evidence for dealing with the leakage problem of uranium tailings reservoir with microbial technology
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