Abstract
Among the methods used to remove metals and their compounds from landfill leachates with low application costs and high efficiency are bioleaching and biosorption. The most effective bacteria used in the metal removal process are Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The aim of the study was to determine the usefulness of the A. ferrooxidans and A. thiooxidans population in removing heavy metals from landfill leachate. In addition, development opportunities for bacterial population using landfill leachate as growth medium were identified. The substrate for the research was the raw leachate before the reverse osmosis process. In order to increase the efficiency of trace elements removal and recovery from leachate, variable combinations have been used which differ by the addition of sulfuric acid, A. ferrooxidans culture, A. thiooxidans culture, mixed culture containing populations of both bacteria, and elemental sulfur. Based on the research, it was found that the removal of heavy metals from leachate was a selective process. High bioleaching efficiency, from 80% to 90%, was obtained for all metals for which the sample acidification or sulfur addition was used. The simultaneous combination of both these additives turned out to be the most advantageous. The A. thiooxidans culture was the most effective in bioleaching reverse osmosis effluents. For the A. ferrooxidans culture used, much lower efficiencies were obtained, while by contrast, the use of mixed culture of two bacterium species had no significant effect.
Highlights
The oxidation-reduction potential (ORP) and pH are the basic indicators in the monitoring of bioleaching
The accurate pH for the development of the biomass of bioleaching bacteria was found in samples of combinations B, E, G, I (Figures 1 and 2)
The results presented by Pacholewska et al [41] and Ojumu et al [42] confirm the effectiveness of the use of A
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The leachates from municipal landfills are generated in chemical, physical and biological transformations taking place during waste landfilling and for many years after the disposal site closure [1]. The leachates are highly contaminated and concentrated liquids containing biodegradable and non-biodegradable organic matter, inorganic pollutants [2], and hazardous substances, e.g., heavy metals or xenobiotics [3]. The formed leachate, depending on the characteristics of the deposited waste and the age of the landfill, is a habitat for functionally very different types of bacteria [4]. The leachate is a reservoir of microplastics (concentrations of 0–291 particles per L), [5] especially polyelethylene and polypropylene [6]
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