Abstract
The Raša Bay (North Adriatic, Croatia) has been receiving various pollutants by inflowing streams laden with untreated municipal and coalmine effluents for decades. The locality was a regional center of coalmining (Raša coal), coal combustion, and metal processing industries for more than two centuries. As local soil and stream water were found to be contaminated with sulfur and potentially toxic trace elements (PTEs) as a consequence of weathering of Raša coal and its waste, some clean-up measures are highly required. Therefore, the aim of this study was to test the remediating potential of selected microorganisms and synthetic zeolites in the case of soil and coal-mine water, respectively, for the first time. By employing bacterial cultures of Ralstonia sp., we examined removal of sulfur and selected PTEs (As, Ba, Co, Cr, Cu, Ni, Pb, Rb, Se, Sr, U, V, and Zn) from soil. The removal of sulfur was up to 60%, arsenic up to 80%, while Se, Ba, and V up to 60%, and U up to 20%. By applying synthetic zeolites on water from the Raša coalmine and a local stream, the significant removal values were found for Sr (up to 99.9%) and Ba (up to 99.2%) only. Removal values were quite irregular (insignificant) in the cases of Fe, Ni, Zn, and Se, which were up to 80%, 50%, 30%, and 20%, respectively. Although promising, the results call for further research on this topic.
Highlights
Coal is a valuable resource in terms of cheap electricity production, and is an economic source of strategically important elements (Ge, Ga, U, V, Se, rare earth elements, Y, Sc, Nb, Au, Ag, and Re) [1,2,3]
The present study applied bacterial cultures of Ralstonia sp. on SHOS Raša coal and soil polluted with coal and coal-combustion waste
The removal of organically bound sulfur from coal was negligible, while soil desulfurization was up to 60%
Summary
Coal is a valuable resource in terms of cheap electricity production, and is an economic source of strategically important elements (Ge, Ga, U, V, Se, rare earth elements, Y, Sc, Nb, Au, Ag, and Re) [1,2,3]. Coal combustion emissions, enriched in S and potentially toxic trace elements (PTEs), such as Se, U, Cd, Hg, Pb, As, Ni, Cr, V, etc., could be hazardous for soil, water, air, and crop quality [4,5,6,7]. Soil and water degraded by the coal industry must be remediated and conserved using a strategy which needs to be achieved as cheaply and effectively as possible. Various physical and chemical technologies of metal removal and/or stabilization from soils and sediments have been reported, each one with potential advantages and drawbacks. They include, for example, soil washing, thermal extraction, ion exchange, electrokinetic treatment, reverse osmosis, Water 2019, 11, 1419; doi:10.3390/w11071419 www.mdpi.com/journal/water
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