Biosulfides Precipitation in Weathered Tailings Amended with Food Waste-based Compost and Zeolite

Abstract

Tailings are mine wastes in the form of slurries stacked in mine sites abandoned after the exhaustion of ores. There are approximately 5000 abandoned mine sites in Korea, and tailings have become a serious environmental problem. Long‐term environmental exposure of tailings can cause release of acidic and high concentrations of sulfate‐ and metal‐contaminated water (acid mine drainage, AMD). Organic and/or inorganic amendments have been studied for AMD prevention and passive in situ treatment of pore water. This study tests locally available food waste‐based compost as a viable amendment, in addition to the need for sustainable ways to dispose of compost, in response to a new environmental law. To examine the feasibility, three bioreactors were constructed, filled with mixtures of tailings, food waste‐based compost, and zeolite. During the 4‐wk experimental period, feeding water ormedium were poured in one reactor. The leachates were investigated in terms of chemistry and microbiology. Compared with the unamended reactor, the leachate from two mixture‐filled reactors showed increased pH, formation of sulfate reduction conditions, and highly efficient metal removal. Black‐colored precipitates observed at the end of the experiment suggested the formation of metal biosulfides, following the activity of sulfate reduction mediated by sulfate‐reducing bacteria (SRB). Mineralogical analysis of these precipitates confirmed the presence of biosulfides, mainly of Fe and Pb. Moreover, microbial and molecular biological analyses revealed that several species of heterotrophic bacteria (SRB and iron‐reducing bacteria) were present in the solids recovered from the bioreactors. Microbial consortium, such as SRB species (Desulfotomaculum putei), and cellulosic‐degrader (Ruminococcus sp.) were identified. This study provides promising results on the application potential of food waste‐based compost for prevention of AMD generation and passive in situ treatment of pore water in weathered tailings in Korea and elsewhere.

Study on the Effectiveness of Sulfate-Reducing Bacteria Combined with Coal Gangue in Repairing Acid Mine Drainage Containing Fe and Mn

“…The leaching solution of Coal Gangue 1-3 was neutral or weak alkaline, and the leaching solution of Coal Gangue 4 was acidic. Neutral pH can promote SRB growth [32], accelerate the metabolic activity of SRB, increase pH and reduce ORP. In the second stage, the average pH values of the effluent from the 4 columns were 7.93, 7.86, 9.09 and 8.02, and the average ORP value were −204.33 mV, −236.92 mV, −262.83 mV and −112.83 mV, respectively.…”

Study on Growth Influencing Factors and Desulfurization Performance of Sulfate Reducing Bacteria Based on the Response Surface Methodology

“…At 35 °C, the pH value increases most obviously, mainly because SRB has high growth activity and large reproduction quantity at this temperature, so the alkalinity generated by metabolism is large. At the same time, the alkaline pH value of the solution further promotes the growth and metabolism of SRB …”

“…At the same time, the alkaline pH value of the solution further promotes the growth and metabolism of SRB. 27 It can be seen from Figure 2c that the ORP values under different culture temperatures decreased significantly with the extension of culture time. After 8 days of incubation, the ORP values of the solution were −297, −371, −393, −128, and −102 mV, respectively.…”

Dynamic Experimental Study on Treatment of Acid Mine Drainage by Bacteria Supported in Natural Minerals

“…Hao T. [21] found the sulfate reduction process is accompanied by organic carbon mineralization, bicarbonate production and, subsequently, an increase in pH and alkalinity. At the same time, bagasse and medical stone absorbed the free H+ by electrostatic adsorption, so the pH of the effluent was stable in the neutral range, which can provide favorable growth conditions for SRB [22] and promote the growth of SRB. Studies have shown that the composite minerals such as quartz and feldspar in the medical stone [23] have a strong regulatory effect on acidic pH.…”