Abstract. Acid mine drainage (AMD) are a worldwide problem leading to ecological destruction in river basins and the contamination of water sources. AMD are characterized by low pH and high content of heavy metals and sulphates. In order to minimize negative impacts of AMD appropriate treatment techniques has to be chosen. Treatment processes are focused on neutralizing, stabilizing and removing pollutants. From this reason efficient and environmental friendly methods are needed to be developed in order to reduce heavy metals as well as sulphates. Various methods are used for remediation of acid mine drainage, but any of them have been applied under commercial-scale conditions. Their application depends on geochemical, technical, natural, financial, and other factors. The aim of the present work was to interpret the study of biological methods for sulphates removal from AMD out-flowing from the shaft Pech of the deposit Smolník in Slovak Republic. In the experimental works AMD were used after removal of heavy metals by precipitation and sorption using the synthetic sorbent Slovakite. The base of the studied method for the sulphates elimination was the anaerobic bacterial sulphate reduction using sulphate-reducing bacteria (SRB) genera Desulfovibrio. SRB represent a group of bacteria that uses sulphates as a terminal electron acceptor for their metabolism. These bacteria realize the conversion of sulphate to hydrogen sulphide under anaerobic conditions. For the purposes of experiments a few variants of the selective medium DSM-63 culture media were used in term of the sulphates and sodium lactate contents in the selective medium as well as sulphates in the studied AMD. IntroductionSulphates are found in almost all natural water, where the raised concentration can originate from landfill leaching. Sulphate and metal containing wastewater from the mining and metallurgical industry are a major source of natural water bodies pollution, but high sulphate loads can be the result of prolonged high atmospheric deposition, application of sulphate-containing fertilizers and a wide range of industrial processes including power generation, tanneries, paper and pulp production.Sulphates present are not considered to be toxic, but negatively affect the taste of water and concentration higher than 600 mg/L usually results in a laxative effect [1]. However, sulphide produced from sulphate at anaerobic condition has toxic effects in the aquatic environment causing lack of oxygen resulting fish, plant and plankton deaths. Hydrogen sulphide can also increase eutrophication in natural water bodies by generating chemical cycle that release phosphate [2,3]. Moreover, waters rich in sulphate have a high corrosive and scaling potential and induces an unbalance in the natural sulphur cycle [4].
Acid mine drainage (AMD) is a worldwide problem leading to contamination of water sources. AMD are characterized by low pH and high content of heavy metals and sulphates. The barium salts application presents one of the methods for the sulphates removing from AMD. Barium chloride, barium hydroxide and barium sulphide are used for the sulphates precipitation in the form of barium sulphate. Because of high investment costs of barium salts, barium sulphide is recycled from barium sulphate precipitates. It can be recycled by thermic or bacterial reduction of barium sulphate. The aim of our study was to verify experimentally the possibility of the bacterial transformation of BaSO 4 to BaS by sulphatereducing bacteria. Applied BaSO 4 came from experiments of sulphates removal from Smolnik AMD using BaCl 2 .
The submitted paper deals with the study of combination of chemical and biological-chemical methods for the heavy metals elimination from the acid mine drainage. The experiments were carried out at the laboratory scale using a synthetic solution with similar properties to the real sample of acid mine drainage, originating from the zinc mine located in Tùnel Kingsmill outflow of the Rio Yaulì (district of Yauli - Perù). The successive repetition of the metal precipitations as hydroxides (chemical method) and sulphides (biological-chemical method) at the various acid mine drainage pH was the basis of the examined processes. For the hydrogen sulphide production the sulphate-reducing bacteria of genus Desulfovibrio were used. Results confirmed the precipitation of Fe, As, Al and Mn in the hydroxide form; Cu and Zn in the form of sulphides. For the selective removal of Cu, Zn, Al and Mn the excellent results were received. Selective precipitation of Fe and As was not so successful since the co-precipitation of Fe and As was later determined as a main mechanism of the precipitate forming.
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