Coal Processing Activities Research Articles

Coal mine wastes: Effective mitigation of coal waste slurry and acid mine drainage through bioflocculation using mixotrophic bacteria as bioflocculants

Acid mine drainage (AMD) and coal waste slurry, byproducts of global mining and coal processing activities, represent significant environmental pollution concerns due to their acidic nature and high total suspended solids (TSS) content. The exploration of microbial treatment methods, specifically the utilization of microorganisms and their metabolic byproducts as bioflocculants, is underway to mitigate the adverse effects of these byproducts. This investigation assessed the effectiveness of 54 mixotrophic bacterial strains in treating coal waste slurry and AMD from coal mines located in Kalimantan, Indonesia. The bacterium Citrobacter freundii (strain SKC-4), cultured in SKC1 medium (comprising 225 mL of seawater from the Java Sea and 15 g/L molasses), demonstrated superior performance, reducing the TSS value from 4998.20 ppm to 16 ppm within an hour. Fourier Transform Infrared (FTIR) analysis revealed an increase in the intensity of the CO and CN groups from protein amides and CH2 from carbohydrates, suggesting an interaction between bacteria and clay minerals in the coal waste slurry. The bacteria also played a crucial role in adjusting the pH of AMD, elevating it from 3.82 to 6.07 after one hour of conditioning with a bacterial culture to AMD ratio of 1:9. The interaction between bacteria and their metabolic products was further substantiated by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis, which detected the presence of an extracellular polymeric substance (EPS). To our knowledge, this study represents the first exploration of the potential of mixotrophic bacteria as bioflocculants in the biotreatment of coal waste slurry and AMD from coal mining operations.

On the feasibility of South African coal waste for production of ‘FabSoil’, a Technosol

Appropriate handling and disposal of coal waste is key to maximizing a sustainable approach towards coal processing activities. This paper investigates the feasibility of using the desulfurised fraction of coal processing slurry (<500 µm) streams from a colliery in the eMalahleni coalfields of South Africa as the main component for the manufacture of ‘FabSoil’, a fabricated soil or technosol, for use as topsoil in the rehabilitation of mine sites. Compost and anaerobic digester sludge were added as organic matter and nutrient source, whilst malt residue was used as physical ameliorant. Native soil from the study area was used as control. Validation of the potential of the fabricated soils was conducted through germination and growth experiments using the grass species Teff (Eragrotis tef), an indigenous grass from the Mpumalanga region of South Africa commonly cultivated on degraded mine land. Results showed that soils produced with coal waste and native soil in a 3:1 ratio amended with compost or anaerobic digester sludge and malt residue had the highest biomass production after 90 days. According to this study, the use of these soil substitutes can reduce the amount of topsoil used in coal mine restoration, while also reducing the amount of fine coal disposed in dump deposits significantly. This minimises the land-use footprint and the social and environmental impact of mining activities as part of circular economy and zero-waste strategies.

Environmental and Climate Dilemma: Coal for Heating or Clean Air for Breathing: A Case of Prishtina

Abstract Air pollution as a global issue is an essential health problem, faced by millions of people all over the world. It is a huge problem encountered by the citizens of the city of Prishtina, too. The benefit from the cheapest forms of energy, that generated from coal-fired power plants, and the one derived from the low financial cost, raises the question: do we have to compensate this energy with our health? This paper presents the analysis of the emanations, such are coal-fired power plants in the vicinity of the city of Prishtina, and aims to determine the accepted level and health framework boundaries for coal-fired power plants and coal processing activities. The research methods consist of empirical observations and data analysis on health degradation, environmental and greenhouse gas contribution to the climate change. The actual state of energy production is not the most effective pathway to the stability of basic load for energy. Hence, the debate focused around environment tends to fail the essential need for supplying Kosovo with electricity, something for which power plants are suitable. Unfortunately, with all our environmental stubborn beliefs, renewable sources such as sun and wind are not, in the present efficiency for Kosovo. The present hazardous air quality requires well defined lawful steps and activities. Thus, the research findings recommend and promote precise immediate environmental measures.

Leaching characteristic and environmental implication of rejection rocks from Huainan Coalfield, Anhui Province, China

Rejection rocks including intra-seam parting, boundary roof and floor intimately associated with coal seams, are commonly produced along with bulk coal. In general, these non-combustible rocks are rejected during coal processing activities, accumulated on the surface, and subjected to natural weathering and leaching. The degree that the rejection rocks threaten the surrounding ecosystems is determined by total concentrations, modes of occurrence of hazardous elements and minerals therein. Three hundred and ninety-four samples of coal seam parting (30), roof (182) and floor (182) in the Huainan coalfield were collected to investigate the geochemical characteristics and environmental risks of rejection rocks. The morphological analysis revealed that rejection rocks are composed of lithic fragments with organic and inorganic layering, clay minerals, quartz, pyrite and chlorite. Correlation analysis between elements and ash yield suggested that most of the environmentally sensitive elements (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, Sn V and Zn) are associated with inorganic matter, but boron is mainly associated with organic matter. In-house sequential leaching experiments conducted on selected rejection rocks showed that the rejection rocks from Huainan Coalfield could be suitable for landfill under high regularization and management. However, in the currently unconfined deposits, trace elements (such as Cu, Ni, Pb, Sb, Sn and Zn possibly) may pose a medium risk to the ecosystem.

Environmental assessment: contamination of phreatic aquifer in areas impacted by waste from coal processing activities

The objective of the present work was to evaluate the degree of contamination of groundwater in areas under influence of inadequate disposal of residues from coal-processing activities. Charqueadas and São Jerônimo Counties were selected for the study. The contamination of groundwater from the phreatic aquifer was evaluated in a sequence of steps: initially, the target area was selected; then, the piezometers were installed and groundwater was sampled. The location of piezometers was based on the results obtained from the mapping of pollution sources, geophysical and hydrogeological studies. The results showed that the groundwater (phreatic aquifer) from the region studied is influenced, in variables degrees of intensity, by the type and characteristics of residues, the lithological profile of the site and the distance from the pollution sources. Physical and chemical characterization revealed that coal waste influenced more significantly groundwater contamination, evidenced by acidic pH values, as well as high values of conductivity, total dissolved solids (TDS), sulfates, ferrous iron and metals (Ni, Fe, Co, Cr and Mn). The statistical analysis applied to the variables studied gave a General Groundwater Index for each well. By the application of this index, it was possible to highlight the kind of residues and variables that are affecting the groundwater quality.