Acid Mine Drainage pH Research Articles

Association of rare earth elements with secondary mineral phases formed during alkalinization of acid mine drainage

Rare Earth Elements (REE) are present in acid mine drainage (AMD) in micromolar concentrations and AMD discharge may lead to an environmental risk. Alkaline Passive Treatment Systems (PTS) are often used to treat AMD and trap toxic trace elements. This study was set up to identify mechanisms by which REE are trapped in or on secondary phases formed in a PTS. Batch alkalinization experiments were performed to simulate PTS by sequentially increasing the pH of AMD collected from the Tharsis mining area inside the Iberian Pyrite Belt and synthetic AMD water samples via CaCO3 addition. The solids that precipitated up to pH ~4 and between pH 4–6 were collected and characterized by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in combination with Scanning Electron Microscope/Energy Dispersive X-ray spectroscopy (SEM/EDX) and synchrotron-based X-ray Absorption Spectroscopy (XAS) and synchrotron-based Micro-X-ray Fluorescence (μ-XRF). Results reveal that REE are mostly scavenged between pH 4–6 in association with Al and Fe phases, whereas a smaller fraction is scavenged at pH ~4 by association with gypsum. Synchrotron-based analysis evidences the incorporation of La3+ into the gypsum structure by substituting Ca2+, indicating a co-precipitation mechanism with gypsum occurring mainly at low pH. Results from parallel adsorption and co-precipitation tests suggest that the REE scavenging between pH 4–6 could be due to a combination of adsorption and co-precipitation on Al(OH)3 and ferrihydrite. This implies that in PTS, REE would be mainly found in Al- (and Fe-) oxyhydroxides occurring in deeper layers of the PTS, i.e., where higher pH-values occur, though a small fraction, especially the light REE, could also be found incorporated into gypsum in the upper layers.

High acidity notably influences acid mine drainage treatment performance in constructed wetlands packed with composite organic substrates by affecting both abiotic and biotic routes

The impact of influent pH value (2.0–5.0) on remediation performance of constructed wetlands (CWs) packed with composite organic solids consisting of walnut shells, biochar and plastic filters for acid mine drainage (AMD) was evaluated in this study. Reed straw broth was supplemented to drive the microbial remediation process. Influent pH had a notable impact on both abiotic and biotic remediation performance, with very low efficacy at pH 2.0 and the best performance achieved at pH 5.0. The adsorption capacity of CW substrates for heavy metals and the growth of functional microbes for AMD treatment were restrained at high acidity. Moreover, the removal of conventional pollutants, plant growth and metal deposition in the CWs were negatively impacted by the dosing of AMD with low pH. A low pH of 2.0 resulted in a distinctive microbial community in the CWs with almost no sulfate-reducing bacteria (SRB). In other CW systems, SRB (Desulfosporosinus and Desulfobulbus) and organic degrading bacteria (Cellulomonas and Geobacter) were identified as keystone taxa to carry out AMD bioremediation synergistically in phase Ⅱ. CWs filled with composite organic substrates are promising systems for AMD treatment, but the pH of AMD should be preneutralized to ≥ 3.

The development of an efficient precipitation-flotation-dewatering (PFD) process for acid mine drainage treatment

Acid mine drainage (AMD) stands as a prevalent environmental challenge across numerous mining sites, often addressed through the high-density sludge (HDS) process, a typical neutralization and sedimentation process. However, despite its widespread use, the HDS process requires prolonged treatment durations and presents challenges in sludge dewatering and site relocation, thus falling short of an optimal solution. In this study, an efficient precipitation-flotation-dewatering (PFD) process was developed and optimized as a viable alternative to the HDS process, offering efficient AMD treatment. The experimental results indicate that over 90 % of ions were successfully precipitated by employing CaO as a neutralizing agent to adjust AMD pH to 10.0. Flotation was then conducted with a low-profile flotation column after adding an optimal concentration of 10 mg/L of A-100 flocculant and 400 mg/L of NaOL. Compared with original AMD, the final removal of toxic and hazardous ions of Fe, Al, Cd, Sn, Co, Ni, Zn, and Mn were 97.61 %, 98.85 %, 98.21 %, 97.78 %, 97.22 %, 99.34 %, 99.89 %, and 99.14 %, respectively. Additionally, the solid content of produced sludge was 27 %. Mechanistic inquiries revealed that A-100 and NaOL both chemically adsorbed on the particle surface and respectively enhanced the collision and attachment probabilities between precipitate particles and bubbles, thereby augmenting the separation efficiency. Furthermore, shortening the flotation column reduced the particle flotation path, thereby improving the flotation efficiency. The efficient PFD process exhibits significant advantages of rapid and effective AMD treatment, high sludge solid content, small footprint, and high relocatable convenience, demonstrating satisfactory cost effectiveness and significant potential as a replacement of the HDS process for AMD treatment.

A pilot-scale study on the in-situ remediation of acid mine drainage with supplemental of external nutrition: Performance, heavy metal removal and microbial community evolution

Acid mine drainage (AMD), a common environmental problem around the world, is characterized by low pH, high concentrations of heavy metals and sulfate. AMD treatment technology based on stimulating in-situ microorganisms has received widespread attention, but lack of organic matter is a limiting factor that restricts the remediation by heterotrophic microorganisms such as sulfate-reducing bacteria (SRB). In this study, a pilot scale reactor was set up next to an acid reservoir to evaluate the effect of livestock wastes on the in-situ bioremediation of AMD, focusing on performance assessment, heavy metal removal efficacy, and the evolution of the microbial community. Results indicated that the pH of AMD rises rapidly from 3.23 to 4.11, and metals (e.g., Fe, Cu, and Zn) rapidly got removed in Stage I. However, AMD experienced significant stratification in Stage Ⅱ (biogas slurry supplemented). The pH of surface layer (0.5 m below the surface) gradually dropped to 3.67, and the bottom layer (2.3 m below the surface) remained around 4.1, and the metal removal efficiencies further improved. Microbial communities were dominated by Fe-OB and Fe-RB in surface layer, while SRB dominated in bottom layer. The addition of biogas slurry significantly increased the relative abundance of functional microbe in bioremediation. The growth of SRB in the bottom of the reactor made an important contribution to heavy metal removal. Heavy metals were mainly removed through the formation of insoluble hydroxide and sulfide precipitation and co-precipitation. This study innovatively integrates low-cost, locally sourced livestock waste as nutrient supplements into AMD bioremediation processes, and demonstrated the potential for integrating AMD treatment with livestock waste management, addressing both the nutrient needs for AMD processing and the challenge of livestock waste disposal. The findings contribute to the development of cost-effective and eco-friendly strategies for AMD management while advancing the understanding of microbial mechanisms of in-situ bioremediation.

The possible application of fly ash (FA) to ameliorate acid mine water (AMD) for irrigation of potato (Solanum tuberosum L.)

Some areas in Johannesburg abounds with mine wastes namely, acid mine drainage (AMD) as well as fly ash (FA), which are by-products of gold mining and coal burning, respectively. Studies show that a solution formed through mixing these wastes neutralises the acidity of AMD and is an alternative source of irrigation. While studies show improved growth and yield of plants irrigated with fly ash-amended AMD, there are rarely sufficient studies conducted in South Africa showing evidence of altered pH of AMD and that food crops irrigated with fly ash-amended AMD exhibit improved concentration of essential nutrient elements. In this study, AMD was sourced from a gold mine in Johannesburg and fly ash collected from a coal-burning power station in the Mpumalanga Province, mixed at 1:0, 1:1, and 3:1 (w/v) of fly ash to AMD and used to irrigate potatoes. The objective was to assess whether the solutions of FA-amended AMD alter the pH of the AMD and to evaluate if irrigating potatoes with the aforementioned improve the concentration of essential nutrient elements and heavy metals in the tubers. Results show that the pH of AMD was increased in the 1:0 and 1:1 solutions but decreased in the 3:1 solution. The concentrations of Pb and Co were decreased in tubers irrigated with the 50 % AMD and 75 % AMD while that of Ni and Cd were markedly increased in tubers irrigated with solutions of fly ash-amended AMD. In the main, the potato tubers exhibited significantly higher concentrations of Al, Mo, Cu, Ca, Mg, and Zn when irrigated with fly-ash-amended AMD. The pH range levels from FA-AMD treated samples were within the acceptable pH range (5.5–6.5) which is acceptable for water that could be used for irrigation of crops. Also, the decreased Co and Pb and improved concentration of essential nutrient elements indicate that the constituents absorbed large quantities of the heavy metals while releasing the nutrients. In conclusion, the selected fly ash has proven as an alternative low-cost readily-available, affordable, and accessible adsorbent that neutralize the acidity of AMD, decrease the concentration of heavy metals, and increase the concentration of essential nutrient elements. Importantly, the liming potential among other traits of the fly ash improved the quality of the AMD such that the wastes were proven in this study suitable to irrigate potatoes.

Peningkatan pH dengan Pemberian Bahan Organik pada Pengelolaan Air Asam Tambang Menggunakan Metode Passive Treatment

Mining is the process of extracting beneficial minerals from the surface of the earth that have an impact on the formation of acid mine drainage (AMD). One method of passive AMD management is passive treatment. This study used the Nested Factorial Experiment Design method. The types of organic matter used were empty fruit bunch oil palm (EFB) and cow dung, with doses of 0 Mg ha-1 (control), 50 Mg ha-1, 100 Mg ha-1, 150 Mg ha-1 and 200 Mg ha-1. Each treatment was three repeats so that 30 units of experimental units were obtained. The pH value of AMD in the untreated (control) reactor was 3.67. The initial reaction (pH) of AMD (0 days) with EFB application at a dose of 50 – 200 Mg ha-1 ranged from 3.63 – 4.28 and the initial pH of cow dung was 3.84 – 4.13. The reaction (pH) of the 1st to 4th weeks of AMD after adding EFB organic matter at a dose of 50 – 200 Mg ha-1 show a pH range (6.38 – 7.59) and cow manure at a dose of 150 – 200 Mg ha-1 show a pH (6.09 – 7.01). The conclusion are that the application of EFB organic matter on constructed wetland media for 4 weeks had a very real effect on increasing the pH of the AMD dose of 100 – 200 Mg ha-1 while cow dung 150 – 200 Mg ha-1 are the most effective against increasing pH.

ACCUMULATION OF HEAVY METAL IN CHINESE WATERCHEST-NUT (Eleocharis dulcis Burm.f.) Trin. Ex Hensch.) IN PHYTOREMEDIA-TION OF COAL ACID MINE WATER ON CONSTRUCTED WETLANDS.

The coal open mining is an activity that has an impact on the environment, including acid mine drainage (AMD). The management of AMD can be done by phytoremediation using Chinese Waterchestnut (Eleocharis dulcis Burm.f.) Trin. ex Hensch.) on system of constructed wetlands (CWs). So the research was carried out with the aim of evaluation the accumulation of heavy metals iron (Fe) and Manganese (Mn) which were absorbed in E. dulcis in constructed wetlands system at WTP Air Laya PT. Bukit Asam. The accumulation of Fe in the roots of E. dulcis was 986.42 ppm (w/w) while the accumulation of Fe in the leaves was 392.22 ppm (w/w). The accumulation of Mn in the roots of E. dulcis was 24.49 ppm (w/w), while the accumulation of Mn in the shoots was 96.83 ppm (w/w). E. dulcis is known to have the potential to increase AMD pH and reduce levels of Fe, Mn and SO42- so that it can meet the quality standards of coal mining activity wastewater. The accumulation of Fe and Mn in the roots and shoots of E. dulcis and on AMD can be used as an effort to monitor the success of AMD phytoremediation on Constructed Wetlands system at WTP Air Laya.

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.

Selection of organic matter as a wetland substrate for acid mine drainage treatment

Acid mine drainage (AMD) is one of the problems arising from mining activities. Acid mine drainage is formed due to the oxidation of sulfide minerals such as pyrite (FeS2) by water and oxygen. Alternative management of AMD in a sustainable and eco-friendly way is constructed wetland. Therefore, this study was conducted to determine the type and composition of potential organic matter that can improve AMD quality. The study consisted of three stages: a screening of organic matter, a combination of two organic matters, and a combination of cow manure and empty fruit bunches (EFB) in various compositions. Types of organic matters used are cow, goat, and chicken manure, three types of compost, EFB, sawdust, wood chips, chopped water hyacinth, cocopeat, fresh waste and compost waste cajuputi leaf, waste of citronella distillation, baglog waste, and bagasse. The results showed that several types of organic matter could increase the pH of AMD. The combination of EFB and cow manure with a ratio of 2:1 is the best result because it can increase pH, reduce dissolved heavy metals and sulfates, and availability of raw materials that are abundant in nature, especially in Indonesia.

A clay-coal fly ash based dual hydraulic-reactive liner for controlling acid mine drainage.

Hydraulic liners are used to restrict hazardous leachates such as acid mine drainage (AMD) from entering the hydrogeological system. In this study, we hypothesized that: (1) a compacted mix ratio of natural clay and coal fly ash with a hydraulic conductivity of at most 1 × 10- 8 ms- 1 can be achieved, and (2) mixing clay and coal fly ash in the right proportion can result in increased contaminant removal efficiency of a liner system. The effects of adding coal fly ash to clay on the mechanical behavior, contaminant removal efficiency, and saturated hydraulic conductivity of the liner were investigated. All clay:coal fly ash specimen liners with less than 30% coal fly ash had significantly (p < 0.05) lower cohesion stress values, and were discarded without further tests. Saturated hydraulic conductivity values showed no significant effect (p > 0.05) on the results of clay:coal fly ash (7:3) specimen liners and compacted clay liner. The clay:coal fly ash mix ratios of 8:2 and 7:3 significantly (p < 0.05) reduced the leachate concentration of Cu, Ni, and Mn. The pH of AMD increased from an average of 2.14 to 6.80 after permeating through a compacted specimen of mix ratio 7:3. Overall, the 7:3 clay to coal fly ash liner showed superior pollutant removal capacity and its mechanical and hydraulic properties were comparable to compacted clay liners. This laboratory scale investigation emphasizes potential limitations with column scale evaluation of liners and provides new information on the application of dual hydraulic reactive liners for engineered hazardous waste disposal systems.

Reduction in acidity and heavy metal concentrations of acid mine drainage with organic matter and coal fly ash treatments in two different reclaimed-mining soils

Organic matter (OM) has a very crucial role in the management of acid mine drainage (AMD) using a passive treatment system, although information on the use of this system in different reclaimed-mining soils (RMS) is very limited. Therefore, this study aimed to determine the effect of adding OM to RMS with different characteristics. It was carried out by adding only OM or in combination with coal fly ash (CFA) to two RMS with different characteristics (Palam and Cempaka Soils) and quartz sand (control) in a batch reactor experiment. This was followed by the incubation of the mixture of soil/quartz-OM or soil/quartz-OM-CFA at 60% water holding capacity for 15 days. After incubation, AMD slowly flowed into the reactor, and its pH in the reactor was monitored every day for 30 days, while the concentrations of Fe (iron), Al (aluminum), and Mn (manganese) were measured on the 30th day. The results showed that the application of OM on Palam Soil only increased AMD pH by 0.38 units, while Cempaka Soil and quartz sand increased by 4.83 and 5.36 units, respectively. The addition of OM to Cempaka Soil and quartz sand also showed a higher reduction in heavy metals concentration in AMD than those in Palam Soil. It was also discovered that the application of OM combined with CFA led to a higher improvement in AMD quality than only using OM. This study demonstrated that the effect of OM addition on increasing pH and decreasing metal concentration on AAT management with the passive treatment system is controlled by soil characteristics.

Continuous and effective treatment of heavy metal in acid mine drainage based on reducing barrier system: A case study in North China

The acid mine drainage (AMD) resulting from human mining activities has adversely affected across the worldwide. The heavy metals and acidity contained in AMD cause great harm to the ecological environment, which are difficult to remove at low cost and effectively. In this study, the acid regulation and heavy metal removal of AMD were investigated by using the reducing barrier system constructed with common industrial wastes of activated sludge and fly ash as the reaction medium. The optimized results indicate that more than 99% of Cu2+ and 100% of Zn2+ in the AMD are effectively removed, as well as a neutral pH of AMD is achieved. It was attributed to alkaline substances in the reducing barrier system regulate the pH of AMD effectively, while the reducing atmosphere created by the self-respiration of microorganisms in the system reduces SO42− to S2− and HS−, achieving the purpose of removing heavy metal ions by forming the precipitation of metal sulfides. Based on SEM-EDS, BET, FITR and Zeta potential characterizations, the removal mechanism of metal ions by the reducing barrier system were systematically elaborated. Moreover, the long-term effectiveness of the reducing barrier system is evaluated by several repeated simulated leaching experiments. This discovery achieves the purpose of “treating waste with waste” and provides an environmentally friendly, economic and long-term treatment method for local AMD.

Construction and carbon source optimization of a microbial-plant coupled reactor for treating acid mine drainage.

Acid mine drainage (AMD) is recognized as one of the most serious contamination sources in the nonferrous metal mining industry. In this study, aerobic strains VCZ02 and VCZ09, which were identified as Leclercia adecarboxylata and Klebsiella aerogenes, were screened from 11 strains of copper-zinc-resistant bacteria in the soil of the Dexing copper mine with Cu2+/Zn2+ removal rates of 46.32%/41.03% and 57.96%/67.05%, respectively. The composition of extracellular polymers plays an important role in the removal of heavy metals by these two strains. A mixed community consisting of VCZ02 and VCZ09 was coupled with Sagittaria trifolia L.var.sinensis (Sims) Mak to construct a microbial-plant coupled reactor to remediate AMD. Under the optimal condition of sodium acetate as carbon source, the pH of AMD increased from less than 5 to above 6.5, showing Cu2+/Zn2+ removal rates of 70-80% and above 30%, respectively. SEM-EDS results showed that VZC02 and VZC09 in the coupled reactor also helped with resisting the toxicity of heavy metals to plants by forming biofilms on the root surface and increasing the content of heavy metals on the surface of roots, thus improving the treatment effect of plants. This study provides a theoretical basis for the bioremediation of AMD and its application.

Experimental Simulation Study of Mine Water Acidification under the Action of Pyrite

The discharge of acidic water has become an environmental issue of great concern worldwide. In order to investigate the characteristics and mechanism of acidic water induced by pyrite in sulfur-rich mines, indoor static precipitation and dynamic leaching simulation experiments were carried out under the conditions of pyrite content, rock particle size, media combination, and ambient temperature. At the same time, this paper used the gray correlation method to quantitatively analyze the influencing factors. The results showed that the degree of groundwater acidification was negatively correlated with the rock particle size and temperature and positively correlated with the pyrite content. The quantitative analysis of the effect of each factor on acid mine drainage pH was pyrite content &gt; temperature &gt; rock size. When considering different media conditions, the combined effect of the three media on reducing the acidification degree of mine water was limestone &gt; gangue &gt; coal. In addition, dynamic leaching and static soaking have different effects on the acidification of the mine water, with the latter acidifying more rapidly. It is also concluded that although pyrite enrichment was the main controlling factor affecting the acidification of mine water in nature, complexation of trivalent iron ions adsorbed in the formation was more likely to be the main causal mechanism for the rapid acidification of mine water in coal mining areas.

Microbial Sulfate Reduction (MSR) as a Nature‐Based Solution (NBS) to Mine Drainage: Contrasting Spatiotemporal Conditions in Northern Europe

AbstractAn emerging solution in mine waste remediation is the use of biological processes, such as microbial sulfate reduction (MSR), to immobilize metals, reducing their bioavailability and buffering the pH of acid mine drainage. Apart from laboratory tests and local observations of natural MSR in, for example, single wetlands, little is known about spatiotemporal characteristics of freshwater MSR from multiple locations within entire hydrological catchments. We here applied an isotopic fractionation (δ34S values in SO42−) and a Monte Carlo‐based mixing analysis scheme to detect MSR and its variation across two major mining regions (Imetjoki, Sweden and Khibiny, Russia) in the Arctic part of Europe under different seasonal conditions. Results indicate a range of catchment‐scale MSR values in the Arctic of ∼5%–20% where the low end of the range was associated with the non‐vegetated, mountainous terrain of the Khibiny catchment, having low levels of dissolved organic carbon (DOC). The high end of the range was related to vegetated conditions provided by the Imetjoki catchment that also contains wetlands, lakes, and local aquifers. These prolong hydrological residence times and support MSR hot spots reaching values of ∼40%. The present results additionally show evidence of MSR persistence over different seasons, indicating large potential, even under relatively cold conditions, of using MSR as part of nature‐based solutions to mitigate adverse impacts of (acid) mine drainage. The results call for more detailed investigations regarding potential field‐scale correlations between MSR and individual landscape and hydroclimatic characteristics, which, for example, can be supported by the isotopic fractionation and mixing scheme utilized here.

Study on the precipitation of iron and the synchronous removal mechanisms of antimony and arsenic in the AMD under the induction of carbonate rocks.

The ecological environment can be severely polluted and destroyed by the acid mine drainage (AMD) generated during the exploration and utilization of minerals. However, neutralized by carbonate rocks (a natural material in Karst regions), the AMD secondary iron flocs containing a large number of iron oxides or hydroxide can be precipitated in AMD. The metal ions, such as antimony (Sb) and arsenic (As), can be effectively removed by these neutralizing products. In this paper, the neutralization reaction of different acid solutions in an iron-antimony-arsenic system was induced by carbonate rocks to explore the removal effect of metals during this neutralization process. Meanwhile, taking the release amounts of iron (Fe), Sb, and As as well as the phase transformation of minerals at different pH levels as stability indexes, we quantitatively analyzed the chemical stability of AMD neutralizing products (secondary iron flocs) containing Sb and As under the typical acid-base environment (pH = 3.0 ~ 9.0) of AMD and other waters. Results showed that the neutralization reaction with carbonate rocks induced the co-precipitation of Fe with Sb and As. When the concentration ratio of Fe, Sb, and As was 30:1:1, the pH of AMD raised from 3.0 to 7.28 within 72h, and the three elements were removed by 99%, 85%, and 90%, respectively. After soaking the AMD secondary iron flocs in an acid environment (pH = 3.0) for 30days, the release amount of Fe reached its peak of 0.070mg/g. Then, when the pH value increased to 4.0, the As and Sb showed their maximum release amounts of 14.90µg/g and 19.19µg/g, respectively. In addition, under acidic conditions, these AMD secondary iron flocs were easily transformed into the goethite with better crystallinity and higher structural stability. This study could help reveal the development of the secondary mineral during the treatment of AMD by carbonate rocks and understand the release characteristics of metals from AMD secondary products containing Sb and As, which sheds light on and provides theoretical foundations for the passive treatment of AMD containing these two elements in the future.

Increases in pH of acid mine drainage with coal fly-ash application

Coal fly-ash (CFA), waste materials resulted from coal processing in power plants, contains oxides that have capability to neutralize hydrogen ions of acid mine drainage (AMD). A batch reactor experiment was conducted by adding different amounts of CFA (0, 50, 100, 150, 200, and 250 Mg ha−1) to reclaimed mining soils (RMS) to quantify the effect of CFA addition on changes in the pH of AMD. AMD was then flowed into the reactors following the incubation of the mixtures of RMS and CFA for 7 days, and the changes in pH of AMD in the reactors were monitored over 35 days. Results of the study showed pH and specific surface areas (SSA) of soils increased significantly with the addition of CFA. pH of AMD over 35 days also improved with CFA application, in which the degree of pH improvement was controlled by the amounts of added CFA. The addition of CFA <200 Mg ha−1 was not able to result in pH of AMD >6.0, and AMD pH of 6.0 was obtained when the amount of applied CFA reached to 200 Mg ha−1. Increasing pH of AMD is attributed to the CaO and MgO contained in the CFA neutralizing the H+ ions of AMD. Results of the study demonstrate the potential of CFA in remediation of AMD, in particularly in increasing pH of AMD.

Role of the Tree Species Selected in Developing Swampy Forest System for Passive Treatment of Acid Mine Drainage

Coal mining is one of economic sector that requires forestry area in Indonesia. Most of coal mining concession are forestry area loan use from the government and during mining operation facing with acid mine drainage (AMD). AMD passive treatment can be integrated with revegetation process that related with better handling of overburden (OB) with potential acid forming (PAF) during reclamation processed. The most expensive methods and uncertainty process are the use of quick lime in treatment of AMD. During operation and preparing mine closure stage need to create the effective one to comply with the regulation. “Swampy Forest (SF) system” is an alternative method of sustainable and naturally process. Selecting the appropriate tree species as a preliminary process to develop a better SF system by batch experiment in the form of a forest constructed wetland. The tree species selected are Nauclea orientalis (lonkida tree) and Melaleuca cajuputi (kayuputih tree) as non-local species then Nauclea subdita (bangkal tree) and Melaleuca leucadendron (galam tree) as local species have been selected. Local species higher in Fe and Mn adsorption in pH of AMD &lt;4 then nonlocal species higher in Fe and Mn adsorption on pH of AMD &gt;4 condition.

Bioremediasi air asam tambang batubara dengan pengayaan bakteri pereduksi sulfat dan penambahan substrat organik

Acid mine drainage (AMD) has a negative impact that must be managed because it can cause environmental pollution and disrupt mining operations. Acid mine drainage contains dissolved heavy metals that are harmful to the ecosystem. Sulfate-reducing bacteria (SRB) can be used in acid mine drainage bioremediation. This study aims to analyze pH, C-organic and BPS growing in acid water sediments of coal mines and several other ecosystems, analyze C/N ratio and pH of potential organic substrates, and recover AMD by enrichment of indigenous SRB and addition of organic substrates. The ecosystems observed were AMD sediment, paddy field mud, mangrove sediment, in situ sediment, ditch sediment, and rhizosphere soil. The organic materials tested included water hyacinth compost, a mixture of paddy field mud with wood sawdust, oil palm empty fruit bunch (EFB) compost, chicken manure, cow manure, dairy factory waste, and mixtures thereof. The results showed that SRB could be found in all studied ecosystems in the range of 5.8E+2 – 1.26E+5 MPN-unit/dry weight. The value of the C/N ratio with variations from 9.23-89.5 had a negative correlation with increasing pH. The application of organic matter with concentrations of 3%, 5%, 7%, and 10% helped SRB to raise the pH of AMD to more than 6 and reduced Fe by 88.18 – 97.27%. The highest SRB population was obtained in the mixed treatment of EFB and chicken manure with a population of 2.41E+12 MPN- unit/dry weight.

Adsorption of Iron (Fe) Heavy Metal in Acid Mine Drainage from Coal Mining

Adsorption is one of effective method to overcome acid mine drainage issue because of its economy and abundant availability of adsorbents. The research aimed to analyze the adsorption effectiveness and capacity of composite as the iron adsorbent in acid mine drainage. Composite consists of claystone from coal overburden, zeolite, and activated carbon from coconut shell. This study used experimental approaches in laboratory. Types of mineral contained in adsorbent materials (claystone, zeolite, and activated carbon) were: kaolinite, mordenite, and cristobalite. Composites were constructed with the following ratios: 50:25:25, 25:25:50, and 25:50:25 (Claystone[C] : Zeolite[Z] : Activated carbon[A]). The composite with a ratio of 25:25:50 had the greatest surface area of 62.44 m2/g, according to the results of the surface area analyzer test. Adsorption was performed in a batch system with a hot plate stirrer and composite mass of 2.5, 5, and 7.5 grams, for contact time variations of 30, 60, 90, 120, and 150 minutes. The adsorption test revealed that the composite was successful in increasing the pH of acid mine drainage to neutral (7.0) and lowering the Fe concentration to meet the quality standard. The best effectiveness of iron lowering was 99,35% with composite mass of 5 grams. However, the 2.5 grams composite mass is more efficient in terms of efficiency because it can lower the Fe concentration to 0.1484 mg/l with only 30 minutes contact time, ensuring that the Fe concentration fulfills the quality standard. The composite with a mass of 2.5 grams has the best adsorption capacity (1,286 mg/g).