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This study investigated the implications of using two grades of limestone from a paper and pulp industry for neutralization of acid mine drainage (AMD) in a pilot sequencing batch reactor (SBR). In this regard, two grades of calcium carbonate were used to neutralize AMD in a SBR with a hydraulic retention time (including settling) of 100 min and a sludge retention time of 360 min, by simultaneously monitoring the Fe(II) removal kinetics and overall assessment of the AMD after treatment. The Fe(II) kinetics removal and overall AMD treatment were observed to be highly dependent on the limestone grade used, with Fe(II) completely removed to levels lower than 50 mg/L in cycle 1 after 30 min using high quality or pure paper and pulp limestone. On the contrary, the other grade limestone, namely waste limestone, could only achieve a similar Fe(II) removal efficiency after four cycles. It was also noticed that suspended solids concentration plays a significant role in Fe(II) removal kinetics. In this regard, using pure limestone from the paper and pulp industry will have advantages compared with waste limestone for AMD neutralization. It has significant process impacts for the SBR configuration as it allows one cycle treatment resulting in a significant reduction of the feed stock, with subsequent generation of less sludge during AMD neutralization. However, the use of waste calcium carbonate from the paper and pulp industry as a feed stock during AMD neutralization can achieve significant cost savings as it is cheaper than the pure limestone and can achieve the same removal efficiency after four cycles.

Discharged water from mines shows alteration in its physical properties and may be acidicdepending upon the concentration of heavy metals and sulphate ions which pose hazardous effects ongroundwater and ecosystem. This paper deals with the characterisation of water being affected by coalmining in the Basharat area of Punjab. Total eleven samples were collected from different water sourcesincluding groundwater, mine outflows, mine inflows and surface water in the vicinity of Hassan KishorCoal Mine. All samples except that of groundwater showed higher turbidity, lower pH values and highertotal solid contents. Higher concentration of iron and copper in all samples indicate higher acid minedrainage (AMD). Relatively larger concentration of calcium in groundwater as compared to its presencein other samples demonstrates quashing effect of overlying limestone to the AMD. Keywords: water pollution, ground water, coal mine, acid mine drainage Introduction The rapid growth of population particularly in developingcountries such as Pakistan demands more naturalresources for the fulfillment of needs of human beings.These large quantities of natural resources are obtainedthrough increased mining activities and amplified rateof extraction. The growing mining activities are vigorouslyendangering the environment (Monjezi

El problema del drenaje ácido de mina se hace especialmente tangible en el agua embalsada en las cortas mineras de la Faja Pirítica Ibérica. Los últimos estudios en investigación para la remediación se centran en el uso de materiales alcalinos. En este trabajo se presentan los resultados de un trabajo realizado con residuos de bajo coste, procedentes de la industria papelera, para la recuperación de aguas ácidas. Se tomaron muestras de agua en cortas mineras, y se sometieron a ensayos para comprobar el poder de neutralización de diferentes residuos alcalinos (cenizas de combustión de biomasa, cenizas de caldera de recuperación y lodos calizos). Se obtuvieron resultados positivos para los tres reactivos, siendo los lodos calizos los que mostraron valores más significativos The problem of acid mine drainage is especially tangible in water stored in open pits in the Iberian Pyrite Belt. Recent research studies focus on remediation using alkaline materials. This work presents the results of an experiment carried out with low cost waste coming from the paper industry for the recovery of water and its subsequent use as irrigation. Few samples of acid mine drainage from open pits were collected and subjected to tests in order to verify the neutralizing power of the different alkaline residues (biomass combustion ash, recovery boiler ash and lime mud). Positive results were obtained for the three reagents, the lime mud showed the most significant values

A 12-year-old planted woodlands Searsia lancea tree, grown on acid mine drainage for phytoremediation of polluted groundwater on gold and uranium mines in South Africa, was used in this research. The research describes the fuel-related characteristics and the influence of different operating conditions on the hydrothermal carbonization of the biomass and the combustion profiles of discard coal/biomass hydrochar pellets. The raw biomass was treated at temperatures ranging from 200-280 °C and residence time of 30-90 min. The hydrochar produced at 280 °C and residence time of 90 min had the highest calorific value of 29.71 MJ/kg compared to 17.23 and 16.73 MJ/kg obtained from the raw biomass and discard coal, respectively. Regression equations developed using the central composite design (CCD) indicated that the values obtained experimentally agree with the predicted values from the models for mass yield, calorific value, and ash content. The reactivity tests showed that the 100% hydrochar pellet had the highest reactivity and lowest ignition and burnout temperature compared to biocoal pellets and discard coal. The process water contained relatively low concentrations of major elements, and the study had shown that different high-grade biocoal pellets can be produced from the S. lancea tree.

Metal contamination from base metal sulphide mines is a major environmental challenge that poses many ecological and health risks. We examined the metal concentrations in the Dabaoshan mine in South China in water, sediments, and aquatic organisms and their specific characteristics (i.e. size, body tissue, species, and habitat) along the Hengshi and Wengjiang River courses to assess acid mine drainage remediation efforts. Metal concentrations of arsenic, cadmium, chromium, copper, lead, nickel, thallium, and zinc were examined in tissues (i.e. gills, intestines, and muscles) of 17 freshwater species of fish, shrimps, and crabs. Metals in tissues followed the trend: intestines > gills > muscles; nearly all intestine samples exceeded the safe limits of metals analysed in this study. There is a positive correlation between distance from the mine and metal concentrations related to the flow of surface water and the habitat of aquatic organisms. The concentrations of arsenic, copper, and zinc were the highest in aquatic organisms, and the distribution was influenced by physical (distance from mine, currents, and seasonality), chemical (pH and competing ions), and biological (species, habitat, and predator-prey relation) factors. Large demersal fish and benthic fauna had higher concentrations of metals. Bioaccumulation and biomagnification of metals, as well as the high metal pollution index and target hazard quotient (arsenic, cadmium, copper, lead, thallium, and zinc), occurred in bottom feeders (C. aumtus, X. argentea) and fish belonging to higher trophic levels (P. fulvidraco, O. mossambicus). Lead and cadmium indicated the highest level of biomagnification from prey to predator. Health risks exist from the dietary intake of common aquatic species such as tilapia and carp besides crustaceans due to high arsenic, cadmium, lead, and thallium levels. Further reduction of metals is necessary to improve the effects of acid mine drainage in the catchment. Funding Agencies|Linkoping University-Guangzhou University Research Center on Urban Sustainable Development; Natural Science Foundation of Guangdong Province, ChinaNational Natural Science Foundation of Guangdong Province [2018A030310309]; Joshua Wat proofread the thesis for WSC

The accessibility of clean water and green environment are the major requirements for survival and sustainable development. In this study, iron-coated sand, derived from acid mine drainage effluent, has been applied as a heterogeneous catalyst. Treatment with H2O2, iron-coated sand, and iron-coated sand-Fenton processes is compared for the COD removals from municipal wastewater effluent. The results showed that the iron-coated sand catalyzed Fenton process could generate hydroxyl radicals (•OH) and oxidize the organic pollutants. Fenton process based on the iron-coated sand catalyst proved to be the most efficient process. The effect of operating conditions such as initial pH and Fenton’s reagent doses, i.e. initial H2O2 and iron on the organics oxidation from such wastewater was investigated. The results showed that 70% removal efficiency of COD was obtained within 30 min under optimized conditions (pH 3.0, H2O2 400 mg/L and iron 40 mg/L). The rate equation of iron-coated sand-Fenton system was simply expressed by the second-order equation and the model was found to fit well the data. Thermodynamic analysis of the results indicated that the iron-coated sand-Fenton oxidation is non-spontaneous and endothermic in nature. Regeneration of iron-coated sand was attempted and the catalyst had a good stability and reusability for successive treatments and reducing the quantity of sludge produced in Fenton reactions. Thus, expanding the sustainability scope of iron-coated sand based Fenton catalyst and offer new sustainable and inexpensive alternatives for the classical Fenton process.

A laboratory-scale up-flow anaerobic sludge blanket (UASB) reactor was developed and constructed for the treatment of landfill leachate and acid mine drainage (AMD). The removal of chemical oxygen demand (COD), sulfate, and metal ions was studied. The maximum COD and sulfate removal efficiency reached 75% and 69%, respectively, during the start-up phase of the UASB. The hydraulic retention time (HRT) had a significant influence on the system. The maximum removal efficiency for COD and sulfate reached 83% and 78%, respectively, at an HRT of 20 h. The methane production process competed with the sulfate reduction process in the UASB. The fractionation of metals in the sludge was analyzed to facilitate metal recovery in a later processing stage. The most abundant sulfate-reducing bacteria was Desulfobulbus, and the methanogen archaeal community in the reactor was mainly composed of Methanobacterium.

Typically, sulfate-reducing bioreactors used to treat acid mine drainage (AMD) undergo an initial incubation period of a few weeks to acclimatize sulfate-reducing bacteria (SRB), although necessity of this preincubation has rarely been evaluated. To reduce time and economic cost, we developed an SRB acclimatization method using the continuous flow of AMD into bioreactors fed with rice bran, and compared with the conventional acclimatization method. We found that the SRB sufficiently acclimatized without the preincubation phase. Furthermore, we examined the performance and SRB communities in bioreactors operated for >200 days under seven different conditions, in which the amount of rice bran added and hydraulic retention times (HRTs) were varied. A comparison of the various bioreactor conditions revealed that the lowest rice bran amount (50 g) and the shortest HRT (6 h) caused a deterioration in reactor performance after day 144 and 229, respectively. In both cases, relatively aerobic environments developed due to the lack of organic matter seemed to inhibit sulfate reduction. Of the conditions tested, operation of the bioreactors with 200 g of rice bran and an HRT of 12.5 h was the most effective in treating AMD, showing a sulfate reduction rate of 20.7–77.9% during days 54–242. Data and materials availability All data needed to evaluate the conclusions of this study are presented in the paper and/or the appendix.

Acid mine drainage (AMD) in the coal mining industry is recognized as one of the major sources of environmental damage. The active treatment of AMD involves adding alkaline reagents to wastewater so as to raise pH and to precipitate dissolved metals in the form of oxides/hydroxides. Studies have shown that yellow pigment (goethite) can be produced from the iron present in AMD. However, the presence of other metals can prevent the formation of pigment. Therefore, this paper seeks to evaluate several processes for purifying iron sludge so as to obtain raw material that can be recovered from AMD and thereby obtain a good quality of yellow pigment. The experiments were carried out by causing precipitation with strong and weak bases and removing other metals from the sludge by washing and filtering the sludge or by centrifugation. The results show that the color, type and morphology of the compounds changed, depending on the number of contaminants, and that these factors are strongly dependent on the type of reagent and less dependent on the separation process and the repetition of washes.

This study introduces iron sludge recovered from acid mine drainage (AMD) waste, as advanced oxidation processes, that is, AMD/H2O2 (Fenton’s reagent) to treat vehicle-washing wastewater. Vehicle-w...

Ex-mining pond water is widely used for the daily needs of the people these days, such as bathing, washing, and even drinking. Over time, it turns out that coal mine acid water has polluted the environment. The use of membrane technology to produce water that meets drinking water quality standards by the Minister of Health Regulation No. 492 of 2010 can be a solution to this problem. The NF270 membrane is a membrane process between reverse osmosis and ultrafiltration, which has a lower flux and operating pressure below 0.2-1.53 Mpa compared to reverse osmosis. Membrane NF270 is used for the reclamation of wastewater, water purification and softening, seawater desalination, and others. Its high rejection of organic molecules with a molecular weight of 200-2000 Da ions and multivalent can remove suspended solids, natural organic matter, bacteria, viruses, salts, and divalent ions contained in water, including coal mine acid water. The purpose of treating acid mine drainage with the NF270 membrane is to remove COD, TSS, TDS, and Fe metals. The NF270 membrane was used in this study to treat the coal mine acid water of PT. Bukit Asam. The performance of the NF270 process was assessed from the effect of pressure (4, 5, and 6 bar) on the flux and rejection rate of each parameter in a single solution, mixed and aqueous coal mine acid solution. The optimum pressure of the NF270 membrane for all parameters was 6 bar. This optimum pressure was then used to compare the phenomenon of flux that occurred and the level of rejection produced in the original sample of coal mine acid water. In the original coal mine acid water, there was a significant decrease in flux due to fouling deposition on the membrane surface. This phenomenon of decreasing flux was caused by fouling and polarization concentration. The rejection rates produced for the parameters of COD, TSS, TDS, and Fe with NF270 membranes were 56.4-93.1%; 78.5-100%; 43-69.3%; 67-100% respectively. Treated coal mine acid water using NF270 membrane technology can be used as drinking water that meets the standards of the Indonesian Ministry of Health Regulation. Thus, NF270 membrane technology can be used to process coal mine acid water into environmentally friendly drinking water.

A techno-economic evaluation of a lignocellulosic bioethanol facility that uses acid mine drainage for the pre-treatment of weeping love grass (Eragrostis curvula) was performed. Both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) reactor configurations were evaluated. Results were compared to an evaluation of the same process with biomass pre-treated with dilute H2SO4. Capital and operating costs were estimated and a simple economic evaluation was conducted. It was found that all scenarios made a loss except for biomass pre-treated with H2SO4 in the SHF reactor configuration, although the high capital cost resulted in a payback period of 80.7 years, which is unfeasible. SHF was found to produce more ethanol at a lower capital cost than SSF, indicating that it is more economically feasible. Incorporating the remediation of AMD into a simultaneous process could help improve process economics. It is thus recommended that a techno-economic evaluation be conducted on a process that produces bioethanol through SHF and simultaneously remediates AMD.

The acid mine drainage (AMD) can causes negative impacts to the environment. Physico-chemical methods to treat AMD can have high operational costs. Through passive biological methods, such as anaerobic reactors, sulfate reduction, and recovery of metals are promoted. This study evaluated the performance of a horizontal anaerobic immobilized biomass (HAIB) reactor for the treatment of synthetic AMD using polyurethane foam as support material, and anaerobic sludge as inoculum. Ethanol was used as an electron donor for sulfate reduction, resulting in an influent chemical oxygen demand (COD) in the range of 500-1,500 mg/L and COD/sulfate ratio at 1. A gradual increase of sulfate and COD concentration was applied that resulted in COD removal efficiencies higher than 78%, and sulfate removal efficiencies of 80%. Higher sulfate and COD concentrations associated with higher hydraulic retention times (36 h) proved to be a better strategy for sulfate removal. The HAIB reactor was able to accommodate an increase in the SLR up to 2.25 g SO

The objective of this study was to evaluate performance of a co-treatment method of industrial acid mine drainage (I-AMD) and municipal wastewater (MWW) by dual-chamber microbial fuel cells (DC-MFC). Sewage sludge and MWW were used as inoculum-fuel in anodic chamber. I-AMD was fed to the cathode side of the chamber. A 100 Ω resistor was used to externally connect the anode to the cathode (DC-MFC-A). A second cell was operated at the open circuit potential (DC-MFC-B). In both cells, the efficiency of organic matter removal was ~15% and the wastewater alkalinity was reduced by more than 50% in both cells. On the other hand, the physicochemical characteristics and composition of I-AMD were modified. The pH increased from 2.50 to 4.12 ± 0.6. The S O 4 2 − concentration was reduced ca. 20 and 8% for the DC-MFC-A and DC-MFC-B, respectively. N O 3 − Concentration decreased in both cells by >90%. Different heavy metals (HMs) and metalloid removal values were observed in the cells: 42, 84, 71, 77, 55 and 42% for Cd, Cu, Fe, Al, Pb and As, respectively. Finally, a maximum volumetric power of 14,000 mW/m3 was reached by DC-MFC-A. The DC-MFCs achieved simultaneous treatment of MWW, partial neutralization of I-AMD, HMs removal, and bioelectricity generation. Hence, DC-MFCs seem to be an encouraging alternative for bioremediation of both MWW and I-AMD.

Iron recovered from acid mine drainage (AMD) waters effluent and introduced as an advanced oxidation processes (AOPs) source, namely, Fenton reagent (FR) for municipal wastewater (MWW) treatment. A...

Acid and metalliferous drainage (AMD) oxidation reaction rates were determined using oxygen consumption rates in a high sulfur overburden rock from the Australian Latrobe Valley coal provinces, and a mid to low range sulfur waste rock from a porphyry copper deposit in Papua, New Guinea. Nine grain sizes were tested, ranging from material retained by a 0.038 mm sieve through to a 40 mm sieve. Oxygen consumption rates in sealed cells were measured to establish pyrite oxidation rates (POR) in each sample. The oxygen consumption rates displayed a strong exponential reaction correlation with particle size for the material. The POR was found to range from 0.28 to 10.90 wt%/year FeS2 for the materials tested. A relationship between particle size and POR was established for comparative purposes. The smaller grind sizes included in this study extend the AMD/POR particle size data set available in the literature and will assist with geochemical engineering for designing tailings storage facilities. The potential economic and mine design ramifications of additional reactivity of fine mine materials is assessed and discussed using a unit cost framework for applying neutralizing materials.

A major problem in the active treatment of acid mine drainage (AMD) is the generation of large volumes of sludge through pH neutralization, oxidation of iron (II) and subsequent metal precipitation. The sludge settling rate, sludge volume index (SVI) and sedimentation process are ones of parameters identifying a good treatment of AMD. Sodium ferrate (VI) (Na2FeO4) is one reagent currently used to treat water due to its quick reaction rate, easy implementation and relatively low chemical and operational costs. However, very limited information is available in the literature related to the detailed characterization and dewaterability of Na2FeO4-treated AMD sludge. This study aimed at characterizing and monitoring settling rate and densification process of synthetic AMD sludge after treatment with Na2FeO4. The results confirmed a complete removal of iron from the synthetic AMD due to high oxidation strength of ferrate (VI) in acidic medium (Eᵒ = 2.2V) and showed the presence of different minerals formed in the sludge after treatment. The concentrations of the sludge collected at different intervals were justified by the densification process and high density of the sludge was obtained after 25 minutes while high weight percent of iron was found at 10 min and Fe and O dominated other elements in the sludge. The study demonstrated very good settling properties of the sludge and the low SVI value ranging between 30 and 60 mL/g TSS.

The high levels of sulfate and the metals in acid mine drainages generate important environmental problems. This paper describes the synergistic combination of a biosorption process and a new sulfate removal process. The treatment for the elimination of metals by biosorption with a Bacillus strain allowed reducing the high metal concentrations that had a toxic effect on the sulfate-reducing bacteria (SRB). On the other hand, the sulfate removal process used a microbial sulfate-reducing halotolerant consortium, which was able to reduce the sulfate concentration using low-cost organic substrates such as spirulina, cellulose and industrial starch. Independent of substrate present in the culture medium, the SRB was the predominant group. The sulfate-reducing consortium was cultured on a bench-scale upflow anaerobic packed bed bioreactor filled with Celite R-635. It was possible to reduce the concentration of sulfate in the culture medium in batch or semi-continuous operation. This integrated process is an inexpensive alternative for the elimination of metals by biosortion and the elimination of sulfate using a sulfate-reducing consortium.

In this paper, a batch experiment was conducted to evaluate the water quality obtained from using pervious concrete (PERVC) technology to treat acid mine drainage (AMD). The study proposes an innovative application of PERVC as a permeable reactive barrier liner in evaporation ponds. The effectiveness of PERVC adsorbent in removing heavy metals was compared with that of zero-valent iron (ZVI) of particle size 1.0 to 1.8 mm. The AMD used in the study was obtained from abandoned gold and coal mines. PERVC mixtures consisted of granite aggregate and ordinary Portland cement CEM I 52.5R (CEM I) or CEM I containing Class F 30% fly ash (30%FA) as a cement replacement material. ZVI was prepared from a mixture of silica sand and iron grit of specific sizes. PERVC and ZVI media were used to conduct batch reactor tests with AMD, for a period of 43 days at a ratio of 1 L of reactive material to 3 L of AMD. The quality of treated AMD was compared against effluent discharge standards. The contaminants Al, Fe and Zn were effectively removed by both PERVC and ZVI. Also, both adsorbents reduced Ni, Co and Cu to levels below those measured in raw AMD. However, PERVC was more effective in removing Mn and Mg while ZVI was ineffective. Although PERVC removed more heavy metals and with greater efficiency than ZVI, the PERVC-treated water showed high pH levels and exhibited elevated Cr 6+ concentrations, owing to leaching from the cement and fly ash materials used in PERVC mixtures. Keywords : Pervious concrete, zero-valent iron, acid mine drainage, batch test, permeable reactive barrier

Acid mine tailings may affect several environmental matrices. Here, we aimed to stabilize acid-generated mine tailings using several alkaline and cementitious amendments, which were tested in columns for 361 days. The alkaline amendments consisted of 10 and 20 wt.% limestone, while the cementitious amendments consisted of different binders at a total dosage of 5 wt.% binder. The different formulations for the cementitious amendments were: 50% Kruger fly ash and 50% class F fly ash, 20% ordinary Portland cement, 40% Kruger fly ash, and 40% class F fly ash, 80% ordinary Portland cement and 20% Kruger fly ash, and 20% ordinary Portland cement, 40% Kruger fly ash, and 40% fly ash. Kinetic testing on the amendment formulations showed that the pH values increased from &lt, 2.5 to circumneutral values (~7.5). The mobility of various chemical species was greatly reduced. Cumulative Fe released from the unamended tailings was ~342.5 mg/kg, and was &lt, 22 mg/kg for the amended tailings. The main mechanisms responsible for metal(loid) immobilization were the precipitation of secondary phases, such as Fe-oxyhydroxides, physical trapping, and tailing impermeabilization.

The anaerobic biological treatment of sulfate-rich effluents, such as acid mine drainage (AMD), is mediated by sulfate-reducing bacteria (SRB). This process involves the reduction of sulfates in the presence of an electron donor. Complex carbon compounds can be used as electron donors. In the present study, was used an upflow anaerobic sludge blanket (UASB) reactor to co-treat a low-pH synthetic AMD and cheese whey wastewater (CWW). Were observed higher sulfate and COD removal rates (1,114 ± 88 and 1,214 ± 128 mg L-1 day-1 , respectively) at higher sulfate and applied COD loading rates (1,500 mg L-1 day-1 ). The overall pH of the effluent remained above 6.4 without any bicarbonate supplementation. Almost 100% of the Fe, Zn, and Cu was removed and the presence of metals improved the process. The use of a single reactor to treat AMD and CWW is promising. PRACTITIONER POINTS: Wastewater cheese whey was electron donor for treating acid mine drainage in an UASB reactor. Metals additions in the system indicated an increased removal of COD. About 99% of the metals were removed with the treatment.

Coal mining is an activity to exploit land to get coal stored underground. Environmental problems in coal mining activities are generally associated with Acid Mine Drainage (AMD). The purpose of this study was to find out the best combination of organic matter and incubation time in remediating acid mine drainage on wetlands with water hyacinth plants. This research was conducted at PT Berau Coal in Tanjung Redeb, Berau, East Kalimantan. This study used a split-plot design. The main plot was the treatment of a combination of organic matter which consisted of 4 levels: A0 as a control (without organic matter), A1 with a combination of compost + sawdust (1:2), A2 with a combination of compost + sawdust (1:1), A3 with a combination of compost + sawdust (2:1). The subplot was treatment incubation time consisting of 2 levels, namely for 15 days and 33 days. Data analysis used variance analysis at the 5% level followed by the Duncan Multiple Range Test with a level of 5% when there were significant differences. The results showed that the addition of organic matter had a significant effect on the increase in pH and a decrease in the concentration of Mn in water, but it did not significantly affect the decrease in Fe concentration in water. The best combination of organic matter in acid mine remediation in this study was compost + sawdust (2:1) during the incubation time of 33 days

Portland cement is an effective but expensive option for source control of acid mine drainage (AMD); the cost could be reduced by blending the cement with cheap waste materials such as fly ash from coal combustion and sludge produced from neutralization of acid mine drainage with lime. To test how these two additives affect cement performance in reducing AMD generation, blended cement slurries were applied to sulfidic waste rocks from Brukunga, South Australia, in leaching columns monitored for around 1 year. Acidity, metal and sulfate loads decreased greatly (by 80–95%) for all cement applications but the effect varied, depending mostly on the depth of penetration of the cement in the column (a function of slurry viscosity). The fly ash-blended cements penetrated further into the columns than the more viscous surface-capping sludge-blended cements, causing a greater decrease of leachate acidity loads and sulfide oxidation due to better coverage of the waste rocks and more acidity neutralization by cement dissolution. The AMD sludge showed no evidence of releasing its adsorbed heavy metals, but the fly ash released some Si, indicating that it is not chemically stable in the cement. There was little secondary mineral growth in the blended cements; the ettringite in the AMD sludge-blended cement formed from bassanite present in the sludge rather than exposure to acid mine drainage. Overall analysis of the long-term effectiveness of the blended cement applications shows that cement placed as a surface cap on top of the waste rock provides more value, because the slower cement dissolution rates ensure continued effectiveness for many years. Scaling up the results from the laboratory study to the field scale at the Brukunga mine site suggests that benefit/cost ratios in the order of 20–30 might be achieved compared to the present use of lime neutralization for AMD treatment.

This study examined the applicability of two mine sludge wastes, mine tailing sludge (MTS) and acid mine drainage sludge (AMDS) as iron-rich bio-stimulant for enhancing organic matter degradation in anaerobic process. Batch treatment of domestic sewage having 343 ± 10 mg/L chemical oxygen demand (COD) using MTS and AMDS as additives mixed with septic tank sludge as anaerobic inoculum produced lower start-up time, higher efficiency of COD removal, enhanced biomass retention, and higher acidogenic and methanogenic activity after stabilization. Biostimulation induced by mine sludge waste additives in anaerobic system were observed to have correlation with percentage of iron content in the additives, as well as difference in surface charge between biomass and the additives. Treatment efficiency induced by the two mine sludge waste based additives were similar at 90% confidence limit, however, was found to be higher than lower iron containing additive laterite soil, while lower than higher iron containing synthetic zero valent nano iron as additives used for comparison. The study was supported by scanning electron microscope, atomic force microscope and optical microscope images of sludge granule sand surface charge measurement.

Novel application of alkaline waste materials from the alumina industry (Bayer precipitates) to both neutralize and remove dissolved metals from acid mine drainage (AMD) has been demonstrated. The hypothesis was that Bayer precipitates could not only economically treat a wide range of AMD compositions but also do this in an environmentally acceptable manner. Therefore, the aim was to synthesise a range of Bayer precipitates and test their remediation effectiveness with a variety of real AMD samples. Thermal activation of Bayer precipitate at 380 °C produced a material which required the least mass to neutralize AMD and removed greater amounts of problematic species such as manganese (e.g. 74 to 82.8% reduction for Bayer precipitate and 83.7 to 91.6% reduction for thermally activated Bayer precipitate). The presence of an amorphous mixed magnesium/aluminium oxide and lack of carbonate species in the thermally activated Bayer precipitate was proposed to explain the improved performance. The resultant sludge was composed of hydrotalcite and possibly calcium sulphate and calcium carbonate, with precise quantities dependent upon the AMD tested. Exposure of sludge to water promoted the dissolution of a fraction of the hydrotalcite which enhanced concentrations of Mg and Ca in solution; albeit, contact of the sludge with AMD resulted in further removal of dissolved metals and raised the pH of the AMD. In summary, this study has developed a new process using two industrial waste products to solve a critical environmental problem. Future research should investigate the commercial feasibility.

Acid mine drainage (AMD) is among the most serious threats to water and the typical alkali-based treatment costs are high. This study’s main objective was the establishment of a highly efficient biological process using an upflow anaerobic sludge blanket (UASB) reactor to treat AMD based on a shorter hydraulic retention time (HRT) and lower organic matter input. The process was evaluated for a long-term operation (739 days) in terms of the influence of HRT (14–24 h), metal addition, sulfate loading rate (0.5–2.6 g SO42− l−1 d−1), and the COD/SO42− ratio (0.67–1.0) using ethanol as the only electron donor at a pH of 4.0. Neutral effluent pH was achieved throughout the time apart from operational modifications. The reduction in HRT from 24 to 16 h and an increase in the sulfate loading rate (SLR) up to 2.25 g SO42− l−1 d−1 improved the sulfate removal to (92.1 ± 1.8)% with 80% chemical oxygen demand (COD) removal. However, the sulfate reduction was less than 80% when the HRT and SLR was changed to 14 h and 2.6 g SO42− l−1 d−1, respectively. The oxidation of organic matter by sulfate reduction was greater than 50% regardless of the conditions imposed but the use of ethanol to treat AMD was more efficient when either the HRT was 16 h (1.5 g SO42− l−1 d−1) in the presence of Fe, Zn, and Cu or the HRT was 14 h (2.6 g SO42− l−1 d−1) but the COD/SO42− ratio was reduced to 0.67. The fully optimized conditions of the UASB reactor were set at an HRT of 16 h, SLR of 1.5 g SO42− l−1 d−1, and a COD/SO42− ratio of 1.0.

The main objective of the present investigation was to analyze, evaluate, and model the behavior in the treatment of real acid mine drainage (AMD) with commercial spiral-wound nanofiltration membranes (NF270 and NF90). Both membranes showed operational differences regarding the effect of pH, temperature, continuous operation, concentration polarization, and fouling. Both NF90 and NF270 presented a high rejection of divalent ions (∼100%); however, NF90 showed a greater fouling with AMD. Adjustment of pH in the continuous tests reduced the precipitation of aluminum, and gypsum was identified as the main compound generating a significant decrease in the permeate flow in the membrane. The Spliegler–Kedem model was used to represent rejection and permeate flows, identifying the contribution of convective and diffusive transport in both membranes with a good fit of the model. The results obtained represent important information for a future industrial application to the treatment of AMD by means of commercial N...

In this study walnut shells, an inexpensive and readily available waste, were used as carbonaceous precursor for preparation of an innovative adsorbent (walnut-shell powder (WSP)) which was successfully tested for the removal of FeII from synthetic acid mine drainage (AMD). Then, the exhausted iron-contaminated adsorbent (WSP-FeII) was recovered and treated with sodium borohydride for the reduction of adsorbed FeII to Fe0. The resulting material (WSP-Fe0) was subsequently tested for the removal of CrVI from aqueous solutions. Treatability batch experiments were employed for both FeII and CrVI-contaminated solutions, and the influence of some important experimental parameters was studied. In addition, the experimental data was interpreted by applying three kinetic models and the mechanism of heavy metal removal was discussed. The overall data presented in this study indicated that fresh WSP and WSP-Fe0 can be considered as promising materials for the removal of FeII and CrVI, respectively. Furthermore, the present work clearly showed that water treatment residuals may be converted in upgraded materials, which can be successfully applied in subsequent water treatment processes. This is an example of sustainable and environmentally-friendly solution that may reduce the adverse effects associated with wastes and delay expensive disposal methods such as landfilling or incineration.

Acid mine Drainage (AMD) is a low pH, sulphate and heavy metal rich leachate that is produced from oxidation of sulphide bearing minerals commonly found in the host rocks of some mineral ores. The pH augmentation, and sulphate and metal removal in AMD is often achieved by adding alkaline reagents in it. CaCO3 and/or its derivatives are commonly used for this purpose due to their abundance and affordability as compared to other neutralizing reagents. The problems associated with the use of this naturally occurring reagent do not only include the emission of greenhouse gases and ecological disturbances but also include a disastrous implication of depleting their reserves. To avoid these predicaments, green liquor dregs (GLD) from two Kraft pulp manufactures in South Africa were used as alternative alkaline reagents to neutralize AMD originating from Witwatersrand goldfields in Johannesburg. These GLD samples were referred to as GLD A and B. CaCO3 was used as a reference material. The GLD samples had neutralizing values that are comparable to that of CaCO3. Thus, CaCO3, GLD A, and GLD B had a neutralizing value of, 26.0, 21.2, and 21.0% CaO respectively. Different dosages 1, 2, 6, 10, and 20 g/L of these neutralizing reagents were used to neutralize the AMD. Results of this study showed that raising the pH of AMD was possible even at a low dosages of 1 g/L. At this dosage, the acidity of the AMD sample changed from 183.36 to 21.7, 36.4, and 48.72 mg/L CaCO3, and changed the pH from 5.6 to 8.84, 8.21, and 8.0 respectively. However, the SO42− and Ec had increased from 2093 to 2360, 2538, and 2407 mg/L and from 3.6 to 4.0, 4.3, 4.2 mS/cm respectively, indicating that caution should be taken to keep these values low by keeping the reagent dosage low and being cognizant of the carbonate mineral present in GLD. The x-ray diffraction patterns of the reacted samples confirmed the presence of metal oxides and Ca and Mg compounds that were depicted by SEM/EDX micrographs. In conclusion, the results from this study showed that the pH of AMD can be raised to optimum pH process value and reduce the acidity at a low dosage, a competitive advantage over commercial CaCO3. The proposed concept can be adopted by both the mining and pulp and paper industries, for the upscaling of co-disposing GLD and AMD contaminants as an eco-friendly alternative for the CaCO3.

Acid mine drainage (AMD) waters are one of the most important ecological risks at the global level because of its high heavy metals content and strong acidity. Treatment of AMD water is a complex and expensive. One of the most widely used treatment process is the neutralization process of AMD. The result of neutralization is the production of sludge which may contain various other (heavy) metals, depending on the chemical characteristics of the mine water treated. In this paper, leachability and toxicity of the sludges obtained during the neutralization process of wastewater from Saraka and Robule acid mine drainage and the sludges after the stabilization process at different temperatures is tested. Sludge produced in the neutralization process of Robule AMD R4 (40) and stabilized on 105°C and 200°C shows a H8-corrosiveness characteristic. Stabilized sludge show tendency to lower leachability of zinc and copper, but without influence on sulphate leachability. Sludges that show a H8-corrosiveness needs additional stabilization/neutralization pretreatment prior temperature treatment.

The paper presents the research activities oriented to solving two environmental issues of concern: acid mine drainage that poses a great risk to soils and water, and wood ash disposal, which can be done only under strict conditions, with high costs. After trials with synthetic acid waters, the behavior of four types of ash has been investigated. The ashes used were originated from two boilers belonging to a fiberboard manufacturer, individually and mixed according to their production process, using acid mine drainage from a copper mine. Acid mine drainage has been characterized in what concern pH, fix and mineral residues, as well as Fe, Cu, Zn and Mn content. For all ashes and their mixtures, the pH (water suspension 1:5), humidity, as well as their neutralization capacity have been determined. The obtained results have been very good, proving that wood ash has better neutralization capacity than calcium carbonate, thus enabling to pursue and extend the present research work.

The mining industry is known to be a major producer of sulfate-rich waters that are harmful to aquatic systems, accelerate acid mine drainage formation and hinder the reuse and recycling of process water. In recent years, many treatment techniques have been studied and developed to treat sulfate-rich streams. One such technique, electrocoagulation (EC), was proposed as a possible alternative to conventional treatment technologies. Electrocoagulation has been used for the removal of nitrate, cyanide and toxic metals from mining waters, but the information about sulfate removal is scarce. In this paper, the results from a systematic study on sulfate removal by EC with iron electrodes applying a 33-full factorial design are discussed. The results show the leading role of applied current on sulfate removal. In addition, the study concludes that the utilisation of iron electrodes was more efficient in terms of sulfate removal comparing to aluminium electrodes. The removal of sulfate was as high as 54% and 10% using iron and aluminium electrodes respectively. Under the studied experimental conditions, sulfate was proposed to be removed because of particle charge neutralisation and enmeshment of the studied anion in iron oxides and hydroxides. Post-print / Final draft

The feasibility of using iron extracted from acid mine drainage (AMD) as Fenton's reagent for removal of organics pollutants from polymer and plastics manufacturing effluent was investigated in this study. AMD iron dose, H