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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.

Acid mine drainage can be curbed or reduced significantly by covering tailings sites with an oxygen barrier. In this study, the ability of pulp and paper residues, more specifically deinking residues, to function as such a barrier was investigated. Field data from two sites show that O2 diffusion through the barriers can be greatly reduced. To better understand how oxygen migrates through deinking residues and to develop prediction tools for future design with deinking residues, one-dimensional effective diffusion coefficients (De) were determined by fitting laboratory experimental curves (O2 concentration versus time data) to curves obtained from computer simulations. The results obtained confirmed the behaviour observed in soil covers: the effective diffusion coefficients are highly dependent on the degree of saturation (Sr) of the compacted material. The De values obtained in this study compare well with those published in the literature for several materials compacted at similar Sr. The De values varied from 8.3 × 10-9 m2/s (Sr approximately 91%) to 9.7 × 10-7 m2/s (Sr approximately 76%). The O2 consumption by biodegradation appears to be an important factor in the reduction of the O2 flux that can reach the bottom of the barrier.Key words: oxygen diffusion, pulp and paper residues, barrier, acid mine drainage.

Mine tailings generating acidic effluents were neutralized by alkaline sludges produced in pulp and paper mill operations. Depending on the proportion of sludge added, the resulting pH values increased from 3.96 to between 10.9 and 12.4. The sludge incorporation also increased the buffer capacity of the mining residues. Leaching studies conducted in laboratory columns for a period of about 25 weeks showed the efficacy of sludge incorporation with acid mine tailings. The basic sludges were well mixed with the mining wastes in varying proportions (33, 50, 67, and 75% v/v). It was observed that this incorporation improved the leachate quality considerably. Therefore the leachate pH of the mixtures remained stable between 11.5 and 12.5 compared to a pH of 3.7 for the leachate coming out of the blank column. The metal concentration of Cu, Zn and Mn in the leachate was reduced by 80 to 100 %. In the case of Pb, however, the reduction was not as significant. On the other hand, microbiological tests revealed that...

Metal removal and neutralization of acid mine drainage (AMD) in treatment systems is often controlled by addition of alkaline reagents and metal hydrolysis reactions. To overcome the disadvantage of high cost by conventional treatments, the use of paper mill wastes was evaluated as an alkaline additive to treat AMD at sites within the Iberian Pyrite Belt (IPB) through batch experiments in the laboratory. Paper wastes include three by-products from kraft pulping in a nearby mill: Green liquor dregs, slacker grits, and lime mud. When paper mill wastes interacted with AMD, the initial pH increased up to circumneutral values and enhanced greatly the metal removal, reaching average ratios of up to 100% for Al, 98% for Fe, and 66% for Zn (major elements) and 100% for As, Cr, and Cu, 84% for Cd, and 75% for Ni (minor elements). After reaction, gypsum and poorly crystalline Fe-Al oxy-hydroxides and oxy-hydroxysulfates were the main precipitates identified by X-ray diffraction and scanning electron microscopy. Trace metal uptake is mainly attributed to co-precipitation and/or adsorption onto the newly formed Fe-Al precipitates. Geochemical modeling of solutions using the PHREEQC code predicted supersaturation of the observed phases. The experimental results were optimized with the PHREEQC code and combined with the annual production of each waste to quantify the extent of a possible treatment at field-scale. According to our estimations, the system proposed is able to treat effectively an annual total volume of 11.6 hm3, which is equivalent to a mean discharge of 368 L/s. Green liquor dregs alone would be able to treat 86% of the total volume. This result demonstrates the possibility of using alkaline paper mill wastes for treatment and restoration of worldwide natural resources extremely contaminated by AMD such as the IPB.

The authors have presented an interesting paper on the use of deinking residues to create an oxygen barrier. The paper includes some results from laboratory tests, which can be difficult to perform, and an interpretation based on Fick’s laws solutions. Although the writers, like other researchers active in this field, have expressed some reservations regarding the placement of organic cover materials on reactive (acid producing) tailings (as opposed to inorganic materials such as soils and non-acid generating tailings), it is nevertheless recognized that the proposed approach for controlling the production of acid mine drainage (AMD) is certainly worth investigating. Covers made with deinking residues may eventually be added to the few control methods available for mine operators faced with the prospect of dealing with sulfidic mine and milling wastes. In the following paragraphs, the writers would like to discuss some issues relevant to the problem at hand, including some comments and questions for the authors and interested readers. Air versus equivalent porosity

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

The leaching of potentially toxic elements or the generation of acidity from mine waste often creates significant environmental pollution. A great deal of research has been undertaken to find an effective solution to the problem of acid mine drainage. An attractive solution has been proposed, not only efficient but also economical, as it uses another waste material. The objective of this study was to investigate the feasibility of stabilizing acidic mine waste using alkaline industrial waste, paper sludge ash (PSA), produced by the pulp and paper industry, under laboratory conditions. By mixing mine waste with (PSA) (the weight ratio of mine waste to (PSA) is 10:4), the eluted solution became neutral, and the concentrations of almost all metals dropped below the Japanese effluent standard. The inhibition of acid mine drainage with addition of PSA is sustainable. Although Radish sprouts did not grow on mine waste, they could be grown on the waste mixed with PSA. These results suggest that it is possible to use PSA for the remediation of a mine waste site.

The leaching of potentially toxic elements or the generation of acidity from mine waste often creates significant environmental pollution. A great deal of research has been undertaken to find an effective solution to the problem of acid mine drainage. An attractive solution has been proposed, not only efficient but also economical, as it uses another waste material. The objective of this study was to investigate the feasibility of stabilizing acidic mine waste using alkaline industrial waste, paper sludge ash, produced by the pulp and paper industry, under laboratory conditions. By mixing mine waste with paper sludge ash (the weight ratio of mine waste to paper sludge ash is 10: 4), the eluted solution became neutral, and the concentrations of almost all metals dropped below the Japanese effluent standard. The inhibition of acid mine drainage with addition of PSA is sustainable. Although Radish sprouts did not grow on mine waste, they could be grown on the waste mixed with paper sludge ash. These results suggest that it is possible to use paper sludge ash for afforestation of a mine waste site.

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

Calcium hydroxide (Ca(OH)2), a combination of calcium carbonate (CaCO3) and Ca(OH)2 (two step) and magnesium oxide (MgO) were used as a neutralizer in the treatment of synthetic Horobetsu Acid Mine Drainage (AMD) by High-Density Sludge (HDS) recycling method to obtain the appropriate guidelines of optimum AMD treatment. The result during the initial neutralization demonstrated that at pH 7, arsenic, either As(III) or As(V) in solution, could be removed by adsorption to the sludge with a concentration in the supernatant solution below the Japanese regulated environmental effluent standard. The sludge generated in HDS recycling method with Ca(OH)2 neutralization was composed of Fe(III) hydroxide combined with a high amount of gypsum (CaSO4·2H2O), the same as in the two step neutralization in which undissolved CaCO3 was included. The sludge generated in HDS recycling with MgO neutralization was composed of basic ferric sulphate combined with a low content of undissolved MgO. The sludge-settling rate generally decreased as the recycling process proceeded. The settling rate of the sludge from MgO neutralization was faster than that of the sludge from the Ca(OH)2 and two step neutralization. The Fe density of the sludge by MgO neutralization was highest compared to the other neutralization.

Acid mine drainage (AMD) is a common problem in southwestern Missouri and is partly responsible for many contaminated water supplies. Mississippian-aged limestone layers act to buffer the hazardous AMD thus reducing the risk. Five such units were analyzed over a range of four aggregate sizes (Very Fine Gravel, Fine Gravel, Coarse Gravel, and Very Coarse Gravel). As the mean aggregate size decreases, the buffering potential increases. The natural stratigraphy aids in neutralizing the AMD, but natural ground-water flow rates may limit this effect. Neutralization is also hampered by a finite reduction in buffering potential due to repeat exposure. Also, limestone aggregate may be utilized as a control measure for AMD produced in surficial settings such as spoil piles and tailings ponds.

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.