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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...

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.

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.

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.

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.

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.

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...

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...

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 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.

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.

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 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.

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.

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 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

This study investigated the effect of carbon sources (n = 2) on the performance of a microbial community in an anaerobic moving-bed biofilm reactor (MBBR) treating acid mine drainage (AMD). The 1.5 L anaerobic MBBR was operated across a range of hydraulic retention times – HRT's (3–18 days), using different substrates, i.e. brewing wastewater and lactate as sole carbon sources and electron donors. Maximum sulphate reduction and chemical oxygen demand (COD) consumption rate was 21.94 and 24.28 mg SO 4 2 − L−1 h−1, and 0.473 and 0.697 mg COD L−1 d−1 for brewing wastewater and lactate supplemented bioreactors, respectively, at an HRT of 3 days. The maximum COD/ SO 4 2 − ratio was found to be 2.564 in the bioreactor supplemented with brewing wastewater at an HRT of 15 days. The metal removal above 70% in the system supplemented with brewing wastewater followed the order; Be2+ > Fe2+ > Sr2+ > Pb2+ > Mg2+ > Cu2+ > Zn2+ > Li1+ > Ca2+ in comparison to the system supplemented with lactate, Be2+ > Fe2+ > Sr2+ > Mg2+ > Cu2+ > Li1+ > Zn2+ > Pb2+ after an HRT of 18 days. Complete removal of beryllium (II) was observed irrespective of the carbon source used. The results clearly showed that brewing wastewater can be deployed as a nutritional supplement in environmental remediation of AMD.

Mining is an essential human activity, but results in several environmental impacts, notably the contamination of ground and surface water through the presence of toxic substances such as metals and sulfates in mine drainage. Permeable reactive barriers (PRB) have been applied to remediate this environmental impact, but the high costs associated with the maintenance of this system are still a challenge. The main objective of this study was to evaluate the use of kraft pulp mill alkaline residues, known as dregs and grits, as material for PRB, and to determine their capacity for retaining copper and sulfate. The work was carried out in laboratory adsorption kinetics assays, batch assays and column tests. Tests for elemental characterization, point of zero charge, acid neutralization capacity, total porosity, bulk density and moisture of the dregs and grits were conducted. The results showed high retention of Cu due to a chemical precipitation mechanism, notably for dregs (99%) at 5 min in adsorption kinetics. The grits presented similar results after 180 min for the same assay. Sulfate retention was effective at pH below 5, with an efficiency of 79% and 89% for dregs and grits, respectively. Dregs presented the best results for acid drainage remediation, notably with a solid:liquid (S:L) ratio of 1:10.

Flotation tailings rich in carbonate minerals from the tailings deposit of the copper mine Majdanpek (Serbia) were applied for neutralization of the water taken from the extremely acidic Lake Robule (Bor, Serbia). Tests conducted in Erlenmeyer flasks showed that after neutralization of the lake water to pH 7, over 99% of aluminum (Al), iron (Fe), and copper (Cu) precipitated, as well as 92% of Zn and 98% of Pb. In order to remove residual Mn and Ag, the water was further treated with NaOH. After treatment with NaOH, all concentrations of the metals in the lake water samples were below discharge limits for municipal wastewater according to the national legislation of the Republic of Serbia. The results of this work suggest that mining waste could be used for active neutralization of the acid mine drainage. The use of the mining waste instead of lime could reduce&nbsp, the costs of the active treatment of the acid mine drainage.

In this research, two industrial by-products produced close to South African mining regions were used to treat acid mine drainage (AMD): steel slag and sugarcane bagasse, i.e., the shredded...

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...

The main characteristics of coal acid mine drainage (AMD) are a low pH and high concentrations of sulfate and different metallic ions. Response surface methodology using the central composite rotatable design (CCRD) model was used to optimize the parameters for AMD remediation with aquaculture farming waste [shrimp shell (SS) and mussel byssus (MB)]. SS was chosen due to its high chitin (a metal sorbent) and calcium carbonate (an acidity neutralizing agent) content, and MB because of its potential synergistic effect for the treatment. The coefficient of determination and standard error results from the analysis of variance have shown the model to be adequate. The predicted values were in good agreement with the experimental values. The best experimental conditions established from the statistical study were 136 rpm, 11.46 g L−1 SS and 71.6 g L−1 MB. CCRD can efficiently be applied for modeling the AMD remediation with biomaterials and is an economical way of obtaining the maximum amount of information in a short period of time with the fewest number of experiments. Additionally, five kinetic models, i.e., pseudo-first-order, pseudo-second-order, intraparticle diffusion, Bangham and Elovich equation, were tested to investigate the adsorption mechanisms. The kinetic studies revealed that a 200 min contact time is sufficient to transform AMD into water suitable for non-potable reuse. The pseudo-second-order model provided the best fitting of the experimental data, indicating a chemical adsorption mechanism. This research shows the suitability of the proposed treatment, and the information is valuable for designing a low-cost remediation process for AMD.

The research investigates a novel method to treat acid mine drainage (AMD) using lime and sodium hydroxide modified fly ash (NCFA) with varied dose and time. The analysis showed that pH was raised ...

In this study, eggshell (ES) powder was evaluated as a cheap and biocompatible waste material for the pre-treatment of acid mine drainage (AMD) leachate from coal dump. First, the composition of the AMD and physiochemical properties of the ES powder were determined using various standard characterization techniques. Then the removal efficiency of the target metal contaminants and the acid-neutralisation effect were explored in batch and kinetic set-ups. Thereafter, the settling rate of sludge formed after separately reacting ES and limestone powders with AMD was explored. Results revealed that the AMD leachate was highly acidic and contaminated with both cations and anions. Thermogravimetric analysis (TGA) and X-ray fluorescence (XRF) analyses demonstrated that ES powder was thermally stable up to 700 °C and CaO was the main component, respectively. Scanning electron microscopy (SEM) and EDX spectra confirmed the removal of contaminants. Both the decrease in particle size and increase in mass of ES enhanced the treatment efficiency. Although complete Fe and Al removal was achieved, Mn and sulphates posed a challenge as they were partially removed. Meanwhile, ES demonstrated superior acid-neutralizing effect to limestone and the mine water clarity and pH were shifted to acceptable levels. Both Fe and Al removal proceeded through an exothermic process while it was opposite for Mn. Kinetics were rapid and the sludge from ES powder settled faster compared with that from limestone powder. Cost analysis indicated that significant financial savings can be realised by substituting limestone with ES material. The findings suggest that ES waste could be an efficient and cheap material in the pre-treatment of AMD effluents.

A key reason inhibiting commercialization of algal oil as biodiesel feedstock, is cultivation cost. For this reason, the usability of 19 readily available industrial effluents (autoclaved and non-autoclaved) to support heterotrophic growth and lipid accumulation was evaluated using six mixed algal cultures. Autoclaved whey effluent was the best with 14.32 g biomass L−1, 13.23% lipids, resulting in a lipid production of 1.91 g lipids L−1. Biomass production and lipid accumulation were in many cases inverse, e.g. mixed algal culture termed TUT4 accumulating 84.25% lipids on autoclaved acid mine drainage, with very little biomass produced. Biomass production was dependent on the effluent type, whereas the lipid accumulation was influenced mostly by the specific mixed algal cultures. The fatty acid composition of the algal oil (fish cannery and whey effluents) showed high saturation, leading to acceptable cetane numbers, kinematic viscosity, good oxidative stability, but poor cold flow properties.

Pervaporation process is an excellent and potential way applied for desalting acid mine drainage water. Nevertheless, the water flux was reduced gradually due to the issue of membrane fouling. To resolve this problem, cleaning process was chosen to maintain the water flux of silica-pectin membranes. This study aims to recover the water flux and salt rejection of the silica-pectin membranes via chemical cleaning process applied for acid mine drainage water desalination with various temperature of feed water (25-60 °C). Silica-pectin membrane was formulated by employing TEOS functioning as silica precursor and pectin as carbon template from banana peels. Chemical cleaning of the membrane carried out by employing TiO2 solution + UV light radiation for an hour. Performance of the silica-pectin membrane was evaluated via pervaporation process under dead-end system. The performance of silica-pectin banana peels membrane found flux recovery from 10.6 kg.m− 2.h−1 and flux recovery of 17.54 kg.m− 2.h−1. It shows that flux recovery higher than before backwashing process. Also, silica-pectin membrane results in all of the salt rejection

Acid mine drainages (AMD) are the most harmful and chemically complex aqueous waste produced by the mining industry, causing contamination of fresh water sources, affecting human communities and the environment surrounding the mine facilities. Nowadays, AMD treatments use a high amount of reagents that produce a considerable quantity of waste, limiting the opportunity for recovering valuable metals. AMD typically can contain high quantities of copper that could be potentially recovered as a saleable product. Accordingly, this study proposes a novel combination of metal sulfide precipitation with membrane microfiltration process to clarify and separate those previously formed metal sulfide, focused on enhancing the copper recovery and the performance of clarification, evaluated in terms of turbidity of treated solution and separation rate. Three synthetic AMD were assessed, varying the copper content in a mono tubular ceramic membrane of 0.14 µm pore size. Results were promising: flux values were higher than 0.1 L/m2s, at least one order of magnitude higher with respect to other matrices. Copper recoveries were closer to 100% and turbidity values in the treated solution were lower than 2 NTU for sulfide stoichiometric dosages of 120%. Hence, this method could be an excellent alternative to efficiently recover copper from AMD.

This paper considers the evaluation of the performance of the biological sulphate reduction in continuous mode using grass cutting. Initially the reactor was operated in batch mode for 26 days, followed by a change to a continuous feeding mode at a Hydraulic Retention Time (HRT) varying from 8 to 2 days. At the start of the experimental period the bioreactor was filled with 89 kg of ceramic rings as support medium for Sulphate Reducing Bacteria (SRB) and 50 L SRB (COD = 852 mg/L and SO 4 2 = 600 mg/L) obtained from an existing biological sulphate reducing bioreactor. Rumen fluid was collected from a slaughterhouse and added to the bioreactor. Grass cuttings (10 kg) were added to the bioreactor as a carbon and energy source. The results showed that from day 59–106 the bioreactor was operated in continuous mode and the percentage SO 4 2− reduction efficiencies were 73%, 85% and 71%, corresponding to the HRT of 8, 6 and 4 days respectively.

Surface paste tailings’ disposal has emerged recently as an optimal and efficient method to favor tailings’ self-containment after being deposited into dams. This disposal method can improve the reuse of water and reduce the generation of acid mine drainage (AMD) and the release of leachates (e.g., acid and heavy metals). However, the implications of chemical factors or mixed-water chemistry in the stability of paste tailings over time are not clear. In this work, we evaluated the release of sulfate from tailing samples and the role of sulfate as a critical factor in the tailings’ strength, consistency, and stability. Our results showed that the release of acid runoff with high sulfate load from the tailings is negligible. Leaching tests were performed for 180 days and did not show a significant release of sulfate, heavy metals, or acid waters. However, the presence of sulfate salts derived from the binders used in the pretreatment of the paste tailings shows an impact on the tailings’ consistency. Undrained triaxial monotonic compression tests revealed low effective cohesion forces in the tailings samples. In addition, it was observed that, in tailings slurries prepared with varying concentrations of sulfate (0, 500, and 1000 mg/L), the slump test value dropped Δ−55% when the sulfate concentration increased from 0 to 1000 mg/L. These results support the idea that the presence of sulfate within the tailings could be relevant for the paste consistency after storage. This knowledge will contribute to a better understanding of the critical chemical factors that affect the stability of paste tailings over time.

The development of compact and cost-effective passive treatment systems is of critical importance for acid mine drainage (AMD) remediation in Japan. The purpose of this study was to construct an AMD treatment system comprising a sulfate-reducing bioreactor using rice bran as a carbon source for sulfate-reducing bacteria (SRB) and to demonstrate its stable operation for at least a year in terms of continuous sulfate reduction and metal removal. Our 35 L bioreactor comprised a packed inoculum layer of a mixture of rice husks, limestone, and field soil, which was covered with rice bran. During operation, the AMD input flow rate was adjusted to 11.7 mL/min (hydraulic retention time, HRT; 50 h). Throughout the year, physicochemical analyses of system input and output AMD samples revealed that both pH and oxidation–reduction potential values were consistent with the process of sulfate reduction by SRB, although this reduction was observed to be stronger in summer than in winter. Efficient metal removal was observed, with concentrations at the outlet port of

The present study discusses the potentiality of using anaerobic Packed Bed Bioreactor (PBR) for the treatment of acid mine drainage (AMD). The multiple process parameters such as pH, hydraulic retention time (HRT), concentration of marine waste extract (MWE), total organic carbon (TOC) and sulfate were optimized together using Taguchi design. The order of influence of the parameters towards biological sulfate reduction was found to be pH > MWE > sulfate > HRT > TOC. At optimized conditions (pH - 7, 20% (v/v) MWE, 1500 mg/L sulfate, 48 h HRT and 2300 mg/L TOC), 98.3% and 95% sulfate at a rate of 769.7 mg/L/d. and 732.1 mg/L/d. was removed from the AMD collected from coal and metal mine, respectively. Efficiency of metal removal (Fe, Cu, Zn, Mg and Ni) was in the range of 94–98%. The levels of contaminants in the treated effluent were below the minimum permissible limits of industrial discharge as proposed by Bureau of Indian Standards (IS 2490:1981). The present study establishes the optimized conditions for PBR operation to completely remove sulfate and metal removal from AMD at high rate. The study also creates the future scope to develop an efficient treatment process for sulfate and metal-rich mine wastewater in a large scale.