A field trial of seeded reverse osmosis for the desalination of a scaling-type mine water

Hollow fine fiber vs. spiral-wound RO desalination membranes Part 1: Pilot plant evaluation

Anthropogenic activities such as coal mining, oil and gas production, application of salts on roads for de-icing and agricultural practices can result in saline discharges to aquatic ecosystems. Salts are components of all natural waters. Salinity is a measure of inorganic ions or salts. It is mainly comprised of major cations (calcium–Ca, potassium–K, magnesium–Mg, sodium–Na) and major anions (chloride–Cl, sulfate–SO4, bicarbonateHCO3). The ionic composition of mine waters can have varying proportions of major cations and anions. Saline discharges to freshwater ecosystems can increase salinity as well as change the ionic composition. Major ions are also essential for the normal functioning of the organisms. Change in salinity or ionic composition of the surrounding water can have a detrimental effect on organisms. While increased calcium concentration is presumed to decrease the toxicity of saline solutions, the effect of calcium proportion of a mine water ionic composition is not well understood. The aim of this study was to investigate the influence of calcium proportion on the toxicity of a saline solution to Ephemeroptera, Austrophlebioides sp. AV11. The hypothesis tested was that increased calcium proportion decreases the toxicity of a saline solution to Austrophlebioides sp. AV11. The effect of calcium proportion was tested in presence of all the major cations, potassium, magnesium and sodium and the major anions, chloride, sulfate and bicarbonate. The aim of the study was evaluated using static non – renewal 96 h acute toxicity tests. The saline solution used in the present study was based on the ionic composition of mine water from the study of Prasad et al. (2012) and named as artificial mine water (AMW). The term calcium proportion used here refers to the proportion of calcium in relation to all the major ions measured in milliequivalents (% meq). Solutions with increased calcium proportion were prepared using calcium chloride and calcium sulfate salts together. Calcium proportion was increased above that of AMW two fold (Ca Cl.SO4(2)), four fold (Ca-Cl.SO4(4)) and eight fold (Ca Cl.SO4(8)). Additional tests were conducting using calcium chloride and calcium sulfate salts separately to assess the effect of calcium in isolation of the associated anions. Calcium proportion was increased as two fold and four fold designated Ca-Cl(2), Ca-Cl(4) and Ca-SO4(2) and Ca SO4(4). For the experiments with calcium chloride and calcium sulfate together, there was a statistically significant reduction in toxicity for Ca-Cl.SO4(2) and Ca-Cl.SO4(4) solutions compared with AMW, but no difference between Ca-Cl.SO4(8) and AMW. The 96 h LC50 values were: AMW  6.0 mS/cm, Ca-Cl.SO4(2) – 6.9 mS/cm, Ca-Cl.SO4(4) – 8.1 mS/cm and Ca-Cl.SO4(8) – 6.2 mS/cm. These results show that both two fold and four fold increase in calcium reduced toxicity by 15 % and 35 % respectively but that an eight fold increase in calcium did not affect toxicity. The finding of this thesis suggests that calcium concentration beyond 7.5 mM (300 mg/L) has no ameliorative effect or may contribute to increased toxicity to organisms. The observed toxicity associated for solutions Ca-Cl.SO4(2) and Ca-Cl.SO4(4) and Ca Cl.SO4(8) could be due to the influence of calcium on the permeability of ions and water across the cell membranes. The concentration of calcium has been found to influence the sodium influx in aquatic organisms. Increase in calcium can alter the Ca:Na ratio, which has been found to influence the physiological mechanism. For experiments which used calcium chloride or calcium sulfate separately, the chloride solutions were more toxic than AMW, while the sulfate solutions showed similar toxicity to the AMW. The 96 h LC50 values were: AMW – 6.0 mS/cm, Ca-Cl(2) – 4.5 mS/cm and Ca-Cl(4) – 5.4 mS/cm, Ca SO4(2) – 5.2 mS/cm and Ca-SO4(4) – 6.1 mS/cm. These solutions did not show a similar effect as observed for solutions with increased calcium proportion using calcium chloride and calcium sulfate together. This can be due to the change in anion ratio that could have interfered in ion exchange mechanisms across cell membranes. It also suggests solutions with both calcium chloride and sulfate together probably had more balanced anions and were less toxic. The findings of this study will assist in evaluating the toxicity of waters with ionic compositions with a similar relative proportion of calcium. The results suggest that a potential ameliorative effect of calcium should be considered when assessing potential impacts of saline discharges and developing discharge criteria. While this thesis provides the effect of calcium proportion on a complex ionic composition, further research on the effect of Ca:Na ratio and the ratios of other ions on toxicity is needed. This thesis focussed on an Ephemeroptera species; however, the effect of calcium proportion can vary for laboratory cultured organisms that are widely used to evaluate effluent toxicity. The potential for variation in the observed toxicity between laboratory and field collected species needs further investigation.

Investigation into alternative water treatment technologies for the treatment of underground mine water discharged by Grootvlei Proprietary Mines Ltd into the Blesbokspruit in South Africa

Wetland water and acid mine drainage are available in South Kalimantan, Indonesia. However, “Wetland saline water (WSW)” phenomena occur in the wetland areas due to the seawater intrusion, this water which contains a high salt concentration is unsafe to be consumed. While acid mine drainage (AMD) pollution becomes an issue in the mining industry that impact human life and the environment. Salt particles could be removed by using a silica pectin membrane. Banana peel has a high pectin substance. Banana pectin (0.5wt% and 0.1wt%) was employed in silica and calcined at 300 and 400 °C. We demonstrate the silica pectin template’s performance without interlayer for wetland water and acid mine drainage desalination. Membranes were developed through a sol-gel method with silica source deposited from tetraethyl orthosilicate (TEOS) and performed by pervaporation at room temperature (~25 °C). As a result, 0.5wt% banana pectin concentration at 300 °C exhibited excellent performance with the highest water fluxes are 8.4 and 10.4 kg m?2 h?1 for WSW and AMD, respectively. Nevertheless, both membranes achieved high salt rejections up to 92%. Thereby, banana pectin as a carbon source impacts the stronger silica bond.

A critical review on remediation, reuse, and resource recovery from acid mine drainage

Throughout Northern Appalachia and surrounding regions, hundreds of abandoned mine sites exist which frequently are the source of Acid Mine Drainage (AMD). AMD typically contains metal ions in solution with sulfate ions which have been leached from the mine. These large volumes of water, if treated to a minimum standard, may be of use in Hydraulic Fracturing (HF) or other industrial processes. This project’s focus is to evaluate an AMD water treatment technology for the purpose of providing treated AMD as an alternative source of water for HF operations. The HydroFlex™ technology allows the conversion of a previous environmental liability into an asset while reducing stress on potable water sources. The technology achieves greater than 95% water recovery, while removing sulfate to concentrations below 100 mg/L and common metals (e.g., iron and aluminum) below 1 mg/L. The project is intended to demonstrate the capability of the process to provide AMD as alternative source water for HF operations. The second budget period of the project has been completed during which Battelle conducted two individual test campaigns in the field. The first test campaign demonstrated the ability of the HydroFlex system to remove sulfate to levels below 100 mg/L, meeting the requirementsmore » indicated by industry stakeholders for use of the treated AMD as source water. The second test campaign consisted of a series of focused confirmatory tests aimed at gathering additional data to refine the economic projections for the process. Throughout the project, regular communications were held with a group of project stakeholders to ensure alignment of the project objectives with industry requirements. Finally, the process byproduct generated by the HydroFlex process was evaluated for the treatment of produced water against commercial treatment chemicals. It was found that the process byproduct achieved similar results for produced water treatment as the chemicals currently in use. Further, the process byproduct demonstrated better settling characteristics in bench scale testing. The field testing conducted in the second project budget period demonstrated the ability of the HydroFlex technology to meet industry requirements for AMD water chemical composition so that it can be used as source water in HF activities. System and operational improvements were identified in an additional series of confirmatory tests to achieve competitive cost targets. Finally, the application of the HydroFlex process byproduct in produced water treatment was demonstrated, further supporting the commercial implementation of the technology. Overall, the project results demonstrate a path to the economic treatment of AMD to support its increased use as source water in HF, particularly in regions with limited local freshwater availability.« less

Conventional acid mine drainage (AMD) treatment consists of pH adjustment, oxidation, and separation of solid precipitates from discharge quality water. Alkaline addition increases the pH to the range 7 to 9 to precipitate the regulated metals Al and Mn ions as hydroxides. Mechanical or chemical oxidation then converts the reduced iron species Fe2+ to Fe3+ which precipitates at a low pH value as ferric hydroxide (Fe(OH)3). Co-precipitation of Rare Earth Elements (REEs) with hydroxides creates a gangue-rich matrix from which REEs must be separated. Fe(OH)3 is generally the most abundant gangue-forming metal. Current research by the project team has shown raw, untreated AMD has an average total rare earth element content (TREE) of about 287 μg/L (0.287 ppm). Operators of AMD-producing facilities are obliged to treat it to neutralize acidity and remove regulated metals (e.g., iron (Fe), aluminum (Al), and manganese (Mn)) prior to discharge. Ongoing research indicates conventional AMD treatment concentrates TREE in resulting precipitates (AMD sludge) by an average factor of 2,635x to an average dry weight, elemental concentration of 708 g/t (ppm). While the economics of recovering REEs from AMD sludge are appealing, much of the cost of REE recovery would be incurred during separation of REEs from the gangue metals: Fe, Al, and Mn. Significant gains can be made by precipitating REEs when most of these gangue metals are still in solution. Significant improvements in REE extraction efficiency can be obtained through separation of REEs from the aqueous phase AMD, upstream of conventional AMD treatment by: 1) creating an enriched REE feedstock, 2) producing a more consistent feedstock, 3) reducing transportation costs to an REE refinery, 4) reducing acid consumption in the acid leaching step, and 5) reducing the volume of waste produced at the ALSX plant. This project is exploring two novel approaches for extracting REEs upstream of the conventional AMD treatment plants to create a purified REE feedstock while leaving the bulk of the Fe, Al, and Mn in solution for subsequent treatment. While the average TREE concentration of raw AMD is low and individual sites range between 10 and 2,200 μg/L, successful at-source REE separation will generate a superior feedstock to a conventional ALSX process and significantly improve the economics and environmental performance of REE extraction from AMD. AMD can be classified into two types: type A is net acid and iron is partly oxidized while type B is net alkaline, and iron occurs in the reduced, ferrous state. In Case A, the pH is raised slightly, which will precipitate Fe3+ and Al3+ but not REEs. The other important type of AMD is net alkaline water found in flooded, anoxic deep mines. These generally have a pH > 6.0 and are net alkaline. REE concentrations are also much lower than those found in acidic AMD while the volumes and flux are much higher. Most of these are pumped discharges with almost no Al. Case B AMD is strongly reduced and, like Case A water, Fe and Mn ions are similarly reduced and therefore soluble at pH <9.0. REEs and an array of transition ions will be the only trivalent cations in this type of AMD. In Case B, both upward pH adjustment under reducing conditions and application of an electrochemically stimulated supported liquid membrane strategy to separate REEs from ferrous ion will be explored.

Removal of heavy metals and suspended solids from wastewater from wet lime (stone)—gypson flue gas desulphurization plants by means of hydrophobic and hydrophilic crossflow microfiltration membranes

Pumped groundwater in the lignite open-cast mines in Lusatia, Germany, contains a high level of ferrous iron (up to 1000 mg/L) at an initial pH of about 5. In recent R&amp;D projects G.E.O.S. developed an innovative water treatment process for ferrous iron oxidation using the autochthonous microbial consortium in the mine water. The pilot plant is operated in the Nochten open-pit mine in cooperation with the LEAG and produces 5 – 10 t of schwertmannite per year. Extensive research work was carried out in parallel to utilize the produced schwertmannite. Pigment production proved to be technically feasible but difficult due to economic and market constraints. However, the high affinity of schwertmannite to oxy-anions provides the suitability for utilization as adsorbent to remove arsenate, antimonate, chromate, molybdate, vanadate or phosphate from mine water or industrial effluents. In the R&amp;D project SURFTRAPII two kinds of filter-stable sorption materials were developed 1) by compacting schwertmannite or 2) by adhesive curing using an organic polymer, respectively. The produced filter-stable adsorbents were tested under technical conditions in cooperation with potential end users to remove arsenate, molybdate and phosphate from mine and industrial water and to concentrate valuable metals. The results showed a better performance of the material compared to other commercially available iron hydroxide adsorbents.

Acid mine drainage (AMD) is one of the major environmental problems arising from coal mining activities. AMD is formed through the oxidation of sulfide minerals, resulting in acidic water with high concentrations of dissolved heavy metals. This condition is characterized by elevated levels of Fe, Mn, and total suspended solids (TSS), which, if left untreated, can pollute nearby water bodies, damage aquatic ecosystems, and pose risks to human health. Therefore, effective, eco-friendly, and low-cost treatment methods are needed to minimize the negative impacts of AMD. This study aims to investigate the effect of activated carbon derived from sugarcane bagasse as an adsorbent for reducing Fe, Mn, and TSS levels in AMD at the sump of PT Alreksa Bara Mitra. The selection of sugarcane bagasse is based on its abundance as an agro-industrial waste and its high lignocellulosic content, making it a potential raw material for activated carbon. The research involved the preparation of activated carbon through carbonization and activation processes, followed by its application to AMD samples with variations in adsorbent dosage and contact time. Laboratory analyses were conducted to measure the concentrations of Fe, Mn, and TSS before and after treatment. The results showed that sugarcane bagasse-based activated carbon significantly reduced Fe, Mn, and TSS concentrations. The highest removal efficiencies were achieved under optimum conditions, reaching 93.14% for Fe, 95.05% for Mn, and 85.04% for TSS. These findings demonstrate that activated carbon from sugarcane bagasse has a strong adsorption capacity for dissolved metals and suspended solids in AMD. In conclusion, sugarcane bagasse-derived activated carbon has potential as an environmentally friendly and cost-effective alternative for AMD treatment, while simultaneously providing added value to agro-industrial waste. This research is expected to serve as a reference for the development of more sustainable mine wastewater treatment methods.

Initial fouling rate and delay time studies of aqueous calcium sulphate sealing under sensible heating conditions

Recovery of water and valuable metals using low pressure nanofiltration and sequential adsorption from acid mine drainage

The phase behavior of polyelectrolyte complexes and coacervates (PECs) at low salt concentrations has been well characterized, but their behavior at concentrations well above the binodal is not well understood. Here, we investigate the phase behavior of stoichiometric poly(styrene sulfonate)/poly(diallyldimethylammonium) mixtures at high salt and high polymer concentrations. Samples were prepared by direct mixing of PSS/PDADMA PECs, water, and salt (KBr). Phase separation was observed at salt concentrations approximately 1 M above the binodal. Characterization by thermogravimetric analysis, FTIR, and NMR revealed that both phases contained significant amounts of polymer, and that the polymer-rich phase was enriched in PSS, while the polymer-poor phase was enriched in PDADMA. These results suggest that high salt concentrations drive salting out of the more hydrophobic polyelectrolyte (PSS), consistent with behavior observed in weak polyelectrolyte systems. Interestingly, at the highest salt and polymer concentrations studied, the polymer-rich phase contained both PSS and PDADMA, suggesting that high salt concentrations can drive salting out of partially-neutralized complexes as well. Characterization of the behavior of PECs in the high concentration limit appears to be a fruitful avenue for deepening fundamental understanding of the molecular-scale factors driving phase separation in these systems.

The effect of pollutants from the coal industry on the fish fauna of a small river in the South Wales coalfield

Investigations of the microbial community structures, potential functions and physicochemical property are useful for risk assessments, microbial monitoring, and the biogeochemical behaviour of contained environment by Acid Mine Drainage (AMD). In this study, nine sediment sampling sites were selected at Panjiaozhuang Town, in Guizhou, China to analyze the pollution conditions and their influences on microorganisms. The physicochemical property results showed significant differences in sediment and water physico chemical properties at different group. Compared to the DS group, further studies revealed that US group (severely affected areas) showed strong acidity and high concentrations of heavy metals and salts. The community structure analysis indicated that AMD might enhance the functional bacteria, such as Thiomonas and Ferrovum (increases of 1.2 and 8.1 percent, respectively), and significantly increased the concentrations of Fe and sulfate through the oxidation of pyrite. The KEGG enrichment analysis demonstrated showed that the AMD promoted the migration of sulfur and Fe into water by enhancing bacterial metabolic pathways, such as dark oxidation of sulfur compounds and dark iron oxidation. This article is of great significance for understanding the transformation of pollutants by AMD and provides reference for subsequent bioremediation.