Hydrogeochemistry,Elemental Flux,and Quality Assessment of Mine Water in the Pootkee-Balihari Mining Area,Jharia Coalfield,India

Ninety nine mine water discharge samples were collected and analyzed for pH, electrical conductivity (EC), major cations, anions, and trace metals in the Pootkee-Balihari coal mining area of the Jharia coalfield. The mines of the area annually discharge 34.80 × 10⁶ m³ of mine water and 39,099 t of solute loads. The pH of the analyzed mine waters ranged from 6.97 to 8.62. EC values ranged from 711 μS cm⁻¹ to 1862 μS cm⁻¹, and reflect variations in lithology, geochemical processes, and hydrological regimes in the mines. The cation and anion chemistry indicate the general ionic abundance as: Mg²⁺ > Ca²⁺ > Na⁺ > K⁺ and HCO₃ ⁻ > SO₄ ²⁻ > Cl⁻ > NO₃ ⁻ > F⁻, respectively. Elevated SO₄ ²⁻ concentrations in the Gopalichuck, Kendwadih, and Kachhi-Balihari mine waters are attributed to pyrite weathering. The water quality assessment indicated that TDS, hardness, Mg²⁺, and SO₄ ²⁻ are the major parameters of concern in the study area. Except for Fe, all of the measured metals in the mine water were well within the levels recommended for drinking water. With only a few exceptions, the mine water is of good to permissible quality and suitable for irrigation.     

Development and Validation of a Spectrophotometric Method to Measure Sulfate Concentrations in Mine Water without Interference

Sulfate concentrations are determined in mine water by gravimetric, titrimetric, colorimetric, turbidometric, ion chromatographic, inductively coupled plasma absorption spectrophotometric, and other methods. Accurate sulfate measurement of mine water can be difficult due to interfering groups, cations, and anions, mainly arsenate (AsO₄ ³⁻) and phosphate (PO₄ ³⁻). In this paper, a simple and effective spectrophotometric method is described for the determination of sulfate in mine water. When the SO₄ ²⁻ reacts with barium chloranilate at pH 4.5 in aqueous ethyl alcohol solution, it releases acid-chloranilate, which shows maximum absorption at 350 nm and obeys Beer’s law over the concentration range of 10–1,000 mg/L. Results show that the proposed method was significantly more accurate than a conventional method. Absorbance was found to increase linearly with increasing concentration of sulfate, which is corroborated by the calculated correlation coefficient value of 0.999 (n = 7). The slope and intercept of the equation of the regression line were 0.00091 and 0.00778, respectively. The limit of detection and limit of quantification were found to be 0.03861 and 0.06774 mg/L, respectively. The validity of the described procedure was assessed. Statistical analysis of the result indicated high accuracy and good precision. The proposed method was successfully applied in mine water without interference from common groups like AsO₄ ³⁻ and PO₄ ³⁻. The relative standard deviations of the proposed method ranged from 0.03 to 0.26%, with recoveries of 99.79–101.57%.     

Quality Assessment of Mine Water in the Raniganj Coalfield Area,India

In a qualitative assessment of mine water from the Raniganj coalfield, 77 mine water samples were analyzed to assess water quality and suitability for domestic, industrial, and irrigation uses. The pH of the mine water ranged from 6.5 to 8.8. Total dissolved solids (TDS) ranged from 171 to 1,626 mg L⁻¹; spatial differences between the TDS values reflect variations in lithology, activities, and prevailing hydrological regime. The anion chemistry was dominated by HCO₃ ⁻ and SO₄ ²⁻. On average, Cl⁻ contributes 10 and 19% of the total anionic balance, respectively, in the Barakar and Raniganj Formation mine water. F⁻ and NO₃ ⁻ contribute <2% to the total anions. The cation chemistry is dominated by Mg²⁺ and Ca²⁺ in the mine water of the Barakar Formation and Na⁺ in the Raniganj Formation mines. Much of the mine water, especially of the Barakar Formation area, has high TDS, total hardness, and SO₄ concentrations. Concentrations of some trace metals (i.e. Fe, Cr, Ni) were found to be above the levels recommended for drinking water. However, the mine water can be used for irrigation, except at some sites, especially in the Raniganj Formation area, where high salinity, sodium adsorption ratio, %Na, residual sodium carbonate, and excess Mg restrict its suitability for agricultural uses.     

Hydrotalcite Formation for Contaminant Removal from Ranger Mine Process Water

Process water from the Ranger Uranium Mine requires treatment to meet stringent environmental water quality criteria. The acidic water contains substantial SO₄, metals, and U. One novel treatment method under consideration is the use of Na-aluminate to both neutralise the process water and precipitate hydrotalcites. Hydrotalcites are a class of Mg–Al layered double hydroxide minerals with a typical endmember chemical composition: Mg₆Al₂(A)(OH)₁₆·n(H₂O), where A = CO₃ ²⁻, SO₄ ²⁻, etc. Many acidic wastewaters contain Mg and/or Al in sufficient abundance for hydrotalcite formation upon addition of alkali to achieve solution pH > 5, and Mg and/or Al to attain a Mg:Al ratio of 2 to 3:1. The utility of hydrotalcites lies in their ability to incorporate a range of cationic (Cu²⁺, UO₂ ²⁺), metalloid (AsO₄ ³⁻), and (oxy)anionic contaminants (CrO₄ ²⁻). The broad spectrum removal of contaminants, including U, also indicates that hydrotalcites and their derivatives could potentially be used as a containment material in nuclear waste repositories. In this study, Ranger process water derived from extraction of U from chloritic schist was treated with Na-aluminate sourced from Bayer process liquor, in combination with NaOH or Ca(OH)₂. Hydrotalcites formed as the primary mineral during process water neutralisation with the ability to simultaneously remove a suite of contaminants from solution.     

Passive aerobic treatment of net-alkaline,iron-laden drainage from a flooded underground anthracite mine,Pennsylvania, USA

This report evaluates the results of a continuous 4.5-day laboratory aeration experiment and the first year of passive, aerobic treatment of abandoned mine drainage (AMD) from a typical flooded underground anthracite mine in eastern Pennsylvania, USA. During 1991–2006, the AMD source, locally known as the Otto Discharge, had flows from 20 to 270 L/s (median 92 L/s) and water quality that was consistently suboxic (median 0.9 mg/L O₂) and circumneutral (pH ≈ 6.0; net alkalinity >10) with moderate concentrations of dissolved iron and manganese and low concentrations of dissolved aluminum (medians of 11, 2.2, and <0.2 mg/L, respectively). In 2001, the laboratory aeration experiment demonstrated rapid oxidation of ferrous iron (Fe²⁺) without supplemental alkalinity; the initial Fe²⁺ concentration of 16.4 mg/L decreased to less than 0.5 mg/L within 24 h; pH values increased rapidly from 5.8 to 7.2, ultimately attaining a steady-state value of 7.5. The increased pH coincided with a rapid decrease in the partial pressure of carbon dioxide (PCO₂) from an initial value of 10^−1.1 atm to a steady-state value of 10^−3.1 atm. From these results, a staged aerobic treatment system was conceptualized consisting of a 2 m deep pond with innovative aeration and recirculation to promote rapid oxidation of Fe²⁺, two 0.3 m deep wetlands to facilitate iron solids removal, and a supplemental oxic limestone drain for dissolved manganese and trace-metal removal. The system was constructed, but without the aeration mechanism, and began operation in June 2005. During the first 12 months of operation, estimated detention times in the treatment system ranged from 9 to 38 h. However, in contrast with 80–100% removal of Fe²⁺ over similar elapsed times during the laboratory aeration experiment, the treatment system typically removed less than 35% of the influent Fe²⁺. Although concentrations of dissolved CO₂ decreased progressively within the treatment system, the PCO₂ values for treated effluent remained elevated (10^−2.4 to 10^−1.7 atm). The elevated PCO₂ maintained the pH within the system at values less than 7 and hence slowed the rate of Fe²⁺ oxidation compared to the aeration experiment. Kinetic models of Fe²⁺ oxidation that consider effects of pH and dissolved O₂ were incorporated in the geochemical computer program PHREEQC to evaluate the effects of detention time, pH, and other variables on Fe²⁺ oxidation and removal rates. These models and the laboratory aeration experiment indicate that performance of this and other aerobic wetlands for treatment of net-alkaline AMD could be improved by aggressive, continuous aeration in the initial stage to decrease PCO₂, increase pH, and accelerate Fe²⁺ oxidation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The Effects of Sulfate on the Physical and Chemical Properties of Actively Treated Acid Mine Drainage Floc

It is important to consider floc properties when designing acid mine drainage treatment (AMD) systems. Relatively few studies have evaluated the effects of neutralizing base, neutralization pH, and sulfate in solution on floc properties in active treatment systems. We used NaOH and NH₄OH as neutralizing bases, 0:1, 2.5:1, and 5:1 SO₄:Fe molar ratios, and neutralization pH of 7, 8, and 9 in laboratory studies. Neutralizing cation, sulfate content, and neutralization pH had significant effects on floc mass and volume, but SO₄:Fe ratio was the most important parameter. Settled floc volumes were slightly larger in the sodium system. Floc mass and volume both decreased with increasing pH. Floc generated in the presence of sulfate required significantly more time to reach a total suspended solids discharge limit of 70 mg L⁻¹, had slower initial settling rates, and smaller settled volumes than floc generated without sulfate. The systems we studied were less complicated than actual AMD, but understanding the effects of sulfate, neutralizing cation, and neutralization pH on floc properties may help to design more efficient treatment systems. Choosing the appropriate treatment chemical and designing adquate pond sizes will ultimately increase treatment efficiency and improve stream water quality.     

Alkalinity Generation in a Novel Multi-stage High-strength Acid Mine Drainage and Municipal Wastewater Passive Co-treatment System

Passive co-treatment of high-strength acid mine drainage (AMD) and municipal wastewater (MWW) was examined in a laboratory-scale, four-stage continuous flow reactor system with a total residence time of 6.6 d. Synthetic AMD of pH 2.60 and an acidity of 1,870 mg/L (as CaCO₃) was mixed at a 1:2 ratio with raw MWW (pH 7.67, 288 mg/L alkalinity (as CaCO₃), and 265 mg/L BOD₅) from the City of Norman, Oklahoma and introduced into the system. Alkalinity generated by limestone dissolution and bacterial SO₄ ²⁻ reduction (BSR) processes was sufficient to support various metal removal processes and produce an effluent with circumneutral pH (6.98) and a net alkalinity of 10.4 mg/L (as CaCO₃). Alkalinity generation from limestone dissolution was comparable with conventional AMD passive treatment systems. BSR proceeded at a relatively high rate (0.56 mol/m³ day) despite inhibitory pH and metals concentrations. Results indicate that the diverse electron donors in the MWW may be as suitable for BSR and their supporting microbial communities as commonly used substrates, presenting an opportunity to use a common waste as a resource for passive treatment.     

硫酸盐还原菌处理矿山酸性废水的试验研究

采用上流厌氧反应器连续处理矿山酸性废水,研究了水力停留时间、进水pH值、进水负荷对硫酸根还原效果的影响。获得最佳工艺参数为水力停留时间8 d,COD/SO^2-₄=1.6,进水SO^2-₄浓度2.3 g/L和进水pH=6.0。在温度30 ℃,HRT=8 d、COD/SO^2-₄=1.6,进水SO^2-₄浓度2.3 g/L,进水pH=4.5和废水稀释倍数为3倍的条件下,采用上流厌氧反应器连续成功运行59 d,反应器运行24 d后,硫酸根平均去除率为75.35%,铜离子的去除率达99.98﹪, 铁离子的去除率为88.87%,出水达到工业排放标准。     

Stability of As(V)-sorbed schwertmannite under porphyry copper mine conditions

Arsenic (As), a very poisonous inorganic pollutant is a major toxicant in tailings of porphyry copper deposits. Retention of As by Schwertmannite (a ferric-oxyhydroxysulfate mineral) has attracted much attention in recent years due to its strong binding affinity to toxic As species. The stability of As(V)-sorbed schwertmannite under copper mine waste conditions is not fully understood. The present study investigates the effect of Cu²⁺, Fe²⁺, pH, and ageing time on the stability of As(V)-sorbed schwertmannite (Sch-As). The results indicate that Cu²⁺ has no significant effect on the stability of Sch-As and that the As(V) incorporated in schwertmannite can retard or significantly inhibit Fe²⁺-catalyzed transformation of schwertmannite to goethite under acidic conditions (pH 3–4). The Sch-As aged at different pHs from 3 to 11 at 25 °C exhibits no mineralogical phase changes even after ageing for 120-days; however the concentration of As released from the solid phase appears to be strongly pH-dependent even after ageing for only 24 h. The release of As was negligible at pHs from 2 to 7, and there was considerable release of As at extremely acidic and alkaline conditions. This indicates that the release of As from Sch-As was controlled by environmental factors such as pH, Cu²⁺, and Fe²⁺ rather than time.     

Alkalinity generation and metals retention in a successive alkalinity producing system

Alkalinity generation and metals retention were evaluated during the initial year of operation of a treatment wetland, consisting of four 185 m² inseries cells comprised of alternating vertical-flow anaerobic substrate wetlands (VFs) and surface-flow aerobic settling ponds (SFs). The substrate in the VFs consists of spent mushroom substrate (SMS) and limestone gravel, supplemented with hydrated fly ash in a 20∶10∶1 ratio by volume. Approximately 15±4 L/min of acid mine drainage (AMD) from an abandoned underground coal mine in southeastern Oklahoma, USA, was directed to the system in October 1998 (mean influent water quality: 660 mg L⁻¹ net acidity as CaCO₃ eq., pH 3.4, 215 mg L⁻¹ total Fe, 36 mg L⁻¹ Al, 14 mg L⁻¹ Mn, and 1000 mg L⁻¹ SO₄ ⁻²). Flow through the first VF resulted in substantial increases in alkalinity, decreased metal concentrations and circumneutral pH. 258±84 mg L⁻¹ of alkalinity was produced in the first VF by a combination of processes. Final discharge waters were net alkaline on all sampling dates (mean net alkalinity=136 mg L⁻¹). Total Fe and Al concentrations decreased significantly from 216±45 to 44±28 mg L⁻¹ and 36±6.9 to 1.29±4.4 mg L⁻¹, respectively. Manganese concentrations did not change significantly in the first two cells, but decreased significantly in the second two cells. Mean acidity removal rates in the first VF (51 g m⁻² day⁻¹) were similar to those previously reported.     

Acid Mine Drainage at the Abandoned Kettara Mine (Morocco): 2. Mine Waste Geochemical Behavior

Weathering and humidity cell tests were used to predict the potential for acid mine drainage (AMD) and to estimate the mineral reaction rates and depletion of fine and coarse tailings from the abandoned Kettara mine, Morocco. The geochemistry of the fine and coarse mine wastes was similar and, as expected by static tests, the wastes produced significant amounts of AMD. The sulfate production rate of both fine and coarse tailings was very high (2,000–8,000 and 2,400–560 mg SO₄/kg/week, respectively) during the first weeks of kinetics tests. After 9 weeks, sulfate release became low, ranging between 600 and 78 mg SO₄/kg/week for fine tailings and 500–120 mg SO₄/kg/week for coarse tailings. Effluent water samples had low pH (2.9–4.2) and elevated concentrations of acidity, sulfate, iron, copper, and zinc. Most or all of the dissolved K, Na, Al, Mg, and Si in the AMD result from the acidic dissolution of silicates (chlorite, talc, muscovite, and albite). Fine tailings produce much higher concentrations of acidity and sulfate than coarse tailings. However, due to greater transport of oxygen and water within the coarse waste, coarse tailings could be of greater environmental significance than fine tailings. The coarse waste continued to release acid after 378 days of leaching, whereas the fine tailings naturally passivates. These laboratory results agree with field observations; the upper profile of the coarse waste rock dam is highly oxidized (75 cm) whereas oxidation in the fine tailings does not extend more than 5–15 cm beneath the surface. A comparison between weathering and humidity cell tests indicated that the general trend of dissolution of metals was essentially similar for both methods. However, sulfate depletion rates were higher for the weathering cell tests. These tests indicate that the Kettara tailings piles and dam will continue to release acid for a long time unless remedial action is taken.     

Iron Removal by a Passive System Treating Alkaline Coal Mine Drainage

The Marchand passive treatment system was constructed in 2006 for a 6,000 L/min discharge from an abandoned underground bituminous coal mine located in western Pennsylvania, USA. The system consists of six serially connected ponds followed by a large constructed wetland. Treatment performance was monitored between December 2006 and 2007. The system inflow was alkaline with pH 6.2, 337 mg/L CaCO₃ alkalinity, 74 mg/L Fe, 1 mg/L Mn, and <1 mg/L Al. The final discharge averaged pH 7.5, 214 mg/L CaCO₃ alkalinity, and 0.8 mg/L Fe. The settling ponds removed 84% of the Fe at an average rate of 26 g Fe m⁻² day⁻¹. The constructed wetland removed residual Fe at a rate of 4 g Fe m⁻² day⁻¹. Analyses of dissolved and particulate Fe fractions indicated that Fe removal was limited in the ponds by the rate of iron oxidation and in the wetland by the rate of particulate iron settling. The treatment effectiveness of the system did not substantially degrade during cold weather or at high flows. The system cost $1.3 million (2006) or $207 (US) per L/min of average flow. Annual maintenance and sampling costs are projected at $10,000 per year. The 25-year present value cost estimate (4% discount rate) is $1.45 million or $0.018 per 1,000 L of treated flow.     

Extraction of titanium (IV) from acidic media by tri-n-butyl phosphate in kerosene

The extraction of titanium (IV) from sulfate, and nitrate solutions has been studied using tri-n-butyl phosphate (TBP) in kerosene. Extraction of titanium was affected by acid concentration over the range of 0.5–4 mol L^?1. The titanium distribution coefficient reached a minimum between 1 and 2 mol L^?1 acid for both sulfate and nitrate solutions. Third phase formation was observed in the extraction of titanium from acidic media at all condition tested. At the next stage, the stripping of titanium was studied using H₂SO₄, H₂SO₄ + H₂O₂ and Na₂CO₃. The kinetics of the stripping were very slow for H₂SO₄. The use of complex forming stripping agents (H₂SO₄ + H₂O₂) and Na₂CO₃ significantly improved the kinetics of stripping. About 98% recovery was achieved by extracting titanium from an aqueous nitrate solution using TBP and stripping with sodium carbonate.     

The Combined Impact of Mine Drainage in the Ankobra River Basin,SW Ghana

This study assessed the combined effects of seven large-scale gold mines, one manganese mine, and scattered artisanal gold mining sites on the quality of water in the Ankobra Basin in a geologically complex terrain. Water samples from streams, boreholes, hand dug wells, and mine spoil were analysed. Scatter plots of trends among measured parameters were used to assess drainage quality and differential impacts. Drainage quality exhibits wide seasonal and spatial variations; the geology strongly influences the water chemistry. Areas with low pH (<5.5), and high sulphate ions and trace ions are suggestive of acid mine drainage while sites with high pH (>7.5), HCO₃ ⁻, subdued SO₄ ²⁻, and high trace ions are suggestive of sites where acid neutralization is effective. High metal sources are largely confined to mining operations in the Birimian formation with ores containing more than 2% sulphides. However, restricted high metal regimes are observed in drainage in the Tarkwaian formation associated with scatted sulphide-bearing dolerite dykes in the operational areas of the Tarkwa and Damang mines. Earlier studies disputed sulphides in the Tarkwaian formation until recently, when acid-generating dykes were discovered in operating pits. The most degraded waters emanate from the Prestea and Iduapriem mines, and to a lesser extent, the Nsuta mine sites, all mining Birimian rocks. The Tarkwa mine showed minimal metal loading. Zn, Cu, Ni, As, SO₄, pH, and specific conductance are essential and adequate parameters in determining if acid drainage is taking place at these sites, and are recommended for routine mine environmental monitoring.     

Study of the electrodeposition conditions of metallic manganese in an electrolytic membrane reactor

This paper reports the optimization of the process parameters for the electrodeposition of manganese in an electrolytic membrane reactor. The manganese(II) and ammonium ion concentrations, pH, temperature and additives to the electrolyte were varied over a relatively broad range to evaluate the changes in the current efficiency and specific energy consumption of manganese electrodeposition. The catholyte was aqueous manganese(II) sulfate containing ammonia sulfate, and the anolyte was a sulfuric acid solution. An anionic membrane separated the anolyte from the catholyte while maintaining a conductive path between the two. A high current efficiency and low specific energy consumption were favored at a pH of 7.5 with additive incorporation. Under the optimized conditions, a maximum current efficiency of 85.86% was attained with an electrolyte composition of 35 g/L Mn and 130 g/L (NH₄)₂SO₄ at a temperature of 40 °C and a pH of 7.5 in the presence of additives and with a cathode current density of 400 A/m². The electrolysis experiment over time showed that the specific energy consumption was 4779 kW h/t of Mn deposited under the optimum conditions.     

Anaerobic Bioremediation of Acid Mine Drainage using Emulsified Soybean Oil

Abstract  Batch incubation and flow-through column experiments were conducted to evaluate the use of emulsified soybean oil for in situ treatment of acid mine drainage. Addition of soybean oil, soluble substrates, and a microbial inoculum to the batch incubations resulted in complete depletion of SO₄, 50% reduction in Fe, and an increase in pH to >6. A one time injection of emulsified soybean oil, lactate, yeast extract, and a microbial inoculum stimulated SO₄ and metal ion reduction for ≈300 days in laboratory columns packed with mine tailings receiving influent solutions with a pH≈3 and≈5. In all emulsion treated columns, SO₄ and Fe were reduced, pH increased to >6, and Al, Cu and Zn removal efficiency was 99% or greater. Cu, Fe, Mn and Zn were removed as metal sulfides and/or carbonates with removal efficiency decreasing with increasing metal sulfide solubility. The low pH and high heavy metals concentrations did not significantly inhibit biological activity. However, SO₄ removal with associated precipitation of metal sulfides may have been limited by the short hydraulic retention time (6-7 days) of the columns. There was a significant hydraulic conductivity loss in one of the four treated columns, indicating that hydraulic conductivity loss may be an issue under certain conditions.     

Impact of lead/zinc ore mining on groundwater quality in Trzebionka mine (southern Poland)

The intensive mining activity carried out by “Trzebionka” zinc-lead mine causes changes in the hydrodynamic regime of the triassic aquifer as well as essential changes in the chemical composition of the groundwater. The mine water, in comparison with groundwaters collected directly from fractures and Karstic channels and with groundwaters pumped out from wells situated in Chrzanow region, is characterized by higher contents of almost all major dissolved constituents as, well as, many trace elements. Hydrogeochemical background of triassic carbonate series aquifer has been elaborated. Largest anomalies in extent of almost all elements have occurred in area of the “Trzebionka” mine. In this water general trend of increase of pH, total dissolved solids and SO₄ ²⁻ concentration with simultaneous trends of decrease of Zn²⁺ and Pb²⁺ concentrations have been noticed. Water pumped out from the mine in spite of its low quality, is utilized in about 80% as potable water after undergoing complicated treatment.     

Preliminary Studies on Precipitating Manganese Using Caro’s Acid and Hydrogen Peroxide

We report preliminary studies on the precipitation of manganese compounds by oxidation with Caro’s Acid (peroxomonosulphuric acid, H₂SO₅) or hydrogen peroxide (H₂O₂), from solutions with [Mn] = 1.2 g/L to achieve residual [Mn] <1 mg/L at a pH range of 5–9. It was found that with the addition of sodium carbonate and either Caro’s acid or hydrogen peroxide, it was possible to reduce manganese from 1.2 g/L to less than 1 mg/L in 60 min (batch reaction) at 25°C (at pH ≥ 5 using H₂SO₅, and pH = 9 using H₂O₂). By comparison, simple hydroxide precipitation under the same conditions at pH = 9 would only lower [Mn] to 165 mg/L.     

Evaluation of the Potential for Beneficial Use of Contaminated Water in a Flooded Mine Shaft in Butte,Montana

The mines of Butte, Montana include over 16,000 km of abandoned underground workings, most of which are now filled with water. The feasibility of using the flooded mine workings as a source of irrigation water was investigated. The geochemistry and stable isotopic composition of water produced during a 59 day pumping test of the flooded Belmont Mine workings are described. Although static water in the pumping well initially met proposed irrigation standards, the quality deteriorated during pumping as water from deeper in the mine complex was drawn into the well. Stable isotopes show that this lower-quality water was not sourced from the nearby Berkeley Pit lake, but most likely came from the mine shaft itself. At steady state, the water pumped to the surface had pH 5.5–6.0 with high concentrations (in mg/L) of dissolved SO₄ (1,600), Fe (160), Mn (19), Zn (15), and As (1.8). Despite substantial bicarbonate alkalinity (≈150 mg/L as CaCO₃), the water became strongly acidic after equilibration with air due to oxidation and hydrolysis of Fe²⁺. Benchtop experiments were performed to test different strategies for low-cost chemical treatment prior to irrigation. The most feasible alternative involved aeration (to remove large quantities of dissolved CO₂) prior to pH adjustment to >9 with lime or NaOH. Further work is needed to see if such treatment is economically viable compared to the cost of using municipal water. Another concern is whether irrigation of grass with high TDS, high sulfate water is sustainable. The mine water reached a steady-state temperature of 19°C during pumping, and therefore the possibility of using this water to help heat nearby buildings should also be explored.