Mine drainage from the St Louis Tunnel (located at the Rico-Argentine Site) is circumneutral most of the year, with spring freshets increasing flow, decreasing pH and increasing metals concentrations. This study was designed to test the performance of a demonstration-scale horizontal wetlands passive treatment train, comprised of a settling basin, surface flow wetland, horizontal-flow anaerobic wetland, aeration channel, and rock drain, during two years of influent water chemistry at a constant 113 L/min (30 gpm) flow rate. Total Zn, Cd, and Mn effluent concentrations met project treatment goals (PTGs) 75, 96.9, and 100% of the time, respectively, and 93.9, 100, and 100% of the time for the dissolved metals. Most PTG exceedances occurred during the freshet events. Most Zn and Cd attenuation was attributed to sulfide precipitation in the anaerobic cell and capture/filtration of suspended ZnS particles in the anaerobic wetland and rock drain. Manganese was attenuated in the aerobic portion of the anaerobic cell (influent transition zone) as Mn oxides and carbonates. Oxidation of Mn occurred in the rock drain as biogenically formed Mn oxides adhered to the rock matrix. Carryover of dissolved sulfides from the anaerobic cell limited the rock drain’s Mn removal efficiency. Low temperatures did not significantly affect biological activity within the system; the effects of seasonal water quality were more important.
相似文献This publication is a case study of the seasonal variability of mine water drainage from the Saint Louis Tunnel (SLT) at the inactive Rico-Argentine mine site located in southwestern Colorado. It is an introductory paper for the two passive water treatment system technology evaluations contained in this issue. Mine water chemistry changes from baseflow to a snowmelt runoff event (SMRE) where snowmelt runoff follows preferential migration pathways to flush acidic weathering products from the upper mine workings to the SLT. Baseflow mine drainage is characterized as circumneutral, with Zn, Cd, Mn, and Ni concentrations primarily in the dissolved form. Dissolved Zn, Mn, Fe, and potentially Cd illustrate equilibrium with carbonate minerals. Total concentrations of Fe, Cu, Pb, and As are primarily in the suspended form and suggest sorption to Fe oxides. Mine water chemistry during the SMRE reflects mixing of circumneutral baseflow waters with more acidic waters flushing the upper mine workings. Geothermal activity provides for a consistently warm mine water discharge from the SLT. The two seasons that provide the most challenge to passive water treatment of SLT mine drainage are the SMRE period and the low flow stage of the Dolores River. Mine water flow and chemistry during SMRE are highly correlated with Dolores River flow and this site conceptual model was and will be used to assist in pilot project evaluation, water treatment system design, monitoring system design, a seasonal compliance approach, and water management.
相似文献Two semi-passive treatment systems for iron (Fe) and arsenic (As) removal in AMD were installed and monitored in-situ for more than a year. These technologies were designed to treat the As-enriched AMD (≈ 1 g/L Fe(II) and 100 mg/L As(III)) of the ancient Carnoulès mine. The treatment was based on biological Fe and As oxidation by indigenous bacteria, and subsequent immobilization of As by ferric hydroxysulfates. Forced aeration and wood/pozzolana or plastic support were used for biofilm attachment. The system performance ranged from 86 to 98% for Fe oxidation, 30 to 60% for Fe removal, and 50 to 80% for As removal at a hydraulic retention time of 9 h. No significant difference were measured between the two biofilm supports. The wood/pozzolana support had a shorter delay for performance recovery after interruptions. Iron oxidation rates were similar to those obtained in the Carnoulès AMD stream and laboratory bioreactor, while As oxidation seemed to be enhanced. The sludge accumulated between 39 and 91 mg/g of As, mainly in the As(V) oxidation state; jarosite and amorphous ferric hydroxysulfate phases were the main Fe and As scavengers. Challenging environmental conditions during the long monitoring period confirm the robustness of the treatment units. The data will be useful in designing future full-scale treatment systems adapted to As-rich AMD.
相似文献To understand the hydrochemical characteristics and circulation pattern of groundwater in coastal coal mining areas, we analyzed 81 water samples from different water bodies in the Liangjia coal mine (LCM) area using multivariate statistical analysis and hydrochemical methods. The Quaternary groundwater (QW), accumulated water (AW) in the subsidence area, and mine water (MW) in the LCM all exhibit weakly alkaline to slightly saline water chemistry. The dominant cations and anions in the water are sodium (Na+) and chloride (Cl?), reflecting the influence of seawater intrusion. Some ions in QW, AW, and MW exhibited significant annual variations, but Na+ and Cl? concentrations increased with time. The water samples were divided into four categories through cluster analysis: C1 and C2 (bedrock water samples), C3 (water samples prominently affected by seawater intrusion), and C4 (QW and AW in the surface subsidence area). According to the Piper diagram, QW and AW in the surface subsidence area mainly correspond to the Na?Cl type, whereas the MW mainly consists of Na?Cl and Na?HCO3 types. Factor analysis revealed four main factors: seawater recharge, HCO3-rich bedrock water, alkaline water, and Quaternary groundwater (QW) with eigenvalues of 4.18, 2.44, 1.22, and 1.19 respectively, which explained 81.98% of the original data information. The comprehensive results of hydrochemical analysis and mathematical statistics indicated that the recharge sources of MW in LCM include seawater, QW, AW, HCO3-rich bedrock water, and mixed water. Based on regional hydrogeological conditions, a preliminary groundwater circulation model of the coastal coal mining area was constructed. Groundwater generally flows into the Bohai Sea from southeast to northwest, and coal mining has changed the original local groundwater runoff patterns and intensified seawater intrusion.
相似文献The spatial variability in soil water content in the Daliuta mining area in western China was studied before and after coal mining using ground penetrating radar and geostatistical methods. The relationships among soil water content, soil physical properties, topographical factors, and vegetation density were analysed using classical statistics. The average surface soil water content changed slightly between the two detection events at the centre of the subsidence, from 0.084 cm3/cm3 to 0.079 cm3/cm3; there, the distribution of the soil water content was more closely related to terrain than any of the other factors being considered. Along the subsidence boundary, the surface soil water content decreased significantly after mining, from 0.099 cm3/cm3 to 0.083 cm3/cm3 at one location. The total soil porosity, soil organic matter, and soil clay content were positively correlated with soil water content before mining. However, after mining, the relationship between total soil porosity and soil water content significantly strengthened while the relationships between other soil physical and chemical properties and soil water content weakened. Vegetation was determined to be the main factor controlling the surface soil water content before and after coal mining at one location in a small (1,600 m2) area of the subsidence boundary.
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