Acid Mine Wastewater Research Articles

Technical note: Development of a Linear Flow Channel Reactor for sulphur removal in acid mine wastewater treatment operations

Where sulphate removal is targeted in the biological treatment of acid mine drainage wastewaters, a step additional to sulphate reduction is required to prevent the complete oxidation of sulphide back to sulphate. This linearisation of the biological sulphur cycle has presented a technological bottleneck, particularly in passive treatment operations. We report an investigation of sulphur production in floating sulphur biofilms as a means for addressing this problem. These 50 μm to 500 μm structures may be seen to form on the surface of sulphidic, organic waters and in which sulphide is partly oxidised to So and polysulphide. A Linear Flow Channel Reactor was developed in which the formation of the floating sulphur biofilm could be optimised and studied under controlled conditions. In this study the sulphide feed was sourced from a lignocellulose packed bed reactor treating a synthetic acid mine water (2 000 mg∙l -1 Na 2 SO 4 solution) and the Liner Flow Channel Reactors (surface area 1.1 m 2 and 2.2 m 2 ) were operated in a controlled environment chamber. The floating sulphur biofilm was harvested by settling to the bottom of the reactor where it remained largely unreacted until removed. It was shown that up to 88% of sulphide in the feed stream may be removed in this way and that this was achieved mainly by oxidation of sulphide to sulphur (including a polysulphide fraction). A mass balance accounting for the process showed that up to 66% of total sulphur species entering the system were recovered as So. Oxidation of sulphide to thiosulphate and sulphate was not found to be significant. A fraction of fine particulate sulphur is released into the stream on harvesting of the biofilm which does not readily settle in the reactor and may thus be lost to the mass balance account. The effects of temperature, loading rate and reactor surface area were investigated in optimising the performance of the reactor. Scale-up application studies in the use of the Linear Flow Channel Reactor in an acid mine drainage passive treatment environment have been undertaken in field studies. Keywords: floating sulphur biofilms, acid mine drainage, AMD passive treatment, linear flow channel reactor, sulphur biotechnology

Oxidation behavior and kinetics of sulfide by synthesized manganese oxide minerals

Purpose Sulfur is distributed widely in soils and sediments. Sulfide oxidation causes acid mine wastewater, toxicity, and corrosion. Manganese oxide minerals usually affect the migration, transformation, and fate of sulfur. To understand the oxidation behaviors of S2− and influence factors, reaction process and kinetics were investigated by using different manganese oxides.

Using the Low-Cost Waste Materials for Heavy Metals Removal from the Mine Wastewater

The possibility of application of low-cost and easily available materials such as cardboard or sawdust for the heavy metals removal from the acid mine water was investigated. The sawdust was obtained from oak and fir-wood. Those materials were tested on the real acid mine wastewater that contained copper, iron, zinc, nickel, and manganese in the concentrations above the maximal allowed level. The adsorption degrees of those elements were investigated. The results were shown that the iron was mechanically removed. The results of chemical analysis of effluent obtained by the use of sawdust from fir-wood indicate that the values for iron and nickel ions were lower than allowed values by the legislative direction. The highest value for copper adsorption degree of 98.31% was achieved at pH value of 7.94. Content of manganese in the effluent and at the end of process, was near the initial value. Using the sawdust obtained from oak as the adsorption material, zinc and manganese concentration in the effluent was near the start values and copper and iron content was decreased but the values were higher than allowed.Using the cardboard, the copper adsorption degree was up to 95 mass%, iron content was under the limit value for the applied chemical detection method. The content of the manganese was not changed and the content of the zinc was decreased but the concentration was over the maximum allowed value.

Treatment of Acid Mine Drainage by Sulfate Reducing Bacteria and Iron at Room Temperature

This study describes a new method to treat acid mine wastewater containing high amounts of heavy metals and sulfate by biotechnology. Sulfate reducing Bacteria (SRB) was inoculated in an up-flow multiple bed bioreactor treating practical wastewater. In addition to precipitation processes, water purification was also possible with the metabolism process of microorganisms. Iron dust was added to the system to enhance the activity of SRB and ensure the treatment efficiency. The results indicates that treating acid mining drainage using SRB and iron at room temperature (20°C~25°C) is possible, the reduction rate of sulfate is up to 61%, pH of wastewater raises from 2.75 to 6.2 and the copper concentration of effluent is less than 0.2 mg/L.

Heavy Metal Removal and Neutralization of Acid Mine Waste Water ‐ Kinetic Study

AbstractThe influence of the apatite on the efficiency of neutralization and on heavy metal removal of acid mine waste water has been studied. The analysis of the treated waste water samples with apatite has shown an advanced purification, the concentration of the heavy metals after the treatment of the waste water with apatite being 25 to 1000 times less than the Maximum Concentration Limits admitted by European Norms (NTPA 001/2005). In order to establish the macro‐kinetic mechanism in the neutralization process, the activation energy, Ea, and the kinetic parameters, rate coefficient of reaction, kr, and kt were determined from the experimental results obtained in “ceramic ball‐mill” reactor. The obtained values of the activation energy Ea >> 42 kJ mol−1 (e.g. Ea = 115.50 ± 7.50 kJ mol−1 for a conversion of sulphuric acid ηH2SO4 = 0.05, Ea = 60.90 ± 9.50 kJ mol−1 for ηH2SO4 = 0.10 and Ea = 55.75 ± 10.45 kJ mol‐1 for ηH2SO4 = 0.15) suggest that up to a conversion of H2SO4 equal 0.15 the global process is controlled by the transformation process, adsorption followed by reaction, which means surface‐controlled reactions. At a conversion of sulphuric acid ηH2SO4 > 0.15, the obtained values of activation energy Ea < 42 kJ mol‐1 (e.g. Ea = 37.55 ± 4.05 kJ mol‐1 for ηH2SO4 = 0.2, Ea = 37.54 ± 2.54 kJ mol‐1 for ηH2SO4 = 0.3 and Ea = 37.44 ± 2.90 kJ mol‐1 for ηH2SO4 = 0.4) indicate diffusion‐controlled processes. This means a combined process model, which involves the transfer in the liquid phase followed by the chemical reaction at the surface of the solid. Kinetic parameters as rate coefficient of reaction, kr with values ranging from (5.02 ± 1.62) 10‐4 to (8.00 ± 1.55) 10‐4 (s‐1) and transfer coefficient, kt, ranging from (8.40 ± 0.50) 10‐5 to (10.42 ± 0.65) 10‐5 (m s‐1) were determined.

High-Rate Fluidized-Bed Ferric Sulfate Generation for Hydrometallurgical Applications

An overview is presented of a multi-year research effort on developing high-rate fluidized-bed bioprocesses for ferric sulfate production to be used as a unit process in various hydrometallurgical applications including indirect tank leaching of ore concentrates, regeneration of heap leach liquors and control of iron containing acidic mine wastewater. Iron oxidation rates of over 26 kg m-3 h-1 were achieved at hydraulic retention times of less than 1 h at 37 °C. Oxygen supply became the rate-limiting factor even with 99.5% dioxygen aeration. Fe2+ oxidation proceeded at pH below 1 even in the presence of 60 g Fe3+ L-1 allowing the regeneration of concentrated ferric sulphate solutions required in indirect tank leaching of sulfidic ore concentrate applications. Of several tested FBR carrier materials activated carbon was the most suitable based on its availability, long-term durability and the achieved high iron oxidation rates. Jarosite precipitates accumulating to the top of the inert carrier materials played an important role in the FBR biomass retainment. For regeneration of synthetic and actual sulfidic ore heap leaching liquors, a gravity settler was installed in the recycle line of the FBR. The system produced iron precipitates with good settling characteristics and settling tank effluent with low turbidity and suspended solids concentrations. These results revealed the potential of FBR process in both heap leach liquor regeneration and controlling the iron containing waste streams. The PCR-DGGE-partial seguencing of the 16S rRNA gene protocol revealed that the FBR culture at 25-37 °C remained dominated by Leptospirillum ferriphilum over a range of operational conditions studied over the years. A modeling approach for managing Fe3+ production by FBR in combination with heap leaching was based on an artificial neural network-back propagation algorithm (ANN-HEAP) and resulted in excellent match between the measured and the predicted concentrations. High-rate fluidized-bed iron oxidation is amenable to regeneration of tank and heap leaching solutions as well as controlling iron containing waste streams.

Removal and recovery of metal ions from acid mine drainage using lignite—A low cost sorbent

Acid mine drainage (AMD), has long been a significant environmental problem resulting from the microbial oxidation of iron pyrite in presence of water and air, affording an acidic solution that contains toxic metal ions. The main objective of this study was to remove and recover metal ions from acid mine drainage (AMD) by using lignite, a low cost sorbent. Lignite has been characterized and used for the AMD treatment. Sorption of ferrous, ferric, manganese, zinc and calcium in multi-component aqueous systems was investigated. Studies were performed at different pH to find optimum pH. To simulate industrial conditions for acid mine wastewater treatment, all the studies were performed using single and multi-columns setup in down flow mode. The empty bed contact time (EBCT) model was used for minimizing the sorbent usage. Recovery of the metal ions as well as regeneration of sorbent was achieved successfully using 0.1 M nitric acid without dismantling the columns.

Removal of pollutants from acid mine wastewater using metallurgical by-product slags

The removal of pollutants from acid mine drainage using metallurgical by-product slags was studied in laboratory scale. Metallurgical by-product furnace slags were used as sorbents for metal ions and dispersed air column flotation was employed for the solid/liquid separation of the loaded slags. Batch sorption/pH/kinetic studies were conducted using simulated Cu and Pb bearing wastewater. The calcium glass type of slags had high surface area and porosity. Promising result was succeeded from the combined process of slag sorption/flotation on the treatment of an acid mine drainage from a South African gold mine.

Effects of Copper Pollution on the Benthic Community in the Le An River, China

ABSTRACT Pollution by heavy metals and acid mine wastewater completely eradicated the benthic community from a section of the Le An River, China. Downstream changes in the benthic community directly reflected the degree of metal pollution in the sediments.

The effect of growth conditions on the biodegradation of tributyl phosphate and potential for the remediation of acid mine drainage waters by a naturally-occurring mixed microbial culture.

The biodegradation of tributyl phosphate (Bu3-P, TBP), releasing phosphate at a high enough concentration locally to precipitate uranium from solution, was demonstrated by a mixed culture consisting primarily of pseudomonads. The effect of various parameters on Bu3-P biodegradation by growing cells is described. Growth at the expense of Bu3-P as the carbon and phosphorus source occurred over a pH range from 6.5 to 8, and optimally at pH 7. Bu3-P biodegradation was optimal at 30 degrees C, reduced at 20 degrees C and negligible at 4 degrees C and 37 degrees C. Incorporation of Cu or Cd inhibited, and Ni, Co and Mn reduced its degradation. Inorganic phosphate (above 10 mM) and kerosene (up to 1 g/l) reduced Bu3-P biodegradation significantly, but nitrate had no effect. Sulphate (10-100 mM) was inhibitory. When pregrown biomass was used the fastest rates of tributyl and dibutyl phosphate biodegradation were 25 mumol h-1 mg protein-1 and 37 mumol h-1 mg protein-1 respectively. Microcarrier-immobilised biomass decontaminated uranium-bearing acid mine waste water by uranium phosphate precipitation at the expense of Bu3-P hydrolysis in the presence of 35 mM SO(4)2-. At pH 4.5, 79% of the UO2(2)+ was removed at a flow rate of 1.4 ml/h on a 7-ml.test column.

Use of immobilized microorganisms for bioremediation of acidic mine wastewater

Use of immobilized microorganisms for bioremediation of acidic mine wastewater

Electroprecipitation treatment of acid mine wastewater

The utilization of electroprecipitation for the treatment of acid solutions associated with the non-ferrous mining industry on a laboratory scale is explored. The electrolytic couple involved in the active process includes a consumable metal anode and an inert cathode. Mechanistically, oxidation of the anode is matched by the reduction of dissolved hydrogen ion to H 2 gas resulting in a pH increase in solution. Heavy metal removal is accomplished by either precipitation of hydrous oxides or by adsorption. Reduction of the solution metal content of from 100% for Al 3+ to 25% for Mn 2− is accomplished using a stainless steel rod anode; final solution pH stabilizes at a value of 4.9. Stabilization of solution pH reflects the attainment of kinetic equilibrium with respect to the rates of oxidation at the anode and diffusion of the oxidized products to the cathode where they precipitate as the hydroxide. Zinc and lead sacrificial anodes are also studied.