Acute and Chronic Toxicity of Acid Mine Drainage to the Activated Sludge Process

The combined treatment of acid mine drainage (AMD) and municipal wastewater using the activated sludge process is an innovative approach to AMD remediation. The toxicity of synthetic AMD to activated sludge was evaluated using oxygen uptake rate (OUR) inhibition tests, which showed that activated sludge can withstand high proportions of AMD (EC₅₀ 19?C52% AMD by volume). The EC₅₀ values of municipal and industrial activated sludges were significantly different (p?<?0.05), with municipal sludges exhibiting higher tolerance to AMD. Although the EC₅₀ values for heterotrophic and nitrifying activated sludges were not statistically significantly different, the EC₅₀ values for heterotrophic bacteria were generally higher. Laboratory-based sequencing batch reactors were used to examine the treatability of AMD. Increased concentrations of COD and suspended solids, associated with turbidity and poor floc morphology, were observed in the final effluent after extended AMD loading. Protozoan community structure changed during the AMD loading period, and overall abundance tended to decrease over time. OUR decreased in the AMD-loaded reactors, particularly in the reactor receiving the highest AMD load, indicating reduced biomass activity over the acclimatization period. Results from OUR inhibition tests on the acclimatized activated sludge indicated that over a relatively short timescale (21?days), the activated sludge microbial community can adapt to AMD sufficiently so that shock loads of metals and acidity do not significantly inhibit OUR. These preliminary studies indicate that it is possible to treat AMD successfully in admixture with municipal wastewater using the activated sludge process.     

Valorization of acid mine drainage treatment sludge as remediation component to control acid generation from mine wastes,part 2: Field experimentation

The possibility of using acid mine drainage (AMD) treatment sludge as a cover component to control AMD generation from mine wastes was investigated through laboratory characterization and kinetic column testing (companion paper). The results showed that mixtures of sludge and waste rock, and sludge and tailings, may be integrated in an AMD prevention and control strategy at Doyon mine site (northwestern Quebec, Canada). In order to further investigate these scenarios in realistic climatic conditions, instrumented field test cells were installed on site to evaluate the performance of the mixtures to control AMD generation from tailings and waste rock under natural field conditions. The main findings from two seasons of monitoring are presented in the paper. The waste rock-sludge mixture placed over waste rock was able to reduce the generation of AMD from the waste rock, therefore confirming lab results, and was able to produce a neutral effluent with low concentrations of dissolved metals. The tailings-sludge mixture placed over tailings, with an evaporation protection layer, maintained a high volumetric water content and reduced sulphide oxidation from the tailings as exhibited by a neutral effluent. Monitoring of the field cells will continue to provide valuable information on the possible sludge valorization options.     

Start-up,adjustment and long-term performance of a two-stage bioremediation process,treating real acid mine drainage,coupled with biosynthesis of ZnS nanoparticles and ZnS/TiO2 nanocomposites

Acid mine drainage (AMD) generation is a widespread environmental problem in Europe, including Portugal. Previous experience has shown that a combined process consisting of an anaerobic sulphate-reducing bioreactor, following neutralization with calcite tailing, produces water complying with legal irrigation requirements from synthetic AMD. Aiming the treatment of real AMD a new bioreactor was inoculated with a SRB enrichment obtained from sludge from a local WWTP anaerobic lagoon. In the initial batch phase, sulphate supplementation was needed to achieve high sulphate-reducing bacteria counts before continuous feeding of AMD was started. The system quickly achieved good performance, proving it is easy to start-up. However, this time the neutralization step failed to keep bioreactor affluent pH higher than 5 for longer than three weeks. This was due to armouring of calcite by precipitates of various metals present in AMD. A new configuration, replacing a packed-bed column by a shallow contact basin, proved to be more robust, avoiding clogging, short-circuiting and providing long-term neutralization. The treated effluent, with excess of biologically generated sulphide, was successfully used to synthesize zinc sulphide nanoparticles, both in pure form and as a ZnS/TiO₂ nanocomposite, thus proving the feasibility of coupling an AMD bioremediation system with the synthesis of metal sulphide nanoparticles and nanocomposites.     

Removal of Metals and Acidity from Acid Mine Drainage Using Municipal Wastewater and Activated Sludge

Co-treatment of acid mine drainage (AMD) and municipal wastewater (MWW) using the activated sludge process is an innovative approach to AMD remediation that utilizes the alkalinity of MWW and the adsorptive properties of the wastewater particulates and activated sludge biomass to buffer acidity and remove metals. The capacity of these materials to treat AMD was investigated in batch mode metal removal tests using high-strength synthetic AMD (pH 2.8, Al 120–200 mg/L, Cu 18–30 mg/L, Fe 324–540 mg/L, Mn 18–30 mg/L, and Zn 36–60 mg/L). Using material from a range of MWW treatment plants, the performance of screened and settled MWW, activated sludges with mixed liquor suspended solids (MLSS) concentrations of 2.0 and 4.0 g/L, and return activated sludges with 6.0 and 7.4 g/L MLSS were compared. Similar trends were observed for the MWW and activated sludges, with removal efficiency generally decreasing in the order Al = Cu > Mn > Zn > Fe. Trends in Fe removal using settled MWW and activated sludges were highly variable, with removal <30 %. Using activated sludges, average removal efficiencies for Al, Cu, Mn, and Zn were 10–65 %, 20–60 %, 10–25 %, and 0–20 %, respectively. Sludge solids concentration was an important controlling factor in metal removal, with removal of Al, Cu, Mn, and Zn increasing significantly with solids concentration. Municipal wastewaters had greater neutralization capacities than activated sludges at high AMD loading ratios. Mixing AMD with screened MWW gave the highest removal efficiency for all metals, achieving average removal of 90–100 % for Al, Cu, and Fe, 65–100 % for Zn, and 60–75 % for Mn. These empirical findings are useful for developing process design parameters in co-treatment systems. Utilizing MWW and activated sludge to remediate AMD can potentially reduce materials and energy requirements and associated costs.     

Valorisation of acid mine drainage treatment sludge as remediation component to control acid generation from mine wastes,part 1: Material characterization and laboratory kinetic testing

In operating mines, acid mine drainage (AMD) is often treated using lime treatment. This process generates a significant amount of sludge that contains metal hydroxide precipitates, gypsum, and unreacted lime. The sludge may have interesting geotechnical and geochemical properties to be used as a part of covers (oxygen barriers) to prevent AMD generation from waste rocks and tailings. The main results of a project aiming to evaluate the use of sludge from the Doyon mine site (Canada) as a material in mine site rehabilitation are presented. The first part of the project involved detailed characterization of sludge, waste rock, and tailings samples. Then, laboratory column leaching tests were performed to evaluate the performance of the mixtures to control AMD produced by tailings and waste rocks. It was found that a sludge–waste rock mixture placed over waste rock reduces the metal loads in the column effluent, which remained acidic, as well as a mixture of sludge and tailings deposited over tailings can reduce metal content in effluents from tailings.     

Upper and Lower Concentration Thresholds for Bulk Organic Substrates in Bioremediation of Acid Mine Drainage

Acidic pit lakes can form in open cut mine voids that extend below the groundwater table. The aim of this research was to determine what bulk organic material concentrations best stimulated sulphate-reducing bacteria (SRB) for acid mine drainage (AMD) treatment within a pit lake. An experiment was carried out to assess the effect of different substrate concentrations of sewage sludge on AMD bioremediation efficiency. Experimental microcosms were made of 300 mm long and 100 mm wide acrylic cores, with a total volume of 1.8 L. Four different concentrations of sewage sludge (ranging from 30 to 120 g/L) were tested. As the sewage sludge concentration increased, the bioremediation efficiency also increased, reflecting the higher organic carbon concentrations. Sewage sludge contributed alkaline materials that directly neutralised the AMD in proportion to the quantity added and therefore played a primary role in stimulating SRB bioremediation. The lowest concentration of sewage sludge (30 g/L) tested proved to be inadequate for effective SRB bioremediation. However, there were no measurable beneficial effects on SRB bioremediation efficiency when sewage sludge was added at concentrations >60 g/L. We compared our results with existing literature data to develop a conceptual model for remediation of AMD in pit lakes through organic material amendments. The model indicated that labile organic carbon availability was more important to the bioremediation rate than AMD strength, so long as iron and sulphate concentrations were not limiting. The conceptual model also indicates that bioremediation may still occur when only low concentrations of organic carbon are present in the pit lakes, albeit at a very slow rate. The model also demonstrates the presence of an organic material amendment threshold where excess organic carbon does not measurably influence the final outcome. The conceptual model defined is well supported by the results of the microcosm experiment.     

Enhancement of Sludge Sedimentation Properties in a Concentrated Acid Mine Drainage Using Nano- and Micro-magnetite Particles

Conventional treatment of AMD involves neutralization with consequent precipitation of metals as hydroxides. In AMD with a high concentration of metals, the settling rate of the sludge/water interface is low. We investigated the use of nano- and micro-magnetite particles to assist the settling and thickening of floc particles. The magnetite was produced from ferrous sulphate crystals (melanterite, Fe₂SO₄·7H₂O) obtained by leaching pyrite from a coal mine. AMD was obtained from the treatment plant at the same mine and the water was neutralized with Ca(OH)₂ at pH 8.7?±?0.1. Laboratory studies were conducted in 1 L test tubes with and without the addition of magnetite particles and a flocculant. Sedimentation curves (interface settling) were generated to evaluate the rate of sedimentation. For the studied effluent, the best option was 4 g L^?1 of magnetite particles and 5 mg L^?1 of high molecular weight anionic polyacrylamide. The magnetite particles were recovered magnetically from the sludge with ≈ 90% efficiency. Thus, the combined use of magnetite and a flocculant increased the sludge settling rate and, consequently, reduced the area needed for settling basins.

     

麦饭石生物固定化颗粒最优成分配比正交试验

针对煤矿酸性废水(AMD)处理效果不佳的问题,采用L9(34)正交试验,考察了麦饭石生物固定化颗粒中SRB污泥、玉米芯、铁屑各成分的最优配比,并按此配比制备生物固定化颗粒,对成品颗粒进行物相分析。结果显示,在SRB污泥含量30%,玉米芯含量5%,铁屑含量5%条件下,麦饭石生物固定化颗粒处理AMD性能最佳。SEM和XRD分析结果表明,制备的生物固定化颗粒结构性能优良,纯度较高。     

Lime Treatment of Mine Drainage at the Sarcheshmeh Porphyry Copper Mine,Iran

Laboratory and field treatment tests were performed to evaluate the effectiveness of lime treatment for mitigation of environmental effects of acid mine drainage (AMD) at the Sarcheshmeh porphyry copper mine. AMD associated with the rock waste dumps is contaminated with Al (>36,215 μg/L), Cd (>105 μg/L), Co (>522 μg/L), Cu (>53,250 μg/L), Mn (>42,365 μg/L), Ni (>629 μg/L), and Zn (>12,470 μg/L). The concentrations of other metals (Fe, Mo, Pb, and Se) are low or below detection limits (As, Cr, and Sb). Due to the very high Al and Mn content and the low concentration of Fe, a two-stage lime treatment method was chosen for the laboratory tests. In the first stage, the AMD was treated at four pH set points: 7.5, 8.9, 9, and 10. In the second stage, after removing the sludge at pH 9, treatment was continued at pH 10 and 11. The results indicated that a two-stage treatment method was not necessary because elements such as Al, Cu, Co, and Zn were easily treated at pH 7.5, while complete removal of Cd, Mn, and Ni only required a pH of 10. Increasing pH during the treatment process only caused a slight increase in Al. Field treatment tests support the laboratory results. Lime treatment of highly contaminated AMD from dump 11, using simple low density sludge pilot scale equipment, show that contaminant metals are treatable using this method. The mean treatment efficiency for contaminant metals was 99.4% for Al, % for Cd, 99.6% for Co, 99.7% for Cu, 98.5% for Mn, 99.7% for Ni, 99% for U, and 99.5% for Zn. The optimum pH for AMD treatment by lime was in the range of 9–10. The produced sludge in the treatment process was highly enriched in the contaminant metals, especially Cu (>7.34%), Al (>4.76%), Mn (>2.94%), and Zn (>1.25%). A correlation coefficient matrix indicates that the distribution pattern of the contaminant metals between soluble and precipitated phases is consistent with the hydrochemical behavior of the metals during the lime treatment process.     

铁屑协同SRB污泥固定化颗粒处理AMD动态试验研究

针对煤矿酸性废水(AMD)具有污染组分多、环境污染严重、传统处理方法容易造成二次污染及占地面积大等问题,采用微生物固定化技术制备高活性SRB污泥固定化颗粒,构建以1#(不含铁屑)、2#(含铸铁屑)和3#(含生铁屑)SRB污泥固定化颗粒为填料的动态柱实验模型,研究各基质材料处理AMD的效果和机理。结果表明:动态柱对AMD处理效果3#2#1#,3#动态柱的出水pH值为8.06,TFe、Mn2+、SO42-平均去除率分别达到99.93%、48.38%、45.85%,COD释放量为60 mg/L。因此,生铁屑作为固定化颗粒主要基质材料,与SRB协同体系能够强化固定化颗粒处理AMD的过程,具有较强的抗冲击负荷能力。     

Use of organic covers for acid mine drainage control

Organic covers may be used to prevent diffusion of oxygen into reactive sulphide wastes and subsequently to eliminate sulphide compounds oxidation and generation of acidic waters. The main advantages over other types of covers are related with their low hydraulic permeability, high cation exchange capacity and high alkalinity. In addition, the establishment of organic covers, which is considered as a low cost solution for the prevention of acid mine drainage generation, does not disturb the natural environment, since they consist of industrial wastes rather than natural materials and allow the development of vegetation, which improves the aesthetics of the reclaimed areas. However, treatment of municipal sewage sludge is necessary prior to discharge, in order to minimize potential health and environmental risks, resulting from the presence of toxic elements.In the present paper, all processes associated with the function of an organic cover are described and discussed, including potential health and environmental risks resulting from land application of municipal sewage sludge. In addition, preliminary laboratory data, derived from the application of organic covers over reactive sulphidic concentrates are presented and discussed, in order to evaluate the performance of the covers and to determine the critical factors affecting their performance. The final aim of this research work is the development of an experimental model, that predicts the performance of an organic cover, by taking into account critical parameters such as annual rainfall rate, organic material height, initial moisture and moisture under saturation conditions.     

Use of activated silica sol as a flocculant in the treatment of acid mine drainage to promote sludge stability

The most common treatment for acidic drainage is lime neutralization. The process involves neutralization and precipitation of a metal hydroxide-gypsum sludge using a flocculant, generally Percol. In the short term, the sludge is stable, but in the long term, any tendency of pH to drop can re-dissolve metal hydroxides and contaminate the surrounding area and groundwater. The use of activated silica sol, an inorganic silicate polymer used in municipal water treatment, as a replacement to Percol is investigated to improve long term stability of sludge. Silica sol is an effective flocculant, has neutralization potential, and forms metal–silica bonds more resistant to pH variation than metal hydroxides. Various mine effluents and simulated solutions were treated with lime and silica sol or Percol to pH 9–10. Results show that settling characteristics with low dosages of silica sol and Percol are similar. Leachability tests showed that the stability of the sludge improved when silica sol was used for one cycle, and after 4 cycles results were similar to Percol. Activated silica sol, therefore, has the potential to increase sludge stability in a single stage lime treatment process.     

A novel low pH sulfidogenic bioreactor using activated sludge as carbon source to treat acid mine drainage (AMD) and recovery metal sulfides: Pilot scale study

In this work a pilot scale sulfidogenic bioreactor was used to treat acid mine drainage (AMD) from Zijinshang copper mine. In this process, S²⁻ produced in the Up-flow Anaerobic Sludge Bed (UASB) reactor were recycled in the two precipitation tanks for copper and iron precipitation, activated sludge from local waste water treatment plant was used as the carbon source. The reactor were steady operated in acid condition (with no pH control) for 4 month, AMD with a copper concentration of 100–120 mg/L, iron concentration of 170–200 mg/L, sulfate concentration of 2000–2500 mg/L and pH of 2.34–2.56, were feeding into the reactor under a feed rate of 1 m³/days and HRT of 3 days, copper and iron removal were 60.95%, 97.83% respectively. The precipitant in the precipitation tank containing 15.7% Cu and 22.66% Fe, thus indicating a recovery possibility of copper by pyrometallurgy process. From these results we can conclude that an SRB process would be a viable method of treating Zijinshan AMD.     

Secondary Sulphate Minerals in a Cyprus-Type Ore Deposit,Apliki, Cyprus: Mineralogy and Its Implications Regarding the Chemistry of Pit Lake Waters

The Apliki mine, a Cyprus-type massive sulphide deposit in Cyprus, was exploited for copper until the mid-1970s. Abandonment of the mine left a deep pit that now hosts a lake fed by surface runoff from the surrounding mineralized zone and hydrothermally altered basalt. Oxidation of the sulphide minerals and factors such as climate and terrain relief control the water–rock interactions that generate acid mine drainage (AMD), which ultimately affects and defines the quality of the lake waters. Pyrite and chalcopyrite constitute an almost inexhaustible sulphide source that leads to the formation of a variety of secondary iron and copper mineral phases. The secondary mineral assemblages in the ore zone are mainly iron, copper, and magnesium sulphates, whereas the lakeshore assemblage is dominated by magnesium-, calcium-, sodium-, and aluminum-bearing sulphate minerals. Near the lakeshore, the highly soluble iron sulphate salts dissolve in the lake water, increasing its iron content. Other less soluble salts are more stable and persist in the lakeshore environment. The precipitation and dissolution of efflorescent salts, and, to a lesser extent, the oxidative weathering of the remaining ore minerals, produce additional AMD. Due to the perpetual cycle of mineral dissolution and precipitation, the lake has a low pH (≈3) and contains high concentrations of some contaminants. The processes that contribute to the formation of the efflorescent mineral assemblages and their environmental impact on pit lake waters, and indeed the complete geochemical system, is a typical example of secondary mineral formation in Cyprus-type Cu-pyrite massive sulphide ore deposits.     

The application of wood ash as a reagent in acid mine drainage treatment

The paper deals with a possible utilisation of wood ash as a reagent in treating acid mine drainage (AMD) from opencast mining of brown coal. Wood ash samples were obtained having combusted deciduous and coniferous tree wood in a household furnace. The dominant mineral phases in wood ash are calcite, quartz, lime and periclase. The used AMD is characteristic of high contents of sulphates, iron, manganese, heavy metals and low pH. The AMD treatment process included dosing of wood ash to adjust pH values about 8.3 (a dose of 0.5 g l⁻¹) or calcium hydroxide (a dose of 0.2 g l⁻¹) for comparison. The reaction time was 20 min. Dosing of wood ash in AMD resulted in an increase of pH in solution from 3.5 to 8.3, which caused the removal of metal ions mainly by precipitation, co-precipitation and adsorption. Comparing the application of Ca(OH)₂ in AMD treatment, at an almost identical pH value the concentrations fell in both cases for Fe, Mn, As, Co, Cu, Ni, Zn, Mg, Al and Mo. Applying wood ash the drop was even more distinct in Mn, Zn and Mg. The results of sedimentation tests in an Imhoff cone confirm that the settling capacities of sludge using wood ash are significantly better than when using calcium hydroxide in acid mine drainage treatment.     

Treatment of acid mine drainage through a ferrite formation process in central Hokkaido,Japan: Evaluation of dissolved silica and aluminium interference in ferrite formation

A two-step neutralization process, leading to the formation of ferrites has been developed for the treatment of acid mine drainage (AMD). In the first neutralization step magnesium oxide was used to raise the pH to around 4.5 to eliminate aluminium (Al) and to reduce the silica (Si) concentration. In the second neutralization step sodium hydroxide was used to complete the neutralization and to precipitate ferrous and ferric hydroxides, from which ferrite could be formed. The AMD of a closed gold mine in central Hokkaido, Japan was treated in a continuous-flow bench-scale plant of the process. During the first neutralization step the removal of Si was more difficult than the removal of Al; the presence of both Al and Si interfered in the ferritization of the sludge. When the Al removal decreased from 94.5% to 64.3% the magnetism per unit mass of the sludge was reduced by 36.7% and when the Al removal decreased to 21.8% the magnetism of the sludge was reduced by 51.5%. The interference of coexisting Si was even stronger: the sludge showed a 26% and 36.7% decrease in magnetism when the removal of Si was reduced by 15% and 18%, respectively.     

A Geotechnical Solution to Reduce Acid Mine Drainage Generation at Recreio Mine

Coal mining is frequently associated with acid mine drainage (AMD) generated by tailings and waste dumps containing sulphide minerals. A practical and economical alternative to minimise AMD generation is to avoid the contact between water and waste dumps using a compacted soil cover. This study evaluates the use of distinct raw materials as cover layers. The study area was an open pit coal mine in the south of Brazil. Geotechnical characterization, physical, chemical and mineralogical analyses were carried out on two different soils from this mine. Hydraulic conductivity tests were performed using Flexible-Wall Permeameter. The results obtained from the hydraulic conductivity tests for two compacted soils suggest their applicability as impermeable layers. Considering the operational aspects at the mine and the characteristics determined for the soils a new construction scheme for the dump site was suggested.     

Performance of Semi-passive Systems for the Biological Treatment of High-As Acid Mine Drainage: Results from a Year of Monitoring at the Carnoulès Mine (Southern France)

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.

     

污泥活性炭对焦化废水中COD的深度处理

以污水厂脱水污泥、锯末和焦油的混合物为原料,采用ZnC l2和KOH为活化剂制备出过渡孔发达、强度大的污泥活性炭S-AC(ZnC l2)和S-AC(KOH),并将其应用于焦化废水生化出水中COD的深度处理。结果表明:2种吸附剂对焦化废水中COD的吸附行为均符合Langmuir等温方程,吸附量随着温度的升高而增大。伪二级方程可较好地描述2种吸附剂对COD的吸附行为,静态动力学数据结果符合液膜扩散方程,液膜扩散为吸附过程的主控步骤。动态吸附与脱附研究表明:吸附流速为10 BV/h(BV为吸附剂装柱体积)时,S-AC(KOH)对COD的穿透吸附量和饱和吸附量分别为11.75 mg/mL和13.54 mg/mL;S-AC(ZnC l2)对COD的穿透吸附量和饱和吸附量分别为12.46 mg/mL和14.53 mg/mL;以质量分数5%NaOH为脱附剂,脱附流速为5 BV/h时,吸附剂的脱附率可达90%以上。     

Removal of Metals and Acidity from Acid Mine Drainage Using Liquid and Dried Digested Sewage Sludge and Cattle Slurry

The metal removal and neutralization capacities of digested sewage sludges from municipal wastewater treatment plants, cattle slurry (liquid manure), and Biofert granules (dried granular anaerobic sludge) were compared under batch conditions using synthetic AMD (pH 2.8) containing high concentrations of Al, Cu, Fe, Mn, Pb, and Zn (100, 15, 270, 15, 2, and 30 mg/L, respectively). The effects of contact time and solids concentration were examined. Metal removal was variable for all materials. Contact time had a significant effect, with total removal often increasing over the experimental time interval (i.e. 30 min to 24 h). Removal efficiency (%) was generally highest for Cu, Pb, and Al, while Mn and Zn were the least removed. Cattle slurry was the best material for metal removal, with the following maximum removals at a solids concentration of 12.9 g/L: Cu >98 %, Al >98 %, Fe >60 %, Mn >18 %, Pb >96 %, and Zn >60 %. Metal removal using digested sewage sludge reached 88 % for Al, 98 % for Cu, 94 % for Pb, and 30 % for Zn. Neutralization was complete within 30 min after AMD was mixed with digested sludges or cattle slurry, with the pH reaching a maximum of 5.5 with the slurry. In contrast, neutralization by the Biofert granules only reached equilibrium after 300 min, and pH remained <4.0 except at high solids concentrations. It appears that recycled waste-derived organic materials can neutralize AMD and remove dissolved metals by adsorption and precipitation, creating a more treatable waste stream or one that could be discharged directly to surface water. Potential methods of safe disposal of metal-enriched organic materials are discussed.