Passive Treatment Technologies Research Articles

Heavy metal removal by the photosynthetic microbial biomat found within shallow unit process open water constructed wetlands

Nature-based solutions offer a sustainable alternative to labor and chemical intensive engineered treatment of metal-impaired waste streams. Shallow, unit process open water (UPOW) constructed wetlands represent a novel design where benthic photosynthetic microbial mats (biomat) coexist with sedimentary organic matter and inorganic (mineral) phases, creating an environment for multiple-phase interactions with soluble metals. To query the interplay of dissolved metals with inorganic and organic fractions, biomat was harvested from two distinct systems: the demonstration-scale UPOW within the Prado constructed wetlands complex (“Prado biomat”, 88 % inorganic) and a smaller pilot-scale system (“Mines Park (MP) biomat”, 48 % inorganic). Both biomats accumulated detectable background concentrations of metals of toxicological concern (Zn, Cu, Pb, and Ni) by assimilation from waters that did not exceed regulatory thresholds for these metals. Augmentation in laboratory microcosms with a mixture of these metals at ecotoxicologically relevant concentrations revealed a further capacity for metal removal (83–100 %). Experimental concentrations encapsulated the upper range of surface waters in the metal-impaired Tambo watershed in Peru, where a passive treatment technology such as this could be applied. Sequential extractions demonstrated that metal removal by mineral fractions is more important in Prado than MP biomat, possibly due to a higher proportion and mass of iron and other minerals from Prado-derived materials. Geochemical modeling using PHREEQC suggests that in addition to sorption/surface complexation of metals to mineral phases (modeled as iron (oxyhydr)oxides), diatom and bacterial functional groups (carboxyl, phosphoryl, and silanol) also play an important role in soluble metal removal. By comparing sequestered metal phases across these biomats with differing inorganic content, we propose that sorption/surface complexation and incorporation/assimilation of both inorganic and organic constituents of the biomat play a dominant role in metal removal potential by UPOW wetlands. This knowledge could be applied to passively treat metal impaired waters in analogous and remote regions.

Photocatalytic treatment of organoselenium in synthetic mine-impacted effluents.

Biological selenium reduction processes are commonly employed as the best available technology (BAT) for selenium removal; however, as a by-product they produce trace amounts of organoselenium compounds with orders of magnitude greater bioaccumulation potential and toxicity. Here, we assessed buoyant photocatalysts (BPCs) as a potential passive advanced oxidation process (P-AOP) for organoselenium treatment. Using a synthetic mine-impacted water solution, spiked with selenomethionine (96 μg/L) as a representative organoselenium compound, photocatalysis with BPCs fully eliminated selenomethionine to <0.01 μg/L with conversion to selenite and selenate. A theoretical reaction pathway was inferred, and a kinetics model developed to describe the treatment trends and intermediates. Given the known toxic responses of Lepomis macrochirus and Daphnia magna to organoselenium, it was estimated that photocatalysis could effectively eliminate organoselenium acute toxicity within a UV dose of 8 kJ/L (1-2 days solar equivalent exposure), by transformation of selenomethionine to less hazardous oxidized Se species. Solar photocatalysis may therefore be a promising passive treatment technology for selenium-impacted mine water management.

Performance of denitrifying bioreactors in southern Alberta

Denitrifying bioreactors are an edge-of-field passive treatment technology that can reduce nutrient export from subsurface drainage waters to aquatic ecosystems. This technology is gaining popularity in many parts of the world including eastern Canada, but has not gained widespread acceptance in the Canadian prairies. This study evaluated the performance of pilot-scale denitrifying bioreactors for removing nitrate under agricultural field conditions in southern Alberta. Local agricultural residues– barley straw and hemp straw– were tested in comparison to wood chips for nutrient removal potential under varying retention times and temperatures during the growing season. Results from this study identified that the primary factors affecting nitrate-nitrogen removal in this region were temperature, flow rate, carbon source material and the age of the materials in the bioreactor. Both agricultural residues exceeded wood chip performance in the first year of operation, but all fill materials performed similarly in the second year of operation– the percent reduction of nitrate-nitrogen dropped from 72% to 34% and 55% to 32% for barley straw and hemp straw, respectively, while increasing from 27% to 29% for wood chips. These results indicate that more research is needed on the use of barley straw and hemp straw in bioreactors after an overwinter period.

Microbial Community Diversity Dynamics in Acid Mine Drainage and Acid Mine Drainage-Polluted Soils: Implication on Mining Water Irrigation Agricultural Sustainability

Environmental degradation related to mining-generated acid mine drainage (AMD) is a major global concern, contaminating surface and groundwater sources, including agricultural land. In the last two decades, many developing countries are expanding agricultural productivity in mine-impacted soils to meet food demand for their rapidly growing population. Further, the practice of AMD water (treated or untreated) irrigated agriculture is on the increase, particularly in water-stressed nations around the world. For sustainable agricultural production systems, optimal microbial diversity, and functioning is critical for soil health and plant productivity. Thus, this review presents up-to-date knowledge on the microbial structure and functional dynamics of AMD habitats and AMD-impacted agricultural soils. The long-term effects of AMD water such as soil acidification, heavy metals (HM), iron and sulfate pollution, greatly reduces microbial biomass, richness, and diversity, impairing soil health plant growth and productivity, and impacts food safety negatively. Despite these drawbacks, AMD-impacted habitats are unique ecological niches for novel acidophilic, HM, and sulfate-adapted microbial phylotypes that might be beneficial to optimal plant growth and productivity and bioremediation of polluted agricultural soils. This review has also highlighted the impact active and passive treatment technologies on AMD microbial diversity, further extending the discussion on the interrelated microbial diversity, and beneficial functions such as metal bioremediation, acidity neutralization, symbiotic rhizomicrobiome assembly, and plant growth promotion, sulfates/iron reduction, and biogeochemical N and C recycling under AMD-impacted environment. The significance of sulfur-reducing bacteria (SRB), iron-oxidizing bacteria (FeOB), and plant growth promoting rhizobacteria (PGPRs) as key players in many passive and active systems dedicated to bioremediation and microbe-assisted phytoremediation is also elucidated and discussed. Finally, new perspectives on the need for future studies, integrating meta-omics and process engineering on AMD-impacted microbiomes, key to designing and optimizing of robust active and passive bioremediation of AMD-water before application to agricultural production is proposed.

Remediation of Metal Contaminated Simulated Acid Mine Drainage Using a Lab-Scale Spent Mushroom Substrate Wetland

The performance of an innovative pilot-scale spent mushroom substrate wetland for the attenuation of simulated acid mine drainage (SAMD) similar in composition to wastewater from the Irish mining region in Avoca, Co. Wicklow was investigated. The small-scale surface flow wetland, consisting of four cells in triplicate, measuring 0.46 m in width, 0.622 m in length and 0.489 m in depth, received approximately 4.32 l/day of simulated acid mine drainage. Over a period of 800 days, average removal efficiencies of Al (99 %), Zn (99 %), Cu (99 %), Fe (97 %) and Pb (97 %) were recorded, with no removal noted for Mn. These high removal rates were found to be comparable with other published results and in most cases surpassed removal rates of published results. Despite the reduction in pH and alkalinity over the duration of the trial, the rise in sulphate concentrations and the production of ammonia within the system were of concern, especially if a similar treatment system was utilised on a large scale basis. Temperature was also found to have an effect on metal removal rates, with poor removal rates recorded at low temperature events (< 1oC). The high metal removal rates of the system still make it a very attractive and environmentally sustainable remediation technology, which could be further expanded to include other passive treatment technologies, to enhance and increase the longevity of the system.

Mine drainage: Remediation technology and resource recovery.

Drainage from current and historic mining operations remains a persistent environmental problem. Numerous research and development efforts were made in 2019 with a goal to minimize the impact of mine drainage on the environment, while other research endeavors addressed the mine drainage issue from a different perspective, where mine drainage was considered a resource for water and valuable products, such as metals, sulfuric acid, and rare earth elements. Thus, this review has two main sections: (a) focusing on research efforts in mine drainage remediation technology, and (b) emphasizing advances in resource recovery from mine drainage. The first section covers traditional and emerging passive and active treatment technologies. The second section summarizes resource recovery efforts using various technologies, such as selective precipitation, membrane process, and biological systems. PRACTITIONER POINTS: Significant progress continued to be made in the management of mine drainage and related issues. Recent remediation technology advances in mine drainage were presented. Technologies focusing on resource recovery from mine drainage were reviewed.

Mine drainage: Treatment technologies and rare earth elements.

The recent research and development on mine drainage published in 2018 was summarized in this annual review. In particular, this review was focused on two main aspects of mine drainage: (a) advances in treatment technologies and (b) rare earth elements in mine drainage and its recovery. The first section covers passive treatment technologies and active treatment options, including physiochemical treatment and biological treatment. The second section includes the characterization of rare earth elements in mine drainage and recovery technologies. Due to the importance of rare earth elements and the growing interest in their recovery from mine drainage, rare earth elements are reported as a separate section for the first time in this review. PRACTITIONER POINTS: Advances in treatment technologies for mine drainage are reviewed. Rare earth elements in mine drainage and its recovery are summarized. Reviewed technologies include passive, active, advanced and novel processes.

Microalgal–Bacterial Flocs and Extracellular Polymeric Substances: Two Essential and Valuable Products of Integrated Algal Pond Systems

The integrated algal pond system (IAPS) is a passive wastewater treatment technology that can be used to remediate liquid waste from domestic, industrial and agricultural sources. The system exploits the mutualistic interaction between microalgae and bacteria to generate water of a quality suitable for discharge and/or reuse. During the treatment process, biomass in the form of microalgal–bacterial flocs (MaB-flocs) is generated, and this can be harvested and beneficiated in downstream processing. Here, we review literature on MaB-floc and extracellular polymeric substance (EPS) formation and discuss how essential microalgal–bacterial mutualism is at effecting IAPS-based wastewater treatment. Aggregation of microalgae and bacteria into MaB-flocs is clearly an outcome of EPS production by these microorganisms and arises for purposes of chemical and developmental interaction, protection, communication, aggregation and adhesion. The polymeric compounds which form the scaffold of this extracellular matrix comprise polysaccharides, proteins, uronic acid and nucleic acid. Natural EPS can be used as bioflocculant in water purification and in the dewatering and settling of sludge and is therefore an ideal natural replacement for commercially available synthetic polymers. Additionally, EPS are considered high value and can be used in many commercial applications. Thus, and to ensure sustained MaB-floc production in IAPS-based wastewater treatment plants, it is important that correct levels of EPS are maintained to facilitate settling and biomass recovery. Furthermore, it is the associated environmental and operational conditions that most impact EPS production and in turn, MaB-floc formation, and quality of the final IAPS-treated water.

Review of Constructed Wetlands for Acid Mine Drainage Treatment

The mining industry is the major producer of acid mine drainage (AMD). The problem of AMD concerns at active and abandoned mine sites. Acid mine drainage needs to be treated since it can contaminate surface water. Constructed wetlands (CW), a passive treatment technology, combines naturally-occurring biogeochemical, geochemical, and physical processes. This technology can be used for the long-term remediation of AMD. The challenge is to overcome some factors, for instance, chemical characteristics of AMD such a high acidity and toxic metals concentrations, to achieve efficient CW systems. Design criteria, conformational arrangements, and careful selection of each component must be considered to achieve the treatment. The main objective of this review is to summarize the current advances, applications, and the prevalent difficulties and opportunities to apply the CW technology for AMD treatment. According to the cited literature, sub-surface CW (SS-CW) systems are suggested for an efficient AMD treatment. The synergistic interactions between CW components determine heavy metal removal from water solution. The microorganism-plant interaction is considered the most important since it implies symbiosis mechanisms for heavy metal removal and tolerance. In addition, formation of litter and biofilm layers contributes to heavy metal removal by adsorption mechanisms. The addition of organic amendments to the substrate material and AMD bacterial consortium inoculation are some of the strategies to improve heavy metal removal. Adequate experimental design from laboratory to full scale systems need to be used to optimize equilibria between CW components selection and construction and operational costs. The principal limitations for CW treating AMD is the toxicity effect that heavy metals produce on CW plants and microorganisms. However, these aspects can be solved partially by choosing carefully constructed wetlands components suitable for the AMD characteristics. From the economic point of view, a variety of factors affects the cost of constructed wetlands, such as: detention time, treatment goals, media type, pretreatment type, number of cells, source, and availability of gravel media, and land requirements, among others.

Sunlight mediated passive wastewater treatment technology using photochemical reduction of ferric iron for decontamination of various aqueous contaminants

This paper demonstrates the feasibility of a very simple and novel, “passive” sunlight mediated photochemical process using ferric chloride for degradation of a wide range of organic contaminants. Batch experiments were conducted under natural sunlight to study the degradation of carbamazepine (CBZ), sulfolane and acid extractable organics of oil sands process water (OSPW) in the presence of 100 mg/L of ferric chloride at pH 2.7–3. The efficacy of the process was also evaluated by studying the degradation of the contaminants in actual wastewater and groundwater samples. All three contaminants were resistant to photodegradation under sunlight in the absence of ferric chloride. CBZ in wastewater and pure water was completely degraded in the presence of ferric species under sunlight within 2 h. Kinetics of degradation of CBZ was fastest in groundwater as more than 99.9% of CBZ was degraded within 30 min. Rate of reduction of Fe(III) to Fe(II) was proportional to kinetics of CBZ degradation in aqueous samples. Over an irradiation period of 7 h, more than 50% of TOC was removed by sunlight mediated iron reduction of CBZ in spiked water and secondary treated wastewater. In contrast to CBZ, sulfolane degraded faster in deionised water (4.5 h−1) with more than 50% reduction in TOC. Unaltered rates of increase in Fe(II) concentration in groundwater spiked with sulfolane and CBZ signifies the presence of easily degradable organics in groundwater competing with sulfolane for the reactive species. GC–MS analysis showed more than 60% reduction in acid extractable organics present in OSPW 7 h of sunlight irradiation in the presence of ferric chloride. Overall, photochemical iron reduction shows great promise as highly sustainable treatment process for decontamination of variety of recalcitrant contaminants in their inherent aquatic environments with marginal effects imparted by other aquatic species.

Assessing the clogging and permeability of degrading packed bed reactors

In South Africa, the need for water treatment is increasing, especially in the mining sector. As active water treatment technologies are expensive, the mining sector has an increasing need for passive water treatment technology, with low maintenance and operating costs, yet efficient water treatment ability. Literature on passive water treatment suggests that these systems only offer a narrow range of treatment capabilities. Therefore, hybrid water treatment systems could be a solution to low-cost water treatment in South Africa. The degrading packed bed reactor (DPBR) is one of the units comprising the hybrid treatment group. The DPBR’s main action is to convert sulfates into sulfides and alkalinity, since this reduces the impact on the environment by increasing the pH and reducing the salinity. In this study, 6 small-scale DPBRs were constructed. Each was classified according to its unique organic source (manure, straw, vegetable food processing waste, wood shavings, chicken litter and a combined sample with layers of all the carbon sources). Synthetic acid mine drainage (AMD) was fed through the 6 bioreactors for a period of 3 months. Permeabilities, leachate samples and effective void volumes were measured from the DPBRs. From the experiments conducted, it was found that the manure and combination bioreactors (with equal layers of manure, straw, compost, wood shavings and chicken litter) had the lowest overall permeabilities, with straw and compost having the highest permeabilities. Linked to this, the experiments showed that the manure and combination bioreactors had the largest decreases in effective porosity with straw and compost having the least. Hydraulically, the combination bioreactor performed the best by incorporating the best attributes from each carbon source. Wood shavings preformed almost as well. Chicken litter clogged within 18 days after the initiation of the experiment and thus was the least effective substrate.

International Trials of Vertical Flow Reactors for Coal Mine Water Treatment

Vertical flow reactors (VFRs) were tested at coal mine sites in New Zealand, South Korea, and the USA. The objective was to evaluate the iron removal efficiency and iron removal mechanisms during field trials at low pH and circumneutral pH, and to evaluate the potential use of VFRs as stand-alone systems or in combination with other passive treatment technologies. Total iron and manganese removal efficiencies at circumneutral pH (6–8) often exceeded 90%, with effluent concentrations less than 1 mg/L. This is attributed to both homogeneous and heterogenous Fe(II) oxidation and filtration of the precipitated ferrihydrite. Iron removal efficiencies at moderately acidic conditions (pH 3–4.5) averaged close to 40%, with an average 71.0% removal in one of the trials after iron removal capacity was stabilized. Microbial Fe(II) oxidation and precipitation as schwertmannite together with aggregation of colloidal and nano-particulate Fe(III) are suspected to be the main removal mechanisms. Iron solubility limited removal under very acidic conditions (pH < 3). The reproducibility of the results with respect to previous research confirmed that VFRs can be used as stand-alone passive treatment systems for iron removal from mine waters with a footprint less than half of the area required by a conventional aerobic wetland. A VFR can also provide useful iron pretreatment for other passive treatment systems under circumneutral conditions, but would have to be combined with alkaline generating systems to achieve full iron removal from acidic mine waters.

Remediation of Acid Mine Drainage-Impacted Water

The formation of acid mine drainage (AMD), a highly acidic and metal-rich solution, is the biggest environmental concern associated with coal and mineral mining. Once produced, AMD can severely impact the surrounding ecosystem due to its acidity, metal toxicity, sedimentation and other deleterious properties. Hence, implementations of effective post-mining management practices are necessary to control AMD pollution. Due to the existence of a number of federal and state regulations, it is necessary for private and government agencies to come up with various AMD treatment and/or control technologies. This review describes some of the widely used AMD remediation technologies in terms of their general working principles, advantages and shortcomings. AMD treatment technologies can be divided into two major categories, namely prevention and remediation. Prevention techniques mainly focus on inhibiting AMD formation reactions by controlling the source. Remediation techniques focus on the treatment of already produced AMD before their discharge into water bodies. Remediation technologies can be further divided into two broad categories: active and passive. Due to high cost and intensive labor requirements for maintenance of active treatment technologies, passive treatments are widely used all over the world. Besides the conventional passive treatment technologies such as constructed wetlands, anaerobic sulfate-reducing bioreactors, anoxic limestone drains, open limestone channels, limestone leach beds and slag leach beds, this paper also describes emerging passive treatment technologies such as phytoremediation. More intensive research is needed to develop an efficient and cost-effective AMD treatment technology, which can sustain persistent and long-term AMD load.

Performance of municipal waste stabilization ponds in the Canadian Arctic

Abstract The majority of small remote communities in the Canadian arctic territory of Nunavut utilize waste stabilization ponds (WSPs) for municipal wastewater treatment because of their relatively low capital and operational costs, and minimal complexity. New national effluent quality regulations have been implemented in Canada, but not yet applied to Canada's Arctic due to uncertainty related to the performance of current wastewater treatment systems. Waste stabilization pond (WSP) treatment performance is impacted by community water use, pond design, and climate. The greatest challenge arctic communities experience when using passive wastewater treatment technologies is the constraints imposed by the extreme climate, which is characterized as having long cold winters with short cool summers that can be solar intense. The removal of carbonaceous biochemical oxygen demand (CBOD 5 ), total suspended solids (TSS), and ammonia-nitrogen were measured during the summer treatment period (late June until early September) from 2011 to 2014 in the WSP systems of four Nunavut communities; Pond Inlet, Clyde River, Grise Fiord and Kugaaruk. Monitoring results showed that WSPs in their current single cell design can achieve greater than 80% removal of CBOD 5 and TSS but were challenged to produce effluent quality that meets secondary wastewater treatment standards ( 5 and TSS). This study points to the need for revisions of design guidelines for facultative WSPs in the Arctic, as current systems are anaerobic and do not contain sufficient dissolved oxygen required to consistently support aerobic biological treatment processes.

Formulation of a Permeable Reactive Mixture for Groundwater Remediation Based on an Industrial Co-product: Permeability and Copper Retention Study

The objective of this research is to formulate a permeable material based on apatite gel having the ability to retain heavy metals, to be used in a permeable reactive barrier (PRB), an in situ passive groundwater treatment technology. This new material is produced from non-toxic waste in the research laboratory of a chemical company. It is characterised by a thixotropic behaviour and a high ion exchange capacity. The apatite gel is the active agent of the reactive material; it ensures the retention of heavy metals by ion exchange. Sand and an organic binder are also incorporated into the mixture, providing both high permeability and mechanical strength to the mixtures. An original experimental apparatus intended for measuring both water permeability and the retention of heavy metals has been specially designed and developed for this study. The mixture consisting of 95 % silica sand, 5 % apatite gel and 3 % epoxy was qualified as a suitable PRB mixture, due its high permeability, its good retention capacity and its acceptable mechanical strength.

Passive Treatment of Mining Influenced Water: An Overview of Available Technologies and the Periodic Table

Introduction There are basically three kinds of passive treatment technologies for treating mining influenced water (MIW): Abiotic, Limestone-based methods for treating net-acidic MIW have been eff...

English

The Bureau of Land Management (BLM) Abandoned Mined Land Program has built and is operating the Eveline Mine Drainage Treatment Vault near Silverton, CO to investigate innovative passive treatment technologies for acid mine drainage (AMD) in high alpine environments. Column tests of several materials were conducted to determine treatment media to use in the vault. This case study examines the potential of combining Bauxsol TM Acid B Extra™ (an alumina refining by-product) with biochar, pea-gravel, and porous concrete to reduce AMD metal concentrations. The objective of the trial was to create a passive treatment system that (1) reduces metal concentrations in effluent waters, (2) reduces operational costs, (3) utilizes waste streams from industry, and (4) operates in cold weather climates with limited space for infrastructure. Results suggest that the combination of Acid B Extra™ and biochar achieved optimal near term results with >95% removal of Cd, Cu, Fe, Mn, and Zn, and >60% removal of Al, while not clogging the pilot test columns.

Life cycle assessment analysis of active and passive acid mine drainage treatment technologies

Acid mine drainage (AMD), resulting from open-cast coal mining, is currently one of the largest environmental challenges facing the mining industry. In this study, a life cycle assessment (LCA) was conducted to evaluate the environmental impacts associated with the construction, operation and maintenance of different AMD treatment options typically employed. LCA is a well-reported tool but is not documented for AMD treatment systems despite their ubiquitous implementation worldwide. This study conducted detailed LCA analysis for various passive and active AMD treatment approaches implemented or considered at a major coal mine in New Zealand using a comparative functional unit of kg acidity removed per day for each treatment option. Eight treatment scenarios were assessed including active limestone and hydrated lime treatments, and compared to passive treatments using limestone and waste materials such as mussel shells. Both midpoint and endpoint LCA impact categories were assessed. Generally, the active treatment scenarios demonstrated greater LCA impacts compared to an equivalent level of treatment for the passive treatment approaches. Lime slaking had the greatest LCA impacts, while passive treatment approaches incurred consistently less impacts except for one passive treatment with a purchased energy scenario. A 50% reduction in transportation distances resulted in the lowest LCA impacts for all scenarios. This study highlights the importance of evaluating the environmental and social impacts of AMD treatment for the mining industry.

The Use of Bench-scale Treatability Studies in the Design of Engineered Wetlands for the Remediation of Acid Mine Drainage (AMD) and Leachate in the Vicinity of Coal MinesA Case Study in Ohio, United States

Engineered wetland systems are a passive treatment technology which are versatile, environmentally-friendly, and cost-effective for the remediation of acid mine drainage (AMD) and leachate.Experience derived from a site in Ohio, United States, showed that the preliminary design of an engineered wetland system downstream of a former coal mine/landfill could be significantly improved by the performance of bench-scale treatability studies. Results from the bench-scale treatability study showed that in order to achieve significant reductions of iron in the water discharging to the surface water bodies. The pH of the water would have to be increased to 8 by the addition of limestone.

Fluidized bed ash and passive treatment reduce the adverse effects of acid mine drainage on aquatic organisms

Elevated concentrations of acidity and metals in acid mine drainage (AMD) may be effectively addressed by active and passive treatment technologies. However, typical evaluations consider only chemical water quality with little if any regard for biological metrics. Robust evaluations including both chemical and biological indicators of water quality improvement are needed. In this study, injection of alkaline fluidized bed ash (FBA) into a flooded underground coal mine was coupled with a five-cell passive treatment system to ameliorate an abandoned AMD discharge in eastern Oklahoma. The passive system included process units promoting both aerobic and anaerobic treatment mechanisms. Resulting water quality changes and biological responses were evaluated. Organisms of two distinct functional groups (the filter-feeding mollusk Corbicula fluminea and the wide-spectrum feeding fish Lepomis macrochirus) were exposed to mine waters in several treatment cells. The combination of treatment technologies was hypothesized to limit potential negative effects on these aquatic organisms. Tissues were harvested and analyzed for concentrations of several metals (Al, Fe, Mn, Mg, Ca, Ni, Cu and Zn) of interest. Organismal responses, such as hepatosomatic index, condition factor, and condition index, did not vary significantly among organisms exposed within different treatment cells when compared to non-AMD impaired waters. Metal tissue accumulation trends, compared to aqueous concentrations, were observed for Fe, Ni and Zn. Exposure experiments with these two organisms indicated that FBA introductions coupled with passive treatment decreased the potential adverse effects of AMD to biological systems.