Robert W. Nairn

Phosphorus removal in created wetland ponds receiving river overflow.

Water quality changes and biogeochemical development were evaluated over 2 years in two newly created freshwater riparian wetland ponds (1 ha each) in an agricultural and urban watershed. Both wetlands received pumped river water and had similar hydrologic regimes. One wetland was planted with 13 species of vegetation typical of Midwestern US marshes; the other received no planted vegetation. Water quality sampling was conducted weekly and detailed hydrologic budgets were developed from data collected twice daily. Hydrologic budgets were dominated by pumped surface flows (mean inflow=1480 m3 day−1). Two floods accounted for 32% of inflow in 1 year. Both wetlands significantly decreased turbidity (62 to 27 NTU) and increased dissolved oxygen (9–11 mg l−1). Inflow dissolved reactive phosphorus (DRP) and total phosphorus (TP) concentrations (17±3 and 169±11 μg P l−1) were significantly higher (P<0.05) than outflow concentrations (DRP: 5±1 and 6±1 μg P l−1; TP: 69±8 and 74±9 μg P l−1) for planted and unplanted wetlands, respectively. Phosphorus removal was related to decreases in turbidity and the level of biological activity. Extensive and highly productive algal coverage in both wetlands and the subsequent deposition and decomposition of the algal mat influenced P retention through biological uptake and chemical sorption and coprecipitation. Mean removal rates were 1.0 g P m−2 year−1 for DRP and 5.4 g P m−2 year−1 for TP and did not differ significantly between wetlands (P<0.05). Approximately 35% of TP mass removal occurred during two floods. A conservative tracer (Cl) indicated limited and negligible effects of dilution on decreases in P concentration. Water flow rate and P concentration did not affect P removal which was loading-limited and seasonal. Initial development of macrophytic vegetation demonstrated no influence on water quality changes. Both wetlands acted as effective P sinks in the initial 2 years of operation.

Biochemical oxygen demand and nutrient processing in a novel multi-stage raw municipal wastewater and acid mine drainage passive co-treatment system

A laboratory-scale, four-stage continuous flow reactor system was constructed to test the viability of high-strength acid mine drainage (AMD) and municipal wastewater (MWW) passive co-treatment. The synthetic AMD had pH 2.60 and 1860 mg/L acidity as CaCO(3) equivalent with 46, 0.25, 2, 290, 55, 1.2 and 390 mg/L of Al, As, Cd, Fe, Mn, Pb and Zn, respectively. The AMD was introduced to the system at a 1:2 ratio with raw MWW from the City of Norman, Oklahoma USA containing 265 ± 94 mg/L BOD(5), 11.5 ± 5.3 mg/L PO(4)(-3), and 20.8 ± 1.8 mg/L NH(4)(+)-N. During the 135 d experiment, PO(4)(-3) and NH(4)(+)-N were decreased to <0.75 and 7.4 ± 1.8 mg/L, respectively. BOD(5) was generally decreased to below detection limits. Nitrification increased NO(3)(-) to 4.9 ± 3.5 mg/L NO(3)(-)-N, however relatively little denitrification occurred. Results suggest that the nitrogen processing community may require an extended period to mature and reach full efficiency. Overall, results indicate that passive AMD and MWW co-treatment is a viable ecological engineering approach for the developed and developing world that can be optimized and applied to improve water quality with minimal use of fossil fuels and refined materials.

Review of Passive Systems for Acid Mine Drainage Treatment

When appropriately designed and maintained, passive systems can provide long-term, efficient, and effective treatment for many acid mine drainage (AMD) sources. Passive AMD treatment relies on natural processes to neutralize acidity and to oxidize or reduce and precipitate metal contaminants. Passive treatment is most suitable for small to moderate AMD discharges of appropriate chemistry, but periodic inspection and maintenance plus eventual renovation are generally required. Passive treatment technologies can be separated into biological and geochemical types. Biological passive treatment technologies generally rely on bacterial activity, and may use organic matter to stimulate microbial sulfate reduction and to adsorb contaminants; constructed wetlands, vertical flow wetlands, and bioreactors are all examples. Geochemical systems place alkalinity-generating materials such as limestone in contact with AMD (direct treatment) or with fresh water up-gradient of the AMD. Most passive treatment systems employ multiple methods, often in series, to promote acid neutralization and oxidation and precipitation of the resulting metal flocs. Before selecting an appropriate treatment technology, the AMD conditions and chemistry must be characterized. Flow, acidity and alkalinity, metal, and dissolved oxygen concentrations are critical parameters. This paper reviews the current state of passive system technology development, provides results for various system types, and provides guidance for sizing and effective operation.ZusammenfassungPassive Systeme können über einen langen Zeitraum unterschiedlichste saure Grubenwässer (AMD) effizient und wirksam reinigen, sofern sie sachgerecht geplant und errichtet werden. Die passive Reinigung saurer Grubenwässer beruht auf natürlichen Prozessen der Säureneutralisation, Oxidation oder Reduktion und Ausfällung von metallischen Schadstoffen. Die Anwendung passiver Reinigungssysteme ist besonders geeignet für kleine bis mittlere AMD-Ströme mit entsprechendem Chemismus. Die periodische Überprüfung und Instandhaltung und gegebenfalls Erneuerung sind aber generell notwendig. Die passiven Reinigungstechnologien können in biologische und geochemische Typen eingeteilt werden. Die biologische Reinigung beruht generell auf bakterieller Tätigkeit und kann organisches Material nutzen um beispielsweise die mikrobielle Sulfatreduktion anzuregen und Verunreinigungen zu adsorbieren. Beispiele für biologische Systeme sind Pflanzenkläranlagen, vertikal durchströmte Pflanzenkläranlagen und Bioreaktoren. Geochemische Systeme bringen alkalisch wirkende Stoffe, wie z. B. Kalkstein, in Kontakt mit sauren Grubenwässern (direkte Reinigung) oder mit dem Frischwasseranstrom von sauren Grubenwässern. Die meisten passiven Reinigungssysteme verwenden multiple Methoden, um die Säureneutralisation, Oxidation und Ausfällung von Metallen zu fördern. Bevor ein geeignetes Reinigungssystem gewählt wird, müssen die AMD-Bedingungen sowie der Chemismus charakterisiert werden. Wesentliche Parameter sind der Durchfluss, die Acidität und Alkalinität sowie die Konzentration von Metallen und Sauerstoff. Der vorliegende Artikel bewertet den aktuellen Stand der Entwicklung passiver Systeme, stellt Ergebnisse verschiedener Systemtypen vor und bietet Hilfestellung bei der Dimensionierung und einem erfolgreichen Einsatz solcher Systeme.ResumenLos sistemas pasivos, apropiadamente diseñados y mantenidos, pueden proporcionar un efectivo y eficiente tratamiento, y por largo tiempo, de muchos drenajes ácidos de minas (AMD). Los tratamientos pasivos utilizan procesos naturales para neutralizar la acidez y oxidar o reducir y precipitar los metales contaminantes. Los tratamientos pasivos son más adecuados para pequeñas y moderadas descargas de AMD de química apropiada, pero se requieren generalmente periódicas inspecciones y periódico mantenimiento, más eventuales renovaciones. Las tecnologías pasivas de tratamiento pueden ser separadas entre biológicas y geoquímicas. Las biológicas utilizan la actividad bacteriana y pueden adicionar material orgánico para estimular la reducción microbiana de sulfato y para adsorber los contaminantes; ejemplos estas tecnologías son los humedales artificiales, los humedales de flujo vertical y los biorreactores. Los sistemas geoquímicos utilizan materiales generadores de alcalinidad como la caliza en contacto con AMD (tratamiento directo) o con agua fresca gradiente arriba del AMD. La mayoría de los sistemas de tratamiento pasivo emplean múltiples métodos, frecuentemente en serie, para lograr la neutralización de ácidos y la precipitación de los metales. Antes de seleccionar la tecnología de tratamiento apropiada, se deben caracterizar las condiciones del AMD. Los parámetros críticos son flujo, acidez y alcalinidad y concentraciones de oxígeno disuelto y metales. Este trabajo revisa el actual desarrollo de la tecnología de sistemas pasivos, muestra resultados obtenidos en varios tipos de sistemas y proporciona una guía orientativa sobre el tamaño necesario para una operación efectiva.酸性废水被动处理系统综述

A Place to Call Home: Amphibian Use of Created and Restored Wetlands

Loss and degradation of wetland habitats are major contributing factors to the global decline of amphibians. Creation and restoration of wetlands could be a valuable tool for increasing local amphibian species richness and abundance. We synthesized the peer-reviewed literature addressing amphibian use of created and restored wetlands, focusing on aquatic habitat, upland habitat, and wetland connectivity and configuration. Amphibian species richness or abundance at created and restored wetlands was either similar to or greater than reference wetlands in 89% of studies. Use of created and restored wetlands by individual species was driven by aquatic and terrestrial habitat preferences, as well as ability to disperse from source wetlands. We conclude that creating and restoring wetlands can be valuable tools for amphibian conservation. However, the ecological needs and preferences of target species must be considered to maximize the potential for successful colonization and long-term persistence.

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.

Evaluation of a universal flow-through model for predicting and designing phosphorus removal structures.

Phosphorus (P) removal structures have been shown to decrease dissolved P loss from agricultural and urban areas which may reduce the threat of eutrophication. In order to design or quantify performance of these structures, the relationship between discrete and cumulative removal with cumulative P loading must be determined, either by individual flow-through experiments or model prediction. A model was previously developed for predicting P removal with P sorption materials (PSMs) under flow-through conditions, as a function of inflow P concentration, retention time (RT), and PSM characteristics. The objective of this study was to compare model results to measured P removal data from several PSM under a range of conditions (P concentrations and RT) and scales ranging from laboratory to field. Materials tested included acid mine drainage residuals (AMDRs), treated and non-treated electric arc furnace (EAF) steel slag at different size fractions, and flue gas desulfurization (FGD) gypsum. Equations for P removal curves and cumulative P removed were not significantly different between predicted and actual values for any of the 23 scenarios examined. However, the model did tend to slightly over-predict cumulative P removal for calcium-based PSMs. The ability of the model to predict P removal for various materials, RTs, and P concentrations in both controlled settings and field structures validate its use in design and quantification of these structures. This ability to predict P removal without constant monitoring is vital to widespread adoption of P removal structures, especially for meeting discharge regulations and nutrient trading programs.

Unabated acid mine drainage from Cerro Rico de Potosí, Bolivia: uncommon constituents of concern impact the Rio Pilcomayo headwaters

Intensive mining and processing of the polymetallic sulfide ore body of Cerro Rico de Potosí (Bolivia) has occurred since 1545, leading to severe degradation of surface and subsurface waters, stream sediments, and soils at the headwaters of the economically vital, yet highly impacted, Rio Pilcomayo. Previous studies have documented extremely elevated concentrations of a limited suite of metals in local waterways from acid mine drainage (AMD), terrestrial and in-stream tailings, and ore processing plant discharges. However, contamination from a wider variety of ecotoxic metals/metalloids was considered likely due to the highly mineralized polymetallic nature of the ore body. To screen for this broader range of ecotoxic elements in AMD and receiving streams, data were gathered during two sampling events timed for the most extreme periods of the dry and wet seasons of one water-year. Concentrations of Ag, B, Ba, Mo, Sb, Se, Sn and V in AMD and receiving streams were greater than Bolivian discharge limits and receiving water body guidelines as well as international agricultural use standards. Locally, results indicate that contamination from mining Cerro Rico has a larger scope than previously thought and underscore the importance of remediation. Globally, the results raise the possibility that other mining regions could have unquantified hazards from overlooked ecotoxic elements and that screening for a broader range of contaminants may be warranted.

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.

A LEGACY OF NEARLY 500 YEARS OF MINING IN POTOSÍ, BOLIVIA: ACID MINE DRAINAGE SOURCE IDENTIFICATION AND CHARACTERIZATION 1

Intensive mining and processing of silver, lead, tin and zinc ores have occurred in various locations within and around the city of Potosi, Bolivia since 1545. Surface and subsurface waters, stream sediments and soils are contaminated with various heavy metals. Acid mine drainage and processing plant effluent are primary contaminants in the headwaters of the economically vital, yet highly impacted, Rio Pilcomayo watershed. Previous studies have documented downstream heavy metal contamination. The acid mine drainage sources documented in this study help to link downstream pollution to primary origins. Selected acid mine drainage sources, from both operating and abandoned mines contributing to local streams, contained total metal concentrations of 0.284- 977 mg/L Al, 0.03-191 mg/L As, 0.025-50.68 mg/L Cd, 0.03-161 mg/L Cu, 0.15- 7,320 mg/L Fe, 0.3-438 mg/L Mn, 0.03-15.0 mg/L Pb and 1.46-11,760 mg/L Zn, with pH and specific conductance ranging from 2.46-6.39 and 893-19,070 μS/cm, respectively. Data were gathered during the dry season with flows ranging from nil to 4.59 L/s. Metals concentrations and pH values in all mine drainage sources sampled are several orders of magnitude above compliance with Bolivian environmental law.

GENERATION OF 400-500 MG/L ALKALINITY IN A VERTICAL ANOXIC LIMESTONE DRAIN 1

Alkalinity generation in a vertical anoxic limestone drain (VALD) at an abandoned coal mine discharge near Hartshorne, Oklahoma was evaluated. The VALD consists of a 9-m 2 abandoned vertical air shaft filled with approximately 22 m of >90% CaCO3 limestone overlying approximately 34 m of dolomitic stone. The VALD and a downstream passive treatment system were designed to treat a net-acidic discharge (~40 L/min) characterized by elevated concentrations of metals (Fe 765 mg/L; Mn 18 mg/L; Na 1900 mg/L), anions (Cl - 225 mg/L; SO4 2- 7800 mg/L), with pH 5.4 and net-acidity 1400 mg/L. System construction was completed in late 2005, but discharge from the VALD did not occur until January 2007 due to a prolonged regional drought. Upon initial discharge, alkalinity concentrations from the VALD outflow were 550±14 mg/L. During the first year of operation, alkalinity concentrations consistently remained >400 mg/L. The effects of elevated pCO2, mine water ionic strength, detention time, and other factors impacting alkalinity concentrations exiting the VALD were assessed. It appears that multiple factors, especially the brackish nature of these particular mine waters, influence treatment effectiveness. In addition, the down-gradient 12-cell passive treatment system is effectively removing metals and discharging net alkaline waters to the receiving stream.