Rapid manganese removal from mine waters using an aerated packed-bed bioreactor

In the UK, the Environmental Quality Standard for manganese has recently been lowered to 30 microg/L (annual average), which is less than the UK Drinking Water Inspectorate's Maximum Permitted Concentration Value (50 microg/L). Current passive treatment systems for manganese removal operate as open-air gravel-bed filters, designed to maximize either influent light and/or dissolved oxygen. This requires large areas of land. A novel enhanced bioremediation treatment system for manganese removal has been developed that consists of a passively aerated subsurface gravel bed. The provision of air at depth and the use of catalytic substrates help overcome the slow kinetics usually associated with manganese oxidation. With a residence time of only 8 h and an influent manganese concentration of approximately 20 mg/L, >95% of the manganese was removed. The treatment system also operates successfully at temperatures as low as 4 degrees C and in total darkness. These observations have positive implications for manganese treatment using this technique in both colder climates and where large areas of land are unavailable. Furthermore, as the operation of this passive treatment system continually generates fresh manganese oxyhydroxide, which is a powerful sorbent for most pollutant metals, it potentially has major ancillary benefits as a removal process for other metals, such as zinc.     

Trace Metal Uptake By Pichia Spartinae, an Endosymbiotic Yeast in the Salt Marsh Cord Grass Spartina Alterniflora

The ascosporogenous marine yeast Pichia spartinae is a dominant endosymbiont of the marsh grass Spartina alterniflora. Results of previous studies suggested that P. spartinae is involved in iron transport processes in the grass. of particular interest has been the mechanisms of metal uptake and metabolism by the yeast, and the ecological and plant biochemical significance of these processes. This investigation examined the uptake of iron and other metals (Zn, Cu, Cd, Ni, Pb, Cr) by P. spartinae, and provides data on possible mechanisms of this activity. the results suggest a) the yeast can assimilate divalent and trivalent forms of inorganic iron, as well as large organic-Fe(III) complexes, b) the uptake of inorganic trivalent iron under soluble iron-deficient conditions proceeded by a different mechanism than that of soluble Fe(II), with intracellular loadings of iron much increased under the former conditions; c) trivalent iron uptake is not mediated by hydroxamate siderophores at levels detectable by sensitive screening assays; d) the assimilation of some trace metals (Cu, Zn, Cd, Ni) is likely to be mediated by low molecular weight cysteine rich proteins, possibly metallothionein, and; e) siderophores from other fungi can provide iron for P. spartinae. the iron assimilation data suggested that multiple mechanisms are involved, and are influenced by the concentration and speciation of iron in the system. in general, iron assimilation mechanisms are comparable to those described for closely related yeasts, such as Saccharomyces cerevisiae. Among other things, these results indicated that future studies of trace metal mobilization and plant assimilation in salt marsh ecosystems must account for the activities of microbial symbionts associated with the plants.     

The impact of pumped water from a de-watered Magnesian limestone quarry on an adjacent wetland: Thrislington, County Durham, UK

Although quarrying is often cited as a potential threat to wetland systems, there is a lack of relevant, quantitative case studies in the literature. The impact of pumped groundwater discharged from a quarry into a wetland area was assessed relative to reference conditions in an adjacent fen wetland that receives only natural runoff. Analysis of vegetation patterns at the quarry wetland site, using Detrended Correspondence Analysis and the species indicator values of Ellenberg, revealed a clear disparity between community transitions in the quarry wetland and the reference site. Limited establishment of moisture-sensitive taxa, the preferential proliferation of robust wetland species and an overall shift towards lower species diversity in the quarry wetland were explicable primarily by the physico-chemical environment created by quarry dewatering. This encompassed high pH (up to 12.8), sediment-rich effluent creating a nutrient-poor substrate with poor moisture retention in the quarry wetland, and large fluctuations in water levels.     

Effective remediation of grossly polluted acidic, and metal-rich, spoil heap drainage using a novel, low-cost, permeable reactive barrier in Northumberland, UK

A permeable reactive barrier (PRB) for remediation of coal spoil heap drainage in Northumberland, UK, is described. The drainage has typical chemical characteristics of pH<4, [acidity]>1400 mg/L as CaCO3, [Fe]>300 mg/L, [Mn]>165 mg/L, [Al]>100mg/L and [SO4]>6500 mg/L. During 2 years of operation the PRB has typically removed 50% of the iron and 40% of the sulphate from this subsurface spoil drainage. Bacterial sulphate reduction appears to be a key process of this remediation. Treatment of the effluent from the PRB results in further attenuation; overall reductions in iron and sulphate concentrations are 95% and 67% respectively, and acidity concentration is reduced by an order of magnitude. The mechanisms of attenuation of these, and other, contaminants in the drainage are discussed. Future research and operational objectives for this novel, low-cost, treatment system are also outlined.     

The effect of pH on plant litter decomposition and metal cycling in wetland mesocosms supplied with mine drainage

The long term effectiveness of compost-based wetland systems treating net-acidic mine waters is reliant upon a continuing supply of decomposed organic matter which provides the basic foodstock for sulphate reducing bacteria. The annual turnover of wetland vegetation within these systems has been suggested to be the primary source for this material once the original substrate has been consumed. This study aimed to determine whether plant litter (of Common Reed, Phragmites australis) decomposition rates and release of metals and nutrients were affected by pH using controlled experiments under laboratory conditions. Loss of plant biomass was found to be unaffected by pH (3.0-6.5) suggesting that plant litter could be an important source of organic molecules for bacterial populations even under acidic conditions. The decomposing plant litter also acted as a focus for the precipitation of Fe oxides and sorption of Zn thereby acting as a short-term sink for these contaminants. This has important implications for geochemical cycling within the wetland system and potential transport out of the system. The essential nutrients (K and Mg) released from plant litter were affected by pH which could be important in nutrient availability for re-use by vegetation and other organisms within the system.     

Influence of fur trade,famine, and forest fires on moose and woodland caribou populations in northwestern Ontario from 1786 to 1911

Hudson’s Bay Company records were used to estimate the 1786–1911 annual number of moose (Alces alces andersonii) and caribou (Rangifer tarandus caribou) involved in trade by northern Ojibwa natives to the company post at Osnaburgh House (51°10′N 90°15′W) in northwest Ontario, Canada. The human population for the early 19th century, and the number and severity of human starvations from 1786 to 1911 were estimated. The extent of forest fires in the region around Osnaburgh was documented using a “fire-day” index computed from Hudson’s Bay Company journals and using qualitative archival information. It is argued that the human population was too small to have caused the observed early 19th century moose and caribou population decline solely through predation. Likewise, severe early 19th century famines were caused by climatic factors rather than by declines in moose and caribou numbers. Habitat change caused by increased forest fires correlates with the observed decline of caribou, while moose increased and subsequently collapsed as winter shelter was destroyed. A burgeoning human population, sustained during winter food shortages on potatoes donated by the Hudson’s Bay Company, then kept ungulate populations to low levels until the late 19th century. Only then did maturing forests and a new outbreak of fires provide renewed habitat for resurgences of, respectively, caribou and moose.     

Hydrochemical stratification in flooded underground mines: an overlooked pitfall

The fact that flooded underground mines are commonly hydrochemically stratified is often not appreciated. Water samples taken from the water surface in partly flooded shafts are often wrongly assumed to represent the water quality existing throughout the entire water column. In some cases, treatment systems have been designed on the basis of these often misleading water surface samples. Stratification can build up within a slowly recovering system where there are few lateral inflows and outflows to the system. Less mineralised, shallow-sourced water enters at the top of the water column and more heavily mineralised water tends to remain at the base of the water column. This water has a high dissolved solids content due to dissolution of increasing amounts of pyrite oxidation salts and other minerals as the water level rises through the old workings. However, such stratification can easily be lost following hydraulic disturbance of the system (either by pumping or by natural decant when the water level reaches an outflow pathway from the mine system, such as an old adit or shaft collar) and often results in surface discharges of poor water quality. Test pumping of one such stratified system (Frances Colliery, Scotland) has provided useful information about how stratified systems develop, and how they can behave when disturbed. The water quality observed after stratification was disturbed by pumping was worse than would have been anticipated on the basis of water samples taken from the surface of the water column prior to pumping (with concentrations of contaminants such as iron and zinc being around two orders of magnitude greater than in water surface samples). Taken together with other information from the literature, the experience at Frances Colliery supports the proposal of criteria for recognising when stratification of mine water quality might be anticipated, thus facilitating the timely deployment of measures required for its detection at an early stage.     

Dominating Chemical Factors in Mine Water Induced Impoverishment of the Invertebrate Fauna of Two Streams in the Durham Coalfield, Uk

Mine water pollution is causing increasing concern in the UK as some of the world's largest and longest-worked coalfields are abandoned and flooded. Many of the resulting polluting discharges are typified by higher mineral acidity (low pH), and high concentrations of iron and sulphate. Two streams, receiving mine water discharges in the Durham coalfield in northern England, have been studied to identify the major chemical factors affecting the welfare of benthic invertebrates. One of the discharges is strongly acidic (pH 3.9), and the second is marginally acidic (pH 5.3). Simultaneous analyses of hydrochemistry and invertebrate diversity and abundance demonstrate serious faunal impoverishment downstream of minewater discharges. Pathway analysis has been applied to ascertain statistically the dominating chemical factors in this faunal impoverishment. in both cases, total acidity (acidity to pH 8.3 = 612 mg 1^-1 as CaCO³; pH 3.9) and iron concentration (up to 112.5 mg 1^-1) account for nearly all of the faunal impoverishment. Other metals, sulphate and pH (in isolation from mineral acidity) are of lesser importance. Persistence of the detrimental effects of high acidity downstream of the discharges is ascribed to a slow recovery of the carbonate buffering system. These findings assist in the implementation of long-term management and remediation strategies for mine water pollution.     

Growth of Phragmites australis (Cav.) Trin ex. Steudel in mine water treatment wetlands: effects of metal and nutrient uptake

The abandoned mine of Shilbottle Colliery, Northumberland, UK is an example of acidic spoil heap discharge that contains elevated levels of many metals. Aerobic wetlands planted with the common reed, Phragmites australis, were constructed at the site to treat surface runoff from the spoil heap. The presence of a perched water table within the spoil heap resulted in the lower wetlands receiving acidic metal contaminated water from within the spoil heap while the upper wetland receives alkaline, uncontaminated surface runoff from the revegetated spoil. This unique situation enabled the comparison of metal uptake and growth of plants used in treatment schemes in two cognate wetlands. Results indicated a significant difference in plant growth between the two wetlands in terms of shoot height and seed production. Analyses of metal and nutrient concentrations within plant tissues provided the basis for three hypotheses to explain these differences: (i) the toxic effects of high levels of metals in shoot tissues, (ii) the inhibition of Ca (an essential nutrient) uptake by the presence of metals and H+ ions, and (iii) low concentrations of bioavailable nitrogen sources resulting in nitrogen deficiency. This has important implications for the engineering of constructed wetlands in terms of the potential success of plant establishment and vegetation development.