Enhancement of sulfate reduction activity using granular sludge in anaerobic treatment of acid mine drainage

Three laboratory-scale, upflow anaerobic reactors were operated for about 250 d to determine the effect of activated granular sludge with high density of sulfate reducing bacteria in the treatment of artificial acid mine drainage. Sulfate reducing bacteria in the granular sludge taken from the upflow anaerobic sludge blanket reactor were 1–2×10⁶ c.f.u. g^–1, which is at least 10 times higher than that of organic substrates such as cow manure and oak compost. The reactors with granular sludge effectively removed over 99% of heavy metals, such as Fe, Al, Cu, and Cd during the experiment. This result suggests a feasibility of the application of granular sludge as a source of sulfate reducing bacteria for the treatment of acid mine drainage.     

Advances In Biotreatment of Acid Mine Drainage and Biorecovery of Metals: 2. Membrane Bioreactor System for Sulfate Reduction

Several biotreatmemt techniques for sulfate conversion by the sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing acid mine drainage (AMD). This research deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of acid mine water from the Berkeley Pit, Butte, MT, using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase sparged gas bioreactor systems are: large microporous membrane surface to the liquid phase; formation of hydrogen sulfide outside the membrane, preventing the mixing with the pressurized hydrogen gas inside the membrane; no requirement of gas recycle compressor; membrane surface is suitable for immobilization of active SRB, resulting in the formation of biofilms, thus preventing washout problems associated with suspended culture reactors; and lower operating costs in membrane bioreactors, eliminating gas recompression and gas recycle costs. Information is provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in anaerobic digester sludge and sediment master culture reactors and with SRB biofilms in bench-scale SRB membrane bioreactors. Biokinetic parameters have been determined using biokinetic models for the master culture and membrane bioreactor systems. Data are presented on the effect of acid mine water sulfate loading at 25, 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25, 35 and 40 °C) to determine and optimize sulfate conversions for an effective AMD biotreatment. Pilot-scale studies have generated data on the effect of flow rates of acid mine water (MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion in those systems. The pilot-scale data indicate that the SRB membrane bioreactors systems can be applied toward field-scale biotreatment of AMD and for recovery of high purity metals and an agriculturally usable water.     

An integrated algal sulphate reducing high rate ponding process for the treatment of acid mine drainage wastewaters

Acid mine drainage pollution may be associated with large water volume flows and exceptionally long periods of time over which the drainage may require treatment. While the use and role of sulphate reducing bacteria has been demonstrated in active treatment systems for acid mine drainage remediation, reactor size requirement and the cost and availability of the carbon and electron donor source are factors which constrain process development. Little attention has focussed on the use of waste stabilisation ponding processes for acid mine drainage treatment. Wastewater ponding is a mature technology for the treatment of large water volumes and its use as a basis for appropriate reactor design for acid mine drainage treatment is described including high rates of sulphate reduction and the precipitation of metal sulphides. Together with the co-disposal of organic wastes, algal biomass is generated as an independent carbon source for SRB production. Treatment of tannery effluent in a custom-designed high rate algal ponding process, and its use as a carbon source in the generation and precipitation of metal sulphides, has been demonstrated through piloting to the implementation of a full-scale process.The treatment of both mine drainage and zinc refinery wastewaters are reported. A complementary role for microalgal production in the generation of alkalinity and bioadsorptive removal of metals has been utilised and an Integrated 'Algal Sulphate Reducing Ponding Process for the Treatment of Acidic and Metal Wastewaters' (ASPAM) has been described.     

Analysis of bacterial diversity in acidic pond water and compost after treatment of artificial acid mine drainage for metal removal

The microbial population of a sludge amended leaf compost material utilized for treatment of artificial acid mine drainage was studied by culture-independent molecular methods. Iron-rich and sulfurous wastewater (artificial acid mine drainage) was circulated through a column bioreactor for 16 months. After 12 months the column was inoculated with a mixed culture from an acidic pond receiving acid mine drainage from a tailings impoundment at a decommissioned site in Kristineberg, North Sweden. Hydrogen sulfide odor and the formation of black precipitates indicated that sulfate-reduction occurred in the column. 16S rDNA gene analysis by denaturing gradient gel electrophoresis, cloning, and sequencing as well as fluorescent in situ hybridization confirmed the presence of microorganisms closely related to sulfate-reducing bacteria and microorganisms from the genera Pseudoxanthmonas, Dechlorosoma, Desulfovibrio, Agrobacterium, Methylocapsa, Rhodococcus, Sulfobacillus, and some unidentified bacteria. Sulfate-reducing bacteria were found in the column bioreactor 2 weeks after inoculation, but not thereafter. This suggests they were in low abundance, even though sulfate remediation rates were significant. Instead, the population contained species similar to those previously found to utilize humic substances released from the compost material.     

Treatment of acid mine drainage by sulphate-reducing bacteria using permeable reactive barriers: A review from laboratory to full-scale experiments

Acid mine drainage in-situbioremediation has in the last decades drawnthe attention in the field of environmentalbiotechnology. The most recent treatmenttechnique are the permeable reactive barriersusing sulphate-reducing bacteria. This viewdescribes the basis of many of the currentapproaches to use sulphate-reducing bacteria inacid mine drainage treatment, from laboratoryto full-scale realisations, and the limitationsencountered when applied to full scaleapplications.     

Dynamics of bacterial community in up-flow anaerobic packed bed system for acid mine drainage treatment using wine wastes as carbon source

The dynamics of the bacterial populations in an up-flow anaerobic packed bed system (UAPB), applied in acid mine drainage treatment using wine wastes as carbon and nutrients source was elucidated by temperature gradient gel electrophoresis (TGGE) analysis. Moreover, TGGE fingerprints of the bacterial communities developed in a UAPB fed with wine wastes and a UAPB fed with pure ethanol were compared. TGGE fingerprinting and phylogenetic analysis showed that the composition of the community in the UAPB fed with wine wastes remained stable during whole time of operation and its bacterial diversity was higher. The bacterial community of the UAPB fed with wine wastes was composed by bacteria affiliated with Desulfovibrio, Clostridium, Citrobacter and Cronobacter genera and with Bacteroidales order, sp. The dominant community developed in the UAPB fed with ethanol was composed by bacteria affiliated with Desulfovibrio sp. The presence of several bacterial groups in the bioreactor fed with wine wastes suggests a synergistic interaction between the different populations. Syntrophic interaction may be the key factor for the utilization of wine wastes, a complex organic substrate, as carbon and electron source for sulphate reduction.     

Single‐cell sequencing unveils the lifestyle and CRISPR‐based population history of Hydrotalea sp. in acid mine drainage

Acid mine drainage (AMD) is characterized by an acid and metal‐rich run‐off that originates from mining systems. Despite having been studied for many decades, much remains unknown about the microbial community dynamics in AMD sites, especially during their early development, when the acidity is moderate. Here, we describe draft genome assemblies from single cells retrieved from an early‐stage AMD sample. These cells belong to the genus Hydrotalea and are closely related to Hydrotalea flava. The phylogeny and average nucleotide identity analysis suggest that all single amplified genomes (SAGs) form two clades that may represent different strains. These cells have the genomic potential for denitrification, copper and other metal resistance. Two coexisting CRISPR‐Cas loci were recovered across SAGs, and we observed heterogeneity in the population with regard to the spacer sequences, together with the loss of trailer‐end spacers. Our results suggest that the genomes of Hydrotalea sp. strains studied here are adjusting to a quickly changing selective pressure at the microhabitat scale, and an important form of this selective pressure is infection by foreign DNA.     

Chelation of ThIV, EuIII and NdIII by dianionic N,N'-bis(pyridoxylideneiminato)ethylene, (Pyr2en)2-. On the search of feasible modelings for heavy metals damage inhibition in living beings

The neutral Schiff base N,N'-bis(pyridoxylideneiminato)ethylene {H(2)pyr(2)en} reacts with Th(NO(3))4.4H2O, NdCl3.6H2O and EuCl3.6H2O to give [Th(pyr(2)en)2(H2O)] (1), [Nd(pyr(2)en)(Hpyr(2)en)].12H2O (2) and [Eu(pyr(2)en)(Hpyr(2)en)] (3). In the three not yet reported bimolecular chelate systems the endo hydroxyl groups of the rings undergo deprotonation confirming the remarkable ability of the pyridoxal-containing ligand H(2)pyr(2)en to yield stable heavy metal chelates with unusual coordination polyhedra. Complexes 2 and 3 show a coordination number 8 for Nd and Eu, achieving a distorted quadratic antiprism. In complex 1 the additional water molecule increases the coordination number of Th to 9 producing a capped square antiprism. The synthesis and structural elucidation of the title complexes starting from a probably non-toxic metabolite like H(2)pyr(2)en should represent a useful contribution to the research on models of prevention and therapy of damage caused by radioactive and heavy elements.