Community Research and Development Information Service - CORDIS

Final Report Summary - BIOTREATMIW (Improved biological treatment of acid mine drainage and nitrogen impacted waters from mining industries)

The objective of the project was improved treatment of mine effluent, thereby mitigating its impact on ecosystems of recipient waters and surrounding environments. This was achieved through a multidisciplinary approach that integrates analytical chemistry, environmental engineering, and microbiology for the application and development of methods for functional analysis of biogeochemical reactors treating acid mine drainage and nitrogen impacted waters from mining industries.

Mining impacted waters (MIW), and more specifically acid mine drainage (AMD) and nitrogen (N) emissions, discharged as a function of current or legacy mining activities represents a significant threat to human health, the ecology of receiving waters, and economic prosperity. The low pH and high concentration of sulfate and metals released through AMD is one of the most important mining-related pollution problems in the world with a global treatment cost in the order of tens of billions of U.S. Dollars. Thus, the impact of AMD-generation must be controlled and treatment options applied. Similarly, N-pollution from mining activities, such as leaching from undetonated ammonium nitrate fuel oil (ANFO) or breakdown of cyanide used in gold extraction processes, may cause eutrophication of recipient waters, toxification of fish, and the release of N2O, which in addition to being a greenhouse gas is the most important ozone-depleting substance of our century. To address these issues, the specific objectives were:
1. Revealing the geochemical zonation linked to spatial distribution of microorganisms affecting performance of sulfate reducing bioreactors (SRBRs) treating acid mine drainage.
2. Development of treatment strategies for biological sulfate reduction in SRBRs receiving AMD.
3. Estimation of actual and potential greenhouse gas emissions (CH4 and N2O) from SRBRs and denitrifying barrier systems.
4. Analysis of distributional patterns of functional genes in denitrifying biofilms, coupled to process performance and N2O-emissions

Work performed and achieved results
During the first period of the project, SRBR experiments were set up and executed along with analyses of AMD per se in order to delineate the biogeochemical processes that govern the performance and structure, both spatial and temporal, of these lignocellulose-based reactors. In order to attain a comprehensive understanding of these processes, three methodological paths were explored in concert:
Fluorescence-independent microbial visualization techniques were developed to allow future visualization of microbe mineral interactions. Through gold-labeling of microbial cells, using a modified protocol for in situ hybridization, circumventing the need for aggressive oxidants, this method (Polygold-FISH) is intended for use together with synchrotron-based and similar techniques for detailed analysis of the microbe-mineral interface (1).
Advanced geochemical analyses of immobilized contaminants revealed new insights into the nature of metals precipitated in SRBRs. This was made possible through collaboration with Stanford Synchrotron Radiation Lightsource (SSRL) and resulted in new data on the potential mobility of precipitated metals as an effect of bioreactor permutations (2).
The geochemistry and process performance of these systems is tightly linked to their microbial ecology. It was shown that different ratios of three lignocellulose substrates resulted in distinct performances which were reflected in the microbial community composition. The study suggests that in order to predict SRBR performance, the cellulose-degrading bacterial community rather than the sulfate-reducing bacteria, who produce the hydrogen sulfide which precipitates the dissolved metals, is the microbial guild most crucial for reactor performance (3). A whole genome shotgun sequencing effort was undertaken to provide further insight into SRBR microbial ecology and assign function to phylogenetic identity obtained via parallel 16S sequencing. While analysis of this dataset is currently being finalized (4), the genome of a novel sulfate-reducing bacterium belonging to the family Desulfobacteraceae was characterized (5) along with two Acidimicrobiaceae genomes from an acid mine drainage site (6). In addition, a manuscript describing the advantages of the utilized setup for column experiments was recently accepted for publication (7).

The second period of the project focused on mitigation of MIW contaminated by nitrogen release resulting from the use of ANFO-based explosives. Sweden is the largest iron ore producer in the EU and most of these mines are located in the northernmost, subarctic part of the country. However, little is known regarding the functionality, nature and structural properties of denitrifying biofilms residing under low temperature conditions. Therefore a long-term experiment investigating the effect of different lignocellulosic substrates on denitrification capacity, community composition and N2O-release in cold (10ºC) water was initiated and is currently running.

Socio-economic impact and societal implications:
The European Water Framework Directive states that in order to avoid the costly restoration of water bodies, discharge water from mine sites must not lower the ecological status of recipient waters. The proposed research aiding in implementation of systems for MIW treatment will not only result in benefits for the environment, but also for the European mining industry along with increasing public acceptance. This may in turn increase possibilities for commissioning of new environmentally responsible mining sites and avoiding delays in production due to excessive contamination.
Through this project, our understanding of the biogeochemical processes governing
lignocellulose-based bioreactors have improved significantly, which will aid the implementation of these and analogous systems which are employed for other purposes such as groundwater treatment.

1. Almstrand R, Drennan DM, Sharp JO. 2015. Polygold-FISH for signal amplification of metallo-labeled microbial cells. J Basic Microbiol 55:798–802.2.

2. Almstrand R, Drennan DM, Landkamer L, Ladderud JA, Bokman CM, Webb SM, Figueroa LA, Sharp JO. 2017. Geochemical evolution and precipitate speciation in sulfate-reducing bioreactors treating mining influenced water has implications for mobility and stability of resulting precipitates. Submitted Manuscript.

3. Drennan DM, Almstrand R, Lee I, Landkamer LL, Figueroa LA, Sharp JO. 2016. Organoheterotrophic Bacterial Abundance Associates With Zinc Removal in Lignocellulose-Based Sulfate Reducing Systems. Environ Sci Technol 50:378–87.

4. Almstrand R, Pinto AJ, Drennan DM, Jones ZL, Figueroa LA, Sharp JO. 2017. Microbial ecology of sulfate-reducing bioreactors treating mining-impacted water in relation to process performance parameters. Manuscript in Prep.

5. Almstrand R, Pinto AJ, Figueroa LA, Sharp JO. 2016. Draft Genome Sequence of a Novel Desulfobacteraceae Member from a Sulfate-Reducing Bioreactor Metagenome. Genome Announc 4:1–2.

6. Pinto AJ, Sharp JO, Yoder MJ, Almstrand R. 2016. Draft Genome Sequences of Two Novel Acidimicrobiaceae Members from an Acid Mine Drainage Biofilm Metagenome. Genome Announc 4:4–5.

7. Drennan DM, Almstrand R, Lee I, Landkamer LL, Figueroa LA, Sharp JO. 2016. Pilot-Scale Columns Equipped with Aqueous and Solid-Phase Sampling Ports Enable Geochemical and Molecular Microbial Investigations of Anoxic Biological Processes. Bioprotocol 6(24). In Press.

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