Dynamics of Bacterial Communities Mediating the Treatment of an As-Rich Acid Mine Drainage in a Field Pilot

Abstract

Passive treatment based on iron biological oxidation is a promising strategy for Arsenic (As)-rich acid mine drainage (AMD) remediation. In the present study, we characterized by 16S rRNA metabarcoding the bacterial diversity in a field-pilot bioreactor treating extremely As-rich AMD in situ, over a 6 months monitoring period. Inside the bioreactor, the bacterial communities responsible for iron and arsenic removal formed a biofilm (“biogenic precipitate”) whose composition varied in time and space. These communities evolved from a structure at first similar to the one of the feed water used as an inoculum to a structure quite similar to the natural biofilm developing in situ in the AMD. Over the monitoring period, iron-oxidizing bacteria always largely dominated the biogenic precipitate, with distinct populations (Gallionella, Ferrovum, Leptospirillum, Acidithiobacillus, Ferritrophicum), whose relative proportions extensively varied among time and space. A spatial structuring was observed inside the trays (arranged in series) composing the bioreactor. This spatial dynamic could be linked to the variation of the physico-chemistry of the AMD water between the raw water entering and the treated water exiting the pilot. According to redundancy analysis (RDA), the following parameters exerted a control on the bacterial communities potentially involved in the water treatment process: dissolved oxygen, temperature, pH, dissolved sulfates, arsenic and Fe(II) concentrations and redox potential. Appreciable arsenite oxidation occurring in the bioreactor could be linked to the stable presence of two distinct monophylogenetic groups of Thiomonas related bacteria. The ubiquity and the physiological diversity of the bacteria identified, as well as the presence of bacteria of biotechnological relevance, suggested that this treatment system could be applied to the treatment of other AMD.

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

“…Passive treatment of As-rich AMD via iron biological oxidation showed that the biogenic precipitate formed is dominated by iron-oxidizing bacteria (FeOB) such as Gallionella, Ferrovum, Leptospirillum, Acidithiobacillus, and Ferritrophicum, and arsenite-oxidizing Thiomonas spp. (Laroche et al, 2018). Similarly, passive bioremediation system enriched with Ignavibacterium, Pelotomaculum, and Petrimonas and species known to catalyse the dissimilatory reduction of ferric iron (Geobacter psychrophilus), oxidation of sulfur (Polaromonas hydrogenivorans, Flavobacterium johnsoniae, Dechloromonas aromatica, Novosphingobium sediminicola, Clostridium saccharobutylicum, and Pseudomonas extremaustralis), and reduction of nitrate (Sulfuricella denitrificans, A. ferrooxidans, and Acidithiobacillus thiooxidans), methylotrophs (methane/methanol-oxidizers), and anaerobic aromatic compound-degraders (Syntrophorhabdus sp.)…”

Functional redundancy imparts process stability to acidic Fe(II)‐oxidizing microbial reactors

“…In the low pH FeOX reactors examined in this study, geochemical conditions and temporal distances influenced microbial community composition without affecting Fe(II) oxidation rates (Sheng et al ., 2016; Sheng et al ., 2017), which may be imparted by the presence of multiple FeOX taxa that were able to co‐exist. These results are consistent with previous studies, which showed that microbial communities in flow‐through Fe(II)‐oxidizing reactors changed over time without affecting reactor performance (Jones and Johnson, 2016; Laroche et al ., 2018). Metabolic potential for Fe(II) oxidation at low pH could derive from a variety of populations including Acidithiobacillus sp., Ferrovum sp.…”

The Microbiology of Metal Mine Waste: Bioremediation Applications and Implications for Planetary Health

“…Fe oxide precipitates have been shown to scavenge arsenic from AMD in passive treatment systems (Elbaz-Poulichet et al, 2006;Fernandez-Rojo et al, 2019;Valente et al, 2011). Analysis of the oxide precipitates identified that Fe(II) oxidising bacteria dominated and known arsenite oxidisers were also present, therefore microbes were likely contributing to As removal from solution (Laroche et al, 2018). The release of 25,000 -50,000 m 3 of acidic mine water from the Wheal Jane mine to the Fal River estuary (Cornwall, England) over 24 h in 1992 induced the Government to investigate remediation options (pumping 90 -300 L s -1 ) (Younger et al, 2005).…”