Decline in Performance of Biochemical Reactors for Sulphate Removal from Mine-Influenced Water is Accompanied by Changes in Organic Matter Characteristics and Microbial Population Composition

Abstract

Successful long-term bioremediation of mining-influenced water using complex organic matter and naturally-occurring microorganisms in sub-surface flow constructed wetlands requires a balance between easily and more slowly degrading material. This can be achieved by combining different types of organic materials. To provide guidance on what mixture combinations to use, information is needed on how the ratio of labile to recalcitrant components affects the degradation rate and the types of microbial populations supported. To investigate this, different ratios of wood and hay were used in up-flow column bioreactors treating selenium-and sulphate-containing synthetic mine-influenced water. The degradation rates of crude fibre components appeared to be similar regardless of the relative amounts of wood and hay. However, the nature of the degradation products might have differed in that those produced in the hay-rich bioreactors were more biodegradable and supported high sulphate-reduction rates. Microorganisms in the sulphate-reducing and cellulose-degrading inocula persisted in the bioreactors indicating that bio-augmentation was effective. There was a shift in microbial community composition over time suggesting that different microbial groups were involved in decomposition of more recalcitrant material. When dissolved organic carbon (DOC) was over-supplied, the relative abundance of sulphate-reducers was low even through high sulphate-reduction rates were achieved. As DOC diminished, sulphate-reducers become more prevalent and their relative abundance correlated with sulphate concentrations rather than sulphate-reduction rate.

Diversity and Abundance of Microbial Communities in UASB Reactors during Methane Production from Hydrolyzed Wheat Straw and Lucerne

“…At the end of experiment, besides the decreases in the abovementioned phyla, two uncultured clones, AUTHM297 (belonging to family Petrotogaceae, phylum Thermotogae), and NB1-n (belonging to class Mollicutes, phylum Tenericutes), appeared in reactors 2A and 2B, and were also positively correlated with the level of organic acids in the CCA. Clone AUTHM297 has been found in various AD systems, including UASB reactors [80], batch reactors [81,82], and anaerobic migrating blanket reactors (AMBR) [83]. There is no information available about the putative functions of AUTHM297, as no cultured representatives have been identified for this group.…”

“…There is no information available about the putative functions of AUTHM297, as no cultured representatives have been identified for this group. A recent study found AUTHM297 to be enriched at the end stage of a UASB process operating with a wood and hay mixture and selenium-and sulfate-containing synthetic mine-influenced water, while the organic acid concentration in the reactor was very low [80]. It has also been hypothesized that AUTHM297 has a specialized metabolism that allows it to survive in environments with highly degraded organic matter [80].…”

“…A recent study found AUTHM297 to be enriched at the end stage of a UASB process operating with a wood and hay mixture and selenium-and sulfate-containing synthetic mine-influenced water, while the organic acid concentration in the reactor was very low [80]. It has also been hypothesized that AUTHM297 has a specialized metabolism that allows it to survive in environments with highly degraded organic matter [80]. The relationship between AUTHM297 and methanogens has not been studied, but one study has pointed out that members of the Thermotogae can grow on acetate in the presence of the methanogen Methanobacteriaceae [84].…”