Novel cost effective full scale mussel shell bioreactors for metal removal and acid neutralization

Evaluating the microbial community and gene regulation involved in crystallization kinetics of ZnS formation in reduced environments

“…Higher Zn concentrations are also a possibility, as the Whirlwind Seep serving as the source for the MSB in question was characterized by a Zn concentration of 0.26 mg L -1 (± 0.05) and an influent flow rate and residence time of 1-6 L s -1 and 0.37-2.2 days (dependent on seasonality), respectively, enough to saturate the bioreactor with high levels of metals. Furthermore, targeted extractions identified Zn as being highly associated with reducible phases at the depth of the bioreactor analyzed (DiLoreto et al, 2016a;DiLoreto et al, 2016b). Surprisingly, few cells were observed associated with ZnS phases in the raw bioreactor material, a stark contrast to observations in other work (Moreau et al, 2004).…”

“…Despite this constraint on sulfur reduction, sulfate removal rates were within ranges typically measured for passive treatment technologies, specifically, which are often comprised of multiple bacterial groups (DiLoreto et al, 2016a). However, an additional consideration with mixed bacterial enrichments is that total sulfate removal may not be translated directly into hydrogen sulfide production, i.e., the sulfate removal rate cannot be quantified as the sulfur reduction rate.…”

“…Analysis has shown that a geochemical gradient develops within the bioreactor, going from oxic, to suboxic, to reducing with depth. The redox change is concomitant with distinct reaction layers, including an upper allochthonous sediment zone, an iron-rich oxidized zone, an aluminum-rich zone, and a lower, unreacted shell material zone at the bottom (DiLoreto et al, 2016a). Bacterial communities in the reducing zone are hypothesized to contribute to metal removal (primarily Zn, Tl, and Ni) via biogenic sulfide precipitation, however this biotic mechanism has yet to be explored thoroughly within the bioreactor.…”

Biogeochemical Characterization of Metal Behavior from Novel Mussel Shell Bioreactor Sludge Residues

“…Details of the MSB and mine site have been described in past studies [9,[13][14][15]. The coal mine is located on the west coast of New Zealand within the Brunner Coal Measures, a formation containing 1-5 wt% pyrite and is potentially acid forming (PAF) [14,16,17].…”

“…A novel full-scale mussel shell bioreactor (MSB) was constructed in 2011 and is currently treating an AMD seep at a coal mine on the west coast of the South Island of New Zealand. The MSB removes approximately 99% of all metals and raises the pH from 3.3 to 7.9 and is estimated to be 15 times more cost-effective than other methods [9]. The MSB has distinct geochemical layers including: an allochthonous sediment/sludge layer (0-15 cm), Fe oxide reacted shell layer (15-35 cm), Al oxide reacted shell layer and reduced unreacted shells (60-130 cm).…”