9:50am - 10:15am
Lake Kepwari: Western Australia’s First Successfully Relinquished Mine Lake.
Mine Lakes Consulting, Australia
Mine pit lakes typically present significant mine closure liabilities in perpetuity though large volumes of contaminated waters. Lake Kepwari represents a significant achievement in mine closure planning as the first successfully rehabilitated and relinquished pit lake in Western Australia.
Lake Kepwari uses seasonal flow to remediate water quality and provide ecological connectivity to the broader catchment. State government endorsed the approach with a formal opening on December 2020 with significant infrastructure developments. Lake Kepwari demonstrates pit lake planning that presents a significant local opportunity for the mining town with regional benefits to state tourism and recreational opportunities too.
10:15am - 10:40am
Passive Treatment Of AMD Using a Full-Scale Up-Flow Mussel Shell Reactor, Bellvue Coal Mine, New Zealand
Verum Group, New Zealand
This work presents the results of the first full-scale up-flow mussel shell reactor to treat AMD reported in the literature. In an up-flow configuration, the theory suggests that reducing conditions would be prevalent throughout the reactor, resulting in sulfate reduction and formation of sulfides rather than hydroxides which can reduce permeability with time in downflow reactors. The system raises the pH of the AMD from a median of 2.74 to a median of 6.94 and lowers metal concentrations by 97.2% (Fe), 99.8% (Al), 98.2% (Zn) and 97.0% (Ni). The benefits and challenges of up-flow reactors are discussed.
10:40am - 11:05am
Full-scale Compact Passive Treatment System for a Japanese AMD by Aerobic Bioreactor for Fe Removal and Sulfate Reducing Bacteria Bioreactor for Zn Removal
Japan Oil, Gas and Metals National Corporation, Japan
Full-scale compact passive treatment system (flow rate: 100 L/min) was started at an abandoned mine site in Japan. AMD containing iron (35 to 40 mg/L) and zinc (15 to 20 mg/L) was treated in two biological steps: aerobic bioreactor with iron oxidizing bacteria and anaerobic reactor with sulfate reducing bacteria (SRB). In the aerobic reactor, iron was treated to below the wastewater standards by using a water transfer method such as a cascade. In the anaerobic bioreactor, two process utilizing rice bran and ethanol respectively, SO4 reduction and zinc removal were performed.
11:05am - 11:30am
Successful Passive Treatment of Sulfate Rich Water
1SLR Consulting Limited, United Kingdom; 2SLR Consulting Limited, United Kingdom; 3SLR Consulting Limited, United Kingdom
A passive sulfate reduction system was used to treat elevated sulfate within leachate from an old landfill and bench scale trials were established in 2019. This used of Biochemical Reactors to culture sulfate reducing bacteria. The resulting treated leachate was then passed through different iron media types to remove sulfide generated by the bacteria. An aerobic wetland used to polish the effluent. The success of the bench scale project led to a pilot scale system being constructed in 2020 providing insights into management of the system particular in winter months.
11:30am - 11:55am
Mobilization of Bound Arsenic and Antimony from Peat used for the Treatment of Mining-Affected Waters
1University of Oulu, Finland; 2University of Applied Sciences FH Aachen, Germany
Mining-affected waters need to be purified for their safe discharge into water bodies. In Finland, peatlands are frequently used in the polishing phase of water treatment. Changes to inflow water quality to the treatment peatlands can trigger release of previously bound contaminants from the peat. A laboratory column experiment was designed to simulate leaching of arsenic and antimony from peat by transition from highly contaminated wastewater to less contaminated water. Inflow water composition change led to leaching and redistribution of bound arsenic and antimony in the peat column. Peak of bound arsenic/antimony shifted towards the outlet during the leaching phase.