Conference Agenda

Passive and semi-passive treatment systems show great potential to treat AMD originating from abandoned mines. The aim of this study was to determine iron and arsenic removal yields of two field treatment devices, which were designed to optimize natural process of bio-oxidation and co-precipitation to clean-up mine waste water. Almost one year of monitoring showed efficiency and stability of the treatment under environmental and operational variations. Using assisted aeration and bacterial support in the devices, average arsenic and iron removals of 67% and 43% were achieved. Additional steps will be considered to reach water quality and sludge disposal requirements.

Acid rock drainage (ARD) is a global crisis that will have long-lasting environmental consequences. The application of semi-passive biological sulfate reduction (BSR) is a potential solution for the remediation of persistent low-volume ARD effluents. However, major challenges of BSR, including slow reaction kinetics and management of the generated sulfide, still need to be addressed. The development of a hybrid Linear Flow Channel Reactor (LFCR) has shown promise for remediation of sulfate-rich effluents. In this study, the operation of two hybrid LFCRs connected as a dual reactor system was assessed for the improved removal of residual sulfide and COD.

Closure of saline pit lakes is problematic as they are considered to have few prospects for future uses. In 2019, we assessed limnology and biodiversity of a two saline pit lakes (≈3.2-10.5 mS cm^-1) from each of Australia’s main coal regions (Hunter Valley and Bowen Basin), one of which was rehabilitated.

Quarterly concentrations of nutrients, metal/metalloids and major ions were measured top and bottom with physico-chemical profiles throughout the water column. Aquatic biodiversity was assessed through macroinvertebrates, diatoms, and plankton communities.

Lakes were temperature but not salinity stratified and had limited metal/metalloid concentrations of concern. Salinity did not appear to limit biodiversity.

Lisheen Mine, located in Tipperary, Ireland, was operational between 1999 and 2015. Through most of mine life, dewatering rates were typically within a seasonal range of 60 to 90 MLD, and rapidly changed with precipitation, which reflected the low storage of the limestone bedrock. After closure, groundwater levels in the mine workings rose over 120 m in the first three months, further demonstrating the low storage of the bedrock. Full recovery of the workings was confirmed in early 2018, 2 years after closure, when the natural seasonal variation in groundwater levels had re-established.

Groundwater rebound is one of the key challenges for the renaturation of underground mines. Numerical models can support the computation of rebound curves and the identification of long-term groundwater levels after steady-state conditions are reached. The present finite-element model case was to test the combination of different flow types and parameter configurations inside mine workings in order to optimally represent the flow patterns in cavity volumes and fractured rock masses. The approach may be an alternative to common pond-and-pipe models, particularly, if estimated cavity volumes of mine workings are uncertain or if groundwater levels in the surroundings are precarious.