Mussel shells cleaning up mine sites capture international interest

December 2017

Mussel shell bioreactor (centre) at Stockton Mine on a spectacular day. Three hundred and twenty tonnes of shells treats two to three litres per second of pH3.2 water, neutralising it to around pH5 and removing dissolved metals as oxides, hydroxides and sulphides. Photo: CRL Energy.

CRL Energy and O’Kane Consultants researchers are gaining an international reputation for innovation in mine site environmental management, with collaboration or uptake of their processes now in the UK, Canada, and the USA. Waste mussel shell-based biogeochemical reactors are of particular interest, “We have been optimising and studying waste mussel shell bioreactors over the last few years in collaboration with the microbial genetics laboratory at the University of Windsor in Canada. These systems have been installed at full scale at two mine sites in New Zealand with a third system under construction and two more planned,” says CRL Energy’s South Island Group Manager, Dr James Pope.  

Dr Pope explains that at the abandoned Bellvue Mine, near Greymouth, 120 tonnes of shells neutralise the acidity by increasing pH from as low as 2.7 to about 7 and remove dissolved Fe, Al, Zn, Ni and other metal contaminants from waste water passing through the system. “There is interest in the UK to utilise this technology and others we have developed over the last few years, and we expect to be involved in either research collaboration or consultancy work related to this technology transfer.”

CRL Energy manage the government-funded New Zealand Mine Environment Life Cycle Guide research programme; a multidisciplinary collaboration including University of Canterbury, University of Otago, Landcare Research, and O’Kane Consultants NZ Ltd. The programme focuses on the environmental science needed to assist the minerals sector in gathering the right data prior to mining or early in mine development so that positive and successful rehabilitation is achieved at mine closure.

The science disciplines are split into geochemical science and ecological science. The geochemical science is mostly related to prediction of waste rock, soil and mine drainage properties and development of passive treatment or management/mitigation technologies. The ecological science is related to ecological impact/ecotoxicity, aquatic ecosystem recovery and terrestrial ecosystem reconstruction.

The research team have case study sites located at about 20 historic or active mine sites throughout New Zealand. Work programmes at these sites are usually multidisciplinary and seek to develop datasets that are regionally significant and can be used at other similar sites and, more importantly, for planning minerals sector development at future mine sites. For example, processes that might be applied for re-establishing vegetation on reshaped mine sites are highly variable depending on vegetation type, climate, rock geochemistry, soil properties, community expectation and other factors.

“Our research identifies different time trajectories of various rehabilitation techniques and critical risks that must be managed for rehabilitation to be successful. Another example is our passive mine drainage treatment research which includes genetic analysis of microbiological consortia that catalyse re-dox reactions that occur during treatment in these systems. Our research seeks to identify critical micro-organisms or communities, optimise conditions for their activity and develop small-footprint, accelerated biogeochemical mine drainage treatment systems.

“In a broad sense, our programme seeks to minimise risk for the New Zealand minerals sector by providing the underpinning science to improve certainty for environmental planning and enable effective decision-making and regulation,” says Dr Pope.