SACNASP CPD EVENT

Natural attenuation of acid mine drainage by various rocks in a typical Karoo coalfield: case study of the Witbank, Ermelo and Highveld coalfields, South Africa

AUTHORS
Sakala1,2, FD Fourie2, M. Gomo2 and G. Madzivire1,3
Council for Geoscience, Pretoria, South Africa
Institute for Groundwater Studies, University of the Free State, South Africa
The University of South Africa, Department of Environmental Science

In the Karoo coalfields, mining operations which release acid mine drainage (AMD) are threatening groundwater resources. An important parameter controlling the extent and severity of AMD impacts is the natural attenuation of rocks in response to introduced of AMD. Very little is known about such responses for Karoo rocks in saturated and unsaturated conditions, a research gap filled by this paper. Laboratory column leach experiments were used to study the responses of different rock types from Witbank, Ermelo and Highveld coalfields of South Africa. The results show that various rocks have varied responses and are a function of the quartz, plagioclase or carbonate mineral content. The presence of oxygen increased the rate of heavy metal removal from the AMD. For all rock samples under saturated and unsaturated conditions, the sulphate and chloride concentrations of the AMD remained unchanged after the leaching process, showing that these parameters are conservative and can be used as potential natural tracers of AMD movement in the subsurface.

The research shows that laboratory leach tests may be used to rank the various rock types found in the Karoo coalfields in terms of their capacities to buffer the impacts of AMD. Such a ranking could inform policy and decision-makers regarding the handling and storage of AMD-generating wastes, as well as the location and design of AMD waste storage facilities.

ABOUT THE PRESENTER
Dr Emmanuel Sakala is a Chief Scientist at the Council for Geoscience with expertise in natural resources exploration using geophysical techniques, design and application of artificial intelligence (AI) systems in geoscience. He has worked as a geophysicist in mining, research and consultancy services for 14 years in 11 African countries. He holds a BSc (Hons) degree in Applied Physics (2005), MSc degree in Geophysics (2007) from the National University of Science and Technology and a PhD degree in Geohydrology (2018) from the University of the Free State. In his career, he received five awards for outstanding research, conference proceedings and competitions.

Extract Presentation Dr E Sakala on Background to the Study
About the Methodology applied in the Study
Test Sheets on column leach results

AMD Natural Attenuation potential map

Energy Source (Fluid & Pollutant Source; Transport, Trap, Aquifer); Relative Rock - AMD reactivity

Thank you Dr Sakala for sharing your Case Study with attendees.
We appreciate the insights into possible tracers, potential handling & storage of AMD-generating wastes, passive treatment and future research suggestions.
(Please contact Mr K Majola (GWD GAU Branch Chair) via info@nullgwd.org.za for CGS liaison regarding the presentation & event recording *CGS disclaimer)

Live Engagement:

D Question : Realistically, is 'clean coal' financially viable in the South African context? And if it is, why is no-one / so few applying the technology? As a non-mining geologist, I'm rather skeptical that any mining is 'little or no environmental harm'?

T Question: Would the idea not be to attempt neutralization before decanting? Has the thought of limestone being given as back filling material?

C Question: In dolerite what about pyroxene dissolution reactions?

A 2016 report by the Council for Scientific and Industrial Research (CSIR) titled Shale Gas Development in the Central Karoo: A Scientific Assessment of the Opportunities and Risks, recommended that “a comprehensive understanding of groundwater conditions is required prior to the commencement of exploration to ensure proper interpretation of changes in groundwater over time. [...] Monitoring data would also be used for calibration and verification of prediction and assessment models, for evaluating and auditing the success of management plans, and for assessing the extent of compliance with prescribed standards and regulations.”

Independent specialists and researchers from the Institute for Groundwater Studies (IGS) at the University of the Free State (UFS), in partnership with specialists from Carin Bosman Sustainable Solutions (CBSS), have been appointed by the Petroleum Agency of South Africa (PASA) to design a regional groundwater monitoring network for the Central Karoo.  The specialists employed by the IGS and CBSS to undertake the project include SACNASP-registered scientists who have expertise and experience in geohydrology and the geology of the Karoo Basin, as well as experts in water governance (including the design and development of water monitoring programmes and the evaluation, interpretation, and visualisation of water quality data), and software developers who can handle large volumes of water monitoring data. 

Visit the CBSS website and learn more & participate!!
https://cbosss.com/igscbss-to-design-gw-monitoring-network-for-karoo/

SACNASP CPD EVENT

The GAKZN Webinar hosted, in association with the GWD and the University of KwaZulu-Natal, had two speakers presenting on current research findings:

Presentation 1

TALK ABSTRACT: The Gravity Recovery and Climate Experiment (GRACE) satellite data interpretation provides an integrated measure of monthly terrestrial water mass changes. The GRACE satellite data has been successfully used to estimate the monthly changes of terrestrial water storage (TWS) including groundwater storage changes. This presentation will provide an overview and application of the GRACE satellite product to determine the groundwater storage changes in Usutu-Mhlatuze Drainage Region in north eastern South Africa.

ABOUT THE PRESENTER: Manish  Ramjeawon  is  a  Hydrology  PhD  candidate  from  the  University  of KwaZulu-Natal. His current  research interest  involves the  impact  of  land use change on surface water and groundwater resources in northern KwaZulu-Natal.

tags

GRACE, GRACE-FO, Modelling, land-use, Usutu-Mhlatuze Drainage Region, monthly images, surface water data, 3 lakes, eastern coast, 9 dams, global land data simulation, NASA, resolution, GLDAS, soil moisture, NOAH land surface model (LSM), storage, anomalies, mean 2002-2009, trend 2002-2006 decrease, DWS, variation, 2017-current steep decline, 2017-2018 gaps in data satellite, not operational, cloud cover, general trend, consistent, soil moisture anomaly, between 2014-2019 decline water levels, purpose of study, primary, secondary aquifer, storage for catchment, steep decline to 2020, groundwater storage, deviation of the mean, size of the secondary aquifer, decreased groundwater storage. Institute data, groundwater monitoring data, DWS stations, compare with GRACE on primary, similar trend, WMA, decreased rainfall, land-use, commercial forestry, eucalypti, 1000 hectares per annum and 35% drain, Lake Sibaya. Limited groundwater monitor stations, GRACE potential

Thank you to my research supervisors

Dr Molla Demlie - demliem@nullukzn.ac.za
& Dr Michelle Tosha
Funders Acknowledged.

---------------

Presentation 2

TALK ABSTRACT: This presentation highlights the results of the development and the calibration of a steady-state and transient three-Dimensional numerical groundwater flow modeling based on a robust conceptual hydrogeological model of the area. The calibrated transient numerical groundwater flow model is further used to understand the advective transport of a hypothetical contaminant released from the site of a proposed nuclear power facility at Thyspunt. The information gained from the numerical groundwater flow and advective transport models help to understand the background hydrogeological conditions to be used as input in the environmental impact assessment and as a reference for future post development conditions of the area.

ABOUT THE PRESENTER: Mr Moneri Joel Modiba is a young professional hydrogeologist. He is a member of the GSSA and worked as a geologist at the Marula Platinum Mine. He holds a BSc honours Degree in Geology from University of Limpopo and a MSc Degree in Hydrogeology from the University of KwaZulu-Natal.

tags

three-dimensional, numerical modelling, testpump area, nuclear station, EIA required, conceptional groundwater flow, hydrological condition, contaminant transport, isotope analysis, study advective transport, eastern cape, 120km west PE, high rainfall, winter, topography, 2 drainage systems, rivers, highlands to Indian ocean, meta-sedimantary rock, metholotic interconnect, geology, TMG fractured, outcrops, preferential pathways, intergranular, aquifers, fractured, less productive than, methodology, climate data, earth data, hydrostratigraphic unit, chemical, trace elements, iron oxidation, robust, 3d model, calibration, converted, advective transport model, hydraulic parameters, arteasian borehole, chemical, PH, EC, classification, fresh water, iron in mix, seawater and surface water, evaporation, tritium analysis, modern water, older water, software, Thyspunt, MODFLOW, upstream package, 2 layers, 2 formations, deepest borehole with constant elevation, pumping, model domain, specified head, model grid, top elevation, steady state, conversion, calibration test, water budget, total inflow, successful model, head distribution, relationship, similar observed, simulated, good fit, simulation, transient, forward particle, flowpath, injected, particles, indian ocean, future, proposed footprint, reversed, tracking, no seawater intrusion, domain, transport, tracking, recommendation, robust, mean absolute error, 4 decades, reach ocean, ongoing monitoring

Special thank you to Prof Demlie and Prof Tumara.
Funders and hosts acknowledged.

Discussions

Talk 1 Q SN: Thanks Manish. Would like to please find out if there is any correlation with the lack of flood releases from Pongolapoort Dam (fills numerous pans) and groundwater recharge, probably focusing on the secondary aquifer.
Manish: Did not look into floodlands and correlation with data that I have. I will let you know if I find anything on that.

Talk 2 Q PR: An EIA has already been done for this site, including a groundwater specialist report including modelling? References - EIA specialist report missing?
MD responds: This study is independent of what has been already done. The researcher was not allowed to refer to the EIA.

Talk 2 Q PR: Figure 20. Conceptually, recharge is postulated to flow from the higher lying TMGA of the Kareedouw Mountains towards Cape St. Francis. Therefore not sure about the no-flow boundary across this area?
Moneri: I think the reason we assigned a north flow boundary from that area. We don't have (e.g. rivers) a groundwater divider that side , it was done not to allow water into the model domain.

Talk 2 Q PR: How were the aquifer parameters such as T and S derived - from test pumping or from previous work? Why not do advective transport from the proposed nuclear installation footprint?

Moneri: They were derived from pumping tests. Pumping test data analysis done by the research from data provided by NNR. Data that were already done in the field. Vector transport from Nuclear footprint was done but not included in the presentation.

Mr Pieter Labuschagne noted that these regular science sharing sessions are of great importance, arranged quarterly by the/ with the students & branch support, and thanked all that attended.

EVENT RECORDING

National Chairperson: Mr Fanus Fourie
Vice-Chairperson: Ms Nicolette Vermaak
National Treasurer: Mr Yazeed van Wyk
National Secretariat: Dr Jaco Nel
National Coordinator: Ms Elanda Schaffner

Please contact this Committee via [email protected]

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