A reduction in mining and industrial effluents in the Blesbokspruit Ramsar wetland, South Africa: Has the quality of the surface water in the wetland improved?

Abstract

The Blesbokspruit Wetland, 40 km southeast of Johannesburg, South Africa, was listed as a Ramsar Wetland of International Importance in 1986. Following discharges of mine-waters in the mid-1990s, the wetland no longer complied with the Ramsar criteria. This paper reports on historical trends in surface water quality of the Blesbokspruit, as a step towards restoration to Ramsar status. Monthly water quality data (SO 4 , Na, Cl and Mg concentrations, pH and EC values), from January 2000 to December 2011, were obtained from Rand Water for sites at: the stream inflow, just after the discharge point of pumped underground mine-water from Grootvlei mine, and the stream outflow point. The major ions were grouped into two distinct time-variation patterns (SO 4 -Mg) and (Na-Cl). Despite extensive reports that the wetland had an acid mine drainage problem, the pH values over an 11-year period were constrained within a range of 6.7 to 8.8. In 2011, following the cessation of underground mine-water pumping operations, mineralisation of the Blesbokspruit showed a large stepwise reduction, in contrast to a slowly decreasing trend over the previous 10 years, in both the SO 4 -Mg and Na-Cl groups, and EC. The stepwise reduction suggests that the pulping plant within the paper mill, a major source of Na-Cl rich effluent, had ceased operations coincidentally with the cessation of underground water discharges. This contradicts previous findings that underground mine-water discharge was the principal contributor to contamination of the Blesbokspruit Wetland. So, while the Blesbokspruit may have had a high mineralisation problem, this was not simply an acid mine drainage problem, but a combination of the effects of mining and industry.

The influence of a high-density sludge acid mine drainage (AMD) chemical treatment plant on water quality along the Blesbokspruit Wetland, South Africa

“…Acid mine drainage (AMD) is one of the most destructive forms of pollution in terms of water quality (Oberholster, 2010;McCarthy, 2011;Ambani and Annegarn, 2015). The process of AMD generation is well understood; through exposure of pyrite and other minerals by mining activities, water arising in or drained from coal and gold mines contains sulphuric acid and toxic heavy metals (Ochieng et al, 2010;McCarthy, 2011).…”

“…Grootvlei Proprietary Mine in Springs was in operation from 1934 until 2010 and is located within the Blesbokspruit Wetland (Ambani and Annegarn, 2015). The mine is upstream of the Marievale Bird Sanctuary that lies within the southern half of the Blesbokspruit Wetland (DWS, 2017).…”

“…The Blesbokspruit Wetland formed during the 1930 construction of road and pipeline embankments for the mining industry (UNEP-AEWA, 2020), and developed as a result of increased flow regimes brought about during the dewatering operations of the mine over many years (Roychoudhury and Starke, 2006;Ochieng et al, 2010). The Blesbokspruit Wetland was first accepted as a Ramsar Wetland of International Importance in 1986 due to the important biodiversity (locally migrant waterbirds and various notable mammals at Marievale Bird Sanctuary) it supported during the accreditation period (Ambani and Annegarn, 2015;Ramsar, 2020;UNEP-AEWA, 2020).…”

“…The Montreux Record is a register which lists potentially threatened or degraded Ramsar sites that no longer meet the Ramsar Convention standards, and the wetland remains on this register to the present day (Ramsar, 2020;UNEP-AEWA, 2020). Grootvlei Mine began pumping again in 1996 on condition that they treated underground water pumped to the surface through the use of a high-density sludge (HDS) process before discharge into the Blesbokspruit (De Wet and Sidu, 2013;Ambani and Annegarn, 2015). The HDS process is an active, abiotic (chemical) treatment designed to neutralise the acidic mine-water and allow for the precipitation and removal of heavy metals (Akcil and Koldas, 2006;Johnson and Hallberg, 2005).…”

“…The HDS process is an active, abiotic (chemical) treatment designed to neutralise the acidic mine-water and allow for the precipitation and removal of heavy metals (Akcil and Koldas, 2006;Johnson and Hallberg, 2005). The original smaller HDS plant undoubtedly improved effluent quality while the mine was in operation; however, it produced water with high dissolved salt content that was discharged downstream (Thorius, 2004;Ambani and Annegarn, 2015).…”