When mining activities in some parts of the Witwatersrand were discontinued in
2000, the defunct workings started to flood. In September 2002 the mine water
started to decant from the West Rand Mine Basin (WRB) next to the Tweelopie East
Stream. Treated water is currently used in the mine's metallurgical plants and 15Ml
per day of treated water is disposed firstly into the Cooke Attenuation Dam and then
discharged into the Wonderfonteinspruit.
The aim of this study was to find and provide remediation measures as a result of
acid mine drainage and other impacting factors on the water quality and volume in
the Wonderfonteinspruit.
Conductivity and total dissolved solids (TDS) were highest at the point where the
tailings dam leached into the Wonderfonteinspruit. Sulphate was very high as was
expected due to acid mine drainage. The best way to treat the high sulphate levels is
with sulphate-reducing bacteria. To avoid the fatal flaw of many other constructed
wetlands, a continuous carbon source is provided to the bacteria in the form of
activated sewage from the Flip Human sewage treatment plant. Iron and other heavy
metals are being precipitated through oxidation reactions to form oxides and
hydroxides from the aerobic cell in the wetland. The wetlands are also known for
their ability to reduce nitrate and microbial values with great success.
In the remediation, four elements that currently do not comply with the SABS criteria
for class 0 water, were chosen for improvement: conductivity, dissolved solids,
sulphate and iron. Conductivity falls within class 1 and has a maximum of 178 mS/m
@25ºC that should be reduced to under 70 mS/m. Total dissolved solids have a
value of 1585 mg/l, which is much higher than the prescribed 450 ml/l, making it
class 2 water. The last two problematic elements are both considered as class 2
water: sulphate peaks at 592 mg/l where the preferred value is 200 mg/l, and iron
should be 0.01 mg/l, not the staggering 0.3mg/l.
iv
Alternative mitigation methods were identified and analysed for the impacts of the
five major contaminators and ultimately the solution comes down to constructed
wetlands. This is not a straightforward solution, however, and a specific design to
accommodate all the different pollutants and water quality ranges was proposed.
The other mitigation methods include a cut-off trench and pump-back system for the
tailings dam, as well as the implementation of a monitoring programme. The sewage
works should be optimised and better managed. Both the settlement and agricultural
sector need to be educated on their representative impacts on the environment and
government assistance should be available. / ENVIRONMENTAL SCIENCES / MSC (ENVIRON MANAGEMENT)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:unisa/oai:uir.unisa.ac.za:10500/2123 |
| Date | 29 February 2008 |
| Creators | Opperman, Ilze |
| Contributors | Mearns, K.F. (Mr.), Van Niekerk, H.J. (Mrs.) |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 1 online resource (xii, 179 leaves) |
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