One of the highs of the last 12 months was being awarded the first phase of the mechanical equipment for the Acid Mine Drainage Central Works (AMD).
SAME Water has recently been fortunate enough to have been awarded the Acid Mine Drainage Central Basin Pre Neutralisation Water Treatment Plant – Mechanical Contract, covering one of the most concerning domestic water treatment challenges which is the treatment of Acid Mine Drainage water throughout Gauteng and beyond.
The mining operations on the Witwatersrand are split among three basins:
- Western Basin stretching from Randfontein to Roodepoort
- Central Basin stretching from Roodepoort to Boksburg
- Eastern Basin stretching from Boksburg to Springs
Mine water started accumulating in the old mine workings as underground operations ceased and withdrew from the basins. The mine water is characterised by acidity, high metal content and high salinity. If the mine water accumulation is allowed to continue, then the Acid Mine Drainage (AMD) will eventually fill the basins and start impacting on shallow groundwater bodies and surface water resources. The Inter Ministerial Committee on Acid Mine Drainage recommended specific actions to manage and control the AMD. As part of the short-term solution for the Central Basin, a new water treatment plant will be designed and built to treat excess mine water to a standard suitable for interim discharge to the environment. The treatment process will incorporate neutralisation and metals removal with limited desalination.
The main components of the mine water collection system include the following:
- Abstraction (feed) pumps at ERPM South West Vertical (SWV) Shaft
- Transfer pipelines from ERPM SWV Shaft to the adjacent Central Basin Water Treatment Plant
The main components of the dosing system for the Water Treatment Plant include the following process units:
- Limestone (CaCO3) dosing system
- Unslaked Lime dosing system (Quicklime, CaO)
- Polymer (polyelectrolyte) dosing system
The main components of the Central Basin Water Treatment Plant include the following process units:
- Feed splitter box
- Two parallel reactor modules consisting of:
- Sludge conditioning tank
- Reactor, consisting of:
- Pre-neutralisation tank
- Neutralisation tank
- Gypsum crystallisation tank
- Dosing mixing box
- Two parallel thickeners
- Sludge recycle pumps
- Sludge mixing tank
The main components of the treated water discharge and waste disposal systems include the following process units:
- Treated water sump
- Utility water pump station
- Treated water transfer pipeline from the Central Basin Water Treatment Plant to Elsburg Spruit
- Waste sludge pumps, pumping out of the sludge mixing tank (to be designed)
- Waste transfer pipeline from the Central Basin Water Treatment Plant to DRDGold transfer pipeline (Knights/Brakpan TSF)
