HybridICE Freeze Crystallization

Cost of desalination technologies

TechnologyRunning cost Income

Difference

R/m3 R/m3 R/m3

CSIR ABC (Alkali-Barium-Calcium) Process 4.04 3.56 -0.49KeyPlan HiPRO Process 9.12 3.35 -5.78AR Technologies Sodium Carbonate Reverse Osmosis Process (ARRO) 12.79 4.29 -8.51Mintek SAVMIN 11.3 3.84 -7.46EARH Ion Exchange 12.95 10.7 -2.25Paques Thiopaq Process/CSIRosure 8.73 5.7 -3.03Biosure 8.73 6.12 -2.61TUT/CSIR MBA (Magnesium-Barium-Alkali) Process (laboratory stage) 2.22 5.58 3.36Lime treatment for Industrial water 5.5 0.7 -4.8

Sulphur import 1 000 000 t/aPrice 2 000 R/tCost of sulphur for SA 2 000 000 000 R/aSA Total imports 70 800 000 000Precentage 2.8

Gypsum from fertilizer industry

Sulphur Recovery flow diagram

CaSO4/Mg(OH)2/CoalD

SulphurPipco

1100 deg C

CaS(s) H2S

H2O

A MgO(s)

CH2OMg(HCO3)2

BCaCO3/Ash MgCO3

CO2 from kiln

PUMPING OR NOT

Pumping cost

Ph = q ρ g h / (3.6 x 106) where

Ph = power (kW); q = flow capacity (m3/h); ρ = density of fluid (kg/m3); g = gravity (9.81 m/s2); h = differential head (m)

Recommendation: Determine whether ECL levels can be moved to higher levels

Parameter BasinWestern Eastern Central Total

Flow (Ml/d) 20 108 60 188Current water depth (m) - 700 500 Head, h (m) 150 400 200Electricity cost:Pump effi ciency (%) 0.5 0.5 0.5Power cost (R/kWh) 0.50 0.50 0.50

Electricity cost (R/m3) 0.41 1.09 0.55 Electricity cost (R/a) 2 983 875 42 967 800 11 935 500 57 887 175Capital cost:Pump cost (R/kW) 16 000 16 000 16 000Pump capital cost (R) 10 900 000 156 960 000 43 600 000 211 460 000Equalization pond cost: 40 095 873 154 892 364 95 494 429 290 482 666

When to pump

• Allow future mining and the protection of tourist sites.• Protect ground water to be contaminated with mine water.• Provide flow-equalization storage areas in sub-surface voids.

(Alternatively, such storage facilities (e.g. ponds) need to be constructed on surface.)

Benefits associated when water is allowed to decant

• Less pyrites oxidation as a result of ingress water running through broken rock; and

• Less pyrites oxidation due to no reciprocating contact of pyrites-rich ore with water and oxygen as the water level fluctuates from water being pumped out at a constant rate while the incoming water flow-rate fluctuates with seasonal rainfall,

• Limited dissolution of limestone/dolomite due to ingress of rain water

Problems/Solutions to rising levels of acid mine water

Problem Solution

Ground water pollution Rand water distribution system

Damage to foundations Injection of clean water

Acknowledgements

• TUT• Rand Water• THRIP• Industrial partners (KSH, Marlow Aquatec)