HeapLeach y Huella Hídrica presentado en Congreso Heap Leaching, Lima 2016

1. Heap Leaching
and Water Footprint
Augusto Chung Ching, Rio Alto Mining
Oswaldo Tovar, Ingeniería de Recursos SRL

2. Overview
• Understand importance of water
• Definition of Water footprint
• Types of water
• Water balance
• Benchmark
• Challenges
• Proposal
• Conclusions

3. Heap Leach & Water Footprint
• Understand your water in the mining industry:
• Communicating water use is fundamental to maintaining
social license to operate
• Water accounting is to focus on reducing your own
consumption
• Water storage in heaps (iceberg)
• Solution inventory (water and dissolved metals)
• Permanent vs On-off pad
• Water problems with communities and regulators
• We license, take water, use, storage, recirculate as much
as possible, evaporate, treat, return to body water

4. Water Footprint
• Water footprint is the volume of fresh water
used to produce a product summed over the
various steps of the supply chain
• Water footprint goes on to:
– Quantity of the volume
– Consider the type of water used
– Consider when and where the water is used

5. Examples of Water Footprint for…
• 1 cup of coffee, 150 liters of water
• 1 kg refined sugar, 1500 liters
• 1 kg of tomatoes, 180 liters
• 1 sheet of A4 paper, 10 liters
• 1 kg of meat, 15,500 liters
• 1 kg of cotton, 11,000 liters
• Treatment of 1 ton of Cu ore, 1050 liters
• Treatment of 1 ton of Au ore, 1250 liters

6. Type of Water used
• Green water = rain water
• Blue water = surface water, river, lakes,
underground water
• Gray water = retreated water, polluted water

7. Green Water
Green Water
(rain)
Impoundment
Incorporated
into the heap
or process
Evaporated

8. Blue Water
Blue Water
(river, lake,
Underground)
Evaporated volume
Returned to another
catchment area or
the sea
Incorporated to
heap or process

9. Gray Water
Gray Water
(volume of
polluted water)
Bypassed
Treated and/or released
into the water body
Consumed
(incorporated to
heap or process)

11. Water Footprint
• Measures fresh water appropriation
• Actual, locally specific values
• Always referring to full supply-chain
• Focus on reducing own water footprint

12. Ground and surface water
rain
Runoff
at field level
Non-production
related
evapotranspiration
Soil and vegetation
HEAP
process
Rivers, lakes
abstraction
Return
flow
farms
Production-related
evapotranspiration
Water-contained
In products
GREEN WF
evaporation
Water contained in products
Water to other catchment
BLUE WF
GRAY WF
Catchment area

13. Evapotranspiration
• Evaporation is the process where liquid water is
converted into vapor water
– Evaporation is predominant when crop is small and water loss is primarily by
soil evaporation, or under high frequency wetting when soil evaporation and
evaporation of free water from plant surfaces can be high
• Evapotranspiration is vaporization of liquid water
and plants / vapor removal from the atmosphere
– ET is an energy controlled process requiring the
conversion of available radiation energy (sunshine) and
sensible energy (heat contained in the air) into latent
energy (energy stored in water vapor)

14. Some Global water footprint
• China, 2900 liters / person / day
• India, 3000 liters / person / day
• Indonesia, 3100 liters / person / day
• Germany, 3900 liters / person / day
• Saudi Arabia, 5100 liters / person / day
• Australia, 6300 liters / person / day
• USA, 7800 liters / person / day
• Mongolia, 1000 liters / person / day

15. Water Footprint
• ISO 14046:2012
“amount of all water flows –controlled and uncontrolled-consumed, used,
evaporated, or contaminated to produce an output unit in”
m3/lb.Cu: for Cu leaching
m3/oz.Au: for Au leaching
m3/ton.Concentrate: for crush-mill-flotation
Perú included this KPI in production statistics since 2005

16. Benchmark
• We have to get agree for a
common reference:
– m3/input (m3/tpd)
– m3/output
– m3/area
– m3/workforce
• Rates of consumption in: USA
(copper mines in Arizona)
Source: Department of Mines and Mineral Resources of Arizona
m3/ton
Cu fino
198
544
223
54
200
393
47

17. Benchmark
• Chile’ consumption
Source: Ministerio de Obras Públicas, Dirección General de Aguas, División de Estudios y Planificación

18. Benchmark
• Perú’ consumption
Source: Ministerio de Energía y Minas. Datos de Agosto 2010

19. Challenges
• Maximize recovery/revenues
• Minimize water usage in the whole
process by zero discharge.
• Which means:
– Eliminate unnecessary inputs
– Ability to predict ionic concentrations en
all flows to avoid incrustations
– Ability to recycle 100%
– Identify sources of contamination in the
process

20. Proposal
Commitment to
optimization
Philosophy of Water
Management
(“In Source
Reduction”)
Comprehensive
Survey (ionic)
Alternatives
Analysis and
Comparison
Decision
Making
Output:
1. Block diagram and mass balance
2. Table of metallurgical parameters and simulation
criteria for each case
3. Alternatives studied and simulated in Matlab-Simulink
4. PFDs
5. OPEX & CAPEX for decision making
6. Risks and Opportunities for decision making
7. Execution plan and schedule for next stages

21. Conclusions
• Standardization is pending task
• Operations in desert (Chile, Nevada) are benchmark. Let’s support them
and then rely on their experience
• Space for improvement in data management.
• We need to internalize that water is a common economic resource.
• This is not an only water/hydraulic problem. We have to understand about
metallurgic, kinetics, catalyst, cycles and optimize not only recovery but
also water usage.

22. Q & A

23. Questions & Answers