The water shortage that has recently struck the Brazilian state of Minas Gerais has led the population and the public authorities to rethink water use in general, re-evaluating its use in the agriculture, industry and services sectors. The mining sector has been the primary focus of this re-evaluation, since it represents approximately 11% of the total water use in the state. One possibility for reducing water consumption by the mining sector would be the use of treated domestic sewage in mining processes. A case study was conducted in the iron ore mines of the Rio das Velhas Watershed (RVW), which encompasses the principal iron ore producing region in the state of Minas Gerais (268 Mt.year-1). A literature review was performed on the different water quality demands and usages in mining sector (processing, transportation and spraying on roads), taking into account the possibility of use of treated domestic sewage for each process. Additionally, the main sewage treatment processes applied in RVW were also evaluated, and the respective physical and chemical parameters of the treated domestic effluents were studied. The eventual need for complementary treatment for the uses in ore mining, as well as the existing legislation on the use of effluents, were assessed.

1. Use of treated sewage in mining
industry: a case study in Brazil´s
most important iron mining region
PIMENTA, Fernando José Gonzaga¹, SILVA, Lucas de Almeida Chamhum¹, BRESSANI
RIBEIRO, Thiago¹, BIANCHETTI, Fábio José¹, CHERNICHARO, Carlos Augusto Lemos¹ and
MOTA FILHO, Cesar Rossas¹*
1. Department of Sanitary and Environmental Engineering, Federal University of Minas
Gerais, Brazil

2. Introduction
• Mining: 7.5% of Minas Gerais
PIB
• Environmental impacts and
water usage
• 29.17 m³/s granted for mining
– 98% surface water
abstraction
– 11% of MG total water
grants
• Focus on iron ore – 83 Mtpa
in study area
Exportaminas, 2016

3. Objectives
• Literature review: water use in mining
• Evaluation of the demand: quality and
quantity
• Definition of most appealing usages for
sewage
• Study case: Rio das Velhas watershed

4. Water in mining
• Usual sources: surface and underground water, recycling
• Reuse: ~80%
• Water use: extraction, processing and other diffuse uses (dust
control)
Vale, 2016

5. Ore Processing
• 5.5 m³ water/ton; 1.18 m³ “new” water, considering reuse and recirculation

6. Ore Processing
• Filtration and water clarification at the port

7. Ore Flotation
• Separation of ore and tailings
• Water consumption: 1.13
m³/ton
• High pH (CaO)
• Chemical reagents: amine and
starch
• Water quality is an important
parameter
• Efficiency measured by ore
recovery
COCHILO, 2006

8. Ore Flotation: Water quality
• Arizona Bureau of mines (1976) – use of secondary
effluents (copper and molybdenum): thick foam and
lower recovery
• Levay, Smart and Skinner (2001) – similar results for
effluent use in nickel flotation
• Carvalho e Peres (2004) – negative effects of excess
calcium ions
• Liu, Moran e Vink (2013) – negative effects of
suspended ions
• Anglo American (2016) – recirculated water with high
conductivity, low DO and low redox potential
– Better with tertiary treatment (active carbon)

9. Ore Flotation: Water quality
Parameter Raw
sewage
Secondary
effluent
Tertiary
effluent
(active
carbon)
BOD
(mg/l)
200-400 20-100 1
COD
(mg/l)
400-600 80-160 30-60
SS (mg/l) 160-350 5-20 0,5
Turbidity
(NTU)
50-150 20-60 0,5
Phosphate
(mg/l)
15-35 10-50 0,4-2,0
• Active carbon treatment: satisfactory results in two studies
• Lower cost in comparison to other tertiary treatments
• Removal of organic matter, nutrients and SS up to 99%
• Scale tests needed: variations in ore, reagents and effluent quality

10. Pipeline transportation
• 0.42 m³ water/ton
transported
• Viscosity and % solids
• Addition of CaO
avoids the
formations of plugs
• pH > 10.5 to avoid
internal corrosion
• MG: Samarco (1630
m³/h) and Anglo
American (1400
m³/h)

11. Pipeline transportation
• Operational and
environmental
security; low cost;
environmental impacts
• Criticism: basin
transposal
• Price paid for water
abstraction vs. treated
water
Adapted from Fraser (2015) and Argus (2014).
Adapted from COPASA (2016)

12. Dust Suppression
• Environmental control
• High demand: 4 liters
per day/m²
• Water lost through
evaporation and
infiltration
• Quality needed: low
• Critical issues:
– Hardness
– Contaminants
– Debris (nozzle opening)
• Domestic effluents are
usually not hard
Mercedes-Benz (2016)

13. Methodology
• Iron ore production data: Vale (2015) and Minérios and
Minerales ranking (2014)
• 1.18 m³/ton of new water: mines using pipelines
– Vale South System (MG): 0.66 m³/ton
• RDV watershed analysis: distance from STPs to mining sites
• Average flow from each STP
• Simulations: % of demand met by treated effluents
– Maximum abstraction distance of 5, 15 and 25 km
• Two scenarios:
– Only operational STPs
– Universal access to sewage collection and treatment

14. Rio das Velhas Watershed
• High RDV basin
– 58% of the watershed
mining areas
– All iron mines
• Estimated demand for
iron mining: 1.73 m³/s
– Vale: 89,84%

15. Mining demand
Mine Enterprise
Ore
processed
(Mtpa)
Estimated
demand
for new
water (l/s)
Sapecado/Galinheiro Vale 20.03 419.3
Capitão do Mato Vale 13.79 288.7
Segredo/João Pereira Vale 11.58 242.4
Capão Xavier Vale 9.66 202.2
Tamanduá Vale 9.34 195.5
Abóboras Vale 6.12 128.1
Várzea do Lopes Gerdau Açominas 4.31 90.3
Mar Azul Vale 3.84 80.4
Miguel Burnier Gerdau Açominas 2.45 51.3
Ponto Verde SAFM Mineração 1.08 22.6
Posse Crusader do Brasil 0.57 11.9
Total - 82.79 1732.8

16. Mapping STPs and mines

17. Results: Current scenario
• Demand surpasses effluent supply in all cases
• 766.8 l/s come from Arrudas ETP (780 m);
mines over 1200 m
• Estimated cost: ~US$ 850/h
Maximum abstraction
distance (km) Demand met by ETPs (l/s) % of global demand
5 10.0 0.58
15 264.8 15.28
25 1086.5 62.70

18. Results: All sewage collected and
treated
• Raise in %
collected and
treated: increased
reuse
• Social and
environmental
interests
Maximum abstraction
distance (km) Demand met by ETPs (l/s) % of global demand
5 100.0 5.77
15 486.5 28.07
25 1304.1 75.26

19. Conclusions
• Low volume of effluents
effectively collected and
treated
• Distance from populated
areas
• High RDV: High distances
and level difference
• Economic factors
– Water abstraction still very
cheap
– “Abundant” hydric supply
– Legal obligation may be needed
Usage Ore processing and
transportation
Dust control
Volume needed High: 1.13 m³/ton
(processing) and 0.42
m³/ton
(transportation)
Moderate: 4
liters/day/m²
Quality needed Moderate to high:
negative effects on
flotation
Low: worst
quality
available
Can the water
be recycled?
Partially (pipeline) No;
evaporation
and infiltration
Post treatment
needed?
Active carbon
adsorption
Probably not
Viability of
effluent use
Medium High

20. THANK YOU