Demand in Water Treatment for Mining Industry

Transcription

1 Demand in Water Treatment for Mining Industry Val S. Frenkel, PhD, PE, DWRE,* and Omar A. Gaete, PM** *ARCADIS-US, **ARCADIS Chile

2 Presentation Outline Introduction Water needs and sources for mining industry Treatment requirements for mining water Water consumption for different minerals Mine water system schematics Particularities/Challenges for Water Treatment in Mining Industry Proposed Strategy to Address Particularities/Challenges for Water Treatment in Mining Industry Summary Q&A

3 INTRODUCTION According to Wikipedia mining is extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or coal seam. Materials recovered by mining include base metals, precious metals, iron, uranium, silver, gold, diamonds, limestone, oil shale, rock salt and potash. Mines are can be found around the globe and mining activities depend on the mineral to be extracted, current demand and market price accordingly. Regardless of mineral characteristics and location, all mines have one common need, water.

4 WATER TREATMENT DEMAND IN MINING Water is needed for the mineral s exploration process, infrastructure, auxiliary equipment and for sanitary and drinkable use. Most mines are located far from populated places, therefore water supply and discharge can be challenging issues. In Chile, most metallic mines are located between 2,500 and 5,000 m.a.s. In mining, water quality that needs to be addressed and where the water treatment is required can be broken down to three major categories: o Feed/make-up water o Waste discharge/tailing discharge o Internal water reuse Water Reuse Make Up Water Mining Operation Tailing Discharge Waste Discharge

5 FEED/MAKE-UP WATER World water availability* Alternative sources of water for feed/make-up water: sea/ocean, groundwater (brackish/sweet), surface, municipal and external reusable water. Availability of each one depends of the quality. Copper mining water demand** (Chile -2009) Copper mining water demand projection** (Chile ) **Source: Cochilco (2009) *Source: Frenkel, V. Desalination Methods, Technology and Economics. Desalination Conference, April 16, 2004, California

6 FEED/MAKE-UP WATER Mining processes can tolerate certain quality of water. E.g.: sea/ocean water can be used for flotation or oxide leaching, but is unacceptable (today) for sulfide leaching and electrowinning. Even desalinated water is not acceptable for electrowinning, whereas the very low chloride water (produced by double pass RO) can be used. Demand in feed/make-up water can be broken down to 4 major categories: o Mining technological process o Operational and auxiliary equipment for mining process o Refining o Municipal water supply Processes which require water: extraction, leaching, flotation and hydro-blasting. This category represents > 80% of entire water demand in mining. Operational and auxiliary equipment need water for heating equipment (boilers), drilling, equipment cooling, remediation and washing. Refining needs the highest quality, in most cases it requires additional treatment. Municipal water supply is for the municipal needs of mine personnel and for drinking water purposes and it has to be safe for drinking needs.

7 FEED/MAKE-UP WATER Mining operations use a cascading concept of water supply and treatment. Example: Concentration Foundry Refinery Sea water Treatment 1 Treatment 2 Treatment 3 Municipal and potable water

8 WASTE DISCHARGE/TAILING DISCHARGE Different mining processes generate wastewater which needs treatment and is discharged back to the environment or to its source. Typical types of wastewater: o Acid mine drainage (AMD) and acid rock drainage (ARD) o Equipment cooling water o Drilling water (frac water) o Tailing water (minerals recovery) o Wash water o Concentrate filtrate water o Desal effluents: brine, pre-treatment Regulatory compliance with discharged water requirements are driving needs in wastewater treatment technologies, which depend on the generated wastewater properties and requirements of the treated effluent prior to the discharge. In order to achieve an optimize solution to water treatment problems, the methodology that has to be applied is as follows: i. Reduction to the source ii. Recirculation iii. Recycling iv. Treatment and discharge

9 WASTE DISCHARGE/TAILING DISCHARGE Treated water quality depends on the kind of receptor body or application: discharge to sea, ocean, river, lake or underground; discharge to the sewer line, or beneficial use for irrigation or recreation. Chilean regulation on this matter is: DS 90, DS 46, DS 609, NCh 1333, NCh 409. As treatment of discharged water and feed/make-up consumption may add significant cost to mining activity, internal water reuse became an integrated part of advanced mining operation.

10 INTERNAL WATER REUSE Internal water reuse complements the mining process by reducing make up water demand. Another motivation is the recovery of valued minerals from tailing water and reduction of wastewater discharge in general. The lack of water, specially in the north of Chile, has encouraged mining companies to increase water recirculation and, consequently, reduce make up usage. Average make up water required in Chilean copper mining* Process 2000 [m 3 /t] 2006 [m 3 /t] 2009 [m 3 /t] Concentration 1,10 0,79 0,72 Hydrometallurgic 0,30 0,13 0,13 When applying internal water reuse, the same may need to be conditioned to avoid oversaturation of the sparingly soluble metals and other species and ions, which may lead to fouling and scaling of equipment. Today most of Chilean copper mines operate with over-saturated water systems, caused by increased water reuse and metallurgical processes have had to adapt to this condition. *Source: Cochilco (2009)

11 SPECIFIC CHALLENGES OF WATER/WASTEWATER TREATMENT IN MINING Mining is a unique industry with a very specific water demand and water and wastewater treatment needs: mines are remotely located, dictated by minerals physical location, which needs to be supported by all required technological and municipal infrastructures. Due to the uniqueness of mining industry, some major challenges of water/wastewater treatment systems for mining needs compared with other industries are: o o o o o Challenging treatment is required depending on the mining type, source water type and quality, and mining technological process (custom solution). Technological solution must be studied prior to the implementation. Unknown lifetime of equipment which may be limited to the relatively short lifetime. Fast project delivery and probable fast project deployment. Often unknown lifetime of mining projects. Discharge water rich in valuable minerals. Oversaturated water system (avoid scaling)

12 PROPOSED STRATEGY TO ADDRESS SPECIFIC CHALLENGES FOR MINING WATER TREATMENT As the mining industry has different particularities when compared to other industries, the following strategy can be proposed when designing water/wastewater treatment equipment for mining: o Packaged treatment systems which can be quickly employed, deployed and relocated to other places. o Pre-fabricated standard equipment components with a wide application range allowing fast assembly of plug and play systems. o Standard equipment components to meet individual/custom needs of a specific site. o Treatment systems are operated by mining workers, not by water workers. It needs to be operator friendly, robust and automated as much as possible. o Service contracts to supply water treatment equipment, service contracts to operate water treatment equipment. o Continuous consultancy service which allows to confront the variability of operational conditions.

13 SUMMARY Demand of water treatment for mining industry is very diverse, it depends on the type of explored minerals, location of mines and water source availability, as well as quality. It can be broken to three major categories: o Feed/make-up water o Waste discharge/tailing discharge o Internal water reuse As mining water has different demands of quality for different processes and needs, a cascading water treatment approach can be considered an economical and sustainable strategy to supply and treat water. As regulations on the discharged wastes are stricter and wastewater may be rich with the explored minerals, the deep wastewater treatment and internal water reuse benefits mining operation by minimizing feed/make-up water supply at the same time. Water/wastewater equipment should be automated in its full extent, robust, easy to install and easy to relocate when required.

14 QUESTIONS Omar Gaete ARCADIS Chile