Waste Water Management in Mining Industry
MINING is a filthy industry this means mining becomes a very water intensive industry, accounting for roughly 3% of water used in the industrial sector. Unfortunately, South Africa has made the list as the thirtieth driest country in the world and with water resources becoming ever scarcer, more stringent policies will need to be implemented to keep the industry viable in a more sustainable way.
During the course of mining, especially hard rock mining, water is used in every step of the process, from cooling equipment to separating waste from minerals to controlling dust. Minerals processing is the most water intensive step in the mining operation and once the water has been utilized, channelling it to other uses becomes problematic. The acid water is allowed to run-off and proceeds to collects in active and abandoned surface and underground mines and processing plants.
The mining industry, relative to how critical water is to its operations, uses a mere 2.5% of the total amount of water in the country, opposed to household use however, recycling water in the mining industry is close to non-existent. Dwindling water supplies have in the recent past, focused the global attention from a supply management problem to a demand management one.
South Africa’s Water Resource Management Strategy, in an effort to introduce measures tom protect water resources, and has set objectives for the desired condition of resources and the mining industry impacts heavily on acceptable waste water limits. Resource Directed Measures (RDMs) focus on the quality of the water itself and reflects the health of the water resource. Source Directed Controls (SDCs) on the other define the limit and constraints imposed on the use of water resources to achieve the desired level of protection.
2. Recycling Waste Water
Pollution problems caused by mining activities include acid mine drainage, metal contamination of ground water and increased sedimentation in lakes and rivers.
The environmental impacts of mining are many and wide reaching. Erosion, the formation of sinkholes and the contamination of groundwater and surface water by runoff acid water are just some of the effects of the industry. Beyond the environmental degradation, the contaminants from runoff water can cause destruction of fragile ecosystems, destroy grazing and croplands and affect the health of the local populace.
Acid water contains higher than normal amounts of TDS, heavy metals and associated radioactive elements that severely limits its use in other ways. In such cases, a lime softening treatment followed by employing reverse osmosis membranes to remove to silica salts, the water can then be used in processes where low water quality is acceptable.
Changes in law, advances in technology and an overall tightening of environmental policies have taken the first, albeit shaky, steps to addressing the most immediate threats posed by acid water drainage. According to Mining, People and the Environment, the mining industry faces three major risks in dealing with water issues:
a. Physical Risks
A reduced water supply could interrupt production due to insufficient process water. Equally, a failure to meet discharge requirements for waste water or any major incident could close a plant.
b. Regulatory Risks: The potential for higher prices for water or fewer abstraction licences issued to mining companies.
c. Reputational Risks: These risks cover conflict with local communities over access to water and concerns raised by shareholders.
3. Flood Water and Environmental Damage
From a mining perspective, climate change will have implications on designs of storm water controls at mines and recovery plants. Flooding that occurs due to mining operations in open caste pits and underground mining operations – due to inefficiently designed and generally undersized storm water controls – costs mine operators millions of Rands in damages and allows polluted water to enter lakes, rivers and dams.
The design capacity of existing storm water control systems and the implications of climate change in terms of flooding and contamination will need to be addressed. How this water can be captured and reused is one of the most important questions facing the mining industry today. An adequate supply of water is critical to the operation and continued growth of the mining industry. The mining industry is equally critical to economic development in mineral rich countries especially in the developing world.
Improving storm water drainage has proven effective in saving mining companies between R40 and R50 million by cutting transportation costs, as water no longer needs to be sourced from other areas to make up the shortfall in areas that generally have limited water resources.
In recent years, the mining sector has faced backlash from environmental activists in Africa and Latin America caused by instances of Mercury poisoning affecting mining communities. Sediment loading into fish-bearing streams, road-building using acid generating waste rock and on-going violations of water quality standards are just more of the preventable and regrettable accidents that have drawn attention to the industry.
The environmental damage caused by flood water seeping into ground water and contaminating freshwater sources has thrown the water recycling in the mining industry into sharp relief making it more imperative than ever, that the industry find alternative ways of dealing with mine water.
4. Future Sustainability
Water management is emerging as the single most important sustainability issue within Global Energy and Mining Resource Industries (GEMRI). The on-going debate surrounding mining’s sustainability in the long run has made it imperative that stakeholders address environmental and social issues related to the industry globally and locally.
Africa has revealed ambitions in terms of moving towards a more sustainable mining industry, with the industry set to grow by a projected rate of 6.4% between now and 2014, partnerships in sustainable development in the mining sector are vital.
Ground and surface water sources are currently used for mining but the reality of the situation is that these sources are insufficient to meeting the demands of the industry. A process of desalinating and using seawater as an alternative source of water is being investigated as a viable solution. The Sea Water Reverse Osmosis (SWRO) desalination process might prove the most successful method for recycling and reusing, especially in mines that have access to seawater.
Sustainable and responsible mining will become the byword as climate change and global warming force a paradigm shift in the sector. Mining companies have already started making the move towards developing strategies to manage water risks and improve reporting on their performance in various areas, including:
a. Corporate water footprints,
b. The levels of water recycling,
c. Water intensity of production,
d. Site specific water management plans and attaining efficiency targets as well as
e. Case studies on water partnerships.
Whether the mining industry can feasibly survive into the future will depend on stringent self-regulation and finding environmentally friendly and sustainable solutions to issues that will resonate with affected communities and stakeholders alike.