Minerals are very important natural resources. These are mined from the earth’s crust and dare used as raw materials in various industries including thermal power plants, iron and steel, aluminium and other non-ferrous metals, refractories, cement etc. About 70% of the energy we use is thermal power, produced from coal. Huge quantities of various metals and alloys which are used in different industries are all mineral based.
Most of the minerals are mined after removing the topsoil and overburden present over the minerals (opencast mining). Some minerals like coal are mined from underground. High-grade minerals are used as such but low-grade ones are upgraded by various techniques using a large quantity of water. During the mining of minerals, a lot of trees are cut
and sometimes water bodies are diverted. The environment of the area looks highly disturbed.
Mining and subsequent mineral upgrading activities need a lot of water. The mineral-based industries include mineral washing, upgradation, beneficiation and agglomeration of mineral fines, which are finally used for the extraction of metals and alloys. In these processes, a large amount of water is needed and a lot of waste water is also generated. In most cases, the untreated wastewater is let out to nearby water bodies. Therefore, various water conservation measures should be adopted through the application of better technology for the above processes requiring less amount of water, setting up procedures for budgeting water, recycling used water etc. In all these industries, water conservation practices should be adopted in different areas.
Major Water Conservation Practices in Mining and Mineral Processing Industries
i. Using fogging nozzle to cool products.
ii. Installing in-line strainers on all spray headers.
iii. Adjusting pump cooling and water flushing to the minimum required level.
iv. If possible, utilise water discharged from one operation in another one.
v. Transportation of water with minimum loss.
vi. Handling of solid materials as far as possible in a dry mode.
vii. Replacing high volume hoses with high pressure and low
viii. Turning off all flows during shutdowns.
ix. Adopting sweeping and shovelling practices instead of hosing down the floors.
x. Recycling wastewater for various purposes including washing of vehicles, watering lawns
and dedusting of roads etc.
In view of the fact that most of the river water is earmarked for agriculture and domestic purposes, water needed in mining and subsequent mineral processing should be generated at the sites through rainwater harvesting in mine pits and also reusing the wastewater if necessary after suitable treatment. Some of this water can be used for plantation on overburden dumped at mine sites and other related activities to maintain the area clean and environment friendly.
The rainwater collected in mine pits in active mine areas in a mineral-rich country like India, is quite large in volume. The water holding capacity of fresh mine pits created every year in all the mines of India has been estimated to be around 350 million cubic litres. It has been estimated that rain water harvesting in newly created mine pits in India every year, can generate water which is sufficient for meeting the domestic consumption of about 30 million people. However, the
water available in mine areas has to be suitably treated to meet the requirements of mining, mineral-based industries, afforestation of mine areas as well as for agricultural, domestic and other purposes in that region.
Water pollution in mine areas is mainly caused due to solubility of toxic metals and materials, biological impurities, suspended particles, dissolved chemicals etc. For example, in a chromite mine of the Sukinda region in Odisha, the mine water is contaminated not only by some of the above impurities but also by chromium along with nickel and cobalt present in the overburden.
Similarly, in copper and zinc mines, the sulphide minerals of the two metals undergo bacteria leaching resulting in the formation of water-soluble acidic sulphates of these two metals. With the rapid increase in mineral-based industries in different parts of India, the mining of various minerals has increased considerably. In most of the open cast as well as underground mines, the water accumulates due to ground water seepage as well as rainwater is pumped out to facilitate the mining operation. Such untreated water pollutes the existing water sources in the region.
In addition to this, the mineral-based industries reject their semi-treated or untreated effluents and solid wastes from the nearby water bodies. In view of this, the Ministry of Environment and Forest, Government of India, has led down some specific norms for mining and mineral-based industries to treat and recycle the effluents and harvest rainwater to meet most of their water requirements. The objective is to avoid water scarcity for domestic and agricultural purposes while meeting the water requirement of mining and subsequent mineral processing industries.
In view of the deteriorating environment in most of the mine areas and the non-availability of sufficient amount of fresh water for various mining and mineral processing activities, some major mining industries in the world are taking necessary steps to manage the water in their mines through rainwater harvesting, storing and treating the used water, in order to meet their requirements.
In India, besides harvesting rainwater in mine pits, it is also necessary to recharge the aquifers in the area with rainwater in order to increase the groundwater resource. For meeting the required amount of water in mining and mineral processing, the concerned companies should harvest rainwater in mine pits and save used water and finally utilise these after proper treatment in their industries. The Central Ground Water Board, Govt. of India, has prescribed certain norms
in water management in mining and mineral processing units. In this way, there may not be much shortage of water for mining and mineral processing activities.
In view of the non-availability of a sufficient amount of fresh water for mining and mineral processing activities and also for avoiding a deteriorating environment in most of the mine areas, some major mining industries of India are taking necessary steps to meet the required amount of water in their activities through rain water harvesting, storing and using the treated water. As a matter of fact, all the mining and mineral processing units in the country for their own interest
should go in the same way.