Water is considered mining’s biggest casualty of all time given the huge scale at which mining of different types are advancing in today’s world. Acid mine drainage (AMD) is one of the largest repercussions of mining on water resources. It is a risk associated with all kinds of hardrock mines for extraction of useful metals and a significant number of coal mines suffer from acid mine drainage.
What is acid mine drainage?
As the name suggests, it is the outflow of acidic water from mining areas. It is identified by appearance of brownish-yellow precipitate with a foul smell and increase in acidity of water. Target ores for metals such as gold, copper, silver etc. or coal sometimes are sulphur bound which are known as ‘metal sulphides’.
Acid mine drainage is most commonly caused by iron sulphide called “pyrite” or “fool’s gold” which is abundantly found with almost all the metal ores. These sulphides are exposed during mining, and undergo oxidation reaction in presence of air and water to form sulphuric acid that is corrosive. The acid run off further dissolves harmful metals such as copper, aluminium, manganese, mercury, lead etc. and poison the ground or surface water system.
Acid mine drainage is an irreversible process that turns undisturbed and relatively unreactive ores into volumes of hazardous waste whose containment is extremely difficult once it reaches a water body. Acid drainage can also occur in non-mining areas such as construction sites, artificially dug areas or naturally weathered rocks termed as ‘acid rock drainage’. The process of pyrite oxidation and acid formation can be further catalysed by bacteria called as ‘extremophiles’ which can thrive in extreme conditions such as acidic environment.
Environmental impacts of acid mine drainage
Acid mine drainage can occur indefinitely for hundreds of years even after the mining activities have ended and thus affects a large horizon – ecologically and economically. The mines continue to produce acidic drainage as long as the rocks are exposed or become devoid of acid producing minerals. It is one of the single biggest non-point sources of pollution.
Some Roman mining sites in Great Britain are still producing problematic acid mine drainage, 2000 years after the stoppage of mining (CNHE, 2017). Moreover, AMD can develop at any point of the mining process – underground working, open pit mine faces, waste rock dumps, tailings deposits and ore stockpiles. In India, acid mine drainage usually comes from coal mines.
Most of the living organisms thrive well in the pH of near neutral which is 7. Acid mine drainage in some of the worst cases could decrease the pH of water to as low as less than 3. Thus it degrades streams, rivers and aquatic life forms in varying degrees depending upon the severity of pH change. It limits the growth of the river ecology in addition to unsuitable use of water for human, agriculture, industrial and recreational activities.
The increase in acidity can cause loss of sodium ions from the blood of fishes, which adversely affects the gill’s function. Prolonged exposure to low pH can be lethal for plants and animals with effects such as stunted growth, lesions, low reproductive rates and deformities (Vyawahre and Rai, 2016). Acid mine drainage is also responsible for loading a huge amount of heavy metals like lead, aluminium, manganese and more into our waterways. Aluminium is toxic to many aquatic animals and limits root development in plants leading to nutrient deficiency.
In addition to increase of acidity and release of toxic metals, neutralisation of the acid water by alkaline rocks could create an additional problem. In case of decrease in acidity, the iron which was in ferrous form turns into ferric and comes out of the water as a yellowish precipitate (solid) called ‘yellowboy’. It effectively chokes the streambed, crevices and prohibits the growth of benthic (bottom dwelling) life forms.
AMD have renouncing affects on the quality of groundwater system if the mines are located in permeable soil formations. The acidic and heavy metal containing water may percolate inside the water aquifers (underground water pockets) and gets spread throughout the underground water system which ultimately reaches human consumption via bore wells.
Prevention, mitigation and treatment of acid mine drainage
Acid mine drainage does bear a significant economic cost and irreversible environmental effects. Prevention of the acid-generating processes seems to be the only way to completely wipe out the problem of acid mine drainage but, stopping of mining is not the viable solution in most cases.
However, sulphuric acid could be stopped from forming by preventing the waste rock and mine tailings to come in contact with air by strategies such as submerging the tailings under water, sealing them behind barriers or burying them underground (groundtruthseeking.org, 2010). Nonetheless, isolating and containing huge amount of the generated waste is practical either above or below ground thus storing it for a future possibility or treating them with the help of technological advancement.
In most cases it is impossible to completely treat the contaminated water from acid mine drainage due to its high cost, inefficient technology and easily diffusible quality of water. But, its consequences could be limited by treating the water before releasing it into the environment through passive and active technologies (Johnson and Hallberg, 2005).
- Passive Treatment- It is the use of naturally occurring biological and chemical reactions that could be employed to reduce the acidity of AMD. For example, ‘bioreactors’ which works on use of sulphate-reducing microbes that precipitate out dissolved harmful metals. Another method is the creation of artificial wetlands where microbes can remove the heavy metals from the mine water. Both these methods are limited to small scale mines since it is expensive and requires a huge area of land. However, operation and maintenance of passive treatment system is comparatively lesser as compared to active treatment.
- Active Treatment- It is the typical water treatment system involving the use of alkaline chemicals such as caustic soda, hydrated lime, sodium carbonate etc. to decrease the acidity of mine drainage. Limestone is one very common chemical used due to its low cost and relative abundant availability. On the other hand, continued active treatment due to precipitation increases the rate of total dissolved solid (TDS) which is an important water quality parameter. Moreover, active treatment technologies are expensive due to chemical usage, equipments and huge manpower.
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In a diverse country like India, where each State is socially, culturally, economically, and politically distinct, measuring Governance becomes increasingly tricky. The Public Affairs Index (PAI 2021) is a scientifically rigorous, data-based framework that measures the quality of governance at the Sub-national level and ranks the States and Union Territories (UTs) of India on a Composite Index (CI).
States are classified into two categories – Large and Small – using population as the criteria.
In PAI 2021, PAC defined three significant pillars that embody Governance – Growth, Equity, and Sustainability. Each of the three Pillars is circumscribed by five governance praxis Themes.
The themes include – Voice and Accountability, Government Effectiveness, Rule of Law, Regulatory Quality and Control of Corruption.
At the bottom of the pyramid, 43 component indicators are mapped to 14 Sustainable Development Goals (SDGs) that are relevant to the States and UTs.
This forms the foundation of the conceptual framework of PAI 2021. The choice of the 43 indicators that go into the calculation of the CI were dictated by the objective of uncovering the complexity and multidimensional character of development governance
The Equity Principle
The Equity Pillar of the PAI 2021 Index analyses the inclusiveness impact at the Sub-national level in the country; inclusiveness in terms of the welfare of a society that depends primarily on establishing that all people feel that they have a say in the governance and are not excluded from the mainstream policy framework.
This requires all individuals and communities, but particularly the most vulnerable, to have an opportunity to improve or maintain their wellbeing. This chapter of PAI 2021 reflects the performance of States and UTs during the pandemic and questions the governance infrastructure in the country, analysing the effectiveness of schemes and the general livelihood of the people in terms of Equity.
Growth and its Discontents
Growth in its multidimensional form encompasses the essence of access to and the availability and optimal utilisation of resources. By resources, PAI 2021 refer to human resources, infrastructure and the budgetary allocations. Capacity building of an economy cannot take place if all the key players of growth do not drive development. The multiplier effects of better health care, improved educational outcomes, increased capital accumulation and lower unemployment levels contribute magnificently in the growth and development of the States.
The Pursuit Of Sustainability
The Sustainability Pillar analyses the access to and usage of resources that has an impact on environment, economy and humankind. The Pillar subsumes two themes and uses seven indicators to measure the effectiveness of government efforts with regards to Sustainability.
The Curious Case Of The Delta
The Delta Analysis presents the results on the State performance on year-on-year improvement. The rankings are measured as the Delta value over the last five to 10 years of data available for 12 Key Development Indicators (KDI). In PAI 2021, 12 indicators across the three Pillars of Equity (five indicators), Growth (five indicators) and Sustainability (two indicators). These KDIs are the outcome indicators crucial to assess Human Development. The Performance in the Delta Analysis is then compared to the Overall PAI 2021 Index.
Key Findings:-
In the Scheme of Things
The Scheme Analysis adds an additional dimension to ranking of the States on their governance. It attempts to complement the Governance Model by trying to understand the developmental activities undertaken by State Governments in the form of schemes. It also tries to understand whether better performance of States in schemes reflect in better governance.
The Centrally Sponsored schemes that were analysed are National Health Mission (NHM), Umbrella Integrated Child Development Services scheme (ICDS), Mahatma Gandh National Rural Employment Guarantee Scheme (MGNREGS), Samagra Shiksha Abhiyan (SmSA) and MidDay Meal Scheme (MDMS).
National Health Mission (NHM)
INTEGRATED CHILD DEVELOPMENT SERVICES (ICDS)
MID- DAY MEAL SCHEME (MDMS)
SAMAGRA SHIKSHA ABHIYAN (SMSA)
MAHATMA GANDHI NATIONAL RURAL EMPLOYMENT GUARANTEE SCHEME (MGNREGS)