Study of coal mining areas in Nagaland and its impact on environment: Part- IV
Our Correspondent
Kohima | January 14
Water pollution due to mining activities can be mitigated and controlled by carefully separating the water runoff from undisturbed areas from water which contains sediments or salt from mine workings, a recent study by NPCB suggested.
The study released in a form of a booklet entitled “Study of Coal Mining Areas in Nagaland and Its Impact on Environment,” was published recently by Nagaland Pollution Control Board (NPCB).
Clean run-off can be discharged into surrounding water courses, while other water is treated and can be re-used such as for dust suppression and in coal preparation plants, it noted.
The NPCB further study stated that when mine water is pumped to a lagoon, it acts as a sedimentation pond. Thus, the overflowing water from the pond which is fairly clean can be drained out to natural drain or used for dust suppression activities.
Referring to the active treatment of polluted water, it suggested dosing the outflow of acidic water from metal mines or coal mines, also known as Acid mine drainage or acid and metalliferous drainage (AMD), with lime to neutralize the acid and then passed through settling tanks to remove the sediment and particulate metals.
Passive treatment of AMD, which aims to develop a self-operating system that can treat the effluent without constant human intervention, can also be implemented, NPCB further advocated.
It also recommended treating the contaminated water from the mines with lime in slurry form to gets it well mixed with water. “Sandstone and limestone are available locally and therefore use of these stones corrects the pH (the acidity or alkalinity of a solution) of the quarry water to near normal,” it stated.
Heavy metal such as copper, zinc, lead and iron are precipitated in the pH range of 7-9 and therefore, may get simultaneously removed, it further observed.
