Limestone can help neutralize Meghalaya streams polluted by coal mining, say experts
After the success of the pilot project in Mukhaialong village in East Jaintia Hills district, construction work has started at two places already earlier this year, says Justice BP Katakey, a retired judge who heads the three-member NGT appointed committee.Updated: Aug 20, 2019 20:59 IST
The project to check rising acidic levels in water streams by using limestone will be expanded to new sites after success of a pilot in the ravaged Jaintia hills of Meghalaya due to rat-hole mining, experts said.
“After the success of the pilot project in Mukhaialong village in East Jaintia Hills district, we requested that it be extended and construction work has started at two places already earlier this year,” said Justice BP Katakey, a retired judge who heads the three-member NGT appointed committee on Meghalaya rat-hole coal mining.
OP Singh, a professor at the Environment Studies Department at the North Eastern Hill University, said the experiment is to be replicated at five places in East Jaintia Hills district, which is most badly affected by coal mining. The three remaining sites are yet to be finalised after resistance from locals.
Meanwhile, in 2016, Singh, his team with assistance from the Meghalaya Basin Development Authority set out to neutralize and restore the ecology of the small Moolawar stream which flows by the Mukaialong village.
Like in most of Jaintia Hills, years of rat-hole coal mining in the vicinity had turned the water of the Moolawar acidic and unfit for use. “The water was reddish in colour indicating high sulphuric acid contamination,” said Wansah Pyrbot, a manager at Meghalaya Basin Management Authority who has been involved in the project closely since 2016.
The coal found in Meghalaya is sub-bituminous and has high sulphur content, Singh explained.
“Even the fish and insect in the stream had died. We had stopped using the water,” said Hundred Phawa, the headman of the village which has around 300 households.
The method to bring down the acid levels of the stream involved basic chemistry and laying an open limestone channel. “After levelling, the streams were filled with pieces of limestone (measuring about 15–20 cm) to a height of about 30 cm. To prevent downstream sliding of limestone pieces, check dams were constructed,” Singh said adding how the whole project involved an expense of around Rs 800,000.
As the acidic water came in contact with alkaline limestone, results showed. A paper titled Neutralization of Acid Mine Drainage Contaminated Water and Ecorestoration of Stream in a Coal Mining Area of East Jaintia Hills, Meghalaya jointly written by Pyrbot, Singh and Lamjingshaihun Shabong published earlier this year in Mine, Water and the Environment, notes the Ph level fell to 6.57 from 4.31 in one of the two channels of the stream.
Hence, bringing the acid content in water to the permissible limit in Meghalaya where water has higher acidic content than in other places. In dry season, the Ph levels would come down to 3-4, the paper notes.
In a few months, “species of aquatic insects such as water penny and dragon fly and two fish species appeared… Algae growth was also noticed in the treated section. This was an encouraging sign of ecorestoration…” the paper notes.
Pyrbot explained how seeing life back in the stream built the confidence of the villagers who started using the water for their domestic use.
Phawa said now the village has several water tanks which store the water from the stream which is then piped to the village for use. “The quality of water has improved a lot,” Phawa said.
Narwan, a village famous for its oranges, is one of the two new sites where construction for the project has already started, home of Krip Chullet, who ran the rat-hole mine in Meghalaya, in which 15 workers were trapped last year. The operation to look for their mortal remains of the remaining 13 trapped workers was called off by the Supreme Court last month.
The project is just tackling a tip of an iceberg in Meghalaya. A December 2018 interim report by Justice Katakey headed committee said there were 24,000 abandoned and existing coal mines in twin Jaintia Hills districts, which were polluting water streams.
“The affected area is very large. At best it (the project) can ease the problem,” said Singh, explaining how it cannot be a solution to the issue.
Singh said a long-term solution can only be if the Supreme Court judgement that mining can only be done after a proper mining plan is followed. In its verdict in July, the apex court lifted the ban and allowed mining but subject to permissions and adherence to norms.
Meanwhile, limestone is not the only solution being explored to treating acidic water. Katakey, who is skeptical of how the experiment would work on bigger streams, said the committee has also approved a pilot project for the use of algae to treat the acidic drainage from mining.