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All about homemade fluoride filter

Dengaon is a beautiful area consists green hills, plains and rivers in Brahmaputr a valley. More than 50 villages and most of its inhabitants are belong to Karbi tribe. This area in border of Nagoan and Karbi Anglong districts in Assam are highly and dangerously fluoride-affected in Brahmaputra valley.

The presence of excess amount of fluoride was tested in the water from rivers, ponds, wells, tube-well and deep-wells. Villagers have been suffering from fluoride for centuries which was detected in last decade. There are no drinking water supply facilities in remote villages which are not easily accessible. Symptoms of excess fluoride induced disorders are prevalent some states of the country including Brahmaputra valley. Karbi Anglong and Hojai districts are the most fluoride-affected districts in Assam.

Fluoride has been an invisible enemy contains in drinking water as chemical contaminant mostly in ground water in Brahmaputra valley. It has been a matter of grave concern that almost all districts in Assam are fluoride and arsenic affected. Villagers from different tribes and communities have been witnessing this demon with dental and skeletal flourosis. A small amount of fluoride is good for health but excess flouride of drinking water causes various health problems including damage of tooth and bone. Fluoride is a deadly poison. A long term ingestion of fluoride in drinking water and cooking water causes to other health problems. Affected villagers had no option to minimize the presence of fluoride and only some families use to drink filtered water. Moreover, general filter cannot remove or minimize fluoride.

Fortunately villagers have found a new low-cost technology to remove fluoride and iron from water recently. Now villagers are using this fluoride filter unit to have fluoride-free water. Villagers have installed Fluoride Nilogon - a low-cost and simple method for removal of fluoride from contaminated groundwater. Fluoride Nilogon is a method for removal of excess fluoride from contaminated groundwater for drinking purpose through phosphoric acid and crushed limestone treatment based on precipitation-absorption developed by a team of researchers led by Dr R K Dutta from Tezpur University, a central university in Assam. The name was coined from fluoride and Nilogon is an Assamese equivalent of 'removal' in English.

The method removes fluoride efficiently and selectively without leaving any toxic residual in the water at a recurring cost of ₹ 1 per 100 liter of water. The Fluoride Nilogon system can be custom designed to meet the requirements of the users ranging from small household to community. It uses a crushed limestone fixed-bed reactor where the water is treated for 3 hours in presence of a small quantity (0.00067 M) of phosphoric acid.


Bhabesh Bhagwati, a local social worker who is in charge of the unit installed near Dengaon Higher Secondary School said, " For small communities like school a 200 or 500 litre plastic drum can be used as the reactor and another 200 litre drum can be used as the sand gravel filter. After filling with crushed limestone, a 200 liter drum can be hold about 88 litre and a 500 litre drum can hold about 220 litre of water. The filter shuld have a 15-20 cm layer of small 2-3 cm size gravels, at the bottom, covered by a thin porous cloth, above which, there should be a 50-60 cm thick layer of clean medium size sand. People have been collecting water from a community unit set up near Dengaon Higher Secondary School for a year which was set up experimentally first.

After long sufferings and government negligence people of some villages of Dengaon region in Karbi Anglong districts have choosed to use "Fluoride Nilogon" unit to get fluoride-free water. "In Fluoride Nilogon, the flouride containing water, mixed with a small quantity of phosphoric acid, is put into a crushed limestone bed plug-flow reactor and kept for a residence time of at least three hour. Fluoride is removed in the reactor. The water is filtered using a sand-gravel filter after three hours" - Dr R K Dutta said.

The Flouride Nilogon method has been developed by a group of researchers lead by Dr. R K Dutta in the Department of Chemical Sciences, Tezpur University. Flouride Nilogon removes the excess fluoride retaining only a small amount of fluoride (0.7 ppm) require for a good health. The treatment water does not contain any residual chemical added from outside. Its pH is about 7.5 which is very safe for drinking. However, the treated water should be consumed only after booiling.

Families can use a Fluoride Nilogon unit with arrangement of minimum two big size buckets as water from upper bucket can come to lower bucket using a tap. It must be sure that the tap of the upper 40 liter bucket which contain crushed limestone container is closed. 15 liter of water is added in the bucket. Then 7 ml of the dilute phosphoric acid solution be added to it and mix. Then the amount of acid solution mixed water poured in the first bucket containing crushed limestone and let it for at least three hours. In a 30 liter crushed limestone bucket, 11 liter water can be treated and and 55.2 ml phosphoric acid has to be added. There is no harm if you leave it like that for longer time even for a day. Fluoride is removed here along with neutralization of the acid. Now water can be filtered using the sand gravel filter in second lower bucket.

A household unit used by common people consists of a plastic bucket of 40 litre capacity for the reactor and another 20 litre bucket for the sand-gravel filter. Both buckets are fitted with a plastic tap each towards the bottom. The 40 litre treatment bucket is kept at a level above the filter. The 40 litre bucket is filled with crushed limestone of 0.1 to 1.5 cm size. This limestone-filled bucket can hold about 15 litre of water. The filter should have an 8-10 cm thick layer of small 2-3 cm size gravel layer at the bottom. The rest of the bucket should be thin porous cloth between the sand and the gravel layer to stop sand from going to the gravel layer.

Families from Dengaon area acknowledged benefits of Fluoride Nilogon to get fluoride-free water. Some people are using water from community set up and some have installed their own set up inside their house. The solution used in the method is a dilute solution (8.5%) of an acid even though it is a weak acid, it shoul be kept carefully. It should be kept away from children. with water in case of its contact with hand, skin or eye.

It is a simple efficient and low-cost method of removing excess fluoride from water. It this method crushed limestone is used along with a very small amount of a solution of a weak acid called phosphoric acid. The use of phosphoric acid in water purification is safe. Phosphoric acid is used in packaged food and soft drinks like Pepsi.

Author info

Chandan Kumar Duarah's picture

The writer is a former Robert Bosch Fellow, an environmentalist and Guwahati based journalist.

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JAC against anti-tribal Bills

19 May 2016 - 7:51pm | AT News Imphal

The Joint Action Committee against Anti-Tribal Bills (JAC) would like to convey its heartfelt gratitude to the tribal people of present Manipur, including the people of Tamenglong, Senapati, Sadar Hills, Ukhrul, Chandel, Singngat, Jiribam, Lamka and JAC units at various sub-divisional headquarters for their support and cooperation in the 48-hours Total Shutdown of all Tribal Territories called by the JAC from the midnight of May 16 to the midnight of May 18, 2016.

The communal attitude, discriminatory policies and prejudiced mind set of the Manipur Government becomes more evident with each passing day. A brief two-month agitation in the Valley resulted in a Special Session of the Manipur State Assembly passing the three anti-tribal bills on August 31, 2015, and a three-day agitation in the Valley for pressurising the Union Government to give President’s assent led to an ‘All Political Party Meeting’ that resolved to send a delegation to voice the concern of the Valley people. However, the Manipur Government has still chosen to turn a blind eye to the 261-day old Tribal Movement in the Hills/Tribal Territories till date; in fact, the Manipur Government still refuses to call a Special Session of the Manipur State Assembly to deliberate on the JAC’s Charter of Demands in spite of the request made by the JAC.

The fact that the ethnic and communal Manipur Government continues to undermine the cries of the tribal people till today only points to the deep, unrepairable gash between the Hills/Tribal Territories and the Valley.

The JAC would like to reiterate that the three anti-tribal bills are very much political in nature and have nothing to do with the Inner Line Permit System (ILPS) –


  1. Identity politics [The Protection of Manipur People Bill, 2016]
  2. Politics of land [The Manipur Land Revenue and Land Reforms (Seventh Amendment) Bill, 2016]
  3. Politics of economy and livelihood [The Manipur Shops and Establishments (Second Amendment) Bill, 2016]

As such, a political solution is the only acceptable and sustainable solution for the tribal people.

It is also our humble request to all media houses to refrain from misleading the public by wrongly projecting and publicizing these three anti-tribal bills as ILP bills and creating unnecessary confusion in the minds of the general public.

New species of bird discovered in Arunachal Pradesh

Himalayan Forest Thrush Dulongjiang  (Photo:  Craig Brelsford)
21 Jan 2016 - 10:16pm | Bilwada Kale

A bird species, locally common in eastern Himalaya and overlooked till now, has been identified as a new species. A team of scientists from India, Sweden, China, US and Russia have described this species from northeastern India and adjacent parts of China as Himalayan Forest Thrush. This is the first Indian bird (Zoothera salimalii), which has been named after Late Dr Sálim Ali, who was closely associated with BNHS-India, including as a researcher, honorary secretary and finally as its president. The bird has been named after him in recognition of his huge contributions to the development of modern Indian ornithology and wildlife conservation.

New bird species are rarely discovered to science nowadays, when most natural habitats are shrinking. Since 2000, an average of five new species have been discovered globally every year, mostly from South America. Himalayan Forest Thrush is only the fourth new bird species described from India by modern ornithologist since independence. Commenting on the development, Dr Asad Rahmani, Senior Scientific Adviser and former Director, BNHS said, “It is a remarkable discovery and shows how much more we have to do in the field of ornithology in India. It also proves that northeastern India is a treasure trove of biodiversity that needs protection from the mega projects that are planned in Arunachal Pradesh without giving any attention to biodiversity conservation.”


The tale of discovery

Dr Per Alström and Shashank Dalvi first discovered the species in May-June 2009 while studying birds at high elevations in western Arunachal Pradesh. It was realized that instead of a single species - Plain-backed Thrush (Zoothera mollissima) – as believed till now, in reality there exist two different species in eastern Himalaya. Till now Himalayan Forest Thrush has been overlooked because of its close similarity in appearance to the Plain-based Thrush, now renamed as Alpine Thrush.

Studies of specimens in 15 museums across seven countries revealed consistent differences in plumage and structure in the birds from the above two populations. It was confirmed that the species - Himalayan Forest Thrust - found to be breeding in the coniferous and mixed forests of eastern Himalaya was not separately classified till now. What first caught the attention of the scientists was the fact that the ones found in forests (Himalayan Forest Thrush) had a rather musical song, whereas individuals found in the same region on bare rocky habitats above the tree-line (Alpine Thrush) had a much harsher, scratchier and unmusical song.

Further analyses of its plumage, structure, song, DNA and ecology throughout the range revealed that a third species was present in central China. While this population was already known, it was treated as a subspecies of Plain-backed Thrush. It is now called Sichuan Forest Thrush, which has an even more musical song than that of Himalayan Forest Thrush. A fourth species from China remains unnamed. Future field studies are required to confirm this. 

Namrup BJP celebrates Karna victory

16 May 2018 - 7:11am | Akshaya Pranab Kalita

Namrup: Local BJP leaders and workers took out a procession in Namrup on Tuesday to celebrate the party’s Good performance in the Karnataka assembly polls where it fell only a couple of seats to get absolute majority.
The mood at the local party office is upbeat and the party men took out the procession as they kept watching the television sets beaming the steep rise in the party’s poll performance on the counting day.

BJP state executive member Ranjit Boruah said , " we are  happy to say that  our party is getting good response in the southern state ." Namrup Booth BJP Provery Bhabha Gogoi , Namrup Town Committee Chairman  Neetu Sonowal Buragohain , BJP District Morcha Secretary  Ankur Phukan were prominent among those who joined  the celebration .