IIT Roorkee professor Abhijit Maiti and his team have developed a simple and affordable technology to remove arsenic and other heavy metals to purify water. He explains how it works.
(Above image of IIT Roorkee researchers showcasing their affordable & point-of-use technology to produce arsenic-free drinking water at last month’s IInvenTiv’ IITs R&D Fair)
Abhijit Maiti, associate professor at the Department of Polymer and Process Engineering, IIT-Roorkee, comes from a state where millions of his fellow residents suffer from consuming arsenic contaminated groundwater.
According to a March 2017 report tabled in the Lok Sabha, West Bengal “topped the list in India” with more than 1.04 crore arsenic-affected persons. The presence of arsenic in groundwater also has a deleterious effect on food crops grown in the state. Experts note that chronic exposure to arsenic can cause not only cancerous health effects, but non-cancerous ones too.
“Furthermore, arsenic contamination in groundwater is found in many other states nowadays. That motivated me to find a cheaper and effective solution to produce arsenic-free drinking water,” says Professor Abhijit Maiti, in a conversation with The Better India.
Under his leadership, a team of researchers at IIT-Roorkee has developed a simple and affordable point-of-use technology that can successfully remove arsenic under a real contaminated water environment. This solution to produce arsenic-free drinking water can also remove other heavy metals like lead, copper, iron, and manganese.
Affordable and minimal
The researchers have developed a novel mechanism that will absorb two of the most hazardous arsenic species of arsenite — As (III) and arsenate As(V) — along with other heavy metal ions.
The adsorbent is prepared from industrial waste called ferromanganese slag, which comes from industrial waste largely found in the steel industry; and laterite rock, a natural rock abundantly available in different parts of India, through a simple chemical treatment.
“Cheap raw materials, minimal use of chemicals, and the ease of scalability of the removal process — these are the three pillars of this innovation. Environmental sustainability is at its heart, given that ferromanganese slag has little commercial value,” notes Professor Maiti.
“About 500 kg of pelletised material has already been prepared in a single batch of chemical treatment process based on technology developed in an industrial setup. Fortunately, we had one industrial partner who was associated with this project through the Science and Engineering Research Board (SERB), a statutory body under the Department of Science and Technology, Government of India, under their ‘IMPRINT 2A’ scheme. Arsenic removal experiments have successfully been done under real arsenic-contaminated water environments,” he adds.
Tackling a global challenge
In a press release issued by the institute, Prof ML Sharma, acting director, IIT Roorkee, said, “Arsenic contamination is considered a global problem, as many from America and Africa are affected by this and other heavy metals in the aquifer. This innovation will be of great benefit not just to India, but to the entire world. To meet high food demand, huge amounts of arsenic-contaminated groundwater are being withdrawn and they cause surface water contamination with arsenic.”
Prof Akshay Dvivedi, the dean of Sponsored Research and Industrial Consultancy (SRIC) at IIT Roorkee, also noted in the press release, “The management of ferromanganese slag presents a challenge for industry and the country. So, [its] utilisation…will be an environmentally sustainable approach. Thus, the process is environmentally friendly as no hazardous chemicals are involved in the manufacturing process.”
Composition of this innovation
The original forms of the two raw materials — laterite rock and ferromanganese slag — found in this absorbent contain irons, aluminium, and manganese compounds that are activated to catch species of arsenic after chemical treatment only.
“The large surface area and large amount of hydroxyl groups of this final media [collection of substances] can easily catch arsenic species from water. The final absorbent comes in granular form and can be poured in the cartridge,” explains Prof Maiti.
He continues, “The filled cartridge can be fitted to any existing water purification device to catch arsenic. The water with arsenic concentration of 400 parts per billion (ppb) can be passed through this cartridge and final water arsenic concentration would be less than 0 to 10 ppb. Other heavy metals like lead, copper, iron, and manganese can be removed using this adsorbent,” explains Professor Maiti.
The amount of water would be treated based on the amount of adsorbent media filled in the cartridge. According to Professor Maiti, “The 1.5 litre (L) volume of media in the cartridge is capable of producing 8,000 litre arsenic free water. These 8,000 L can be produced from a 1.5 L cartridge within 10,000 mins (if water is being continuously passed through the cartridge).”
Thus, the user will run the device according to their requirement. A family with four-five members generally requires 20 to 25 L water for drinking and cooking purposes per day.
“To produce this amount of water, we need to run it for a maximum of 20 to 25 minutes. The components of this point-of-use device are one sand filter cartridge, one carbon filter cartridge, 10 L water storage device, a UV lamp (optional, depending on quality of water), and a cartridge filled with developed material. No external pump is required. The overhead tank pressure is sufficient to get the required flow of water through a media-filled cartridge. This technology has been developed after continuous research efforts extending about 10 years,” he adds.
‘A first of its kind in India’
As raw materials are cheaper, materials developed are much cheaper than commercially available technology to deal with arsenic in our groundwater, Prof Maiti says.
“This media cost is three to four times lower than imported adsorbent. Further, this media can oxidise the most difficult-to-remove arsenic species, namely arsenite (As(III) species), whereas other imported media cannot oxidise arsenite. Further, no complete device is available that can claim to remove arsenic up to safer concentration levels for drinking water. Thus, such a device would be the first of its kind in India as well as in the global market,” he claims.
Another important feature of this technology is that it can be easily integrated into existing water purification systems in households as well as large domestic systems.
“Existing water treatment technology is capable of removing many other harmful ingredients (mainly harmful biological ingredients) except arsenic. A cartridge filled with developed material can be attached with existing water purification devices/systems of varying capacity. So, the final device would be capable of removing arsenic as well as other harmful ingredients. Further, the volume of used media can be scaled up as per the requirement. The material is in granular form, so it will give very negligible pressure drop to the overall existing devices,” he says.
Seeking industry collaboration
Recently, the team at IIT-Roorkee employed a prototype of this technology on groundwater with an initial arsenic concentration of 100-200 µg/L (microgram/litre). With contact time of about two minutes with the absorbent, around 250-300 L of water was produced with an arsenic concentration of less than 10 µg/L (maximum limit set by the WHO).
Currently, this technology is not available in India. Imported adsorbents available in the market are limited, and the cost is also considerably higher.
“Thus far, no government organisations have approached us. But some private organisations have started to talk and hopefully technology would be transferred to any potential industry partner. We are ready to transfer this technology to any potential industrial partner. One Indian patent has been granted and another application is pending on this technology. Our team is very much interested in developing this device for mass use,” he says.