CSIR’S Terafil: Meeting Drinking Water Standards Through Innovation


MEETING drinking water standards through innovation : CSIR’S Terafil

Meeting drinking water standards is most difficult for water systems in developing countries. Some developing countries often cannot afford the equipment and qualified operators necessary to ensure compliance with safe drinking water standards.

In India even though  intermediations in terms of chlorination and monitoring of water quality  in major cities, towns and rural India are increasing, still a large section of individuals have difficulty in getting access to safe drinking water. Many of them depend completely on untreated surface or groundwater, a source of communicable diseases in India while others collects and stores drinking water in unsafe manner.

Groundwater is over and over again observed to be contaminated with fluoride, arsenic, iron and salts. In recent years, the quality of drinking remains a prime concern and a major challenge in rural as well as few part of urban India.  Many of communities are not accessible to regular water monitoring by right agencies due to practical as well as communication problems. Mostly it is the rural population that suffers problems related water contamination irrespective of their economic levels where system has yet been to be devised or put in place to improve water quality inexpensively at the national level.

Water related health is not the only issue; impure water is a major encumbrance on the states as well. Under the present-day circumstances, the most viable option to obtain safe water for individuals is to promote specific disinfection along with hygienic water treatment practices. On a positive note and also for  making quickly available water  for human consumption  CSIR-Institute of Minerals and Materials Technology (IMMT), Bhubaneswar has worked upon and advanced  a user’s pleasant green technology as well as product , called “Terafil”, for purification of both surface and ground water at minimal cost, exclusively for removal of excess iron, turbidity and bacteriological contamination through filtration process.

The laboratory has demonstrated and claims followings under Terafil  based  water filtration:

  • – Turbidity Removal: >99%
  • – Iron Removal: 90-95%
  • – Micro-organism Removal: up to 90%
  • – Rate of Filtration: 4-6 lit/hr (220 mm dia disc); 0.8-1.5 l/hr (100 mm dia disc)
  • – Treatment cost (per liter): Rs. 0.03/l (03 Paisa per liter)

Terafil water filters makes use of  Terafil ,  a burnt red clay (terracotta) porous media, made from a mixture of red clay (Pottery clay), river sand and wood saw dust. The dough of the mixture is sintered at high temperature to make porous terracotta media (disc). Sand particles form nuclei over which clay particles get embedded, leaving pores in between due to burning of wood particles during the process of sintering. These pores are separated from each other by very thin semi-permeable clay walls. The clay wall contains large numbers of ultra-fine capillary openings. The pores are connected with each other by these ultra-fine capillaries only. Suspended particles, iron and many heavy metals get precipitated on the top surface of Terafil disc in long run. As the filtrate clogs top surface of Terafil over time and reduces flow rate. Periodic scrubbing of top surface of Terafil rejuvenates flow rate. Rate of filtration depends on the water head and turbidity of the water. Average rate of filtration is 13ml/hr per unit area (cm2) with raw water having 50 NTU turbidity and 250mm water head. Rate of filtration can be increased many folds with increase of water pressure.

Process of Iron Removal by Terafil

When iron contaminated ground water is exposed to air, Fe2+ is converted to Fe3+ and subsequently hydrolyzed to form colloids in less than 2 min. of exposure. The colloids are mostly larger than 200 nm in diameter and average diameter of the capillary openings of Terafil disc is in sub-micron size (0.2-0.3µm). Due to this, more than 99% of iron is separated from raw water by filtration though Terafil media. Quality of product water is within BIS limits (< 0.3 mg/l).

Removal of Microbes from water using Terafil

Majority of bacteria such as Cholera (Vibrio), Typhoid (Salmonella) and Dysentery (Shigella) are in the size range of 0.3 to 100 µm length. E. coli has the dimension of 3 µm length and 1 µm width. Similarly Protozoa breeds such as Amoebic dysentery (Entamoeba), Cryptosporidium and Giardia are in the size range of 4 µm to 20 µm. Other higher microorganisms like Guinea worm, round worm, hookworm, tape worm etc. are well around 40 µm to 25mm size. Average diameter of the capillary openings of Terafil disc is in sub-micron size (0.2-0.3µm), much smaller than these pathogens. Therefore most of the micro-organisms and turbid particles cannot pass through the ultra-fine capillaries and stay on top surface of the Terafil during filtration. However addition of 2mg/l bleaching powder (Chlorination) makes the filtered water 100% bacteria free. Successful impregnation of nano-silver into Terafil media has been achieved in experimental scale for complete removal of micro-organisms in a collaborative effort.

Techno-economics and know-how of  Terafil production unit:

Terafil media (disc/candle) are  produced from locally available materials like pottery clay, sand and saw dust with minimum artisan skill. The Terafil production unit requires one 5 hp Pulverizer/Grinder for grinding red clay, Manual/motor operated sieves and mixing machine, hand tools for casting of green Terafil, RCC platforms for sun drying and a pottery kiln for sintering of Terafil. Local masons and sanitary marts can install the community Terafil water filters using ferro-cement chambers or FRP/LLDPE structures. Domestic Terafil water filters can be made with terracotta, food grade plastic, metallic and other related containers. The Techno-economics and know-how can be provided by CSIR-IMMT, Bhubaneswar after execution of Technology Transfer agreement.

Terafil Water Purification Systems And The Achievements

Terafil water purification systems are developed in different capacities ranging from 50 to 100,000 lit/day through gravity and pressure filtration. Terafil filters are available for both domestic use and community-level use. The filter units are designed and developed by using different materials like Polypropylene (PP), Fibre reinforced plastic (FRP), Reinforced cement concrete (RCC), Terracotta etc.

Terafil water filters are being disseminated by state and central Govt. in Bharat Nirman, Jalamani programme of Department of Drinking Water & Sanitation, Govt. of India. Cost of purified water is Rs.0.03P per liter considering total cost of filter and its maintenance. More than 2.0 lakh units of domestic filters and 30,000 units of community filters are used in households, Schools, villages etc. in many states of the country including North Eastern States and J&K under JALMANI and NRDWP, national programme of Ministry of Drinking Water and Sanitation (MDWS), Govt. of India. During 2015-16, Madhya Pradesh Laghu Udyog Nigam Ltd (M.P. Govt. Undertaking) installed 20,000 domestic Terafil filters in different Anganwadis/Integrated Child Development Services (ICDS) of Madhya Pradesh. CSIR-IMMT has transferred the Terafil disc manufacturing technology to more than 100 MSMEs/ Entrepreneurs/ Govt. Departments/ SHGs/ NGOs across India and provided adequate training to the licensees. Apart from this, thousands of Terafil water filters have been supplied to cyclone and flood affected area inside and outside Odisha by CSIR.

List of some manufacturing units (Licensees):

Way forward for Terafil Units as well as technologies

Terafil water purification
technology is an efficient, affordable
and sustainable technology for safe
drinking water in both rural and
urban sector. More than 99% of
turbidity and iron and significant
quantity of pathogens are separated
by filtration through Terafil media
without using any chemicals.
Quality of product water is within
BIS limits, particularly for turbidity
and iron. Manufacture of Terafil
disc and plants can be done locally
by sanitary mart, micro-industries,
SHG etc. with ease. Average life
of Terafil filter discs are more
than 03 years. Employment can
be generated for production and
marketing of various Terafil water

Contributed by: CSIR


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