TerafilTM  Water Filter
Features of Technology Maintenance of Terafil Water Filter
Quality of Treated (Product) Water Self Test
Quality of raw water can be treated TTD Certificate "Terafil red clay water filtration media (Disc)"
Capacity of Terafil Water Filters TTD Certificate "Community Gravity flow Terafil Filter without media (Disc)"
Capacity Building    


Terafil Water Filter is a low cost device to filter impure water into clean drinking water. The filter is developed to cater the needs for clean drinking water, especially when the water is rich in sediments, suspended particles, iron and certain micro organisms causing water borne diseases. It is most suitable for areas where water from both surface & ground water sources like dug wells, ponds, tube wells and rivers is used for drinking purpose. TERAFIL has been developed at the Institute of Minerals and Materials Technology (IMMT), (formerly known as Regional Research Laboratory), Council of Scientific and Industrial Research, Bhubaneswar-751013 after long years of research and trials. The filter is already in use by thousands of households in the state of Orissa, Karnataka, Meghalaya & few other states in various forms. TERAFIL water filtration discs are prepared under license and training from IMMT.

Domestic Terafil filter

Features of Technology

is a burnt red clay (terracotta) porous media used for filtration and treatment of water for drinking. It is made from a mixture of red clay (silt clay), river sand and wood saw dust without using any chemicals. The dough of the mixture is sintered at high temperature in a low cost coal / wood fired furnace to make the terracotta disc porous. During sintering process, the wood particles are burnt and clay particles are sintered around the sand particles leaving elliptical / circular large size pores in between. These pores are not connected with each other, unlike white ceramic filter candles, but separated by very thin clay walls which are semi-permeable in nature. The thin clay walls contain large numbers of ultra-fine capillary openings. A set of pores are connected by these ultra-fine capillaries only. Average diameter of the capillary openings is in sub-micron size.

Terafil water filtration disc

During filtration process, water flows from one pore to another pore through the capillary openings by pressure of raw water over the Terafil disc. The pores inside the Terafil disc always work like micro-reservoirs of filtered water. Since opening of the capillaries are in sub-micron, almost all suspended particles & microbes etc. cannot enter into the capillaries; hence sediments & impurities are deposited on top of the Terafil disc during filtration. Therefore the core of Terafil disc is never clogged unlike white ceramic candle during filtration. The Terafil is activated during sintering process and the clay is negatively charged. Soluble iron and some heavy metals present in raw water are also removed by ion-exchange and/or adsorption process. The soluble iron is always precipitated on the top surface of the Terafil. These impurities / sediments are cleaned from the top surface of Terafil periodically.

SEM Pictures of Terafil disc

In this way iron rich or high turbid raw water can be filtered and treated to get clean drinking water. Nearly 99% of turbidity, 95-100% of micro-organisms, 90-95% of soluble iron, colour, bad odour etc. is effectively removed from the raw water by filtration through the Terafil disc. Pathogen free product water can be obtained from ground water by filtration through Terafil disc, while mild chlorination (0.01 gm/ liter product water) is necessary for surface water. Rate of filtration is dependant upon turbidity and pressure of raw water as well as diameter of Terafil disc inside the filter. The filtrates clog the top surface of the Terafil over time during use and hence reduce the flow rate.

Therefore scrubbing or cleaning the top surface of the Terafil disc with a soft nylon brush or coir or similar abrasive materials or by water jet is necessary to remove the sediments and open the new pores for rejuvenation of filtration process. However quality of filtered water is not altered during entire life of Terafil although thickness of the Terafil is reduced by scrubbing its top surface during the filtration process. The Terafil can be made in any shape; but circular disc shape is more preferable in respect of high strength, long operational life, simple production, easy fixing with container or holder, high rate of filtration, and easy operation & maintenance.

TERAFIL disc fitted with holder

Terafil is prepared in shape of solid disc of 50 mm thickness and 100 & 220 mm diameter to obtain maximum benefits. Average rate of filtration is 13ml/hr per unit area (cm2) of top surface of Terafil disc with raw water having 50 NTU turbidity and 250mm water head. Rate of filtration increases many folds with increase of water pressure. Average turbidity of the product water is in the range of 0.5 to 3 NTU, irrespective of high turbid raw water is used. Similarly iron content of the product water is always within permissible limit of BIS even when high iron content (15ppm) raw water is filtered. pH of product water is also improved during filtration of acidic water. Therefore the Terafil water filter is well suitable for treatment of both surface & ground water with
affordable cost and without significant maintenance for a long period. Moreover the filtrates/ sediments collected after filtration does not contaminate the water sources. Electricity is not required for operation of both domestic and community Terafil water purification systems.

Over to Top

Quality of Treated (Product) Water
Turbidity Within BIS limit
Iron Within BIS limit

Within BIS limit for ground water. (For surface water: 0.01gm bleaching powder per liter of product water is sufficient to make complete pathogen free). Impregnation of Nano-silver into Terafil disc is under development for complete removal of micro-organisms.

Increase of pH 1.0
Color & Odour Significantly removed
Rate of filtration 1 to 10,000 liters /hr depending upon type & capacity of filter.

Quality of raw water can be treated
Source Surface and ground water
Turbidity Up to 500 NTU
Iron Up to 15 ppm

Capacity of Terafil Water Filters

Rate of filtration 1 to 10,000 liters /hr at present
Domestic Terafil water filter 20 & 30 liter sizes with 1 to 4 lit/hr rate of filtration.
Community gravity flow Terafil water filter 1,000, 3,000, 10,000, 30,000, 50,000, 80,000, 1,00,000 liter per day.
On-line pressure flow Terafil water filter 60 to 10,000 liter per hour

Cost of Product Water

  • Rs.2/- per ton of filtered water (Considering cost of plant & excluding cost of raw water)

Space for installation of Community Terafil Water Filters

  • 1 to 300 m2 for installation of 1,000 to 1, 00,000 lit/day capacities.

Capacity Building


Community Terafil Water Filter (1000 lit/ day capacity)

Terafil water filtration disc can be manufactured by small and micro-entrepreneurs, like tiny, cottage, small scale industries and Self Help Groups in any place of the country without any prerequisite conditions. However, raw materials such as red clay (clay used by potters), river sand and wood saw dust should be available in the locality. The Terafil production unit requires one 5 hp Atta Chaki (Pulverizer) for grinding red clay, Manual / motorized sieves, mixing machine, hand tools for moulding green Terafil, RCC platforms(60 ft X 40 ft ) for sun drying of Terafil, ‘Queen’ coal/wood fired pottery kiln for sintering of Terafil, and 30ft X 20ft size shed. 3 phase 5 KW power is necessary for operations of the machines. With the chambers made with terracotta, food grade plastic, metallic and ferro-cement etc. Trained manpower without any specific expertise can produce Terafil water filtration disc  Local masons and sanitary marts can install the community Terafil water filters using ferro-cement chambers or masonry/ RCC structures. Domestic Terafil water filters can be made             

Over to Top

Maintenance of Terafil Water Filter

The sediment deposits on the top surface of the Terafil discs are to be cleaned once in a week or as and when required, by mild scrubbing with an ordinary plastic scrubber or coir or water sprayer followed by a rinse with cold water. The Terafil discs in domestic or community filters are easy to dismantle / reassemble the by a person of ordinary skill. Always ensure that the Terafil discs are fitted rigidly on the base of top container with rubber washers in proper places and not damaged in domestic filters. The height of the Terafil discs will reduce over a period of time due to scrubbing but shall remain active till 10 mm above the plastic holder. Care should be taken not to drop the filter/Terafil discs as it may cause accidental break/crack. During first use of a new filter, fill the filter with water repeatedly during first two days and drain out the filtered water. Consume the filtered water for drinking from third day onwards.

Iron sludge on Terafil discs

Self Test

The transparent colour of the filtered water in the lower container is indicative of proper working of the filter. However the user is advised to ensure that water of about half inch height always stands at the bottom of the top container in empty condition (in case of Terafil fitted with holder is used) of domestic filter. Failing of these, the filter discs are to be checked for crack/loose mounting.

Terafil water purification plant
(30,000 Lit/ day capacity)