Water: Low Cost Water Purifiers
New cost-effective water purification technologies remove microbiological, arsenic, and fluoride contamination from drinking water without being dependent on electricity.
- January 2011
- By TR Editors
India faces an enormous challenge in providing its citizens with clean potable water free from pathogenic bacteria, viruses, and cysts which cause diseases such as diarrhea, cholera, typhoid, and amoebiasis. It is estimated that about 10 million illnesses and 700,000 deaths in India could be attributed to diarrhea of which 400,000 are children under the age of five. Moreover, due to over exploitation of ground water, the levels of mineral contaminants such as arsenic and fluoride in water drawn from wells have increased dramatically. High levels of arsenic in drinking water causes serious and sometimes fatal health problems such as nervous dysfunction, cancers of the bladder, skin, kidney, liver and hyperkeratosis of the palms and feet. Consumption of water containing high levels of fluoride causes dental as well as skeletal fluorosis —a crippling bone disease causing severe deformities in adults as well as children.
About 50 million people in West Bengal are presently affected by arsenic poisoning while an additional 70 million people are affected in neighboring Bangladesh which according to the World Health Organization (WHO) is the largest mass poisoning in human history. In addition, about 60 million people across India, mainly in Rajasthan, Gujarat, and Andhra Pradesh consume water with high fluoride content. Given the gravity of the situation, there is an urgent need for deploying technologies for removing microbiological, arsenic, and fluoride contamination from drinking water before it is consumed. Researchers at Tata Consultancy Services Innovation Labs are developing water purification technologies appropriate for India. The team believes the most appropriate technologies for water treatment in India are those which do not require electricity or regular user intervention. TCS has developed counter-top filters, such as Sujal, a rural water filter, and Tata Swach, one of the world’s most economic household water purifiers, for removal of contamination from water before it is consumed.
The key ingredient of Sujal filter was a matrix of pebbles, cement, and rice husk ash, a byproduct of the paddy industry which, while had little or no value to the rice growers, was a highly effective filtration medium. The adsorbent capacity of rice husk ash emanates from its microstructure which consists of porous silica and carbon, forming an intricate network of microscopic holes and channels. A complete unit cost only `200 with a replacement cost of `25 for the filter bed and could remove 95 percent of the turbidity and bacteria present in the input water.
In 2006, the team developed a novel method for modifying the surface of rice husk ash to incorporate millions of silver nanoparticles into its pores resulting in a material that had greatly enhanced bacteria-killing performance. This material was then incorporated into a compact cartridge which forms the heart of Tata Swach Nanotech Water Purifier. The Tata Swach Bulb is capable of purifying 3,000 liters of water without clogging or losing effectiveness and incorporates a Tata Swach Fuse to shut the flow of water when the bulb reaches the end of its useful life.
One of the most effective and economical methods for removing arsenic contamination from water involves coagulation, flocculation, and separation. These steps are commonly employed worldwide in municipal water treatment plants by employing large-scale batch processing equipment. TCS’ household arsenic filter prototype is capable of condensing the same steps to fit in a counter-top package. A compact float and siphon based metering system adds fixed amounts of coagulant to water. This coagulant then forms a dense floc or precipitate which reacts with the arsenic present in the water thus trapping it in a stable complex. The arsenic laden floc is then captured in a floc collection and adsorption system while clean, arsenic-free water flows down to a collection chamber. The fluoride removal solution incorporates a novel coating on rice husk ash to generate a high capacity adsorption medium which is selective to fluoride at specific acidic values. The system also incorporates a pre-defluoridation step to further increase the capacity of adsorption media while simultaneously controlling the alkalinity of the water. Water first enters the pre-defluoridation section wherein a small amount of coagulant is added to it by a solid candle. As with the arsenic removal filter, this coagulant forms a floc which attracts the fluoride ions from the water and gets captured in a floc collector at the bottom of the unit. Water subsequently flows upward through the adsorption media which removes the remaining fluoride ions and fluoride-free water flows out of the outlet of the unit. Each unit is capable of treating 500 liters of water and four such units are combined to form a 2,000 liter capacity household filter.
The arsenic and fluoride filters are currently undergoing extensive in-lab testing. A prototype of the arsenic removal filter was tested over 3,000 liters while multiple 500 liter capacity fluoride removal units were tested against challenge levels of 10 parts per million of fluoride. The output levels of arsenic throughout the life of the filter are within the 10 parts per billion limit set by the World Health Organization (WHO) and Indian standards while the fluoride removal unit is capable of reducing the levels of fluoride ions present in the input water to below the WHO and Indian standard limit of 1.5 parts per million over its prescribed life.
Sujal has been deployed across 30,000 rural households in India while Tata Swach is now available in shops and stores across Maharashtra, Karnataka, West Bengal, Madhya Pradesh, and Uttar Pradesh with subsequent launches planned across the country. By enabling their users to consume bacteria and virus free water, both Sujal and Swach are playing an important part in reducing morbidity, illness, and fatalities due to waterborne disease.
While Sujal is the first “make it yourself” rural water purifier, Tata Swach broke the price barrier in India for affordable household water purification (priced at `999). Subsequently, two more variants costing `749 and `499 have been launched thus starting a revolution in low-cost water purification in the country.