Now a papaya-clay filter

The hybrid clay filter could be the cost-effective answer to water purification

By Manupriya
Last Updated: Saturday 04 July 2015


EVERY year, at least 37.7 million people in India suffer from water-borne diseases; close to 1.5 million children die due to diarrhoea; and about 200,000 habitations deal with chemical contamination, according to a paper published by non-profit WaterAid. The problem is further compounded with the rise of drug-resistant diarrhoeal organisms.

The market is flooded with filters that promise pure water by employing UV-based technologies to Reverse Osmosis. But something is wrong here. These systems are just meant for a select few and are a definite misfit in the milieu of urban and rural poor.

It is for this reason that scientists are constantly pushing for water purification solutions that are inexpensive and robust. One such innovation is a hybrid clay synthesised by German and Nigerian scientists. The clay is actually a composite made up of kaolinite clay and papaya seeds. Writing in their paper, published in ACS Sustainable Chemistry and Engineering, the scientists claim that the hybrid is stable, nonbiodegradable, can be easily recovered from aqueous solution by decantation and available in large amounts. It also has a high cation (positively charged metal ions) exchange rate, which means it can absorb and remove cations of metals like, lead, cadmium and nickel from water.

Emmanuel Iyayi Unuabonah, one of the authors from the Department of Chemical Sciences of Redeemer’s University, Nigeria, says, “We have not tried it on arsenic. But I am confident it will be able to remove arsenic from water since it is positively charged like the metal ions used in my research.” Arsenic is one the biggest metallic polluters of groundwater in India. The hybrid clay is also yet to be tested for its ability to remove contaminating microorganisms from water. Commenting on their work, T Pradeep, professor of chemistry at IIT Chennai, says, “Any technology is welcome in the water sector because the problem is huge.” The capacity they reported is good.

What is important is how this material works in an affected area. Water has multitude of contaminants and a good solution should work under all conditions, he adds. Pradeep has been working on developing solutions for water purification for a long time now. He has recently developed a silver-based nanocomposite material that can filter bacterial and viral impurities from water. This composite by itself cannot remove metallic impurities from water, but Pradeep and his team of scientists have teamed it up with other composites that have abilities to filter metallic impurities. The resultant water purifier, which runs without electricity, can provide clean water to a family of five at an annual expense of USÔÇê$2.5 assuming a daily consumption of 10 litres. The team has published the findings in PNAS on May 21, 2013.

The IIT-Chennai team has installed the purifier in several communities across the country for two years now as part of a field trial. “We are partnering with several organisations to take these technologies to the market,” he says.

There are several composites under the broad umbrella of materials. Purification solutions can be found for all the contaminants by combining these materials. Thus an all-inclusive solution for clean water can be made, Pradeep adds. Which combinations of composites can be truly effective in field remains to be seen.

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  • This piece of development

    This piece of development reported, is really a positive step,in the cause of protecting the health of the community, particularly those belonging to poorer and marginalised sections of india and many other developing countries. The approach is novel, but need to be cost effective, and marketable in regions where it is most needed.I am happy to see that it has multifaceted potential to tackle many pollutants, including toxic heavy metals, which is interesting.
    In this context, I have myself been working on simple affordable technologies to free drinking waters from metal toxins like Arsenic, Lead etc., and have successfully come out with an exclusive gadget, which can efficiently remove above toxic metals ( and others like Iron, Manganese,Cobalt, nickel etc.,).This"Metal Filter" attachment - which has been commercialised and available in the market-,can operate even in the absence of power, which is the reality in a rural scenario, like in parts of West Bengal, where the arsenic problem in ground waters is serious!!.

    Posted by: Anonymous | 6 years ago | Reply
  • Interesting. There were age

    There were age old methods of using copper,brass and silver to purify water which need to be studied Thoroughly for standardisation.
    Use of Copper and Brass - Way to Good health

    Our ancestors used to have good health throughout their life; one of the various reasons was daily use of Copper and Brass utensils. It has been proved that Copper and Brass (Brass 60% +Copper 40% =Zinc) carries lots of medicinal properties, which are tremendously beneficial for human health. According to this the medicinal properties of Copper and zinc, gets leached into water stored in them and this stored water we call 'Tamra-Jal'. Human body gets benefits of these medicinal properties by drinking 'Tamra-Jal' or cooking food in 'Tamra-Jal'.
    Today, to ensure good health how much effort one takes? As a precaution we drink only pure water either boiled or purified with expensive electric purifiers. Instead of all this, one should drink only ÔÇÿTamra-JalÔÇÖ, which is pure and medicated too!
    ÔÇó Loss of wound healing capacity.
    Benefits of Copper:
    ÔÇó Helps healthy growth,
    ÔÇó Regulates blood flow, useful in heart problems,
    ÔÇó Helps to loose extra fat,
    ÔÇó Gives luster to skin.
    ÔÇó Useful in preventing Anaemia, Amoebiasis, Cough, Acidity, Piles etc.
    The influence of copper upon human health is due to the fact that it is part of enzymes, which are proteins that help biochemical reactions occur in every cell. Copper is involved in the absorption, storage and metabolism of iron.
    Benefits of Zinc :
    40% Zinc from the Brass helps human body as:
    ÔÇó Improves resistance power to diseases,
    ÔÇó Improves skin tone and cures skin problems,
    ÔÇó Nourishes healthy hair.

    Mystery of copper & brass ÔÇô Ayurvedic secrecy to health
    Scientists had thoroughly studied many of the ayurvedic granthas, to know more about the medicinal benefits of copper and brass. In the 5 th chapter and 46 th verse, of famous grantha ÔÇÿRasratnasamucchayaÔÇÖ, we find significant information on medicinal properties and its benefits to humans. When water is stored in the copper / brass vessels, copper and brass (brass = 70% copper + 30% zinc) gets leached in the water. Drinking this water benefits human body with their medicinal properties.
    After knowing the importance of copper and zinc, now a days, people have started using the copper and brass utensils for storing drinking water, in big restaurants it is used for serving. You can find decorative copper jugs in many houses too. Along with copper, zinc is also required for many biological activities, which we get from brass vessels.

    Silver - Reliable Alternatives to Chlorine

    Silver Water Purification Systems Offer Reliable Alternative to Chlorine
    Report by: The Silver Institute - Silver News -

    Laguna Niguel, CA (March 25, 1997) - Silver based water purification systems offer the most reliable and cost effective alternative to chlorine, a chemical that is increasingly coming under fire for the carcinogenic by products it leaves in water, according to David Eaton, secretary of The Institute of Water Ionization Technologies in the United Kingdom and technical director of Roseland Hydronics PLC.

    Speaking at the annual meeting of The Gold & Silver Institutes in Laguna, Niguel, CA. this week Eaton said progressively restrictive legislation is confronting the use of chemicals, especially chlorine, which for nearly a century. has been the primary medium for water disinfection.

    With increasing pollution, utilities are forced to put far more chlorine into the supply chain, Eaton explained. The chemical reaction that oxidizes impurities when chlorine is added, also forms carcinogenic byproducts. "Of course these same byproducts have been generated by chlorination for a long time but never in the quantities that are now being seen," he said.

    Silver offers a healthy alternative. The metal has long been known for its biocidal properties, Eaton noted. The Ancient Phoenicians. who stored wine in silver urns to preserve it, provide one of the earliest recorded examples of the metalÔÇÖs use for water purification.

    Applying modern technology to this old fashioned principle, The Institute of Water Ionization Technologies has developed silver ion generators for municipal water supplies. The market for silver ionized swimming pool systems has expanded significantly in the US and overseas, Eaton said. But in Britain, silver ionization is being developed for mainstream water systems. Machines used to clean primary water must be much larger and more powerful than small swimming pool units, and require accurate control mechanisms to ensure that levels of silver are maintained and kept within drinking water standards.

    Eaton discussed a recent project funded by the UK Department of the Environment to study the control of Legionnaires disease by using silver ions. The disease is named after Legionella pneumophilia, an organism that is widespread in small quantities within natural water sources. The bacteria becomes lethal at a water temperature of 95 degrees F and can be killed at temperatures between 135 and 140 degrees F.

    Of three tests, silver/copper ions in soft water produced the best results. The copper ion disrupted the enzyme structures of the cell allowing the silver ion to penetrate inside where it rapidly killed the cell's life support system. US regulations allow a silver level of 100 ppb in drinking water, but a silver level of only 20 ppb kills Legionella.

    Eaton said silver ion generators currently are being used in intensive care and heart transplant units of hospitals, and for poultry processing, engineering, brewing, cooling towers and swimming pools.

    Research Quotes:

    Thanks to eye-opening research, silver is emerging as a wonder of modern medicine. An antibiotic kills perhaps a half dozen different disease organisms but silver kills some 650. Moreover, silver is virtually non-toxic. Dr. Harry Margraf of St. Louis, a pioneering silver researcher, says: "Silver is the best all around germ fighter we have."

    The value of silver in medicine, and as a purifier has been acknowledged for centuries. Egyptians implanted silver plates into skulls with surgery. In Ancient Greece and Rome, people used silver containers to keep liquids fresh. When settlers moved across the American West, they would purify a container of water by putting a silver dollar in it overnight. Towards the end of the 19th century, other medicinal uses for silver were developed including the use of silver and mercury in filling cavities, and the dropping of a silver filtrate solution into the eyes of newborn babies to prevent blindness due to infection.

    Scores of independent tests have shown that silver promptly kills bacteria in water and maintains water purity over long periods of time.

    Russian scientists working on water recycling and purification problems for the Soviet space program have decided on silver as the best long term sanitation agent. Researching the problems of water shortage over periods of several months, as well as purification for immediate use, they determined that ionized silver provides the safest and longest lasting method of transforming polluted waste into potable water.

    After testing 23 methods of purifying water, NASA has also chosen silver as the purifying agent on the Space Shuttle program.

    Silver was used to provide shuttle crews with pure water for drinking, air conditioning, food preparation and other operations. By establishing 100 parts of silver per billion parts of water NASA will totally eliminate the need for chlorine! The most dramatic purification tests occurred in 1976 in a 20,000 gallon swimming pool in Nebraska. There was no disinfectant of any kind in the water. Fifty gallons of municipal sewage waste water was put into the pool. That produced a dangerous concentration of 7,000 E coli cells per 100 millilitre [half a cup] of water. Contents of the pool were then pumped through a tank containing alternating anodic and cathodic silver electrodes for disinfection. Within three hours the pool was entirely free of E. coli and the water contained only 3.2 parts of silver per billion parts of water.

    The Allegheny County Health Department in Pennsylvania conducted tests in a 152,000 gallon pool which previously had been disinfected by a 50 pounds per day chlorinator. The system was replaced by a silver system for the swimming pool season of 1974 and 1975. The County Health Department took up to 50 daily samples and found that silver ions remained in the pool at the low steady rate of 20 parts per billion. The water remained free of bacteria throughout the two seasons. In contrast, 65 water samples from 30 other pools having a concentration of 700 parts per billion of available chlorine showed a mean of 1.3 pseudomonas and 7.3 staph cells per millilitre of water.

    The impact of silver technology continues to grow. More than half of the American soft drink bottling companies, numerous shipping lines and a host of other enterprises in 70 countries, use silver to sterilize water. These and many other examples of the expanding use of silver in water purification have been documented by Dr. Fred Zobist and presented to the Silver Institute in Washington, D.C.

    Dr.A.Jagadeesh Nellore(AP),India

    Posted by: Anonymous | 6 years ago | Reply
  • I designed a low-cost solar

    I designed a low-cost solar disinfection gasdget which uses Solar Thermal and UV. It is cost effective and can be fabricated locally.
    Here are details:
    Safe Drinking for All through Solar Disinfection
    by Dr. Anumakonda Jagadeesh

    Every 8 seconds, a child dies from water related disease around the globe. 50% of people in developing countries suffer from one or more water-related diseases. 80% of diseases in the developing countries are caused by contaminated water. Providing safe drinking water to the people has been a major challenge for Governments in developing countries. Conventional technologies used to disinfect water are: ozonation, chlorination and artificial UV radiation. These technologies require sophisticated equipment, are capital intensive and require skilled operators .Boiling water requires about 1 kg of wood/liter of water which results in deforestation in developing countries. Also halazone or calcium hypochlorite tablets or solutions (sodium hypochlorite at 1 to 2 drops per liter) are used to disinfect drinking water. These methods are environmentally unsound or hygienically unsafe when performed by a layperson. Misuse of sodium hypochlorite solution poses a safety hazard .
    Treatment to control waterborne microbial contaminants by exposure to sunlight in clear vessels that allows the combined germicidal effects of both UV radiation and heat has been developed and put into practice .The SODIS system(Solar Disinfection of water) developed by scientists at the Swiss Federal Agency for Environmental Science and Technology(EAWAG) recommends placing PET bottles (usually discarded mineral water/beverage bottles) painted black on one side, aerating (oxygenating) the water by vigorous shaking three fourths water filled bottles and then filling them full and placing them in sunlight for 6 hours. In this method, the water is exposed to UV radiation in sunlight, primarily UV-A and it becomes heated; both effects contribute to the inactivation of water borne microbes. The use of PET bottles requires periodic replacement because of scratches and they become deformed if temperature exceeds 650C. Also dust accumulates on these bottles in the groves (provided for strength). The PET bottle mineral water manufacturers print on the label, ÔÇÿcrush the bottle after useÔÇÖ in India. Unless cleaned thoroughly everyday, PET bottles turn brown over usage rendering lesser transmission of sunlight.
    Microorganisms are heat sensitive. Table 1 lists up the required temperature to eliminate microorganisms within 1,6 or 60 minutes. It can be seen that it is not required to boil the water in order to kill 99.9% of the microorganisms. Heating up water to 50 ÔÇô 60C (122 ÔÇô 140F) for one hour has the same effect.
    The most favorable region for solar disinfection lies between latitudes 150 N/S and 35 0 N/S. These semi-arid regions are characterised by high solar radiation and limited cloud coverage and rainfall (3000 hours sunshine per year).The second most favorable region lies between the equator and latitude 15 0 N/S, the scattered radiation in this region is quite high (2500 hours sunshine per year).
    The need for a low-cost, low maintenance and effective disinfection system for providing safe drinking water is paramount, especially for the developing countries.
    Materials And Methods
    The innovative solar disinfection system has a wooden frame of length 2 ft,width 1 foot and depth 6 inches with bottom sinusoidal shaped polished stainless steel (curvature slightly larger than standard glass wine bottles, about 5 inches diameter) . On the front is fixed a glass sheet having lifting arrangement with a knob (this glass enclosure will protect the glass bottles from cooling down due to outside wind). There are screws which can be used to keep the contents airtight. On the backside a stand is fixed which will help the unit to be placed according to the latitude of the place for maximum solar insolation.
    In this method clear glass bottles (used wine bottles) are utilised instead of PET bottles as the former are easy to clean, lasts longer and are available at a low cost in India. Solar disinfection is more efficient in water containing high levels of oxygen; sunlight produces highly reactive forms of oxygen (oxygen free radicals and hydrogen peroxides) in the water. These reactive forms of oxygen kill the microorganisms. Aeration of water is achieved by shaking the 3/4 water filled bottles for about 20 seconds before they are filled completely.
    The unit has an advantage in that the rear reflection stainless steel will pass the light through the bottles a second time, to both increase exposure and eliminate shadowing. This reflection system will increase the light intensity minimum 2 times.
    It has been widely experimented and established by earlier researchers that at temperature of 50C (122F), pathogenic microbes are inactivated. The temperatures which cause approximately a 1-log decrease in viability with 1 min are 55C (131F) for protozoan cysts; 60C (140F) for E.coli, enteric bacteria, and rotavirus; and 65C (149F)for hepatitis A virus .Negar Safapour and Robert H.Metcalf in their extensive studies reported enhancement of solar water pasteurization with reflectors and the crucial role of temperature above 50C (122F) in the elimination of pathogens.
    The unit is placed in the south direction (in India) around 10 am with inclination equal to the latitude of the place. The glass bottles are filled with water three fourths and shaken for 20 seconds to generate oxygen and then completely filled. The water filled bottles are fixed with caps and put in the groves of the solar disinfection unit. The glass door is closed and clipped airtight. Water bottles are removed from the unit at 3 pm and taken to a cool place and the disinfected water transferred to a clean vessel, covered for later usage.
    Suspended particles in the water reduce the penetration of solar radiation into the water and protect microorganisms from being irradiated. Solar disinfection requires relatively clear water with a turbidity less than 30 NTU.To remove turbidity traditional methods of putting the paste from seed of strichnos potatorum (Nirmal seeds) by rubbing the seed on a rough stone with water is used. The method is effective, turbidity settles down in half ofv an hour and the seed are available in plenty in forests in India besides being inexpensive.
    Sample Testing
    Water samples from the solar disinfection unit were tested with Most Probable Number (MPN) technique. To estimate the number of aerobic organisms present in water, Pour Plate Technique has been used.
    The test results of various water samples disinfected are presented in Table 2. In the samples from Ambattur Bore Water, Ambattur Well Water, Anna Nagar Bore Water and Kavaraipettai Bore Water, since they are highly contaminated, further dilutions were not carried out. The dilution should be done only when the MPN indicates more than 1100 organisms/100 ml. For these samples only log reductions can be calculated. As regards R.S.M.Nagar Bore Water and Thathai Manji Well Water, the percentage of reduction are 85 and 86.95, which indicates that the water is less contaminated. As MPN index shows less than 3 organisms for 100 ml, after solar disinfection of water, the samples are free from coli forms. The results of Avadi Waste Water and Perambur Waste Water show 3 log reduction (99.8%) and 4 log reduction (99.993%) respectively.
    For comparison PET and Glass bottles were placed with black background as well as in the innovative device I developed. It can be readily seen that solar disinfection of water is complete with the device compared to open.
    Eradication of coli forms from well water, bore water and waste water has been reported from test results. The results confirm that there is 4-log 10 reduction of coli forms in the waste water after solar disinfection..Maximum temperature occurs around 1 pm. Though 6 bottles were used in the system(each of 1 liter capacity),larger units with up to 100 bottles can be designed. The unit destroyed 99.99% of bacterial coli forms both in well water and waste water samples in 5 hours.
    The innovative solar disinfection system has the advantages like:
    1. The unit is portable,
    2. It is cost-effective.
    3. It can be fabricated in South India for US $20.
    4. The unit incorporates the principle of reflection to increase solar intensity and has protection from wind which results in temperature rise inside the unit,
    5. Larger units can be manufactured, Used glass bottles withstand higher temperatures and are available in plenty each for 2 US cents in South India, Since all the materials are available locally, the unit can be manufactured locally with local people.
    6. Temperatures above 30 degrees C occur in south India for more than 10 months in a year and as such this innovative solar disinfection unit will be a boon in this region.
    Dr.A.Jagadeesh Nellore(AP),India

    Posted by: Anonymous | 6 years ago | Reply
  • Excellet Article. Yes, There

    Excellet Article. Yes, There is a constant need in India for Low cost solutions. More important is some solutions derived from local, organic materials.

    I am sure it will get tested on arsenic in a very short time as Mr Pradeep of IIT Chennai says so. The residents of the eastern parts of India will be highly relieved then.

    I wish All the best to Mr Emmanuel Iyayi Unuabonah & his team for this. I am surely sharing this particular article on my web magazine called Mineral Water Project Information.

    Thanks Manupriya for posting content like this !

    Posted by: Anonymous | 6 years ago | Reply
  • Dear Dr Iyengar, Where & how

    Dear Dr Iyengar,

    Where & how can we have the details of the device you just mentioned ?

    Posted by: Anonymous | 6 years ago | Reply
  • Dear Dr Jagdeesh, No doubt

    Dear Dr Jagdeesh,

    No doubt the metals Copper, Brass , Silver are the BEST for filteration. I remember having replaced SS Nozzles of a Liquid Filling Machine on recommendation from an Ayurvedic Medicine manufacturing client.

    Second : Why don't you give some illustration type demonstration of your equipment ?

    Where can I know more about this Sir ?

    Posted by: Anonymous | 6 years ago | Reply
  • We use the papaya system for

    We use the papaya system for our drinking water and I like what it filtersbut I am looking for a whole-house filter that will filter the water that we use to water our plants and that we bathe in. Do you have any good recommendations for that? I dont want just a showerhead filter because I fill the tub with the spigot for our daughters bath. Thank you!

    Posted by: Anonymous | 6 years ago | Reply