Design, Development, and Testing of Innovative Point-of-Use Water Treatment Technologies

Environmental Engineering; Environmental Health (Public Health); Polymer Chemistry; International Economics

This work will begin to design, develop, and test innovative point-of-use (household-level) water treatment technologies for the developing world.

Research Interests
  • Global Economics of Water
  • water pollution
  • Groundwater

In the USA, we have effective centralized water treatment and distribution systems.  Water is available in taps in our homes and work 24/7.  The water has a chlorine residual to prevent consumption of pathogenic microorganisms. The effluent water from treatment plants is highly regulated to insure public safety.  Unfortunately, 2-3 billion people in the world do not have this level of service, mostly because of economic constraints in Asia and Africa.  As a consequence more than 1.5 million children die annually from poor quality drinking water.  The World Health Organization has suggested that decentralizing water treatment, e.g. allowing people to treat their water in their homes right before consumption, is a potential solution to this global problem.  Developing such household, or point-of-use (POU) water treatment technologies, however, is a challenging design problem.  Successful designs must be technology effective, socially acceptable, extremely inexpensive, and very simple to use.

Over the past few years, my laboratory has developed a disruptive POU water treatment technology called the MadiDrop.  The MadiDrop is a porous ceramic tablet infused with silver.  It is placed in a 10-20-L water storage container.  Water is added before bed, and the next morning it is generally safe to drink.  When contacted by water, metallic silver in the MadiDrop are oxidized to ionic silver, which in turn diffuses out of the porous ceramic tablet into the bulk solution.  Silver is a highly effective antimicrobial agent that can disinfect the stored household water.  The MadiDrop works identically day after day for 12 months, treating up to 7000 liters of water.  The technology has been commercialized, and MadiDrops are currently being sold at a wholesale price of $6 per tablet, which corresponds to a cost of only $0.0008 per liter of treated water.

Although the MadiDrop is a successful and promising water treatment technology, it has limitations.  Although silver is highly effective against bacterial pathogens, it is much less effective against viral pathogens like rotavirus and adenovirus.  By contrast, chlorine (e.g. chloramines, chlorine dioxide, hypochlorous acid) are much for effective against viruses than silver.  A few studies have shown that by combining silver ions and chlorine, pathogen disinfection is highly effective for all classes of microorganisms.  And with two disinfectants, the levels of each one can be reduced and still produce highly protective performance.

Another disadvantage of the MadiDrop is that it does not remove other natural chemical pollutants, including fluoride and arsenic, which are global public health hazards.  However, we are increasingly becoming aware of low-cost effective sorbents for fluoride and arsenic, including hydroxy-appatite (bone char), activated alumina, and calcinated oyster shells.

Desired outcomes

A desired outcome of this work is the development of  a polymer impregnated with a chlorine disinfectant.  When placed in water, the chlorine disinfectant diffuses out of the polymer into the bulk solution at a rate appropriate for disinfecting a 10-20-liter volume of household water.  A second desired outcome is development of a solid substrate that can effectively sorb fluoride and/or arsenic in stored household water.  One or both of these technologies will be incorporated into the silver-ceramic MadiDrop to produce a household water-treatment tablet that releases both chlorine and silver ions into the treated water while simultaneously removing fluoride and/or arsenic from the water.  Our ultimate goal is to develop prototypes of this technology for field testing in a developing world setting, with consideration of cost, social acceptability, and ease of use.  Seed-funded research will include molecular simulations for different polymer-chlorine combinations and novel sorbents for fluoride and arsenic removal, laboratory experiments of the most promising technologies, and preparation of multiple proposals to external agencies for long-term funding of this research.