Water Disinfection: It Is Saving Lives

Every hour hundreds of people are dying unnecessarily of waterborne diseases, mostly children under the age of five. This is unforgivable.


To repeat some words from an attachment to an earlier blog (‘Water and Energy: A Critical Nexus’): “The implications of too little fresh water are significant. The World Health Organization estimates that, globally, more than 1 billion people lack access to clean water supplies and more than 2 billion lack access to basic sanitation. The amount of water deemed necessary to satisfy basic human needs is 1,000*cubic meters per capita annually. In 1995, 166 million people in 18 countries lived below that level. By 2050, experts project that the availability of potable water will fall below that level for 1.7 billion people in 39 countries. Water shortages plague almost every country in North Africa and the Middle East.
(*Note: this number is very uncertain and depends strongly on how ‘minimum requirement’ is defined. To illustrate the problem I quote from an article entitled ‘Minimum water requirement for social and economic development’ by Jonathan Chenowth of the University of Surrey: “There is no common understanding of the minimum per capita fresh water requirement for human health and economic social development. Existing estimates vary between 20 liters and 4,654 liters per capita per day, however, these estimates are methodologically problematic as they consider only human consumptive and hygiene needs, or they consider economic needs but not the needs of trade.” To clarify the situation somewhat most people who study the issue consider 10-20 liters per capita per day to be the right range for minimum drinking requirements.)

These shortages have significant health effects. Water-borne diseases account for roughly 80 percent of infections in the developing world. Nearly 4 billion cases of diarrhea occur each year, with diarrheal diseases killing millions of childrenn. Another 60 million children are stunted in their development as a result of recurrent diarrheal episodes. In addition, 200 million people in 74 countries are infected with the parasitic disease schistosomiasis, intestinal worms infect about 10 percent of the population in the developing world, and an estimated 6 million people are blind from trachoma, with an at-risk population of 500 million.”

These are not small numbers. One billion people is one seventh of the world’s population. Two billion people is almost three out of every ten of our global co-habitants. The enormity of the problem was recognized by the United Nations: at its 2000 Summit the UN adopted two Millennium Development Goals related to water and sanitation: to reduce by half, by 2015, the proportion of people without access to (a) safe drinking water, and (b) basic sanitation. Assuming a world population in 2015 of 7.2 billion, to meet these goals 1.6 billion more people will need to be supplied access to safe drinking water and an additional 2.2 billion access to basic sanitation. Even if the 2015 goals are reached, which is still questionable, 600 million people in 2015 will still lack access to clean water and 1.5 billion to adequate sanitation.

The problem in many cases is not the availability of water – the earth is a water-rich planet. Unfortunately most of that water, 97%, is saline and found in the oceans, and too much of the fresh water available for human consumption is contaminated by microbial pathogens (bacteria, viruses,..) and agricultural and industrial runoff. The question then becomes, other than desalinating brackish and seawater which requires energy, how do we convert contaminated water into potable water suitable for drinking, cooking, and hygiene. Many people and organizations have worked on this effort for many years (e.g., see http://www.unicef.org/wash), and progress has been made, but the world’s population is increasing, especially in developing countries with significant levels of poverty, and the numbers of people suffering from inadequate supplies of clean water are still problematic. In the following paragraphs I will describe briefly some of the techniques for water disinfection, with a special focus on disinfection using ultraviolet radiation.

Treating water at the household level has been shown to be one of the most effective means of preventing waterborne diseases. Even collecting clean water at its source is problematic because of the possibility of fecal contamination during collection, storage, and use in the home. Chlorination is the most widely practiced means of treating water at home and community levels. Boiling water to kill microorganisms is also widely used, but requires fuel to heat the water. Passing water through sand filters to remove suspended solids and microbes, and through ceramic filters coated with silver, are other common means of disinfection. Other techniques use exposure to sunlight (a slow process) and flocculation in which common substances like alum are added to water to facilitate sedimentation of harmful substances.

In 1993 Dr. Ashok Gadgil, Director of the Environmntal Energy Technologies Divisin of Lawrence Berkeley National Laboratory (LBNL) and Professor of Civil and Environmental Engineering at UC Berkeley, invented UVWaterworks as a means of disinfecting contaminated water using ultraviolet radiation. He was motivated by an outbreak of cholera in India, his native country, and focused on developing a technology that would be inexpensive and easily maintained without a skilled operator. It works by passing unpressurized water under an ultraviolet lamp which does not come in contact with the water and the radiation from which disrupts the DNA and RNA of bacteria and viruses, preventing their reproduction. The lamp can be powered by a single solar PV panel or another source of electricity. It has long been known that UV radiation in the wavelength range 240-280 nm has this hermicidal effect and recent research seems to pinpoint 260 nm as the most biologically active wavelength. UV lamps used in this application put most of their energy into this wavelength region.


A standard UVWaterworks unit can disinfect about one ton of water per hour at a cost of about five U.S. cents. An exclusive license for manufacture and sales has been granted by LBNL to International Health, Inc. (http://www.waterhealth.com), and units are now being used all over the world.

UVWaterworks - commercial unit

Dr. Gadgil’s work has already had a positive impact on millions of people in developing countries, will impact millions more in the years to come, and has led to several well-deserved awards for Dr. Gadgil. He has also done pioneering work in removal of arsenic from groundwater and in development of cookstoves for use in developing countries.

One further comment on use of UV radiation for disinfection: solid-state Light Emitting Diode (LED) technology has now been extended to the UV wavelength region and would be more energy efficient and potentially more reliable than broader spectrum UV lamps that have been used so far. If UV LEDs can be developed for emission at 260 nm and can be produced inexpensively, they should be attractive replacements for UV lamps in future UVWaterworks or similar disinfection units.