Solar Water Disinfection - Health Impact, Diarrhea Reduction

Health Impact, Diarrhea Reduction

According to the World Health Organization, more than two million people per year die of water-borne diseases, and one billion people lack access to a source of improved drinking water.

It has been shown that the SODIS method (and other methods of household water treatment) can very effectively remove pathogenic contamination from the water. However, infectious diseases are also transmitted through other pathways, i.e. due to a general lack of sanitation and hygiene. Studies on the reduction of diarrhea among SODIS users show reduction values of 30–80%.

The effectiveness of the SODIS was first discovered by Professor Aftim Acra at the American University of Beirut in the early 1980s. Substantial follow-up research was conducted by the research groups of Martin Wegelin at the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and Dr Kevin McGuigan at the Royal College of Surgeons in Ireland. Clinical control trials were pioneered by Professor Ronan Conroy of the RCSI team in collaboration with Michael Elmore-Meegan.

Currently, a joint research project on SODIS is implemented by the following institutions:

• Royal College of Surgeons in Ireland (RCSI), Ireland (coordination)
• University of Ulster (UU), United Kingdom
• CSIR Environmentek, South Africa, Eawag, Switzerland
• The Institute of Water and Sanitation Development (IWSD), Zimbabwe
• Plataforma Solar de Almería (CIEMAT-PSA), Spain
• University of Leicester (UL), United Kingdom
• The International Commission for the Relief of Suffering & Starvation (ICROSS), Kenya
• University of Santiago de Compostela (USC), Spain
• Swiss Federal Institute of Aquatic Science and Technology (Eawag), Switzerland

The project has embarked on a multi-country study including study areas in Zimbabwe, South Africa and Kenya.

Other developments include the development of a continuous flow disinfection unit and solar disinfection with titanium dioxide film over glass cylinders, which prevents the bacterial regrowth of coliforms after SODIS. Research has shown that a number of low-cost additives are capable of accelerating SODIS and that additives might make SODIS more rapid and effective in both sunny and cloudy weather, developments that could help make the technology more effective and acceptable to users. A 2008 study showed that natural coagulants (powdered seeds of five natural legumes (peas, beans and lentils)—Vigna unguiculata (cowpea), Phaseolus mungo (black lentil), Glycine max (soybean), Pisum sativum (green pea), and Arachis hypogaea (peanut)—were evaluated for the removal of turbidity), were as effective as commercial alum and even superior for clarification in that the optimum dosage was low (1 g/L), flocculation was rapid (7–25 minutes, depending on the seed used) and the water hardness and pH was essentially unaltered. Later studies have used chestnuts, oak acorns, and Moringa oleifera (drumstick tree) for the same purpose.

Other research has examined the use of doped semiconductors to increase the production of oxygen radicals under solar UV-A. Recently, researchers at the National Centre for Sensor Research and the Biomedical Diagnostics Institute at Dublin City University have developed a novel printable UV dosimeter for SODIS applications that can be read using a mobile phone. The camera of the phone is used to acquire an image of the sensor and custom software running on the phone analyses the sensor colour to provide a quantitative measurement of UV dose.