Anyone who goes backpacking knows that suitable water can be hard to find. Contaminated water can make for serious health problems. For those areas where people live with contaminated water, the problem is compounded, as children have significantly higher mortality from diarrheal illnesses. Many of these places lack the resources to implement costly solutions to this problem. This paper looks at a relatively inexpensive way to purify water. As a significant component of wilderness medicine is improvisation, it is applicable in survival situations as well.
The authors attempted to answer multiple questions. The first was simply, can solar water disinfection (SODIS) work with the contaminated water from a large city in Pakistan? Second, are there ways to increase the efficiency of the SODIS system? Third, to what effect does the intensity of the sunlight affect disnifection? Fourth, how much plasticizer leaches into the water with heating? Their materials were locally made PET bottles, natural sunlight, the rooftop of the building, and foil and black paint.
The untreated water had 827 CFU/100mL of total coliforms, with 82.3 CFU/100mL of fecal coliform. With all 3 types of vessel (transparent, reflective with foil, and absorptive with black paint), 90% of total coliforms were inactivated within 4 hours. The absorptive vessel had the highest temperature attained, and also had the most effectiveness for removing coliforms in strong sunlight, while the reflective worked best in weak and moderate sunlight. They also determined that the amount of plasticizer present after heating was significantly lower than the WHO guideline value for safety. Even if it weren’t, in a pinch, a single dose of DEHP is less toxic than known enteric pathogens.
This paper continues the trend of showing the efficacy of using passive solar disinfection to make safe drinking water.
Application of solar water disinfection for treatment of contaminated public water supply in a developing country: field observations.