A Microbiological Investigation of a Point of Use Drinking Water Disinfection Technology: Solar Photo-Disinfection and its Challenges in Cambodia

In rural and underdeveloped regions of the world, simple point-of-use water treatment technologies are sometimes the only option available clean drinking water. Using the sun to disinfect drinking water has become internationally known as an efficient method to treat drinking water to a quality approaching and/or surpassing commercially available bottled water. A solar disinfection microbiology study in a Cambodia based laboratory was conducted to describe this point-of-use water treatment option. Various batch experiments were conducted to scientifically assess the technology and its efficiency in handling certain typical user challenges. Utilizing a wild type strain of Escherichia coli as an indicator for pathogenic bacteria, results of the study describe “die-off” or disinfection efficiency when 500ml plastic polyethylene terphthalate (PET) bottle are filled with river water and exposed to the sun for one day. The challenges of turbidity, volume variations, absorptive or reflective surfaces, source water chemistry, and varying weather conditions are described. Regression models are developed to characterize the disinfection efficiency. Major results were that a six-log10 removal of the indicator was possible under a wide variety of conditions including: (1) moderate levels of turbidity; (2) varying reflective/adsorptive surfaces; (3) varying volumes inside the SWD bottle; (4) and under a completely cloudy and overcast day. Additionally, the turbidity disinfection trials were shown to be not attributed to a thermal effect suggesting a potential for photocatalytic action of dissolved organic matter. The study results are specific to the Phnom Penh, Cambodia location and validate other international investigations of SWD efficiency.