- Lack of access to safe water is the leading cause of mortality in the world; approximately 3.4 million people die every year from waterborne pathogens. Inadequate access to safe drinking water and sanitation has contributed to an annual average of 1,980,000 deaths of children under five from diarrheal disease. Three of the most common classes of microbial pathogens that confer waterborne illness are bacteria, protozoa and viruses. The World Health Organization international scheme for household water treatment technologies has set standards for a high pathogen removal qualification. For protozoans, virus, and bacteria, 2-log, 3-log and 2-log reductions are required, respectively.
In our lab at Oregon State University, a microreactor device was designed with a novel approach towards pathogen inactivation in drinking water by utilizing ultraviolet degradation. Through its design approach the microreactor maintains a constant flux of photons into the influent and is modular, energy efficient and portable. In this study, we evaluated the efficacy of microfluidic reactor inactivation of fecal indicators from the three main waterborne pathogens: Escherichia coli (bacteria), Cryptosporidium parvum (protozoa), and Bacteriophage MS2 (viruses). The microbes were exposed to ultraviolet light at a variety of residence times within the microreactor and evaluated post treatment for log-removal. Escherichia coli was exposed to residence times of: 1.5, 5, 8, 15, and 30 seconds with corresponding average log-removal values of 2.18, 4.57, 7.48, 7.30, and 7.90 CFU/mL post treatment. Cryptosporidium parvum was exposed to residence times of 1.57, 15, 120, and 360 seconds and yielded average log removal values of 0.17, 0.95, 1.33 and 1.38 oocyst/mL post treatment. Bacteriophage MS2 was tested at 1.57, 15, 30, 120, 360, and 480 seconds with average log removals at 0.37, 0.95, 2.78, 3.81, 5.02, 6.96 PFU/mL. We conclude that this microreactor is an effective novel device that meets WHO drinking water regulations within 8 minutes of treatment. The generation of this data set is important in order to develop an investigative tool to create a computational model for the inactivation of microbial pathogens within this microreactor and determine kinetic rate constants for optimization in different applications. This research is also a proof-of-concept prototype for future optimization of the microreactor and toward providing sustainable solutions for access to clean drinking water.