Elimination of water pathogens with solar radiation using and automated sequential batch CPC Reactor

Solar disinfection (SODIS) of water is well known, effective process which is practiced at household level in many developing countries. However, this process is limited by the small volume treated and the lack of indication of treatment efficacy. Low cost glass tube reactors together with compound parabolic collectors (CPC) technology, has been shown to significantly increase the efficiency of solar disinfection. However, these reactors still require user input to control each batch SODIS process and there is no feedback that the process is complete. Automatic operation of the batch SODIS process, controlled by UVA-radiation sensors, can provide information on the status of the process can ensure the required UVA dose to achieve complete disinfection received and reduces user work-load through automatic sequential batch processing. In this work, an enhanced CPC photo-reactor with a concentration factor of 1.89 was developed. The apparatus was fully automated to allow exposure to a threshold UVA dose, with treated water subsequently dispensed into a reservoir. The reactor was tested using Escherichia coli as a model pathogen in natural well water. A 6-log inactivation of E. coli was achieved following exposure to the minimum uninterrupted lethal UVA dose. The enhanced reactor decreased the exposure time required to achieve the lethal UVA dose, in comparison to a CPC system with a concentration factor of 1.0. Doubling the lethal UVA dose prevented the need for a period of post exposure dark inactivation and therefore significantly reduced the overall SODIS treatment time. Using this reactor, SODIS can be automatically carried out at an affordable cost, with reduced exposure time and minimal user input.