Elimination of water pathogens with solar radiation using an automated sequential batch CPC reactor

Abstract

Solar disinfection (SODIS) of water is a well-known, effective treatment process which is practiced at

household level in many developing countries. However, this process is limited by the small volume

treated and there is no indication of treatment efficacy for the user. Low cost glass tube reactors, together

with compound parabolic collector (CPC) technology, have 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 is 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 automated to achieve exposure to a predetermined

UVA dose. Treated water was automatically dispensed into a reservoir tank. 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 reduced the overall treatment time. Using this reactor, SODIS can

be automatically carried out at an affordable cost, with reduced exposure time and minimal user input