Disinfection of a farmstead roof harvested rainwater for potable purposes using an automated solar photocatalytic reactor.

Abstract

Access to safe and reliable water supply is a challenge in many parts of the developing world. The use of roof harvested rainwater for domestic and potable purposes is common in households and farmsteads in the rainforest and some parts of savannah ecological zones of  Nigeria in spite of  the health risk associated with ingestion of water from an unimproved source such as untreated roof harvested rainwater. Solar photocatalysis has been proven to be effective in water treatment devoid of the short comings of high fuel cost and formation of carcinogens associated with conventional households water disinfection methods such as boiling and the use of chemicals.  In this study, an automated photocatalytic batch reactor which uses solar radiation as its photon source was developed with materials sourced locally in Nigeria. The automated system  injects contaminated water into the reactor tube and evacuates the water into the treated water tank upon the reception of a preset solar radiation dose. Roof harvested rainwater from a farmstead inoculated with E.coli was used in the evaluation. Results from the experiments show that the  automated photocatalytic batch reactor was faster in bacteria inactivation than other reactors without TiO₂ insert. A solar radiation dose of 160 kJ/L received on the photocatalytic reactor effectively and consistently inactivated  E. coli concentrations of 10⁷ ± (1.3 x 10⁶) CFU/ml to concentrations below the detection limit of 4 CFU/ml as well as prevent E. coli regrowth after 24 hrs storage in the dark. The use of this system as a point-of- use water disinfection system could enhance access to potable water in remote places such as farmsteads.