Potential application of pressurized carbon dioxide for agricultural irrigation water disinfection

Abstract

Irrigation water and recycled water used for farm gardens can be a potential source of contamination of microbial pathogens that cause harmful illness. This study investigated the use ofpressurized carbon dioxide to inhibit pathogens in water sources. An apparatus producing microbubbles was operated with pressure up to 0.7 MPa, room temperature and a common period for disinfection, 25 minutes. Target environmental water samples, including distilled water, artificial ground water and effluent wastewater, were subjected to microbial contamination with desired concentrations of Escherichia coli (ATCC 11303, ATCC 23631 and ATCC 13706) and bacteriophages. Under identical conditions, approxi-mately 4.0 – 5.0 log of E. coli were inactivated in water samples, whereas the reduction ratio of bacteriophages are nearly 3.0 – 4.0 log. The chemical nature of CO 2 molecule (acidification, diffusivity and solubility in water) was indicated to be the main factors causing the microorganism deaths. Besides that, high pressure, depressurization rate, characteristics of microbubbles and pumping cycle contributed to microorganism inhibition. These findings in this investigation may be considered to use carbon dioxide as a novel disinfectant to water treatment in agricultural irrigation. Moreover, carbon dioxide treatment produces no disinfection byproducts and excessive pressure after disinfection can be an advantage to enhance irrigating to plants.