Interference of bicarbonate and carbonate anions in the solar disinfection of water

Sunlight-mediated water disinfection (SODIS) is an important technique, especially when applied in regions where the water treatment system is fragile because the SODIS process has a high capacity for inactivating pathogenic microorganisms. Although the intensity of solar radiation, exposure time, and turbidity of the water are relevant factors for the process, it has also been observed that the chemical composition of the water can interfere with the efficiency of the process. Some chemical species are able to capture radicals that are important for the disinfection process; therefore, the identification of these compounds would contribute to the optimization of the process and increase its efficiency. Thus, the present study aims to evaluate the influence of bicarbonate and carbonate anions using concentrations of Na₂CO₃ (5, 10, 20, 50, 75, 100, 150, 200, and 300 mg dm⁻³) on the solar disinfection process in surface water using total coliforms (C₀ = 10⁴ UFC.100 cm⁻³) and Escherichia coli (C₀ = 10³ UFC.100 cm⁻³) content as performance parameters for disinfection efficiency. It was observed that in all samples exposed to solar radiation (4 and 5 h), there was a reduction in E. coli and total coliform content when compared to a sample that was not exposed to radiation. However, the addition of carbonate and bicarbonate anions negatively interferes with the disinfection process, reducing the efficiency of SODIS by approximately 0.1 log for E. coli and 0.3 log for CT from a Na₂CO₃.

Graphical abstract