Photodecomposition of humic acid and natural organic matter in swamp water using a TiO(2)-coated ceramic foam filter: potential for the formation of disinfection byproducts.

This paper reports on the photodecomposition of aqueous humic acid (HA) by a TiO(2)-coated ceramic foam filter (TCF) reactor and on the potential for the formation of disinfection byproducts (DBPs) upon chlorination of the photocatalytically treated solutions. This photocatalytic reactor can also be applied to the removal of natural organic matter (NOM) in swamp waters. The proposed photocatalytic reaction system was operated as per standardized methodologies. First, the ability of the TCF to decompose HA (a representative compound of NOM) was evaluated from the changes in the total organic carbon (TOC) and UV(254) with the reaction time. Remarkably, TOC removal and UV(254) values ranging from 44% to 61% and from 60% to 83%, respectively, were achieved. The potential for the formation of DBPs (total trihalomethane and total haloacetic acid) by chlorination of the phototreated solution was strongly dependent on the TOC removal and UV(254) values in the solution. The degree of photodecomposition of NOMs in the swamp water samples and the DBP formation potential showed similar trends as in the case of the standard solutions containing HA. The method used in this study could be effectively used to evaluate the efficiency of TCF for reducing HA and NOM, while suppressing the formation of DBP products.

Sterilization efficiency of the photocatalyst against environmental microorganisms in a health care facility.

The photocatalyst equipment consists of a titanium dioxide membrane and an ultraviolet lamp. The authors studied if the photocatalyst equipment is practically useful in sterilizing environmental microorganisms in the health care facility. The number of microorganisms was compared in the cases of no sterilization (control) and the photocatalyst sterilization. As a result, a statistical difference was observed between control and the photocatalyst sterilization against airborne microorganisms (p < 0.01), but not against surface microorganisms (p > 0.2). The photocatalyst uses an air sucking system, so it may be ineffective against microorganisms tightly attached to surfaces. However, the effectiveness of the photocatalyst to sterilize airborne microorganisms in the health care facility was successfully confirmed. Concerning the humidity effect on the photocatalyst sterilization, the authors compared the number of airborne microorganisms in cases of the control, UV alone and photocatalyst sterilization when humidity was changed. A statistical difference was observed between UV and the photocatalyst sterilization (p < 0.01) when humidity was increased to 60-70%, but not observed between UV and the photocatalyst sterilization (p > 0.2) when humidity was not controlled and was around 10-20%. This indicates that maintaining high humidity levels will present satisfactory sterilization results due to a greater production of OH radicals. From data obtained, no effect of the adsorption on the TiO2 membrane could be observed.