Assessment of Using Low-frequency Ultrasound Device for Domestic Drinking Water Disinfection

Abstract

Microorganisms may cause problems in drinking water distribution system (DWDS). It is hard to control and always forms the biofilm, which can result in the deterioration of drinking water quality. At household’s tap, due to the favorable conditions, which incurs an easier formation of biofilm. Therefore, the idea of secondary disinfection at households to control the drinking water quality has come up. Ultrasound disinfection provides an easy-operated way for point-of-use disinfection, which can be influenced by the local hydraulic conditions. Previous studies have monitored the spatial and temporal variations in the microbial community in DWDS but most of cases were based on long-term effect. In this study, a simulated household piping system was sampled intensively over short time scales. Several parameters on the dynamics of microbiological processes such as tATP, cATP, TOC and total cell concentration of drinking water samples were examined at four sampling points under various flow rate at different disinfection time. The results highlighted that ultrasound disinfection can restrain cell activity but the effect was also influenced by flow rate. Both FCM and ATP data described the microbiological dynamics in the drinking water samples. The cell concentrations decreased when the flow rate was lower. Moreover, operation time of the ultrasonic device showed significant influence on the disinfection efficiency. At the same sampling point, when the system was operated at a constant flow rate, the cell activity decreased with the increase of the operation time of ultrasonic device. Considering the time that a cell travel through the system subjected to ultrasonic effects, the so called exposure time, it is observed that the cell activity decreased with the increase of time that the cell experienced ultrasound. As a result, the cell at the furthest sampling point under the most significant flow rate with longest ultrasound disinfection time showed the lowest activity.