The Impact of Unfiltered Source Water Characteristics on UV-LED Disinfection Efficiency

This research aimed to explore the impact of water quality parameters on the efficiency of UV disinfection in unfiltered and small drinking water treatment facilities. The study discovered that the absence of pre-treatment, such as filtration, can lead to an increase the degree of particle-microorganism (p-m) association. This association can decrease disinfection efficacy due to particles shielding the microorganisms from UV light. To investigate the impact of particulate type and concentrations on UV disinfection of unfiltered water, a range of water quality conditions at a bench scale was created by adding humic acid (HA), kaolin clay (KC), and iron hydroxide (Fe(OH)₃) to the raw surface water from two treatment plants. The composition or particle type of the turbidity-causing material was identified as the controlling factor in particle-microorganism association and UV response, especially when the turbidity level was low (less than 5 NTU). Analysis showed that zeta potential was the most significant predictor of UV inactivation in samples with elevated inorganic concentrations, making it a suitable measure of performance in treatment plants with high levels of inorganic particles. However, in samples with high organic content, turbidity was the most critical indicator. In summary, this study highlights the risks associated with UV disinfection of untreated water and provides insights into how to optimize UV disinfection in small or resource-constrained water treatment facilities.