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A Pilot-Scale Study of Flow-Through UV-LEDs System for Secondary Municipal Wastewater Effluent Disinfection
Citation:
Oh, Y., H. Kim, L. Boczek, AND H. Ryu. A Pilot-Scale Study of Flow-Through UV-LEDs System for Secondary Municipal Wastewater Effluent Disinfection. WEFTEC 2023, Chicago, IL, October 02 - 04, 2023.
Impact/Purpose:
This work was carried out as a part of Cooperative Research and Development Agreement (CRADA) between Korea Water Partnership (KWP) and the Center for Environmental Solutions and Emergency Response of the U.S. Environmental Protection Agency (EPA). In this collaboration, we applied multiple wavelength ultraviolet (UV) light emitting diodes (LEDs) for the disinfection of municipal wastewater effluent. Our challenge was to achieve comparable (even greater) reliability for compliance with bio-stability goals, especially by replacing conventional UV lamps to reduce the use of mercury. The United States has signed the Minamata Convention that party nations phase-out or take measure to reduce mercury use in certain products. Although the use of UV lamps for purposes other than lighting are not currently banned, there should create initiatives to reduce the use of mercury in the public water supply and municipal wastewater treatment industries. In this study, we investigated the inactivation efficacy of a pilot-scale flow-through UV-LEDs system against total coliforms, E. coli, and MS2 coliphage in non-chlorinated secondary effluent from a municipal wastewater treatment plant.
Description:
The collaboration between KWP and EPA demonstrated the possible applicability of using UV-LED water treatment systems for the disinfection of municipal wastewater effluent. The on-site evaluation was conducted over 6 months using secondary treated wastewater in the EPA T&E facility, Cincinnati OH. The overall goal of this study was to explore the disinfection performance of the system under various operating conditions, including UVT, UV wavelength, flow rate, and UV radiative power output, and to address optimal operating conditions for achieving high-quality wastewater effluent discharge. The UV transmittance of the wastewater was constant between 55% and 69% during the evaluation period. The active power draw required for UV-LEDs was 107 W, and the operating flow rate varied up to 70 L/min (100 m3/d). A dramatically improved performance was achieved with patented devices and designs for UV-LED water treatment systems. Our result shows a robust inactivation of total coliforms and E. coli by 3.5-log at the lowest flow rate of 20 L/min. Note that this flow-through UV-LEDs system can still achieve 1-log inactivation of these bacteriai with an increased flow rate of 70 L/min. MS2 coliphage was much more resistant to UV irradiation than total coliforms and E. coli. MS2 inactivation at 20 L/min from 1.5-logs decreased to less than 1-log when the flow rate increased over 40 L/min. Despite of the outstanding performance (UV intensity per unit area) of UV-LEDs and their robustness in disinfection, the marketplace has been reluctant to use UV-LEDs for municipal water and wastewater services. Although recently a UV-LED disinfection system started operation at a municipal water supply in Japan, the showcase for the industries still lacks relevant products. In this collaboration, our observation reveals the high adaptability of UV-LED as a game changer and shows that mercury-free alternatives may become a reality in the nearest future.