With the increasing demand for ultrapure water (UPW) in the semiconductor industry, alternative water sources such as wastewater reuse are being considered. However, the presence of low-molecular-weight organic matters like urea in wastewater treatment effluent can impair UPW quality, particularly by increasing total organic carbon (TOC) levels. Standard regulation limits for TOC are 1 ppb. This study examined urea behavior across different treatment processes, focusing on the source water and treatment stage. Three water treatment plants (WTPs) using various raw water sources and one wastewater reuse treatment plant (WRTP) were selected. Urea concentration, TOC, and other properties were analyzed at each stage to assess removal efficiency. In the WTPs, influent urea concentrations varied significantly depending on the water source, ranging from 20 to 250 ppb. Oxidative processes such as ozonation and UV treatment showed urea removal efficiencies of 0 to 30%. Notably, urea concentrations consistently decreased after the filtration–adsorption process (removing 5 to 60%) and in the clearwell. This reduction is likely due to microbial degradation within the filter media and potential reactions between urea and residual chlorine. In the WRTP, the RO process following biological treatment achieved urea removal efficiencies of 80 to 88%. This study reveals that urea behavior is influenced by both source water quality and specific treatment processes. These findings are intended to help in designing and optimizing UPW system operations with alternative water sources.

This research was financially supported by the Ministry of Trade, Industry, and Energy (MOTIE), Korea, under the “Global Industrial Technology Cooperation Center program” supervised by the Korea Institute for Advancement of Technology (KIAT) (P0028402).