Behavior of Urea in Wastewater and Industrial Water Treatment Plants

The current increasing global water demand has raised interest in wastewater reuse. However, urea, a trace organic contaminant present in reused wastewater, has proven difficult to remove. Limited data on urea concentrations in wastewater effluents and reused water underscores the need to establish foundational information. This study monitored urea concentrations in effluent from four different wastewater treatment plants (WWTPs), wastewater reuse plant (WRP) and industrial water treatment plant (IWTP). The results showed that the biological WWTP removed 82.1 ± 2.3% of urea, and reverse osmosis (RO) in WRP removed 51.7 ± 24.9%. In contrast, RO system in IWTP exhibited a lower urea removal of 33.5 ± 4.6%. This system operated with a dissolved organic carbon (DOC) concentration approximately 1.8 times lower than that of the previously mentioned RO in WRP. Correlation analysis between the molecular weight distribution of organic matter (via LC-OCD) and urea concentration revealed no significant statistical relationship. This lack of correlation is likely influenced by physical factors such as the RO membrane manufacturer, recovery rate, cleaning methods, and specific removal mechanisms. Further research into the mechanisms underlying urea removal in various RO processes is necessary to enhance treatment performance.