Odorous compounds from the operation of wastewater treatment plants (WWTPs) have increasingly become public health concerns and civil complaints. This study identifies priority management stages in WWTPs by quantitatively analyzing the distribution of complex odor and designated odor substances across key processes using a dimensionless tool (the Odor Activity Value, OAV), while providing a statistical basis and operational strategies for efficient odor mitigation in public facilities. Although there was a very poor correlation between designated odorous concentrations and complex odor level (dilution ratio), the application of the OAV yielded much more accurate results with a strong correlation (R2 = 0.7) specifically at high-temperature condition. Odor potential in the wastewater treatment processes fluctuates substantially depending on the specific unit. Statistical analysis using Kruskal–Wallis tests demonstrated that influent and sludge treatment process (return flow and centrate) produce much higher odor intensities compared to the biological reactor and secondary clarifier. Based on PERMANOVA analysis, differences in the profiles of complex odor and the OAVs of designated odorants across 6 treatment stages explained 64.1% of the total variance. Principal Coordinates Analysis (PCoA) showed that sludge treatment processes form a distinct, unique cluster, whereas sewage treatment streams present a more gradual transition of odor profiles. Statistical assessment using the Mann-Whitney U test demonstrated that mean odorants levels did not have considerable shift under high-temperature and low-temperature conditions. However, the sensory perception in higher temperatures enhanced relative to the OAVs. In conclusion, the OAV is an effective dimensionless tool, as it establishes priorities in odor management and control, offering a practical supplementary indicator for addressing civil complaints. These findings provide a robust foundation for optimizing deodorization systems designs and operational efficiency of odor mitigation systems within WWTPs.

Time-series and spatial analysis of collected odor complaints in Seoul megacity during 2014~2021 were conducted for the characterization of odor complaints emitted from the living environment. The ratio of odor complaints in the environmental complaints was 16.7%, and odor complaints increased 3.3 times from 9,053 cases in 2014 to a maximum of 29,425 cases in 2019. In the time-based evaluation (monthly, daily (day of the week), and hourly variations), the highest number of complaints occurred in June, Monday, and 9:00 AM, respectively. While the lowest number of complaints occurred in December, Sunday, and 3:00 AM, respectively. Among 25 provinces in Seoul megacity, the odor complaints that occurred from 2014 to 2021 were concentrated in Eunpyeonggu. The odor complaints of Seodaemun-gu and Nowon-gu occurred at the highest levels in January-February and June, respectively. Based on the characteristics of odor complaint occurrence according to the above time-series and spatial analyses, more effective odor management and control can be implemented by focusing on those hotspot areas and specific time periods.