Odor emissions from sewer systems are a persistent environmental concern in urban areas, particularly in combined sewer systems where septic tanks are widely used. However, the contribution of septic tanks as sources of sewer odor has not been sufficiently quantified. This study investigated the characteristics of hydrogen sulfide (H2S) generation in septic tanks and evaluated its potential influence on sewer odor, as well as the effectiveness of odor mitigation technologies. Field investigations were conducted in combined sewer areas to measure aqueous H2S concentrations in septic tanks. The results showed that H2S concentrations in septic tanks were not significantly affected by septic tank capacity (ANOVA, p > 0.05), suggesting that tank size or user population is not a primary determinant of sulfide generation. In contrast, aqueous H2S exhibited a positive correlation with chemical oxygen demand (COD), indicating that organic matter availability plays an important role in sulfide production through microbial sulfate reduction processes. A significant relationship was observed between aqueous H2S in septic tanks and gaseous H2S measured at catch basins, demonstrating that sulfide derived from septic tanks can transfer to the sewer atmosphere and potentially impact human odor exposure in urban environments. In addition, the performance of odor control technologies applied to septic tanks was evaluated with aeration-based technologies found to significantly reduce H2S concentrations. These findings suggest that septic tanks can serve as important sources of sewer odor highlighting the need for effective management and proper operation of septic tank odor control systems in combined sewer areas.

This study investigated odor generation and external leakage characteristics in a combined sewer system through field monitoring of manholes, catch basins, and box culverts. Odor samples were analyzed for malodor intensity in terms of the dilutionto- threshold (D/T) ratio using the air dilution sensory (ADS) test. In addition to the ADS tests, 22 offensive odorants as defined in the Korean Malodor Prevention Act were quantified. Among the odorants monitored, hydrogen sulfide showed not only the highest concentrations but was also the most frequently detected, indicating representative odor compounds. The mean hydrogen sulfide concentration reached 1,132 ppbv, with a maximum of 13,709 ppbv, corresponding to complex odor concentrations of up to 1,442 dilution-to-threshold units. On average, approximately 13% of the internal sewer odors escaped through manhole openings, which could easily cause odor nuisance exceeding the legal threshold at boundary lines. A comparison with national odor management standards indicated that the current regulations, based solely on in-pipe hydrogen sulfide concentration, do not adequately represent human sensory perception. The findings highlight the need to establish practical odor-control criteria that consider external leakage and perceptual intensity for effective sewer odor management in urban environments.

This study was conducted to analyze the characteristics of odorous components that have been generated from the downtown sewer system based on twenty-three survey items for complex odor and designated offensive odor. As a result of the research, the contribution rates for the causative materials of the odor indicated 73.5% of hydrogen sulfide, 26.0% of methyl mercaptan, 0.4% of dimethyl sulfide, and 0.1% of dimethyl disulfide. The occurrence for the odorous materials according to sampling site revealed data of which contribution rates showed 56.9% of hydrogen sulfide and 36.8% of methyl mercaptan from the combined sewer system in the business district; whereas the combined sewer system in the residential area showed 16.4% of dimethyl sulfide and 4.3% of dimethyl disulfide. The seasonal occurrence rate of the odor materials was observed higher in summer and lower in winter And, the combined sewer system in the business district recorded the highest concentration of 4.61 ppm of hydrogen sulfide among the sampling site. An hourly occurrence rate for the odor materials consistently showed the greatest increase between 11:00 and 14:00 at each location and showed a decreasing tendency afterward.

Urban sanitary sewer systems can aid in preventing inundation, and can improve civil health by effectively disposing stormwater and wastewater. However, since sewage odor can cause adverse effects, numerous technical and administrative studies have been conducted for reducing such odor. European countries and the United States of America (USA) built modern sewer systems in the late 19th century, and have since been endeavoring to eliminate sewage odors. Several cities of the USA, such as Los Angeles (LA) that has a separate sewer system and San Francisco (SF) that has a combined sewer system, have produced and distributed odor control master plan manuals. Features common in the odor reduction plans of both these cities are that the odor reduction programs are operated in all the respective local regions and are supported by administrative systems. The primary aspectual difference between the two said programs is that the city of LA employs a sewage air purification system, whereas the city of SF controls the emission of major odor causing compounds. Compared to the existing sewer odor reduction systems of these two cities, South Korea is still in the initial phase of development. Through technical studies and policy implementations for sewer odor reduction, a foundation can be laid for improving the civil health quality.

Odor problems in urban areas have become a common cause of public complaints. In order to gain a better understanding of odor problems, we investigated the emission characteristics of odorants originating from manholes (n=22) and stormwater catch basins (n=48) (SCBs) around Wangsimni station in Seoul. To this end, concentrations of H2S and NH3 were measured after arbitrarily dividing the whole study area into five different districts. Our measurements were made to allow comparisons between three different criteria: (1) manholes vs. SCBs, (2) temporal variation between morning vs. afternoon, and (3) water content in the sewer system. The average concentration of H2S in manholes and SCB were 2.39 ppm and 0.81 ppm, respectively. In contrast, their NH3 counterparts were 1.86 ppm and 1.02 ppm, respectively. According to the contouring method made to identify spatial distribution characteristics, of odorants a relatively lowland site D was expected to work as a significant emission source in light of the transportation patterns of a sewer system. Moreover, higher concentrations of odorants were prevalent in the afternoon (as the prime time for commercial activities) relative to before noon. If concentration data are converted into odor intensity, H2S was the predominant component exerting controls on the odor pollution in these underground environments.