Odor Abatement Research Articles

Assessment of transient hydrogen sulfide peak emissions caused by biogas plant operation

Odor nuisance is a major impediment for public acceptance and wider implementation of biogas plants. Knowledge on composition and dynamics of emissions from these plants is highly needed for development of robust mitigation solutions. In this study, odorant emissions were investigated from two biogas plants of different sizes and capacities. Measurements using proton-transfer-reaction mass spectrometer (PTR-MS) revealed that hydrogen sulfide was the main odorant and constituted 82% and 71% of the odor activity sums (SOAV) at the two studied plants, respectively. Long-term time-resolved measurements furthermore revealed that emissions were highly dynamic with distinct short-term emission peaks. By deploying an array of electrochemical sensors, the main sources of hydrogen sulfide emission were subsequently identified and correlated with operational data to identify the major causes for the highly fluctuating emissions. Addition of biomasses in the form of animal slurry to pre-tanks, were shown to be the major cause of periodic hydrogen sulfide emission within the range of 50–1200 ppm. Such hydrogen sulfide peak emissions could challenge odor abatement from biogas plants and should be taken into account when designing odor abatement technologies for biogas plants.

Review on Odour Assessment Ant Odour Abatement Techniques

Abstract: Odour can be defined as a perception of smell or in scientific terms it can be defined as a sensation resulting from the reception of stimulus by the olfactory sensory system. Odours may cause pleasant or unpleasant sensation and is induced by inhaling volatile organic and inorganic odorants. The sources of odour may be air-borne or water-borne. Foul odour may cause ill health or respiratory symptoms, insomnia, asthama, nausea and discomfort and other environmental nuisance. Odours can be assessed either by sensory measurements or analytical measurements. There are various physical, chemical and biological treatments for odour abatement. The release of unpleasant odours from sewage carrier system as well as sewage treatment system has become a great public concern especially among densely populated countries. These odours cause environmental nuisance and severe damage to locals. Odour is an important physical characteristic of both water and wastewater. Thus, it requires significant attention in terms of measurement as well as abatement. This study reviews the various odour measurement and abatement techniques.

Odor emission measurements: The role of n-butanol as a reference material and origins of large inter-laboratory variability

Malodors negatively impact the quality of life of people who are exposed to them. In order to enforce legal emission limit values that aim to reduce these adverse effects, reliable methods for the quantification of odor emissions are needed. The standard EN 13725 describes a method to quantify odor concentration, which is based on the use of human assessors as sensors. Previously published work that studied the performance characteristics of this method indicates that the variability of results between different laboratories is higher than expected and that the uncertainty associated with this method may be underestimated. We analyze here a unique data set, which contains the response of 368 assessors that participated in 21 odor proficiency tests performed in 2016–2022. By investigating the response of the smallest unit of an odor measurement by EN 13725, namely the individual assessor, as opposed to the panel, we gain unprecedented insight into the sources of inter-laboratory variations in odor measurements. Our results indicate that the assessor sensitivity to n-butanol is not transferable to other odorants and odor mixtures, which is contrary to the assumption made in EN 13725. By Monte-Carlo simulation coupled with our data set, we investigate how the responses of individual assessors transfer to panel responses, focusing on the influence of panel size, panel selection strategy and number of rounds. We find that for the laboratories investigated, larger panels only modestly reduce the inter-laboratory variability and we attribute this effect to non-random selection of assessors for the panels of these laboratories. The present work provides new insight into the sources of inter-laboratory variability in odor emission monitoring and is expected to be useful in the further development of reliable methods for odor concentration measurements and odor abatement technology.

Carbon neutrality in wastewater treatment plants: An integrated biotechnological-based solution for nutrients recovery, odour abatement and CO2 conversion in alternative energy drivers

Wastewater treatment plants play a crucial role in water security and sanitation, ensuring ecosystems balance and avoiding significant negative effects on humans and environment. However, they determine also negative pressures, including greenhouse gas and odourous emissions, which should be minimized to mitigate climate changes besides avoiding complaints. The research has been focused on the validation of an innovative integrated biological system for the sustainable treatment of complex gaseous emissions from wastewater treatment plants. The proposed system consists of a moving bed biofilm reactor coupled with an algal photobioreactor, with the dual objective of: i) reducing the inlet concentration of the odourous contaminants (in this case, hydrogen sulphide, toluene and p-xylene); ii) capturing and converting the carbon dioxide emissions produced by the degradation process into exploitable algal biomass. The first reactor promoted the degradation of chemical compounds up to 99.57% for an inlet load (IL) of 22.97 g m−3 d−1 while the second allowed the capture of the CO2 resulting from the degradation of gaseous compounds, with biofixation rate up to 81.55%. The absorbed CO2 was converted in valuable feedstocks, with a maximum algal biomass productivity in aPBR of 0.22 g L−1 d−1. Dairy wastewater has been used as alternative nutrient source for both reactors, with a view of reusing wastewater while cultivating biomass, framing the proposed technology in a context of a biorefinery within a circular economy perspective. The biomass produced in the algal photobioreactor was indeed characterized by a high lipid content, with a maximum percentage of lipids per dry weight biomass of 35%. The biomass can therefore be exploited for the production of alternative and clean energy carrier. The proposed biotechnology represents an effective tool for shifiting the conventional plants in carbon neutral platform for implementing principles of ecological transition while achieving high levels of environmental protection.

Assessment of dimethyl sulphide odorous emissions during coal extraction process in Coal Mine Velenje

Underground coal extraction at Coal Mine Velenje occasionally gives rise to odour complaints from local residents. This manuscript describes a robust quantification of odorous emissions of mine sources and a model-based analysis aimed to establish a better understanding of the sources, concentrations, dispersion, and possible control of odorous compounds during coal extraction process. Major odour sources during underground mining are released volatile sulphur compounds from coal seam that have characteristic malodours at extremely low concentrations at micrograms per cubic metre (μg/m3) levels. Analysis of 1028 gas samples taken over a 6-year period (2008–2013) reveals that dimethyl sulphide ((CH3)2S) is the major odour active compound present in the mine, being detected on 679 occasions throughout the mine, while hydrogen sulphide (H2S) and sulphur dioxide (SO2) were detected 5 and 26 times. Analysis of gas samples has shown that main DMS sources in the mine are coal extraction locations at longwall faces and development headings and that DMS is releasing during transport from main coal transport system. The dispersion simulations of odour sources in the mine have shown that the concentrations of DMS at median levels can represent relatively modest odour nuisance. While at peak levels, the concentration of DMS remained sufficiently high to create an odour problem both in the mine and on the surface. Overall, dispersion simulations have shown that ventilation regulation on its own is not sufficient as an odour abatement measure.

Evaluation of the effectiveness of filter-based odor abatement systems for pig farm odor reduction

Evaluation of the effectiveness of filter-based odor abatement systems for pig farm odor reduction

Chemical identification and quantification of volatile organic compounds emitted by sewage sludge

The recycling of organic waste products (e.g. sewage sludge, SS) is currently being promoted as a substitute for mineral fertilizers for agricultural lands. The spreading of SS allows the recycling of the nutrients and organic matter it contains. SS contains various pollutants such as volatile organic compounds (VOCs) that adversely affect the ecosystem and human health through ozone production and serve as critical precursors of atmospheric secondary organic aerosols. There are very few studies quantifying the gaseous compounds emitted from SS, and those studies primarily address their odorant properties for identifying suitable odour abatement techniques. There is an urgent need for more comprehensive quantitative information on VOCs emitted from SS as aerosol precursors. In this context, an experimental study was performed on SS samples taken from a wastewater treatment plant located in France. Undigested SS (UDSS), digested SS (DSS) and SS with 30% and 60% dryness were collected from different stages of treatment sequence and analyzed using atmospheric simulation chambers coupled to proton-transfer-reaction quadrupole ion-guide time-of-flight mass spectrometer. Our study revealed that SS samples emitted a large spectrum of VOCs. 380 compounds were detected, quantified and classified into different chemical groups. The VOC emissions increased with the increase in the dryness of the sample; the highest being in SS 60%, followed by SS 30%, UDSS and DSS. OVOCs were dominant in SS 60%. The statistical analysis showed that the anaerobic digestion and the dewatering to 60% of dryness decreased the emissions of sulphuric compounds. Aromatic compounds and indoles (e.g. skatole) were emitted significantly from the UDSS. Some of these VOCs can serve as precursor gases for atmospheric aerosol formation. The experimental dataset obtained in this study provides an accurate inventory reference for the VOC emissions from SS samples and shows the impacts of the treatment on emission characteristics of VOCs.

Odors Emitted from Biological Waste and Wastewater Treatment Plants: A Mini-Review

In recent decades, a new generation of waste treatment plants based on biological treatments (mainly anaerobic digestion and/or composting) has arisen all over the world. These plants have been progressively substituted for incineration facilities and landfills. Although these plants have evident benefits in terms of their environmental impact and higher recovery of material and energy, the release into atmosphere of malodorous compounds and its mitigation is one of the main challenges that these plants face. In this review, the methodology to determine odors, the main causes of having undesirable gaseous emissions, and the characterization of odors are reviewed. Finally, another important topic of odor abatement technologies is treated, especially those related to biological low-impact processes. In conclusion, odor control is the main challenge for a sustainable implementation of modern waste treatment plants.

Odor and Constituent Odorants of HDPE-Lignin Blends of Different Lignin Origin.

The still-rising global demand for plastics warrants the substitution of non-renewable mineral oil-based resources with natural products as a decisive step towards sustainability. Lignin is one of the most abundant natural polymers and represents an ideal but hitherto highly underutilized raw material to replace petroleum-based resources. In particular, the use of lignin composites, especially polyolefin–lignin blends, is currently on the rise. In addition to specific mechanical property requirements, a challenge of implementing these alternative polymers is their heavy odor load. This is especially relevant for lignin, which exhibits an intrinsic odor that limits its use as an ingredient in blends intended for high quality applications. The present study addressed this issue by undertaking a systematic evaluation of the odor properties and constituent odorants of commercially available lignins and related high-density polyethylene (HDPE) blends. The potent odors of the investigated samples could be attributed to the presence of 71 individual odorous constituents that originated primarily from the structurally complex lignin. The majority of them was assignable to six main substance classes: carboxylic acids, aldehydes, phenols, furan compounds, alkylated 2-cyclopenten-1-ones, and sulfur compounds. The odors were strongly related to both the lignin raw materials and the different processes of their extraction, while the production of the blends had a lower but also significant influence. Especially the investigated soda lignin with hay- and honey-like odors was highly different in its odorant composition compared to lignins resulting from the sulfurous kraft process predominantly characterized by smoky and burnt odors. These observations highlight the importance of sufficient purification of the lignin raw material and the need for odor abatement procedures during the compounding process. The molecular elucidation of the odorants causing the strong odor represents an important procedure to develop odor reduction strategies.

Full-Scale Odor Abatement Technologies in Wastewater Treatment Plants (WWTPs): A Review

The release of air pollutants from the operation of wastewater treatment plants (WWTPs) is often a cause of odor annoyance for the people living in the surrounding area. Odors have been indeed recently classified as atmospheric pollutants and are the main cause of complaints to local authorities. In this context, the implementation of effective treatment solutions is of key importance for urban water cycle management. This work presents a critical review of the state of the art of odor treatment technologies (OTTs) applied in full-scale WWTPs to address this issue. An overview of these technologies is given by discussing their strengths and weaknesses. A sensitivity analysis is presented, by considering land requirements, operational parameters and efficiencies, based on data of full-scale applications. The investment and operating costs have been reviewed with reference to the different OTTs. Biofilters and biotrickling filters represent the two most applied technologies for odor abatement at full-scale plants, due to lower costs and high removal efficiencies. An analysis of the odors emitted by the different wastewater treatment units is reported, with the aim of identifying the principal odor sources. Innovative and sustainable technologies are also presented and discussed, evaluating their potential for full-scale applicability.

Evaluation of continuous and intermittent trickling strategies for the removal of hydrogen sulfide in a biotrickling filter

Biotrickling filter (BTF) is a widely applied bioreactor for odour abatement in sewer networks. The trickling strategy is vital for maintaining a sound operation of BTF. This study employed a lab-scale BTF packed with granular activated carbon at a short empty bed residence time of 6 s and pH 1–2 to evaluate different trickling strategies, i.e., continuous trickling (different velocities) and intermittent trickling (different trickling intervals), in terms of the removal of hydrogen sulfide (H2S), bed pressure drop, H2S oxidation products and microbial community. The H2S removal performance decreased with the trickling velocity (∼3.6 m/h) in BTF. In addition, three intermittent trickling strategies, i.e., 10-min trickling per 24 h, 8 h, and 2 h, were investigated. The H2S elimination capacity deteriorated after about 2 weeks under both 10-min trickling per 24 h and 8 h. For both intermittent (10-min trickling per 2 h) and continuous trickling, the BTF exhibited nearly 100 % H2S removal for inlet H2S concentrations<100 ppmv, but intermittent BTF showed better removal performance than continuous trickling when inlet H2S increased to 120–190 ppmv. Furthermore, the bed pressure drops were 333 and 3888 Pa/m for non-trickling and trickling periods, respectively, which makes intermittent BTF save 83 % energy consumption of the blower compared with continuous tirckling. However, intermittent BTF exhibited transient H2S breakthrough (<1 ppmv) during trickling periods. Moreover, elemental sulfur and sulfate were major products of H2S oxidation and Acidithiobacillus was the dominant genus in both intermittent and continuous trickling BTF. A mathematical model was calibrated for the intermittent BTF and a sensitivity analysis was performed on the model. It shows mass transfer parameters determine the H2S removal. Overall, intermittent trickling strategy is promising for improving odour abatement performance and reducing the operating cost of the BTF.

Inhibition of ammonia and hydrogen sulphide as faecal sludge odour control in dry sanitation toilet facilities using plant waste materials

On-site dry sanitation facilities, although cheaper than wet sanitation systems, suffer from high malodour and insect nuisance as well as poor aesthetics. The high odour deters users from utilizing dry sanitation toilets as an improved facility leading to over 20% open defecation in Sub-Saharan Africa. To address this malodour concern, this study first assessed odour levels, using hydrogen sulphide (H2S) and ammonia (NH3) as indicators, on two dry sanitation facilities named T1 and T2. The potential of using biomass (sawdust, rice husk, moringa leaves, neem seeds), ash (coconut husk, cocoa husk) or biochar (sawdust, rice husk, bamboo) as biocovers to remove or suppress odour from fresh faecal sludge (FS) over a 12-day period was investigated. Results showed that the odour levels for H2S in both T1 (3.17 ppm) and T2 (0.22 ppm) were above the threshold limit of 0.05 ppm, for unpleasantness in humans and vice versa for NH3 odour levels (T1 = 6.88 ppm; T2 = 3.16 ppm; threshold limit = 30 ppm limit). The biomasses exhibited low pH (acidic = 5–7) whereas the biochars and ashes had higher pHs (basic = 8–13). Basic biocovers were more effective at H2S emission reduction (80.9% to 96.2%) than acidic biocovers. The effect of pH on suppression of NH3 was determined to be statistically insignificant at 95% confidence limit. In terms of H2S and NH3 removal, sawdust biochar was the most effective biocover with odour abatement values of 96.2% and 74.7%, respectively. The results suggest that biochar produced from locally available waste plant-based materials, like sawdust, can serve as a cost-effective and sustainable way to effectively combat odour-related issues associated with dry sanitation facilities to help stop open defecation.

Additivity between Key Odorants in Pig House Air

The verification of odor abatement technologies for livestock production based on chemical odorants requires a method for conversion into an odor value that reflects the significance of the individual odorants. The aim of the present study was to compare the SOAV method (Sum of Odor Activity Values) with the odor detection threshold measured by olfactometry and to investigate the assumption of additivity. Synthetic pig house air with odorants at realistic concentration levels was used in the study (hydrogen sulfide, methanethiol, trimethylamine, butanoic acid, and 4-methylphenol). An olfactometer with only PTFE in contact with sample air was used to estimate odor threshold values (OTVs) and the odor detection threshold for samples with two to five odorants. The results show a good correlation (R2 = 0.88) between SOAV estimated based on the OTVs for panelists in the present study and values found in the literature. For the majority of the samples, the ratio between the odor detection threshold and SOAV was not significantly different from one, which indicates that the OAV for individual odorants in a mixture can be considered additive. In conclusion, the assumption of additivity between odorants measured in pig house air seems reasonable, but the strength of the method is determined by the OTV data used.

166 Air emissions from swine industrial livestock operations and sleep among residents in nearby residential communities

Abstract Introduction Waste from swine industrial livestock operations (ILOs) produces air pollutants that have been associated with negative health outcomes among nearby residents. Methods Using a repeated-measures design, we assessed the impact of odor emissions on sleep duration and awakenings, important components and determinants of health and quality-of-life. Study participants from 16 residential communities in eastern North Carolina hosting swine ILOs, from 2003 to 2005, completed twice-daily diaries in which they rated the strength of hog odors and indicated whether they were asleep or awake per hour for two weeks. Simultaneously, a monitoring trailer placed in a central location in each community measured the atmospheric concentration of hydrogen sulfide (H2S). Subject-conditional fixed-effects regression models were used to estimate associations between two markers of swine ILO pollutant exposures (H2S and swine odor) and two self-reported sleep outcomes (nightly sleep duration and awakening from sleep). Results Among 80 participants, nightly (across a 12-hour period) swine odor was associated with lower-nightly sleep duration (mean difference = -14.3 minutes, 95% confidence interval -25.0 to -3.3 minutes) compared to odor-free nights and detection of nightly hydrogen sulfide was associated with a 23% increased hazard of awakening (Hazard ratio = 1.23, 95% confidence interval 0.98 to 1.55) compared to nights with no detection of hydrogen sulfide. Conclusion These results suggest that emissions reductions and odor abatement are important public health goals in designing policy and technology solutions to the problems of livestock production and waste management. Support (if any) This work was funded, in part, by the Intramural Program at the NIH, National Institute of Environmental Health Sciences (Z1AES103325-01).

Exploring Odor Minimization in Post-Consumer Plastic Packaging Waste through the Use of Probiotic Bacteria

Plastic packaging represents a large proportion of the plastic consumption throughout the world. The negative environmental impact associated with plastic packaging waste can be in part abated by recycling plastics, and increasing numbers of regulatory frameworks are being adopted towards this goal. Despite recent advances in modern recycling technologies, the production of high-quality polyolefin recyclates remains a challenge. Among other functional requirements, odor plays a crucial role in the acceptance of recycled packaging. This presents a challenge, as odor contamination in plastic packaging waste can stem from diverse sources, such as spoilage processes, and strongly depends on the quality of the post-consumer input material. The present study addressed this issue by exploring potential odor abatement of malodors in packaging waste through the use of probiotic bacteria. Specifically, probiotics were added to a mixed post-consumer plastic packaging waste fraction, which was subsequently evaluated using human sensory and gas chromatography–olfactometric analyses. A comparison of treated with untreated plastic waste fractions revealed significant sensory differences. Further structural elucidation of the causative odorants confirmed a reduction in malodorous microbial metabolites, although complete odor removal was not achieved. However, this environmentally friendly approach may represent an essential step towards overcoming the odor burden in post-consumer plastic packaging recyclates.

Plasma Technology and Its Relevance in Waste Air and Waste Gas Treatment

Plasma technology is already used in various applications such as surface treatment, surface coating, reforming of carbon dioxide and methane, removal of volatile organic compounds, odor abatement and disinfection, but treatment processes described in this context do not go beyond laboratory and pilot plant scale. Exemplary applications of both non-thermal plasma and thermal plasma should underline the feasibility of scale-up to industrial application. A non-thermal plasma in modular form was built, which is designed for up to 1000 m³∙h−1 and was successfully practically tested in combination of non-thermal plasma (NTP), mineral adsorber and bio-scrubber for abatement of volatile organic components (VOCs), odorous substances and germs. Thermal plasmas are usually arc-heated plasmas, which are operated with different plasma gases such as nitrogen, oxygen, argon or air. In recent years steam plasmas were gradually established, adding liquid water as plasma gas. In the present system the plasma was directly operated with steam generated externally. Further progress of development of this system was described and critically evaluated towards performance data of an already commercially used water film-based system. Degradation rates of CF4 contaminated air of up to 100% where achieved in industrial scale.

OVERVIEW OF ODOUR MEASUREMENT METHODS: THE ODOUR OBSERVATORY AS AN INFORMATIVE TOOL FOR CITIZEN SCIENCE BASED APPROACHES TO ODOUR MANAGEMENT

Odour pollution is a well-known problem related to a number of different industrial activities. It is also one of the main causes of citizens’ complaints to local authorities. Specific programs are needed to manage persistent odour pollution problems within communities in order to avoid possible socio-environmental conflicts. The H2020 project D-NOSES (Distributed Network for Odour Sensing, Empowerment and Sustainability) aims to help citizens co-create local solutions in collaboration with industries, regional &amp; local authorities, and odour experts. The project will develop an innovative bottom-up approach to odour pollution governance by combining citizen science and stakeholder management methods using a quadruple helix model. The first aim of this article is to introduce the D-NOSES project and its methodology. Aside from that, the article presents an overview of the existing odour impact assessment methods currently available to quantify odour pollution. Finally, the different odour measurement methods are compared in terms of their applicability and limitations. This overview will be made available online as a first step towards the development of the International Odour Observatory, a platform to be created within the D-NOSES project to help promote odour pollution management and resolve regulation issues. The platform will become a global resource on odour issues and also include information about odour abatement systems, chemical substances in odour emissions, and odour regulations around the world.

Biofiltration of butyric acid: Monitoring odor abatement and microbial communities

The objective of this study is to evaluate comparatively the odor removal efficacy of two biofilters operated under different conditions and to identify taxonomically the microbial communities responsible for butyric acid degradation. Both biofiltration systems, which were filled with non-inoculated wood chips and exposed to gas streams containing butyric acid, were evaluated under different operational conditions (gas airflow and temperature) from the physical-chemical, microbiological and olfactometric points of view. The physical-chemical characterization showed the acidification of the packing material and the accumulation of butyric acid during the biofiltration process (<60 days). The removal efficacy was found to be 98–100% during the first 20 days of operation, even at high odor concentration. Changes in the operational temperature increased the odor load factor from 400 to 1400 ouE/m2·s, which led to the reduction of microbiota in the packing material, and a drastic drop of the odor removal efficacy. However, the progressive increase in gas airflow improved the biodegradation efficacy of butyric acid up to 88% with odor loadings as high as 33,000 ouE/m3, while a linear relationship between odor inlet load and removal capacity was also found. The analysis of the microbial community showed that Proteobacteria was the most abundant phylum along the biofiltration time (58–92%) and regardless of the operational conditions. Finally, principal component analysis applied to the physical-chemical and microbiological data set revealed significant differences between the two biofilters under study.

Optimization of a headspace solid‐phase microextraction‐gas chromatography–mass spectrometry procedure for odor compounds from polyolefin resin used in plastic food packaging

This research investigated the best headspace solid‐phase microextraction (HS‐SPME) extraction conditions and used the response surface Box–Behnken trial design to optimize the parameters for the analysis of volatile compounds in polyolefin resin, which is made from powdered polyolefin resin and additives by heating processing. The results showed that when the extraction temperature was 64°C, the extraction time was 34 min, the sample weight was 2.0 g, the testing matrix was air, and the fiber type was 50/30 μm DVB/CAR on PDMS, and the number of volatile compounds in the resin pellets was the highest. The performance characteristics of the optimized method were also determined, and they showed excellent linear ranges, recovery, repeatability, detection, and quantification limits. In the resin pellets and powdered polyolefin resin, the alkane content was the highest, at 585.346 and 581.789 mg/kg, respectively. In the additives, the benzene content was the highest at 39.495 mg/kg. Compounds with odor activity values (OAVs, ratio of concentration to odor threshold) above 1.0 are considered key aroma‐active compounds. In total, 135 volatile compounds were identified, and 19 of them had an OAV above 1.0, and 4‐methyl‐octane and o‐xylene were identified as the key odorants in the resin pellets. Only one odorant, 4‐methyl‐octane, was detected in the powdered polyolefin resin. In the additives, 18 volatile compounds were identified as key aroma‐active compounds, such as octanal, nonanal, hexanol, octanol, heptanol, and decanol. The significance of this research was to furnish data to support the further study of odor abatement from food packaging materials.

Odor Characteristics and Concentration of Malodorous Chemical Compounds Emitted from a Combined Sewer System in Korea

(1) Objectives: This study was carried out to investigate the characteristics of odors emitted from a combined sewer for the abatement of combined sewer odor. (2) Methods: The odor samples emitted from the combined sewer were collected at 14 sites, and the concentrations of 13 malodorous chemicals were determined by the instrumental analysis such as gas chromatography. To understand the sensory characteristic of the combined sewer odor, the on-site odor intensity (OOI) was evaluated by the direct sensory method using the human olfactory sensitivity of panelists with a normal sense of smell. The primary odor-causing compounds with high contribution were evaluated based on the converted odor concentration (COC), which was calculated by using the compound concentration and threshold limit value. Since the direct sensory method requires a lot of manpower and time, the converted odor intensity method (COI) calculated by the malodorous compound concentration was reviewed and compared with other cases. (3) Results: As a result of the instrumental analysis, four compounds which were higher than other compounds, showed an average of 325 ppb for H2S, 121 ppb for NH3, 102 ppb for CH3SH, and 108 ppb for toluene. The rest of the compounds appeared low, below 60 ppb. Based on the result of evaluating the COC, three compounds which are H2S, CH3SH, and (CH3)3N appeared to be compounds with a high contribution to combined sewer odor. Especially, it was estimated that H2S was the main odor-causing compound in this study. The on-site odor intensity of the combined sewer as judged by 5 panelists appeared to be 2.8 degrees on average, the same as COI. The correlation between the odor intensity and the H2S concentration in the combined sewer showed as the following equation: COI, degree = 1.0757 × log (H2S conc., ppb) + 0.3696. (4) Conclusions: In Korea, the odor emission standard in the atmosphere including sewer odor has adopted 20 ppb for H2S, and less than 2 degrees for odor intensity in the non-industrial area. However, since the mean observed odor intensity was 2.8 degrees and the concentration of H2S was also 325 ppb on average in this study, it was concluded that countermeasures should be prepared to reduce the complaints due to combined sewer odor in residential areas.