Application of Nutech Remote Trigger Sampling Device and Pre-concentration System in Odor Monitoring
Background
Odor refers to any foul-smelling gas that irritates the olfactory system, causing discomfort and impairing the living environment. It primarily comprises six major categories of compounds:
- Aromatic hydrocarbons (e.g., benzene, toluene, ethylbenzene);
- Oxygenated compounds (e.g., phenols, alcohols, ketones, aldehydes);
- Alkanes and alkenes;
- Halogenated hydrocarbons;
- Nitrogen-containing compounds (e.g., ammonia, amines);
- Sulfur compounds (e.g., hydrogen sulfide, carbon disulfide).
These odorous gases are highly perceptible, persistent, and wide-ranging in their pollution impact. In severe cases, they directly endanger public psychological well-being and physical health.
Odor complaints dominate environmental grievances. Odor-related reports accounted for over 20% of all environmental complaints annually, making it one of the most pressing public concerns and a critical livelihood issue demanding urgent resolution from environmental regulators.
Odor pollution originates from a wide range of sources, including waste treatment, livestock farming, chemical industry, rubber and plastic products manufacturing, catering, non-metallic mineral products industry, metal products industry, agricultural and food processing, automotive repair, and pharmaceutical manufacturing. Odor pollution is characterized by its pervasiveness, intermittency, and diversity, with complex chemical compositions. When odor nuisance incidents occur, especially in cases involving multiple interacting pollution sources, tracing the origin of odors becomes extremely challenging.
Traditional methods such as olfactometry and electronic noses cannot identify specific chemical components in odors, making source tracing impossible during odor incidents. Real-time monitoring systems using online chromatographic and spectroscopic instruments face limitations in coverage and detectable components, along with high construction, operation, and maintenance costs, rendering them unsuitable for rapid response to various complaint cases. Laboratory-based manual methods, such as pre-concentration coupled with GC-MS, have significant potential in odor analysis due to their ability to qualitatively and quantitatively analyze organic components in odorous gases and identify tracer/indicator species for pollution sources. However, due to the transient and sporadic nature of odor pollution, timely sample collection during odor events is often difficult, leading to substantial wastage of manpower and resources. Rapid response and representative sample collection during odor incidents remain a critical challenge in odor source tracing.
To address this issue, Nutech develops a remote trigger sampling-based odor monitoring system.
Nutech Solution
The remote trigger sampling-based odor monitoring system comprises remote intelligent sampling equipment, a pre-concentration system, and a gas chromatograph-mass spectrometer (GC-MS).
To address the characteristics of odor pollution, Nutech has developed a remote trigger sampling system based on traditional canister sampling technology. This system enables automated timed constant-flow sampling, concentration threshold-triggered sampling, and remote-triggered sampling. Particularly during sudden or sporadic odor events, it can immediately activate the sampling process to capture odor samples in real time, avoiding the collection of non-representative samples. This ensures the representativeness and integrity of odor samples while overcoming the limitations of traditional sampling methods, such as cumbersome operations, low automation, and high labor requirements.
The pre-concentration system effectively eliminates interference from atmospheric impurities such as CO₂, O₂, H₂O, and N₂. It can concentrate and enrich both polar (aldehydes, alcohols, esters, ketones, ethers) and non-polar volatile organic compounds (VOCs), including sulfur- and nitrogen-containing compounds. When coupled with a GC-MS system, it provides detailed chemical composition and concentration data of odorous gases. The Nutech pre-concentration system is particularly suitable for low-concentration (especially low-odor-threshold) malodorous VOCs, enhancing the sensitivity of gas chromatography-mass spectrometry (GC-MS) and preventing undetected analytes due to extremely low concentrations, thereby ensuring accurate odor source tracing.
Test Results
The remote intelligent sampling-based odor pollution monitoring system was used to collect and analyze organic odorous gases from two pharmaceutical plants (A and B). An odor pollutant inventory was established, and characteristic pollutants for each facility were identified (Figure 3). Although both plants are pharmaceutical manufacturers, their odor concentration and composition profiles differed significantly, likely due to variations in raw materials and production processes.
- Pharmaceutical Plant A exhibited much lower concentrations than Plant B. Its major compounds were toluene, acetone, and ethyl acetate, all below 10 ppbv.
- Pharmaceutical Plant B showed acetone as the dominant species, with concentrations tens of times higher than other compounds.
Since odor thresholds vary widely among compounds, high-concentration substances may not always be the primary odor contributors, while low-concentration ones could have a significant impact. Thus, calculating threshold dilution factors is essential to identify key odorants for targeted control and pollution reduction.
- For Plant A, toluene was the primary odor contributor, with minor input from other compounds.
- For Plant B, despite a tens-fold concentration difference, acetone and toluene contributed equally to odor intensity.
Control Recommendations:
- Plant A: Prioritize toluene emission control.
- Plant B: Focus on acetone and toluene emission reduction to mitigate odor pollution.
This approach ensures efficient resource allocation for odor management based on scientific prioritization.
Green for concentration & red for odor contributition
For sensitive monitoring sites, the sampling system can be immediately triggered upon odor detection. The collected odor samples are then analyzed using a pre-concentration GC-MS system to obtain detailed compositional data of the odorous gases. By comparing these results with source-specific chemical profiles, the origin of the odor pollution can be accurately identified.
Conclusions
The remote intelligent odor sampling and monitoring system enables comprehensive odor sample collection while significantly reducing labor and resource costs. It is particularly effective for detecting low-concentration (especially low-odor-threshold) volatile organic compounds (VOCs).
This system has broad applications, including:
- Investigating public odor nuisance complaints
- Tracing odor pollution sources
- Screening odorants and establishing emission inventories for industrial facilities
Implementation Approach:
- Develop an odor source fingerprint database
- Compare sensitive site monitoring data with source fingerprints to identify potential polluters
- Incorporate meteorological data and other parameters to precisely pinpoint odor origins