Sludge treatment can emit strong sulfur-containing odors such as dimethyl sulfide (DMS) and hydrogen sulfide (H₂S). Here independent measurements show the AirShield removes 100% of these sulfur-containing odors and reduces total odor emissions to 75 ouₑ/m³, a 99.5% reduction.
removal of sulfur-containing gas
removal of total odor
residual odor emissions
Odors from sludge treatment are rarely constant. They fluctuate with the process, the weather, and what is happening on-site at a given moment. When odor escapes, it can quickly turn into a recurring nuisance, especially when emissions vary with operational conditions. A key complication is that odors are site-specific.
To understand these dynamics at WWTP Utrecht, measurements were performed in November 2024 and March 2025, capturing two operating periods. In both cases, GC-MS measurements show that the bulk of the gas consists of sulfur-containing gases (predominantly volatile organic sulfur compounds; VOSC) and a mixture of aldehydes, aliphatic, aromatic and cyclic hydrocarbons.
While the VOSC account for about a sixth of the mass, they account for more than half of the odors. The main culprits are dimethyl sulfide (DMS), dimethyl disulfide (DMDS) and methyl mercaptan.
Our AirShield is designed for broad-range sludge odor control, targeting multiple malodorous gases in a single system rather than targeting a single compound. It is electrically driven and uses sensor-driven power control to adapt cleaning capacity to the odor concentration.
To capture both baseline conditions and real operational peaks, H₂S and VOCs were monitored continuously with electrochemical sensors and PIDs. The continuous results were validated with multiple GC-MS measurements while odor reduction was demonstrated through odor panel (dynamic olfactometry).
| Component | Method | Input | Output | Removal rate |
|---|---|---|---|---|
| Total odor | Odor panel | 15,000 ouₑ/m³ | 75 ouₑ/m³ | 99.5% |
| Total VOC | GC-MS | 3500 µg/m³ | 125 µg/m³ | 96.4% |
| DMS | GC-MS | 85 µg/m³ | Below detection limit | 100% |
| DMS (peak) | Kitagawa tube | 2800 µg/m³ | Below detection limit | 100% |
| DMDS | GC-MS | 220 µg/m³ | Below detection limit | 100% |
| Methyl mercaptan | GC-MS | 2 µg/m³ | Below detection limit | 100% |
The GC-MS measurements show 100% removal of DMS, DMDS and methyl mercaptan, while the odor panel results shows residual odor emissions at only 75 ouₑ/m³ (a 99.5% reduction), which was substantially lower than permitted. However, what matters in practice is not just lower average emissions, but effective treatment during emission peaks. In these periods, that typically trigger odor complaints, the continuous sensors show that the AirShield maintains removal rates when DMS emissions rose 30x the average rate.
Marijn van de Ven, Process Technologist
Hoogheemraadschap de Stichtse Rijnlanden
“In the past, when we experienced odor issues, they were mainly caused by dimethyl sulfide, mercaptans, and other sulfur-containing emissions from our sludge treatment. Luper’s AirShield removes these compounds with 100% effectiveness.”
Curious what our AirShield can do for you? We’re here to answer your questions.
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