A study was executed in 2016 to determine the efficiency of two different neutralizers on odor perception from a sludge drying process. One of the products was injected by fogging system at the inlet of the odor control unit while the other was added directly to the washing solution of the last stage of the odor control unit, according to supplier recommendations.

Performance evaluations encompassed complementary approaches including both sensorial analyses and analytical measures. Odor analyses were performed via dynamic olfactometry according to European Standard EN 13725 coupled with hedonic tone approach according to VDI 3882. Additional analyses on VOC emissions were conducted using gas chromatography screening. In parallel, several odor panels composed of site operators and plant neighbors carried out observations on the WWTP and its perimeter. The main conclusions of this study illustrates:

• Only one test leads to a reduction of the odor concentration at the stack,

• Overall, neither of the two masking agents significantly reduce the odor concentration at the stack,

• The addition of masking agent seems to increase foul odor persistency,

• The local odor panel observed no significant improvement in odor reduction within the environment around the WWTP.

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