What causes these odors?

Most of the odors detected in and around wastewater treatment plants are signals that nature’s treatment process is working; organic matter is decomposing and pollutants are being removed from the wastewater.

As the table Odorous Compounds In Wastewater shows, three major odorous compounds naturally occurring in the treatment process, hydrogen sulfide, amines and mercaptans, are detectable by the human nose at extremely low concentrations.

Odorous Compounds In Wastewater

Compound Name

Recognition Threshold parts per million

Odor Description

Allyl mercaptan


Disagreeable, garlic



Pungent, irritating

Amyl mercaptan


Unpleasant, putrid

Diisopropyl amine



Dimethyl amine


Putrid, fishy

Ethyl amine



Ethyl mercaptan


Decayed cabbage

Hydrogen sulfide


Rotten eggs



Fecal, nauseating

Methyl amine


Putrid, fishy

Methyl mercaptan


Rotten cabbage

From Table 2.1, Odor Control in Wastewater Treatment Plants, 1995, WEF & American Society of Civil Engineers

Were it not for odor control measures, all wastewater treatment processes are capable of emitting odors.

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1. Are baby/adult wipes flushable?
2. Is reclaimed water safe?
3. Is there lead in my drinking water, and if so what can I do about it?
4. Should I put my used cooking grease down the drain?
5. What is reclaimed water?
6. Why do we use reclaimed water and what are the benefits of reuse?
7. Why do we sometimes smell odors near the wastewater treatment plant?
8. What causes these odors?
9. How does ACWWA minimize odors at the wastewater treatment plant?
10. What can I do if I smell an odor I think is coming from the plant?
11. What happens when the LTCWRF receives an odor complaint?