As far as I know a treatment plant's job is to treat black water to become effluent. Part of the process is removing dangerous microbes, grease and other environment damaging substances. However, is it possible that the odor remains in the effluent? Or that safe effluent can still contain odorous compounds unless scrubbed?

NOTE: I live few kms away from one that discharges into a river that has moderate odor but at that distance away from residences, I guess it doesn't matter.

  • $\begingroup$ Not my field, so just a guess - but I'd think that the odorous gases produced by the microbes could remain dissolved in the water even though the microbes themselves are long gone. $\endgroup$
    – brhans
    Aug 13, 2018 at 18:59

1 Answer 1


Where I live (Germany), WWTP are required to clean the water to a degree so it does not harm the receiving water. This is far from drinking water quality. In your area, restrictions may be more lax.

In my experience, WWTP stink, I know one you can smell kilometers away! Especially the larger ones, even when most tanks are covered and there's an odor control. The stinkiest parts are usually near the inflow, rakes etc. Sewage sludge pre-fouling is also very stinky. Secondary clarifiers should not be smelly.

So it may be hard to tell apart if the whole WWTP is stinking or only the effluent, if the effluent stinks this could prompt further questions:

  • What are the (legal) requirements for WWTPs in your locale?
  • How is the ecological health of the receiving water body?
  • Does the effluent smell on all days, or only after strong rain events? Or only ater longer dry spells?

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