ef·flu·ent
ˈe-ˌflü-ənt 
e-ˈflü-,
ə-
: something that flows out: such as
a
: an outflowing branch of a main stream or lake
b
: waste material (such as smoke, liquid industrial refuse, or sewage) discharged into the environment especially when serving as a pollutant
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Effluent comes from the Latin verb effluere, "to flow out". In an older meaning, an effluent was a stream flowing out of a river or lake. But nowadays effluent almost always means wastes that pour into our water and air. Liquid factory waste, smoke, and raw sewage can all be called effluents. An effluent filter keeps treated waste flowing out of a septic tank from clogging up its drainage pipes.
Examples of effluent in a Sentence
Noun
The factory has been accused of discharging effluent into the river.
Recent Examples on the Web
Céline Van De Loo, Sourcing Journal, 16 Dec. 2025
Jun and Arthur finish their effluent business by the time J finishes his own.
—Literary Hub, 15 Aug. 2025
Rob Nikolewski, San Diego Union-Tribune, 1 Jan. 2026
Local water quality has dramatically improved in recent years, as the management and treatment of effluent into the St. Louis River has grown more rigorous, thanks in large part to the work of Resource Renew, formerly known as the Western Lake Superior Sanitary District.
—Peter Passi, Twin Cities, 28 Dec. 2025
See All Example Sentences for effluent
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Adjective
The effluent treatment plant (ETP) is running.
—Céline Van De Loo, Sourcing Journal, 16 Dec. 2025
Jun and Arthur finish their effluent business by the time J finishes his own.
—Literary Hub, 15 Aug. 2025
Noun
All nuclear plants release some effluents, though the nature and amounts can vary by plant site and configuration.
—Rob Nikolewski, San Diego Union-Tribune, 1 Jan. 2026
Local water quality has dramatically improved in recent years, as the management and treatment of effluent into the St. Louis River has grown more rigorous, thanks in large part to the work of Resource Renew, formerly known as the Western Lake Superior Sanitary District.
—Peter Passi, Twin Cities, 28 Dec. 2025
See All Example Sentences for effluent
Cite this Entry
“Effluent.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/effluent. Accessed 18 Jan. 2026.
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