1 of 2


ef·​flu·​ent ˈe-ˌflü-ənt How to pronounce effluent (audio)
: flowing out : emanating, outgoing
an effluent river


2 of 2


: something that flows out: such as
: an outflowing branch of a main stream or lake
: waste material (such as smoke, liquid industrial refuse, or sewage) discharged into the environment especially when serving as a pollutant

Did you know?

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
Sea rise also is pushing the island’s groundwater closer to the surface, allowing the cesspool effluent to mix with the water table and flow into the ocean. Audrey McAvoy, Anchorage Daily News, 10 July 2023 The program can extend awareness about the existence and value of the Santa Cruz River, Bogan said, even when the flow depends on clean effluent discharges. The Arizona Republic, 21 July 2023 Marin County and Sewer Authority Mid-Coastside, the sewage district that includes the city of Half Moon Bay, started testing samples of their community effluent for signs of the drugs in February and November, respectively. Catherine Ho, San Francisco Chronicle, 17 Mar. 2023 Unless the farms are a closed system, effluent from fish pens will pollute the surrounding waters. Chris Mooney, Discover Magazine, 22 Jan. 2010 These efforts resulted in restoration of effluent permit compliance by June 10th. Carlos R. Muñoz, BostonGlobe.com, 8 Mar. 2023 With the Sentinel on hand, he was rescued where Orange County’s Iron Bridge sewage plant releases treated effluent into the Little Econ. Kevin Spear, Orlando Sentinel, 16 Feb. 2023 Chicago's three main treatment plants discharge a combined daily average of about 1.2 billion gallons of treated effluent each day. Dan Egan, jsonline.com, 30 Aug. 2021 Preemptive treatment could also be helpful in hospitals, eliminating antibiotics before effluent flows into the municipal sewage. Jonathon Keats, Discover Magazine, 20 Aug. 2018
As a result, 35 billion gallons of toxic effluent have flowed into San Diego since December and more than 100 billion since 2018, according to the U.S. section of the International Boundary and Water Commission, or IBWC. Tammy Murga, San Diego Union-Tribune, 8 Oct. 2023 In theory, the ground gradually filters bacteria and pathogens in effluent from them. Audrey McAvoy, Anchorage Daily News, 10 July 2023 Failing septic systems, heavy nitrogen loading to create lush green lawns, and farm effluent has been known to cause the harmful algal blooms, as well. Greg Wehner, Fox News, 19 Apr. 2023 Wilson's tenure as a board member and executive director of KWA spanned more than a decade and included the organization's work in removing dangerous dams, taking utilities to court over coal ash groundwater contamination, reducing effluent in the Red River watershed and more. Connor Giffin, The Courier-Journal, 16 Feb. 2023 But the effluent sees additional treatment after it is spread around the soil, where bacteria and plants further break down organic material, according to Jex. Brian Maffly, The Salt Lake Tribune, 5 May 2022 Liquid waste, called effluent, is leftover once the procedure is finished. Eleanor McCrary, USA TODAY, 30 Mar. 2023 The developer for a contentious new subdivision on the Northwest Side wants a wastewater treatment facility that can discharge 1 million gallons of effluent per day into Helotes Creek, prompting frustrations and concerns from nearby communities and environmentalists. Elena Bruess, San Antonio Express-News, 27 Sep. 2022 The upturn is especially noticeable in San Francisco and Oakland, where concentrations of SARS-CoV-2 DNA in effluent have jumped since the end of January. Aidin Vaziri, San Francisco Chronicle, 16 Feb. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'effluent.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History



Latin effluent-, effluens, present participle of effluere to flow out, from ex- + fluere to flow — more at fluid

First Known Use


1726, in the meaning defined above


1859, in the meaning defined above

Time Traveler
The first known use of effluent was in 1726

Dictionary Entries Near effluent

Cite this Entry

“Effluent.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/effluent. Accessed 7 Dec. 2023.

Kids Definition


: liquid (as sewage or industrial by-products) discharged as waste
effluent adjective
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!