Effluent is generally considered to be water pollution. According to Wikipedia effluent is an outflowing of water or gas from a natural body of water, or from a manmade structure. The United States Environmental Protection Agency defines it as wastewater - treated or untreated - that flows out of a treatment plant, sewer, or industrial outfall. Generally, refers to wastes discharged into surface waters.  Wastewater is any water that is affected in quality by human impact on the environment.