An effluent water treatment plant works by removing sludge, scum and bacteria from wastewater before releasing the effluent, or treated water, back into the environment, according to the U.S. Geological Survey. Wastewater enters the treatment plant and goes through several processes before effluent goes into a nearby lake or river.
Treating wastewater begins when water enters the plant and goes through several concrete tanks that aerate water. This air forces particulate matter like coffee ground or sand to settle out of the water while oxygen is replenished. Another set of sedimentation tanks removes organic sludge from water. Sludge is heavier than water and it sinks to the bottom. Scum is then removed as substances such as grease and oil float to the top. The last portion of treating wastewater involves killing bacteria by adding chlorine to water, much in the same way harmful substances are killed in swimming pools. The chlorine is then neutralized before the water is sent back into the environment.
The Patapsco Wastewater Treatment Plant near Baltimore services more than 63 million gallons of water per day. The Blue Plains Advanced Wastewater Treatment Plant goes through more than 330 million gallons of raw sewage daily. The World Bank states modern processes can remove up to 99 percent of impurities from sewage, making the finished effluent almost drinking quality.