ROSENFELD IMAGES LTD / SCIENCE PHOTO LIBRARY ROSENFELD IMAGES LTD / SCIENCE PHOTO LIBRARY
Sewage effluent. Bacterial aerobic treatment of sewage in a pool at a sewage treatment plant. The pool contains organic matter suspended in solution. The water in the pool is agitated to prevent the matter from settling. The water is oxygenated to promote aerobic bacteria which convert the sewage into carbon dioxide and other stable chemicals. The bacteria are then filtered out from the liquid. Inorganic solids are then removed before the water is discharged into the sea or a river. Photographed in Germany.
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