DAVID HAY JONES / SCIENCE PHOTO LIBRARY DAVID HAY JONES / SCIENCE PHOTO LIBRARY
Wastewater treatment. Tanks at a wastewater treatment plant. Heavier particles in the water sink to the bottom of the tank and are pushed into a central drain by the rotating arms. Oil and grease float on top of the water and are skimmed off. Photographed at the Jones Island wastewater treatment plant, Milwaukee, USA.
Model release not required. Property release not required.