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5: Keeping it fresh
Mounds of finished Biosolids are turned over to keep the product fresh at the Downers Grove Sanitary District's Wastewater Treatment Center, 5003 Walnut Ave. on Tuesday, Aug. 6, 2013. The district converts wastewater sludge into "Biosolids," which are used by both municipalities and private citizens to fertilize grass and plant matter. (Matthew Piechalak photo)