Kathryn has long worked in the thick of wastewater treatment. And I mean the actual thick: the solids and sludge that are all part of the treatment process. Enterprise Biosolids and Residuals Superintendent Kathryn Crestani talks with Mike and Donna about how a wastewater treatment plant works (following up on episode 8), how solids are separated out from wastewater, and what the Sewer District does with all that "sludge."