Efforts to reform science education focus on implementing constructivist pedagogy to engage students in scientific practices, promote critical thinking, and provide students with relevant research experiences. In this spirit, this article presents authentic, inquiry-based activities utilizing the real-world bioscience behind wastewater treatment. The activities begin with a tour of a wastewater treatment facility, followed by a guided inquiry activity in which students enumerate E. coli levels from wastewater samples collected from different steps of the treatment process. Students then participate in an open-inquiry experiment to test a unique hypothesis. Learning about wastewater treatment introduces students to important biology content such as bioremediation, microbiology, and nutrient cycling. Additionally, students engage in science practices such as inquiry and constructing evidence-based explanations.