This document summarizes the journey of wastewater from homes through treatment plants before being returned to the environment. It explains that wastewater is collected via pipes and sent by gravity to local treatment plants. These plants treat the water in three levels - primary, secondary, and tertiary - to remove contaminants using physical, biological, and chemical processes. The treated effluent is then returned to streams while nutrient-rich sludge is used or disposed of as fertilizer, fuel, or compost.