I can dispose of hazardous chemicals down the drain, right? The wastewater plant is responsible for clean up.

Wrong. Hazardous materials such as oils and paint thinners disrupt the collection system and the treatment plant. The wastewater plant process can not remove all hazardous chemicals, therefore, some may enter our rivers and bays. The more polluted the water, the harder it is to clean, and the more expensive a process it becomes.