I have been engaged in corrosion research for 43 years and served as a consultant on corrosion-related failures for 32 years. A significant portion of my work involves corrosion associated with wastewater. The specific hazards depend on the specific chemicals. Hydrogen sulfide reacts strongly with iron (e.g., carbon steels and low alloy steels) and generates a solid corrosion product film that might slow down subsequent corrosion. However, the solid sulfide film is often non-protective for several reasons, resulting in significant corrosion of the steel. Zinc is also susceptible to corrosion by hydrogen sulfide. Both iron and zinc typically suffer significant corrosion when exposed to sulfuric acid. Mitigation techniques include: control of oxidizers (such as dissolved oxygen and chlorine); adjustment of pH; addition of organic inhibitors; cathodic protection; electrically insulating coatings (e.g., polymers); sacrificial anodes. I have considered several instances of corrosion caused by hydrogen sulfide and corrosion caused by sulfuric acid.