This industry comprises establishments primarily engaged in operating sewer systems or sewage treatment facilities that collect, treat, and dispose of waste. Cross-References. Establishments primarily engaged in-- ? Operating waste treatment or disposal facilities (except sewer systems or sewage treatment facilities)--are classified in Industry 56221, Waste Treatment and Disposal; ? Pumping (i.e., cleaning) septic tanks and cesspools--are classified in U.S. Industry 562991, Septic Tank and Related Services; and ? Cleaning and rodding sewers and catch basins--are classified in U.S. Industry 562998, All Other Miscellaneous Waste Management Services.