Effluent sewer systems, also called septic tank effluent gravity, solids-free sewer, or septic tank effluent drainage systems, have septic tanks that collect sewage from residences and businesses, and the liquid fraction of sewage that comes out of the tank is conveyed to a downstream receiving body such as either a centralized sewage treatment plant or a distributed treatment system for further treatment or disposal away from the community generating the sewage. Wikipedia