ABSTRACT
Septic tank systems that serve 25% of the US population are installed in a variety of soil types and temperature ranges throughout the country. A primary concern of many septic tank owners is odor, often emitted from house roof vents directly connected to the septic tank. Open tees should be installed only at the effluent discharge point inside the tank to allow trapped gases to escape into the leach field or aquatic plant/microbial filter. Biologically, the aquatic plant systems are far more diverse than present-day mechanical treatment systems. Oxidation ditches and other types of extended aeration treatment systems use energy-intensive mechanical aerators to supply large amounts of oxygen for growing aerobic microorganisms that treat the wastewater. Size of the rock/plant filter system will be dictated by the volume of septic tank effluent and the level of treatment desired. When these systems are properly installed, sewage will not have open-air exposure before treatment has been accomplished.
