Aerobic units have been commercially available for approximately 25 years. They are particularly applicable where enhanced pretreatment is important, and where there is limited availability of land which is suitable for final onsite disposal of wastewater effluent. The lower organic and suspended solids content of the effluent may allow a reduction of land area requirements for subsurface disposal systems. The rate of sludge production for aerobic units is much greater than for septic tanks, necessitating more frequent sludge removal by a licensed transporter. To ensure proper performance of the units, it may be necessary in at least some cases to require a maintenance contract.
Electrical power is required for aerobic units.
Current Austin-Travis County Health and Human Services rules require that this type of system be designed by a licensed professional engineer. Numerous studies have been conducted during the past 20 to 25 years to evaluate the performance of aerobic treatment units. Mean effluent values for various wastewater parameters measured during that study are presented in a table given below, included as the last page of this fact sheet. More recent testing of certain aerobic unit models has been performed by NSF International. Those results indicate that there may have been some design and performance improvements for those models as compared with the systems tested in the earlier studies.