Onsite sewage facility
（重定向自OSSF）
Onsite (or on-site) sewage facilities (OSSF) are wastewater systems designed to treat and dispose of effluent on the same property that produces the wastewater.
A septic tank and drainfield combination is the oldest and most common type of OSSF, although newer aerobic and biofilter units exist which represent scaled down versions of municipal sewage treatments. OSSFs account for approximately 25% of all domestic wastewater treatment in the United States.