Solids must be recovered from the basin every few months. They may be land applied or processed and may be shipped off-site. No cost or revenue has been included in this example for solids handling. The remaining liquid is treated in an upflow aerobic biofilter to reduce the amount of nitrogen. The biofilter is made up of a large tank that contains media on which bacteria may grow.
Liquid waste is aerated by a large blower as it flows through the tanks.
In this example, the biosolids are flushed to the lagoon. The resulting liquid must be applied to nearby land, but should contain less nitrogen than liquid from lagoons typically used by North Carolina hog growers. Because of the solids separation, it should be possible to reduce lagoon size, and odor may be reduced. A mechanical separator made of a screen and press is used to separate solid and liquid portions of wastewater from swine buildings. Solids are then placed in long beds that are stocked with red worms.