4.2. Treatment wetland area and pretreatment
The majority of the wetlands engineered for
livestock wastewater treatment are small, with an
average system size of 0.6 ha and a median size of
0.03 ha. The majority of the swine, poultry and
dairy treatment wetland systems are less than 0.1
ha. Many of these systems were designed forresearch purposes and not as full-scale installations.
Most of the Kentucky swine systems are
larger than 1 ha. The only large animal waste
treatment wetland in the LWDB is the Brenton
Cattle system in Dallas Center, IA, with an area
of about 47 ha.
All of the wetland systems in the LWDB have
some form of pretreatment. The most common
form of pretreatment is a settling basin or anaerobic
lagoon. Performance of these facilities was not
documented for this study but other published
results indicate that 50–75% of the total BOD5
and TSS in the raw livestock wastewaters is typically
removed through pretreatment (US Department
of Agriculture Soil Conservation Service,
1992).