Constructed wetlands for livestock wastewater management

Abstract

In 1995, the Gulf of Mexico Program (GMP) sponsored efforts by the Alabama Soil and Water Conservation Committee and the National Council of the Pulp and Paper Industry for Air and Stream Improvement (NCASI) to conduct a review of the literature concerning the use of constructed wetlands for treating concentrated livestock wastewaters. The scope of the literature review and summary of design/operation data included all of North America. Both published and unpublished data have been provided by researchers to be included in the database. The database format used for the GMP project is only slightly modified from the format developed for the US Environmental Protection Agency (EPA) North America Treatment Wetland Database, which includes information from municipal, industrial and stormwater treatment wetlands. The GMP Livestock Wastewater Treatment Wetland Database includes information from 68 sites with a total of 135 pilot and full-scale wetland systems (systems include parallel units at individual research facilities). Types of livestock wastewater being treated by constructed wetlands include dairy manure and milkhouse wash water, runoff from concentrated cattle-feeding operations, poultry manure, swine manure and catfish pond water. Over 1300 operational data records are summarized in the database. These data indicate that removal rates for 5-day biochemical oxygen demand (BOD 5), total suspended solids (TSS), ammonium nitrogen (NH 4-N), total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD) and fecal coliforms are potentially very high in constructed wetlands receiving animal wastewaters. Average concentration reduction efficiencies were: BOD 5 65%, TSS 53%, NH 4-N 48%, TN 42%, and TP 42%. Removals are a function of inlet concentrations and hydraulic loading rates. Successful wetland design must include adequate pretreatment to protect the health of the wetland biota and must include adequate wetland area to meet the quality goals.