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United States Department of Agriculture

Agricultural Research Service

Title: A Constructed Wetland System for Treating Agricultural Waste

Authors
item Cooper, Charles
item Knight, Scott
item Testa, Sam

Submitted to: International Society Of Limnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 1997
Publication Date: N/A

Interpretive Summary: There is a constant need for improving our on-farm treatment of wastes that have the potential for off-site contamination. Animal wastes are a major concern for landowners and action or regulatory agencies. Natural wetlands have proven to be efficient processors of nutrients, organic matter, and bacteria. Thus, a question relevant to animal waste processing is "Can on-farm constructed wetlands process animal waste efficiently?" This 3 year study found that constructed wetland cells working as a secondary treatment behind a lagoon could process several major cattle manure products effectively. Knowledge of the effectiveness for different specific waste bi-products will help develop more suitable criteria for action agency design. Design is simple, low-cost and environmentally sound, all of which make constructed wetlands an additional tool for farmers to use on-site.

Technical Abstract: In recent years, the ability of natural and constructed wetland ecosystems to improve water quality from a wide variety of degraded sources has become evident. Design criteria for constructed wetlands require quantitative field data. A constructed wetland for treatment of dairy wastewater was built by the USDA Soil Conservation Service and Agricultural Research Service in DeSoto County, MS, USA during 1990. Three parallel wetland cells, planted with giant bulrush (*Scirpus validus*), were monitored for 36 months while receiving wastewater inputs from a 100-head dairy operation. Measures of physical and chemical water quality, BOD, COD, and coliform bacteria were recorded, and average seasonal pollutant and nutrient-trapping efficiencies for the constructed wetland cells were calculated. Discharge from the system occurred at only 103 out of 181 observations (57% of observations), and 75% of observed discharges were less than 0.75 L/min. Suspended solids were reduced 60%, while dissolved solids were reduced only 22%. Filterable ortho-phosphorus was reduced 42% and total phosphorus by 53%. Ammonia nitrogen declined 82%. Nitrate nitrogen concentrations increased by 14%, though outflow concentrations were typically very low (mean = 0.10 mg/L). Carbonaceous biochemical oxygen demand (CBOD5) and chemical oxygen demand (COD) were reduced 75 and 63 percent respectively. Total chlorophyll was 78% less at discharge stations, and total coliforms decreased by 84%. Constructed wetlands have considerable potential as cost-effective on-farm waste management systems.

Last Modified: 4/23/2014
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