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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #72659

Title: ASSESSMENT OF CONSTRUCTED WETLANDS FOR MASS REMOVAL OF NITROGEN FROM SWINE WASTEWATER

Author
item SZOGI, ARIEL
item Hunt, Patrick
item HUMENIK, FRANK
item BROOME, S
item RICE, J

Submitted to: Constructed Wetlands for Animal Waste Management Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Disposal of livestock wastes has become an important problem in the U.S. due to the fast growth of confined animal production. In modern swine production units, wastewater disposal can be a problem when land area is limited for terminal application. Consequently, this may cause odor and water pollution problems. Our objective was to compare the current technology that uses anaerobic lagoon treatment with alternative technologies using constructed wetlands, overland flow, and recirculating media filter to treat lagoon effluent. Although lagoons can reduce N in wastewater up to 80%, residual ammonia-N concentrations in the lagoon remain very high. When using constructed wetlands, N removal efficiencies up to 70% were obtained with rates up to 10 kg N/ha/day. Dilution of the wastewater prior to wetland treatment was required because levels of ammonia-N tolerated by plants were unknown. Aeration of the lagoon effluent seems to be the limiting factor to treat high ammonia loads. Pretreatment by overland flow had a N removal efficiency of 59% with an application rate of 50 kg N/ha/day. With the media filter treatment, up to 32% of the influent N was treated when wastewater was recycled four times. Either overland flow or media filter offers the opportunity to eliminate the dilution of lagoon effluents prior to wetland treatment.

Technical Abstract: Disposal of wastewater generated by confined swine production units is a problem when land is limited for terminal application. Our objective was to compare the mass removal of nitrogen from swine wastewater by the current technology using anaerobic lagoon treatment with alternative technologies using constructed wetlands, overland flow, and recirculating media filter. Lagoons can reduce nitrogen in wastewater up to 80%. However, residual ammonia-N concentrations in the lagoon effluent are very high. When using constructed wetlands, removal efficiencies up to 70% were obtained with rates up to 10 kg N/ha/d. Because levels of ammonia-N tolerated by plants were unknown, lagoon effluent needed dilution with fresh water. In a microcosms study, wetland plants grew vigorously with ammonia-N concentration levels up to 240 mg/L. Since nitrification seems to be the limiting factor to treat high ammonia loads, aeration of the wastewater may enhance treatment. When lagoon waste was pretreated by overland flow, the N removal efficiency was 59% with a rate of 50 kg N/ha/d. Ammonia-N in the effluent was reduced to levels that can be treated by constructed wetlands. In the media filter treatment, up to 32% of the influent TKN was transformed into nitrate-N when wastewater was recycled four times. Either overland flow or media filter offers the opportunity to eliminate the dilution of lagoon effluents prior to wetland treatment.