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CONSTRUCTED WETLANDS FOR TREATMENT OF SWINE WASTEWATER FROM AN ANAEROBIC LAGOON
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2002
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EngineeringEffluent DisposalEnvironmental EngineeringEnvironmental RemediationSwine WastewaterWater TreatmentBiological Waste TreatmentAnaerobic DigestionNorth CarolinaWastewater ManagementMunicipal WastewaterWaste ManagementAnimal Waste ManagementWastewater TreatmentConstructed Wetland
Animal waste management is a national concern that demands effective and affordable methods of treatment. Weinvestigated constructed wetlands from 1993 through 1997 at a swine production facility in North Carolina for theireffectiveness in treatment of swine wastewater from an anaerobic lagoon. We used four wetland cells (3.6 33.5 m) with twocells connected in series. The cells were constructed by removing topsoil, sealing cell bottoms with 0.30 m of compacted clay,and covering with 0.25 m of loamy sand topsoil. One set of cells was planted with bulrushes (Scirpus americanus, Scirpuscyperinus, and Scirpus validus) and rush (Juncus effusus). The other set of cells was planted with burreed (Sparganiumamericanum)and cattails (Typha angustifolia and Typha latifolia). Wastewater flow and concentrations were measured at theinlet of the first and second cells and at the exit of the second cell for both the bulrush and cattail wetlands. Nitrogen waseffectively removed at mean monthly loading rates of 3 to 40 kg N ha 1 day 1 ; removals were generally >75% when loadingswere <25 kg ha 1 day 1 . In contrast, P was not consistently removed. Neither plant growth nor plant litter/soil accumulationwas a major factor in N removal after the loading rates exceeded 10 kg N ha 1 day 1 . However, the soilplantlitter matrixwas important because it provided carbon and reaction sites for denitrification, the likely major treatment component. SoilEh (oxidative/reductive potential) values were in the reduced range (<300 mV), and nitrate was generally absent from thewetlands. Furthermore, the wetlands had the capacity to remove more nitrateN according to denitrification enzyme activitydeterminations. Our results show that constructed wetlands can be very effective in the removal of N from anaerobiclagoontreated swine wastewater. However, wetlands will need to be augmented with some form of enhanced P removal tobe effective in both P and N treatments at high loading rates.