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Constructed wetlands are a natural and passive treatment method for swine wastewaters. We have investigated swine lagoon wastewater treatment in both continuous marsh and marsh-pondmarsh (MPM) type constructed wetlands for their N and P treatment efficiency, ammonia volatilization, denitrification, and treatment system design. Neither type of wetland system was effective in the removing large quantities of P. Continuous marsh systems were able to remove more N than the MPM systems, particularly if planted to rushes/bulrushes (Juncus effusus, Scirpus validus, Scirpus americanus, Scirpus cyperinus). Plant and soil accumulations of N and P were important at very low loading rates; but as the loading rates exceeded 5 kg ha-1day-1, They became a small part of the removal process. Although, ammonia volatilization was present; it was generally <10% of the applied N in the marsh sections, and it was highly correlated to nitrogen concentration. However, the pond sections of the MPM systems had high levels of ammonia volatilization when loading rates exceeded 15 kg N ha-1 day-1. Water depth had a large impact on denitrification, as did the plant cover. Treatment efficiency was reasonably predicted by current modeling techniques used for municipal wastewater treatment in constructed wetlands.