Odor-reduction in swine wastewater constructed wetland

Odor-reduction capability of agricultural wastewater treatment wetlands has been primarily anecdotal and presented as a benefit beyond the already widely recognized attributes of treatment wetlands. The featured project's objective was to determine long-term performance features of an odor-reduction wetland system in an on-farm application. A "rock and reed", subsurface flow wetland system was designed and built at a swine production facility and provided continuous manure treatment for almost two years. The wetland system was protected by an inexpensive greenhouse structure for year-round operation in a cold climate. Filtered manure wastewater was generated with a "bark filter". Using a mixture of this reduced-solids swine manure from a scraped swine grow-finish facility and tap water, wastewater was fed to the constructed wetlands at a rate providing a four day hydraulic retention time.Each part of the entire system (solids reduction, tap water dilution, and wetland treatment) contributed to the overall success in reducing odors. The most significant odor reduction occurred in the wetland treatment. A trained human odor assessment panel determined that odor reduction was significant in terms of intensity and pleasantness. Odor reduction was achieved at all trial dilution levels from 0.21 to 0.53% solids swine wastewater solutions. The wetland plants appeared to be a key component for successful year-round odor reduction and this wetland system documented Scirpus survival in wastewater solutions with up to 1000 ppm ammonium.