Evaluating the effectiveness of a surface flow constructed wetland for the tertiary treatment of nutrients in wastewater during the first year of establishment

     Incomplete treatment of wastewater prior to discharge may compromise the water quality of downstream communities. In the developing world, a lack of wastewater treatment and subsequent contaminated water is... [ view full abstract ]

     Incomplete treatment of wastewater prior to discharge may compromise the water quality of downstream communities. In the developing world, a lack of wastewater treatment and subsequent contaminated water is responsible for millions of deaths each year. Constructed surface flow wetlands offer a low-maintenance and affordable alternative to traditional wastewater treatment for rural and undeveloped areas. This research examined concentrations of bacteria and nutrients in a constructed wetland used in the tertiary treatment, or “polishing”, of wastewater during the first 10 months following its establishment at the Sewanee Utility District. Effluent samples were collected from the final discharge of the current lagoon treatment system and in four locations representing different stages in the new wetland system. Total coliforms, E. coli, and different forms of nitrogen and phosphorus were measured four times within a 10-month period, immediately following wetland construction, and compared with final concentrations of effluent discharged from the lagoon system. Across the sampling periods, we found that total nitrogen and ammonia, as well as e-coli and coliform bacteria, were significantly reduced from the lagoon discharge point to the wetland outflow.  There was also a general trend of decreasing total and reactive phosphorus as effluent passed through the wetland, although the effect appeared to be seasonal.  Surprisingly, the wetland’s effect on nitrogen and bacteria remained significant under reduced flow throughout the winter months when the wetland plants were dormant.  These data demonstrate that during the first year of establishment, wetland processes represent an effective tertiary treatment to reduce nutrients and bacteria that would otherwise be released into the environment from the discharge of effluent treated in the traditional lagoon system at the Sewanee Utility District.