PATHOGEN AND PATHOGEN INDICATOR REMOVAL CHARACTERISTICS IN TREATMENT WETLANDS SYSTEMS

This paper reports the performance of two horizontal subsurface flow constructed wetland systems in the removal of pathogen and pathogen indicators under variable loading and operating conditions. The two constructed wetland systems evaluated under this project are located near Lincoln, Nebr. Firethorn is located in a small housing community and Rogers Farm at a rural single-family dwelling. Samples at Firethorn were collected at the wetland cell influent, effluent, and sand filter effluent (system effluent) from June 1996 through April 2000 and at the influent and effluent points from Rogers Farm from June 1999 through April 2000. The main monitoring parameters were fecal coliform at both sites and Salmonella spp. (from August 1999 through January 2000) at Firethorn. Firethorn demonstrated effective removal of fecal coliforms with 96.3% removal in the wetland cell and 98% by the wetland system, which included a sand filter. Rogers Farm had an average fecal coliform removal of 99.3%. Although Salmonella spp. was not detected at Firethorn, reduction of other bacteria was observed through the wetland system. In general, fecal coliform removal was excellent through the wetland system and no distinct difference in removal efficiency was observed with changes in season and temperature at either facility.