Virus removal from wastewater in a multispecies subsurface-flow constructed wetland

Virus removal was studied in a multispecies subsurface-flow constructed wetland. Tracer studies and a virus survival test were conducted using bromide and bacteriophage PRD1 that were simultaneously added into a 6-year-old gravel-filled wetland. The estimated dimensionless variance and the observed bromide breakthrough curve suggest a plug-flow reactor with some dispersion. Most of the PRD1 was removed during the first 4 days; however, the PRD1 background concentration was not reached by the end of the study. Average bacteriophage removal was 98.8%, whereas bromide mass recovery was 75%. The removal rate of PRD1 was estimated to be -1.17 d(-1); in contrast, its inactivation rate in situ for a 12.4-day period was -0.16 d(-1). Apparently, virus removal is governed by an initial irreversible attachment followed by a comparatively long inactivation period. This study suggests that a subsurface-flow wetland can decrease the virus load by approximately 99% with a 5.5-day detention time.