Survival of Microbial Indicators In constructed Wetlands

Abstract

The purpose of this study was to evaluate the removal of bacterial and viral indicators in a constructed wetland system receiving secondarily treated sewage. Results along a multispecies raceway showed that coliphage and enteric bacteria were removed similarly. Among the enteric bacteria, fecal coliforms were removed to a greater extent than total coliforms and enterococci. No differences were observed in the survival of total coliforms in sunlight or shade. Fecal coliform inactivation, however, occurred more readily in the shade than in sunlight. The inactivation of PRD-lwas the same in either sunlight or shade. However, MS-2 was inactivated more readily in the shade than in sunlight. PRD-1 was more resistant to inactivation than MS-2. Laboratory survival experiments revealed that all tested indicators were more rapidly inactivated at 37°C than at 25° C. At 4° C, however, MS-2, PRD-1, and indigenous coliphage remained relatively stable after 32 days. Among the three, PRD-1 seemed to be the most stable. When exposed to direct sunlight at a constant temperature, PRD-1 was inactivated more rapidly than both fecal coliforms and indigenous coliphage.