REMOVAL OF PATHOGENIC AND INDICATOR MICROORGANISMS BY A CONSTRUCTED WETLAND RECEIVING UNTREATED DOMESTIC WASTEWATER
Journal of Environmental Science and Health, Part A , 36 , 2001

Quinonez-Diaz, M., Karpiscak, M.M., Ellman, E.D., Gerba, C.P.

Wetlands containingfloating , emergent and submergent aquatic plants, and other water-tolerant species have been found to economically provide a mechanism of enhancingthe quality of domestic wastewater. The use of constructed wetlands for the removal of indicator bacteria (total and fecal coliforms), coliphages, protozoan parasites (Giardia and Cryptosporidium) and enteric viruses was investigated. A pilot scale constructed wetland consistingof two cells, one planted with bulrush and the other unplanted bare sand, were used to compare their efficiency in removingpatho gens from raw sewage. Overall more than 90 percent of all microorganisms studied were removed by either of the two systems with a 1 to 2 day retention time. Removal of all mentioned microorganisms was greater from the surface flow in the unplanted cell than in the planted cell, except for Giardia and Cryptosporidium, although the differences were not statistically significant. Enteric viruses, coliphages and indicator bacteria were found to penetrate 2m below the surface, although concentrations were reduced by greater than 99 percent in both cells. Less virus penetration into the sand occurred in the planted wetland versus the unplanted wetland. Water temperature was found to be the most important factor in the removal of enteric bacteria and viruses, while turbidity reduction was related to Giardia removal. These results demonstrate that significant reductions of pathogenic microorganisms can occur in constructed wetlands receivinguntreat ed domestic wastewater with only a 1–2 day retention time.