Reduction of enteric organisms in small scale, subsurface flow constructed wetlands

Abstract

Constructed wetlands can play a critical role in wastewater treatment for rural areas. It has been demonstrated that large constructed wetlands are useful in the reduction of enteric microorganisms. This study evaluated the ability of three small scale, subsurface wetlands to remove total coliforms, fecal coliforms, bacteriophage, Giardia, and Cryptasporidium. These wetlands have three different vegetation densities: no vegetation, partially vegetated, and completely vegetated. Influent and effluent water samples for each wetland were tested for the presence of the microorganisms. In the wetland with no vegetation, total coliform, fecal coliform, bacteriophage, Giardia, and Cryptosporidium percent reductions were 93.5, 95.4, 61.5, >97.8, and 77.1, respectively. In the partially vegetated wetland, percent reduction of total coliforms, fecal coliforms, bacteriophage, Giardia, and Cryptosporidium were 91.0, 96.1, 86.6, >98.6, and >44.3, respectively. Percent removal was greatest in the wetland that was completely vegetated. Total coliforms were reduced by 97.3 percent, fecal coliforms by 99.5 percent, and bacteriophage by 97.1 percent. These results indicate that small scale constructed wetlands can be useful in wastewater treatment and that vegetation may play a role in enteric microorganism removal.