Efficiency of natural systems for removal of bacteria and pathogenic parasites from wastewater.

A combined constructed wetland formed by a facultative pond (FP), a surface flow wetland (SF) and a subsurface flow wetland (SSF) was studied from December 2004 until September 2005 in north-western Spain in order to evaluate their efficiency in the removal of pathogenic and indicator microorganisms and to determine their relationships. Microbial removal ranged from 78% for coliphages to over 99% for helminth eggs, depending on the treatment system. The highest removal of indicator bacteria (total coliforms, E.