Molecular characterization of microbial communities in constructed wetlands: The effect of plant species, organic matter and hydraulic design

© 2015 Nova Science Publishers, Inc. Constructed wetlands are becoming an interesting alternative for wastewater reuse since high concentrations of contaminants and pathogenic microorganisms can be removed with these natural treatment systems. In this study, experimental constructed wetlands treating diluted wastewater were used to study the effect of plant species (Typha angustifolia or Phragmites australis), hydraulic design (free-water flow or sub-subsuperficial flow) and organic loading (3 or 9 gBOD5/m2/d) on the microbial composition of the rhizoplane, gravel biofilm and interstitial water. The analysis of DGGE band patterns showed statistically significant differences in community assemblages between plant species. Hydraulic configuration, and plant presence in a lesser extend, were more important than organic load in shaping microbial communities in the studied wetlands. Distinctive communities were found for roots, gravel biofilm and interstitial water inside the same mesocosm, being differences among these communities higher for Phragmites than Typha planted tanks. Plants had an effect on all the microbial communities studied into the mesocosms, proving that their influence affect interstitial water and gravel-associated bacteria far beyond their roots. Environmental conditions, mainly redox, are suggested as main driving forces in organizing microbial assemblages in the studied wetlands.