Microbial community structure stability, a key parameter in monitoring the development of constructed wetland mesocosms during start-up

Constructed wetlands (CWs) are known to be effective for treating waste streams, and pilot-scale CWs are useful for assessing the impact of pollutants and their remediation. However, little is known with respect to the establishment of these mesocosm systems or the parameters which should be monitored in assessing system equilibration, i.e. when they present stabilised physical and biological patterns. The aim of this study was to evaluate the temporal aspects of CW equilibration as a basis for future studies of system response to amendment. Microbial biomass and hydraulic conductivity values were monitored and microbial community fingerprints were obtained using denaturing gradient gel electrophoresis (DGGE). This study showed that microbial community fingerprinting provides a valuable tool for assessing the time scales of equilibration, as it was the last parameter which stabilised during the equilibration period. Hydraulic conductivity was also an important parameter in determining the time scale for initiation of the equilibration process during the study. For a CW of the dimensions used (173 cm long/106 cm large/30 cm depth), community equilibration times demonstrated on the basis of similar microbial community structures were found to be on the order of 100 days.