Influence of plant species and wastewater strength on constructed wetland methane emissions and associated microbial populations

Wastewater and treatment processes have been regarded as large contributions to sources of methane (CH4). The flux rate of CH4 in constructed wetlands (CWs) was evaluated to test the influence of plant species. Methane emission data showed large temporal and spatial variation ranging from 0 to 16.76 g CH4 m−2 day−1. The highest CH4 flux rate was obtained in the Zizania latifolia systems and higher emission was found with higher influent load. The methanogenic and methanotrophic microbial populations were studied to clarify the mechanisms of CH4 emission. FISH analysis showed highest amounts of methanogens and methanotrophs in the Z. latifolia and Tytha latifolia systems. Linear regression between CH4 emission and environmental parameters showed that the regression lines were not forced to pass through the origin, and the slopes of the lines of different systems were allowed to vary between vegetation cover.