Studies On The Effects Of Plant Diversity And Substrate On Methane And Nitrous Oxide Emissions In Constructed Wetlands

With the growth of the population and economy, the amount of wastewater is increasing and greenhouse gas emissions draw more and more attention in the process of wastewater treatment. As a supplementary way of traditional wastewater treatment plants (WTPs), constructed wetlands (CWs) have the advantages of low greenhouse gas emissions. However, the total amount of CH4 emissions from CWs is still considerable as wastewater it treated is increasing dramatically. In order to find the approach that improves nitrogen removal while reducing greenhouse gases emissions during the process of wastewater treatment in constructed wetlands (CWs), we conducted a microcosm experiment simulating CWs. The experiment consists of two treatments. The first represented plant diversity (species richness level of 0,1,3,4 species and all possible plant species compositions), the other was sand substrate (fine sand and coarse sand). Results showed that (1) in coarse sand microcosms, plant species richness increased nitrogen removal and reduced N2O emission (P< 0.05), the effect of species richness on N2O emission was stronger than species identity, but species richness and species identity did not affect CH4 emission (P> 0.05); (2) in fine sand microcosms, species richness had no effect on CH4, N2O emissions and nitrogen removal, species identity surpassed species richness as a key driver of CH4 emission, and had no significant effect on N2O emission (P< 0.05); (3) the nitrogen removal and N2O emission in fine sand microcosms were higher than in coarse sand microcosms(P<0.05) and (4) Phalaris arundinacea monoculture in fine sand microcosms had a high N removal and low CH4 and N2O emissions, is the ideal plant-substrate composition of CWs.