Research On Methane Emissions Reduction By Vertical Flow Constructed Wetland Treating Wastewater

As the global climate is undergoing significant changes in warming-oriented, control of greenhouse gas emissions are important issues and tasks around the world have to face. Methane as one of the major greenhouse gases in the atmosphere, has been widespread concern in the scientific community. In the source of atmospheric methane, wetlands are most important source of methane emissions in the nature. In recent years, artificial wetland system are increasingly being used for the treatment of domestic sewage, industrial waste and agricultural runoff, due to low energy consumption, low cost, low operating costs and simple operation. But wetland is bound to release methane into the air in the sewage treatment process due to it characteristics. In this study, based on weak oxygen capacity of artificial wetlands, methane emissions reduction effect of wetland when adding natural manganese ores has been studied, wetland methane abatement system driven by manganese has been builded, new methods and theoretical guidance for wetland methane emissions will be provided.This experiment studies the pollutant removal efficiency and methane reduction effect of manganese artificial wetlands and gravel wetland. Questions of the carbon flow within the wetland system has analyzed, through carbon balance calculations in two wetland systems. And the methane-producing bacteria group and bacterial diversity within two sets of wetlands were analyzed.The key results and conclusions were as follows:（1） Manganese wetland system was better for the removal of contaminants. Among them, COD removal efficiency of manganese wetland is very high, reaching 92.60%; the same circumstances, ordinary gravel wetland system also has 89.73%. Two wetland systems for the removal of nitrogen is not ideal, TN removal rate declining over the running time, the end of the experiment natural manganese and ordinary gravel wetland only about 25% and 10% of TN removal. Manganese wetlands in terms of phosphorus removal effect is obvious compared to gravel wetlands, two wetland system TP removal rates were 95.55% and 12.93%. In general, manganese wetland carbon,nitrogen and phosphorus removal is better than gravel wetland.（2） Methane emission reduction has a significant effect in the manganese ore filler wetlands. Manganese constructed wetland reduced methane gas emissions more than 90% compared with gravel wetland. Average methane emission flux of gravel wetland was 2558.9±536.7 mg·m^-2·^d-1. The average methane fluxes of manganese wetland only 46.7±19.3 mg·m^-2·^d-1. With respect to the results of other studies, this study has more obvious methane emissions reduction for constructed manganese artificial wetland system.（3） Through carbon balance experiment, Two wetland system compared to the carbon output difference is mainly reflected in the wetland methane emissions. Gravel wetland system discharges CH4-C to the gas phase is 164.4mg, 16.5%, manganese wetland CH4-C only 2.6mg, accounting for 0.26%. Since the accumulation effect matrix, manganese group matrix carbon storage but also larger than normal gravel group.（4） Two artificial wetland system are present methanogens, belongs methane Sarcina. Two wetland bacteria have significant difference, manganese wetland system contains a large number of metal-reducing bacteria: anaerobic stick bacteria（Anaeromyxobacter） and to the genus（Geobacter）, and the presence of nitrogen and certain related species abundance. In contrast, the gravel wetlands microorganisms to remove organic matter is mainly based bacteria. The presence of gravel wetlands certain amount of aerobic methane oxidizing bacteria, and manganese wetland is almost no such bacteria.