Study On Performance Of Agricultural Non-point Source Pollution By Functional Matrix Strengthening Vertical Flow Constructed Wetland

At present,with the advancement of pollution control work in China,the proportion of agricultural non-point source pollution in China's environmental pollution is growing.In this thesis,four kinds of vertical subsurface flow artificial wetland outdoor simulation devices were constructed for runoff pollution caused by agricultural non-point source:Soil matrix vertical subsurface flow constructed wetland(CW1).Straw and soil matrix vertical subsurface flow constructed wetland(CW2).Water supply sludge,activated sludge,straw and soil matrix vertical subsurface flow constructed wetland(CW3).Water supply sludge,digested sludge,straw and soil matrix vertical subsurface flow constructed wetland(CW4).The operation characteristics of these constructed wetlands for treating the simulated wastewater were studied.The elemental composition analysis,microbial community structure identification,and the crystal phase analysis and phosphorus adsorption performance evaluation of the feed water sludge were carried out for the typical sludge and soil samples in the vertical subsurface flow constructed wetland operation.The results obtained are as follows:Starting up 4 vertical subsurface flow constructed wetlands with fixed hydraulic retention time.COD removal rate is 49.12%?61.12%,TN removal rate is 45.310%?72.5%and TP removal rate is 47.67%?80.33%.Temperature and HRT were the key influencing factors in the treatment of runoff pollution simulated wastewater in four vertical subsurface flow constructed wetlands.Among them,the temperature is about 20? and HRT=48 h.The effluent water quality can meet the first-class emission standard stipulated in GB8978-2002.The operation effects of CW3 and CW4 are better than those of CW1 and CW2,indicating that the addition of sludge and the construction of root holes have significantly enhanced the removal effect of the constructed wetland system.At low temperature,the four vertical subsurface flow constructed wetlands also have certain treatment effects,which can meet the primary and secondary emission standards specified in GB8978-2002,indicating that the vertical subsurface flow constructed wetlands have certain low temperature resistance.XRD analysis showed that the feed water sludge contained a certain amount of aluminum and iron oxide,and its static adsorption saturation capacity for inorganic phosphorus was 8.33 mg/g.The activated sludge added in CW3 and the digested sludge added by CW4 will be cultivated and enriched in microorganisms during wetland operation.Among them,a large number of Protcobacteria and Bacteroidetes were found in the activated sludge and digested sludge matrix.Most of these bacteria can be denitrified.In addition,there are also methanosaetaccae and inethanobacteriaccae in these sludge matrices,all of which belong to the anaerobic methanogenic archaea.The above results indicate that the sludge layer of the vertical subsurface flow constructed wetland can be denitrified and methanogenic.Combined with the research results of this paper,the water quality characteristics of agricultural non-point source runoff wastewater in the Three Gorges reservoir area,the unit structures of surface flow constructed wetland(SFW),horizontal subsurface flow constructed wetland(HFW)and vertical subsurface flow constructed wetland(VFW)with influent water volume of 50 m3/d was designed,and draw the corresponding design drawings.Among them,the pollution load of vertical subsurface flow constructed wetland is 80 kg/(hm2·d).It is expected that the removal rate of BODs in the vertical subsurface flow constructed wetland is 50%.