Impacts Of Structure And Operating Load On Clogging And Microbial Of Constructed Wetlands

In recent years,constructed wetlands(CWs)as a green ecological new wastewater treatment technology has been widely concerned.However,it is very necessary and urgent to study the mechanism of CWs clogging and find the corresponding counter measures on the basis of the existing practice of construction in operation after a period of time.Therefore,this paper analyses the three factors influence of hydraulic load,organic load and suspended load in different flow field at three parallel small-scale experiment were monolayer(CW1),three multilayers(CW3 and CW6).Aiming at the comparison of three kinds of different media structure and load parameters under operating conditions,which caused accumulation of clogging process and the microbial community structure of distribution feature in Horizontal Subsurface Flow Constructed Wetlands(HSSFCWs).The main results were as following:1)In hydraulic loading rate of 0.16m/d and 0.80m/d,the influent loading was positively correlated with the purification load,hydraulic and pollutant loading significantly affected the removal rate of COD and TSS(p<0.05).Under the condition of the hydraulic loading rate of 0.16m/d and high pollutant loading,the removal efficiency of the system was the worst,while in the hydraulic loading rate of 0.80m/d,the bed load capacity was better.The difference between CW1 and CW6 system was significant,the highest and lowest removal rates of COD in the CW6 were 88.9% and 68.5%,respectively,and the highest and lowest removal rates of TSS were 85.8% and 65.3%,which compared to the removal of pollutants in the CW1 increasing by 7.3-22.7% and 8.0-20.7%.2)Studying the change of hydraulic performance of the system before and after the operating load.The results showed that in the condition of low hydraulic loading and high pollutant loading,the hydraulic performance of the system was worse.In the bed structure,due to that clogging and the formation of the "dead zone" are mainly in the surface,there was a "short flow" phenomenon in the bottom.The difference of the hydraulic performance between the CW1 and CW6 was significant,and CW1 system stability was poor.3)In the condition of low hydraulic loading and high pollutant loading,the results showed the composition and distribution of the clogging on filler surface,including the inorganic and organic matter,the microbial extracellular polymer and the number of bacteria on the filler surface.The result showed that component of accumulation in the inlet was more than the outlet of the bed,and the trend was gradually decreasing at the depths.The microbial extracellular polymers and bacteria showed similarity.Among them,insoluble organic matter and inorganic matter have great influence on the formation of matrix clogging.The difference of distribution of the clogging in the CW6 was smaller than CW1..4)The diversity and community structure of microbial populations in different locations of the bed were studied by high-throughput sequencing.The predominant bacteria flora were Proteobacteria,Bacteroidetes and Firmicutes in the CW1,CW3 and CW6 systems,which totally accounted for 81.51%,85.04% and 83.38%,respectively.There was significant difference for microbes from the surface to bottom layer in the inlet,the three predominant phylum were showing a gradual downward trend.Significant difference were found in phylum of the CW1.