Study On Pollutants Removal From Low Polluted Water By Integrated Vertical-flow Constructed Wetland

Low pollution water is the main factor leading to eutrophication of water body,which can't be treated well by the traditional sewage treatment plant.In the study,Integrated Vertical Flow Constructed Wetland system was used to treat simulated low pollution water,According to monitor the water parameters and the structure,species of microorganisms in the system,the removal effect and transformation of CODMn,nitrogen,phosphorus and Structural characteristics and abundance variation of microorganisms were studied.The influent water quality configurated were as follows: CODMn concentration was4.81-5.40mg/L,TN concentration was 11.45-12.35mg/L,NH4+-N concentration was4.96-6.88mg/L,NO3--N concentration was 2.18-4.75mg/L,TP concentration was0.38-0.54mg/L.System flow was 41.7mL/min,The operation cycle were 10 days for flooding water and 2 days drained.The system was in the greenhouse,the average temperature was25?,the operating period was 2016.01-2016.11.The main results are as follows:The cycle test showed the concentration of CODMn and ammonia nitrogen gradually decreased along the direction of water flow,concentrations of TN and TP decreased first and then increased,the removal efficiency of TP in 1# and 2# pool of the front unit is the best,TP release and nitrate accumulation occured in the 3# and 4# pools of the posterior unit.The DO concentration of effluent and the CODMn removal rate are parabolic functions,environmental conditions have a certain impact on the system purification effect.The results of long-term pollutant removal monitoring indicated that The average removal rates of CODMn,TN,NH4+-N and TP were respectively 36.76%,28.29%,94.34%,58.53%.The average effluent concentration of ammonia nitrogen was lower than the levelof grade-? standard of surface water.NH4+-N was removed mostly by nitrification,denitrification,adsorption and ion exchange of zeolite.While NO3--N accumulated gradually in the system,the nitrification was more active than the denitrification,because the carbon source was too lower,denitrification was limited and TN removal rate was not high.The average effluent concentration of TP was removed mainly by adsorption of zeolite and microbial action,The phosphorus was resolved in the rear cell pool.The microorganisms of different zeolite samples in wetland system were analyzed by High Throughput Sequencing,the microbial community structure and abundance of zeolite were analyzed from phylum and genus two aspects,the results showed that: all 22430 sequences belong to 36 phylums of bacteria,the main phylums include Proteobacteria,Acidobacteria,Cyanobacteria,Deinococcus-Thermus,Actinobacteria,Bacteroidetes,which were dominant bacteria,and the proportion were respectively 53.32%,8.78%,8.73%,8.13%,6.72%,4.84%.On the basis of the bacterial phylum,the distribution of microbial genus in the samples were analyzed,among them,the dominant genus had Sphingomonas(9.31%),Deinobacterium(6.70%),Sphingorhabdus(10.04%),Luteimonas(4.18%),Pseudomonas(4.03%).There were differences in microbial community structure between different sites andtimes,this had a certain effect on the removal of contaminants in the system,Luteimonas is a kind of denitrifying bacterium and Pseudomonas is a kind of denitrifying phosphorus accumulating bacteria,two kinds of genus contribute to denitrification in the system,in addition to the Nitrospira genus which contributes to nitrification,the mechanisms of removal of pollutants in low-polluted water by Integrated Vertical-Flow Constructed Wetland were further explained from the perspective of microorganisms.