Comparison Research On Decontamination Effect Of Herbaceous And Woody Mode In The Subsurface Flow Constructed Wetland

Aim at the current situation of most of plant configuration in constructed wetlands using herb,we put forward to furnish woody plants on the basis of arrangement of herbs,so as to build the idea of composite plant model.The inflow water of this experiment is campus sewage,and test materials is Typha orientalis,Acorus calamus,Hibiscus mutabilis,Nerium indicum.The amount of subsurface horizontal flow constructed wetlands which have upper layer,middle layer and lower layer is 8.system 1-system 4 has only one kind of plant,Acorus calamus,Typha orientalis,Hibiscus mutabilis,Nerium indicum,respectively.system 5 has two kinds of herbs(Acorus calamus + Typha orientalis,),system 6 has two kinds of woody plants(Hibiscus mutabilis+ Nerium indicum),system 7 has two kinds of herbs and two kinds of woody plants(Typha orientalis+Acorus calamus+ Hibiscus mutabilis+ Nerium indicum.),system 8 is blank control.The rules of the decontamination effect happened with seasonal variation of the combined plant model and the single plant pattern are compared as well as the difference of the decontamination effect are studied,which contains the plant height,root characteristics,underground biomass,and the accumulation of nitrogen and phosphorus in root and underground soil,also the differences of phosphatase,urease activity and microbial diversity in the filler,and the correlation between these characteristic differences and the removal of pollutants,reveal the The dominant factor of the difference between the combined plant pattern and single plant pattern decontamination effect.The results of this study show that:(1)The CODCr,TN,TP removal rate and DO concentration of the plant-free system were significantly lower than those of the plant system(p<0.05)which indicate that plants play an important role in the removal of pollutants and the supply of dissolved oxygen to the system.(2)The CODCr removal rate of single system is more stable than that of mixed system,and the effect of CODcr removal of single system is less when it is winter,and the removal rate of TN and TP also showed that the average removal rate of single system was better than that of mixed system.(3)The CODCr,TN,TP removal rate and DO concentration of the herbaceous system was higher than that of the woody system at the beginning of the run,but after entering the winter,the phenomenon of woody plants>herbaceous plants appeared.(4)The CODCr,TN,TP removal rate and DO concentration decreased with the depth of the filler.The removal rate of pollutants in the upper and lower layers of the filler was found to be that the removal of CODcr and TP was concentrated in the upper layer of the filler,but the removal of TN was concentrated in the middle and lower layers of the filler.(5)The biomass of woody plants was significantly larger than that of herbaceous plants(p<0.01),especially the hibiscus.However,the growth of hibiscus was inhibited by oleander,and the survival rate and biomass were significantly lower than that of its single system.The same was true of the herbaceous plants,which was weaker when the mixture was mixed with the persimmon and also to the main reason why mixed system pollutant removal is less than a single system,so the same type of plant mixed species must be carefully considered.(6)The nitrogen and phosphorus contents of the woody plant system were significantly higher than that of the herbaceous system.The total phosphorus content of the underground part of the plant was significantly positively correlated with the TP removal rate at the level of 0.01,the positive correlation coefficient of removal rate is also higher.(7)There was a significant positive correlation between the activity of phosphatase and the removal rate of TP(p<0.05).And the activity of urease was positively correlated with the removal rate of TN(p<0.01),which indicated that urease and phosphatase were significantly correlated with TN and TP removal process which played an important role.(8)The bacteria has the most proportion in the three kinds of microorganisms,followed by actinomycetes,fungi is the least,and the number of microorganisms without plant system was 1-2 orders of magnitude lower than that of plant system(p<0.01).The number of microorganisms has a large effect on TP and CODCrand TN removal rate,which shows that the more the number of microorganisms,and the better removal effect on pollutants.