Effects Of Plants On Nitrogen And Phosphorus Removal And Microbial Diversity In Rainwater Bioretention Ponds

Bioretention ponds technology is a stormwater runoff pollution control technology that has been widely used in controlling urban non-point source pollution and protecting urban hydrological environments.At present,the research on bioretention ponds mainly depends on the system design and the efficiency of pollutant removal.Few studies depends on the change of microbial structure of the three plant bioretention ponds of Iris pseudacorus L.,Canna indica L.and Lythrum salicaria L.,it is not conducive to improve the removal efficiency of nitrogen and phosphorus in these three bioretention ponds.To this end,this study carried out continuous operation tests on three different plant bioretention ponds and control system under simulated rainfall conditions.The results of experiments on the removal characteristics of nitrogen and phosphorus in the rainwater bioretention ponds showed that the plants would improve the hydraulic conductivity of the bioretention ponds.Hydraulic conductivity showed: Lythrum salicaria L.(0.0076 cm/s)> Iris pseudacorus L.(0.0071 cm/s)> Canna indica L.(0.0066 cm / s)> control group(0.0044cm/s).The average removal rate of total nitrogen showed: Canna indica L.(76.00%)> Lythrum salicaria L.(73.02%)> Iris pseudacorus L.(41.75%),the average removal of ammonia nitrogen showed: Iris pseudacorus L.(75.01%)> Canna indica L.(74.13%)> Lythrum salicaria L.(73.84%).The average removal rate of nitrate nitrogen showed: Canna indica L.(77.18%)> Lythrum salicaria L.(69.13%)> Iris pseudacorus L.(11.78%).The removal rate of total phosphorus showed: Iris pseudacorus L.(91.74%)> Lythrum salicaria L.(91.05%)> Canna indica L.(89.73%).The p H was expressed as control group(7.68)< Canna indica L.(8.08)< Lythrum salicaria L.(8.10)< Iris pseudacorus L.(8.13).During the steady-state the change of ORP showed: Canna indica L.(211.5)> Lythrum salicaria L.(208.8)> Iris pseudacorus L.(200.7)> control group(198.5).Soil urease activity is consistent with the removal of nitrogen from the system.Plants significantly increase the removal efficiency of total nitrogen,ammonia nitrogen and nitrate nitrogen,and have little effect on the removal efficiency of total phosphorus.ORP and bioretention tanks are positively correlated with the removal efficiency of total nitrogen and nitrate nitrogen.The results of microbial community structure analysis in the rainwater bioretention pond showed that the microbial composition in the same plant system was similar.In the control group,the dominant bacteria in the stable phase was Proteobacteria(64.5%),and the dominant genus was Sphingomonas(24.5%),while Iris pseudacorus L.system in the stable phase,the proportion of Firmicutes(20.2%)increased,the dominant genus is the Micrococcus(18.6%).Canna indica L.in the stable phase,the proportion of the Chloroflexi(6.4%)increased,the dominant genus is the Micrococcus(10.9%).Lythrum salicaria L.system in the stable phase,the proportion of the Chloroflexi(11.0%)and Saccharibacteria(11.9%)increased,while the proportion of Saccharibacteria(11.9%)increased from the genus.The high abundance of Bacillus and Acidobacteria has ideal effects on the removal of nitrate nitrogen,the high abundance of Chloroflexi has ideal effect on the removal of ammonia nitrogen,the removal of total phosphorus is mainly related to the medium.Through the research of this study,we can provide effective suggestions for plant selection and bacterial culture in the bioretention pool.