Effects of Micro-Nanometer Aeration on Nitrogen Removal by Plant Floating-Beds

The effects of micro-nanometer aeration on the nitrogen removal of a Thalia dealbata floating-bed was investigated by comparing the nitrogen removal of a group with three treatments of micro-nanometer aeration,a group with air blow aeration and a group without aeration(the control group).The results showed that compared with the group without aeration,the removal rates of TN and NH4+-N were increased by 13.35% and 21.72%,respectively,in the micro-nanometer aeration plant floating-bed,and increased by 5.64% and 10.61%,respectively,with the air blow aeration method.However,the high concentrations of DO formed by the micro-nanometer aeration had a negative effect on the removal of NO3——N.The removal rates of NO3——N in this group were lower than those of the air blow aeration group and the control group.By comparing the results from the micro-nanometer aeration group with those from the control group,micro-nanometer aeration was found to significantly improve the growth of plants.By the end of the experiment,the biomass in this group had increased by 65.38%,while the biomass increase in the air blow aeration group and the control were 21.05% and 63.93%,respectively.The total nitrogen uptake by the plants was also different among the treatments.The highest uptake of TN was obtained in the micro-nanometer aeration group(90.60 mg),compared to 54.84 and 63.42 mg in the air blow aeration and the control group,respectively.In conclusion,micro-nanometer aeration was the most effective way of increasing DO,changing the microenvironment of the rhizosphere,and enhancing the growth of ammonifying and nitrifying bacteria,but it retarded the growth of the denitrifying bacteria.