Study On Enhanced Nitrogen Removal Characteristics Of Artificial Wetland With Slow-released Solid Carbon Source

In this researcheasily biodegradable PCL/starch blends and PLA/starchblends,uncomfortably biodegradable PBS and PHBV/PLA blends were used as solidcarbon source, characteristics of denitrification was studied in shake flaskexperiments and artificial wetland. And this research analyzed the gaseous product,DOC, microbial community structure and space distribution of the microorganismsinside the biofilm. The conclusions of this research are as the following:(1) Biodegradability of solid carbon source was the key factor to influence theproperties of denitrification. Start time of easily biodegradable solid carbon sourcesystem was short, and denitrification rate was fast. In shake flask experiments, starttime of PCL/starch blends and PBS system were1d and33d respectively. Afterstart-up the denitrification rate was respectively7.15and5.33mg/(L·h). In solidcarbon source and inert carrier gravel mixed system, the biofilm on the surface of thegravel could proceed denitrification taking advantage of DOC in the water, and theextracellular enzymes secreted also involved in the degradation of solid carbonsource.(2) The N2O conversion rate of denitrification system of PCL/starch blends, PBS,PHBV/PLA blends, and PLA/starch blends were0.13%,0.23%,0.26%and3.36%respectively; N2O conversion rate was positively correlated with the concentration ofNO2--N; negative correlation with the pH value; while the temperature had littleinfluence upon the N2O conversion rate in the system.(3) Denitrification reaction mainly occured in solid carbon source populated areain artificial wetlands using PCL/starch blends and PHBV/PLA blends as carbonsource. The denitrification rate was94.84and36.36g/(m3·d) respectively. The mainingredients of DOC were sugar, protein and humic. Humic acid, protein along in thesystem of PCL/starch blends was on the rise, while reducing sugar along decreased.(4) Nitrite reduction rate was higher than nitrate reduction rate in denitrificationsystem using PCL/starch blends as carbon source. When water without ammonianitrogen, the system through the process of DNRA to produce ammonia nitrogen asnitrogen source. When there was ammonia nitrogen in water, the process of DNRAwas restrained. (5) The advantage species on the division level on the surface of PCL/starchblends and PHBV/PLA blends were Proteobacteria, Firmicutes and Chbroflexi. Andthe advantage species on the genus level wasBacillus. The microbial communitystructure of biofilm on gravel surface had similarity with corresponding carbonsource.(6)Bacillus and Acidovorax in the surface biofilm of PCL/starch blends mainlyexisted in the biofilm surface. WhileDesulfovibrio andAlicycliphilus mainly existedin biofilm near the location of the carbon source. Bacillus and Dechloromonas in thesurface biofilm of PHBV/PLA blends mainly distributed in the surface of the biofilm,and Acidovorax was relatively uniform distribution.