Study On Carbon Release Components From Woody Biomass And Utilization Degree In Denitrification Process

The structure and chemical compositions are complex for woody biomass.Its problems included slow denitrification rate and high organic residue when using as carbon source.Therefore,poplar wood was selected as the raw material,compositiones of lignin（RL）,neutral solute（NF）and hemicellulose（AF）were successively removed through chemical methods.Separation components were used for static carbon release experiment,and carbon release solutions during initial and relative stable period were used as carbon sources for denitrification experiments.Variation characteristics of solid components were identified through infrared spectroscopy and van soest method during carbon release process.Variation characteristics of dissolved components were identified by spectroscopy during carbon release and denitrification process.The chemical indexes of carbon and nitrogen were determined,and the kinetic equation of carbon release was fitted.The carbon utilization rate and carbon-nitrogen ratio（C/N）were analyzed under the conditions of woody biomass components in denitrification.Lastly,seepage column experiments were designed under the conditions of woodchip treatment degree,influent p H,and particle size.We measured carbon and nitrogen indexes,and also studied the influence of factors on denitrification efficiency and the problem by-products accumulation.The main results shown as follows.（1）The lignin removal rate was more than 96%for separation compositions,and the infrared spectrum absorption peaks disappeared at 1732 and 1251 cm^-1.The cellulose content reached more than 82%for AF and NF,and the intensity of infrared absorption peaks were significantly weakened at 1627 and 1051 cm^-1.In relative stable period,the carbon release rate reached 0.11 mg·（g·d）^-1 for natural woodchip（NW）,while RL,NF and AF increased to 1.8,1.4 and 1.2 times,respectively.The carbon release process accorded with the second-order reaction kinetic equation（R²>0.90）and the Ritger-Peppas kinetic equation（R²>0.98）.Tyrosine-like,tryptophan-like and fulvic-like substances were main products of carbon release.（2）The utilization efficiency of dissolved organic carbon（DOC）ranged from 38.1%-49.5%for products during initial carbon release after denitrification.For relative stable period products,the orders of DOC utilization efficiency were RL>AF>NF>NW,and reached 49.6%,45.5%,41.1%and 26.5%,respectively.The denitrification C/N ranged from1.0-1.5 under the conditions of excessive nitrate.The humification degree,molecular weight and aromaticity of carbon release products shown reduction after denitrification.The three-dimensional fluorescence spectrum mainly distributed among Ex/Em=200～242/274～375 nm for denitrification solution,which was tyrosine-like substance.（3）The average removal rate of nitrate reached 22.3 mg（d·L）^-1 for NW,while the rate increased to 2.3 and 3.8 times for RL1 and RL2 with increasing treatment degree,respectively.The DOC residue increased to 1.6 and 2.7 times for treatment woodchip.The DOC residue was low under the conditions of low influent p H and coarse particle size.The highest accumulation of nitrous oxide and nitrite appeared under low p H condition,and values reached 17595.0 ppm and 1.8 mg·L^-1,respectively.The highest ammonia reached 8.9mg·L^-1 in RL1 effluent.