Study On Nitrogen Removal Pathway And Mechanism Of Improved Constructed Rapid Infiltration System

In this paper,Modified Constructed Rapid Infiltration system,CRIS is used to treat wastewater,to study the removal effect of artificial rapid infiltration systems under different structures on pollutant removal;the factors that affect the removal effect of COD and TN under different process operating conditions;from the perspective of enzymes and microorganisms The nitrogen metabolism pathway and mechanism of the improved CRI system were analyzed;the distribution of genes corresponding to related enzymes was explained from the perspective of genes;and the nitrogen metabolism law of the same type of improved CRI system during the drying period was studied,and the following conclusions were drawn.in conclusion:（1）In the experiment of percolation rate on the transformation of various forms of nitrogen,the percolation rate has obvious effect on the transformation of various forms of nitrogen.The faster the percolation rate,the lower the total nitrogen removal rate,the greater the nitrite nitrogen production,the The smaller the amount of nitrate produced;in CRIS at different heights,the removal efficiency of total nitrogen is related to the percolation length.The longer the percolation length,the better the total nitrogen removal efficiency.The average removal rate of total nitrogen in the long column is19.25%;in the experiment with or without the adsorption packing layer,the CRIS with the adsorption layer has better COD removal rate than the two columns without the adsorption layer,and the COD removal rate with or without the adsorption packing No apparent effect.The total nitrogen removal rate of the percolation column with adsorption packing is higher than that of the percolation column without adsorption packing layer;in the experiments of different packing layers,the type of adsorption packing has no obvious effect on the removal of COD and total nitrogen.In the same improved CRI system,under the condition of constant hydraulic load,the average removal efficiency of COD in artificial rapid infiltration will decrease slightly after changing the number of water inflows from 1 time/day to 2 times/day.it will also have a certain impact on the stability of COD removal.Changing the influent frequency could not improve the average removal rate of total nitrogen,but when the inefficient period appeared,it could effectively maintain the TN removal rate in the inefficient period.After increasing the hydraulic load,the average removal rate of COD by the artificial rapid infiltration system increased slightly,from 87.50% to 92.52%.The average removal rate of total nitrogen also increased slightly,from 25.52% to 31.42%.After increasing the carbonnitrogen ratio of the influent,the artificial rapid infiltration system did not have much influence on the average removal rate of COD,and the average removal rate of total nitrogen was greatly improved.（2）In the EPS content analysis of the filler,the relationship between the protein（PN）content is the lower adsorption filler layer > the upper adsorption filler layer > the bottom sand layer;the size relationship of the polysaccharide（PS）content is the upper adsorption filler layer > the lower adsorption filler layer> bottom sand layer;EPS content relationship is upper adsorption packing layer >lower adsorption packing layer > bottom sand layer;PN/PS ratio is small;in 3D-EEM,all parts of the filler have characteristic areas peak A（Ex/Em=250/280 nm）;the characteristic region peak B（Ex/Em=290/310 nm）can be observed for loosely bound EPS（LB-EPS）at all positions;In A,the size distributions of urease activity and hydroxylamine oxidase activity are the highest in AU and the lowest in AD;the distributions of nitrate reductase and nitrite reductase activities are both the highest in AD and the lowest in A;in long column C,the activities of urease and nitrate reductase are The size distribution of CD was the highest and the bottom of C was the lowest;the size distribution of hydroxylamine oxidase activity was the highest in CU and the lowest in CD;the size distribution of nitrite reductase activity gradually increased from top to bottom.（3）The dominant bacterial phyla in the artificial rapid infiltration system include Acidobacteria;Bacteroidetes;Chloroflexi,etc.Classes with relatively high relative abundance include Alphaproteobacteria,Betaproteobacteria,Gammaproteobacteria and so on.The genera with higher abundance ratio include Ammoniphilus,Saccharibacteria＿genera＿incertae＿sedis,Nitrospira,Plasticicumulans,Gp16,etc.In the internal and external 16 s high-throughput analysis,they are distributed in the order of outer（CUO）and inner（CUI）,Dominant bacteria phyla include Proteobacteria（57.77%）（61.01%）;Bacteroidetes（25.78%）（21.53%）;unclassified＿Bacteria（4.89%）（4.59%）,etc.;dominant genera include Saccharibacteria＿genera＿incertae＿sedis（4.59%）（2.13%）;Acinetobacter（1.19%）（1.10%）;Enterobacter（1.78%）（0.43%）etc.In the KEGG metabolic pathway analysis of the artificial rapid infiltration system,there are relatively stable genes in the artificial rapid infiltration system that control nitrification,denitrification,assimilation nitrate reduction and dissimilatory nitrate reduction;The rate of nitrification,denitrification,dissimilatory nitrate reduction and assimilated nitrate reduction in the artificial rapid infiltration system will increase after the water COD concentration.（4）The adsorption capacity of sand for ammonia nitrogen,nitrate nitrogen and nitrite nitrogen is relatively small;the saturated adsorption capacity of activated carbon for ammonia nitrogen is about12 mg/g,and the adsorption capacity for nitrate nitrogen and nitrite nitrogen is both.Relatively small;ammonia nitrogen fluctuates less with time during the dry period of the all-sand percolation column,showing a slow upward trend as a whole.The change curves of nitrate nitrogen and nitrite nitrogen concentrations within 0-12 h were also chaotic,and the fluctuations between each time point were large and the trends were not uniform.However,in 12-24 h,the concentration of nitrate nitrogen gradually decreased,and the concentration of nitrite nitrogen increased slowly,which may have occurred denitrification.The ammonia nitrogen in the artificial rapid infiltration system with adsorbent fillers decreased as a whole within 0-6 h during the drying period.The overall trend of ammonia nitrogen in 6-24 h was in a flat trend,indicating that the amount of ammonia nitrogen that could be metabolized during the drying period may have reached the maximum.In 0-15 h,the nitrate nitrogen concentration was in an overall upward trend from 0 mg/L,while in 15-24 h,the nitrate nitrogen concentration was in a downward trend and decreased to 0 mg/L.During 0-15 h,the nitrite nitrogen concentration decreased from the overall trend and decreased to 0 mg/L at the 15 th h,while the nitrite nitrogen overall increased and decreased during 15-24 h.