Enhancement Bacterial Population Structure And The Improvement Of Water Quality By Water-lifting Aerators In Lijiahe Reservoir

In order to explore the specific improvement effect of the water-lifting aerators（WLAs）on the water environment of Lijiahe Reservoir.Through the detection of water physical and chemical indicators and water quality indicators,combined with three-dimensional fluorescence spectroscopy-parallel factor method,high-throughput sequencing and ultraviolet-visible absorption spectroscopy,analysis of the reduction in the concentration of pollutants such as nitrogen and phosphorus and the reduction of organic matter.And explore the effect of WLAs on the microbial population structure and richness of the water source reservoir,and provide theoretical basis for in-situ improvement of water quality in water source reservoirs.The main research contents are as follows:（1）Analysis of the improvement effect of artificial forced mixing on the water environment of Lijiahe Reservoir.（2）Mechanism of in-situ reduction of organic matter in Lijiahe Reservoir by mixed oxygenation.（3）Effects of artificial forced mixing on bacterial community richness and diversity.The main conclusions are as follows:（1）The operation of the system can improve the anaerobic environment at the bottom and inhibit the release of endogenous pollution.In the three system operations in2021,the thickness of the thermocline was reduced by 93.86%,81.28%,and 68.77%,respectively,and the thermal stratified structure stability index（RWCS）was reduced by75.17%,39.71%,and 43.61%,respectively.The water-lifting aerators can effectively reduce the thickness of the thermocline,change the thermal stratification structure of the water body,and realize the homogenization of the surface and bottom water bodies.（2）During the three system operation periods in 2021,the mass of TN was reduced by 1.06 t,8.92 t and 19.82 t,and the mass of TP was reduced by 0.6 t,0.62 t and 0.4 t.The average concentration of TN and TP will be reduced by 2.8%,21.6%,6.9%and68.4%,38.5%,18.6%;the average concentration of ammonia nitrogen and nitrous nitrogen will be reduced by 28%62.9%,35.18%and 21.7%,60.9%,57.7%during the three system operations;the reduction rates of DOC and iron ion concentrations were2.1%,9%,0.5%and 81.8%,50%,75%during the three system operations.The water quality index（WQI）increased by 13,8,and 1and the TLI index decreased by 15,8 and1.The water environment gradually improved.（3）During the forced mixing process of water body,the metabolic activity of bacteria is strengthened,the degradation of organic matter and the proportion of high molecular weight DOM increase:The COD_Mn,DOC,a355,total fluorescence intensity,protein-like concentration（Fn（280））and humus-like concentration（Fn（355））are all reduced at different levels,and the organic matter concentration is reduced during the three operation phases of the water-lifting aeration system in 2020.UV-Vis absorption spectroscopy（UV-Vis）shows that E2/E3 and S_R have significant differences before and after system operation,and the proportion of large molecular weight DOM including humus increases;The three-dimensional fluorescence spectroscopy-parallel factor analysis method（EEMs-PARAFAC）showed that the humification index（HIX）decreased,the self-generating index（BIX）increased,and the degree of humification of the water body weakened during the operation stage of the water lifting aeration system.（4）The operation process of the water-lifting aeration system promotes the increase in the number and activity of beneficial bacteria that degrade organic matter,nitrogen and phosphorus and other pollutants,which is beneficial to the improvement of the water environment.Analysis of the bacterial community structure found that all bacteria in the sample belonged to 54 phyla,160 classes,350 orders,567 families,1005 genera and 1860species.Among them,the main dominant bacterial communities at the phylum level are Proteobacteria,Actinobacteria,Bacteroides,Cyanobacteria,and Acidobacteriota;The dominant bacterial communities at the genus level are CL500-29＿marine＿group,hgc I＿clade,etc.The operation of the water-lifting aerators（WLAs）promotes the growth of beneficial bacteria such as hgc I＿clade,CL500-29＿marine＿group,Flavobacterium,Acinetobacter,and Pseudomonas,which is conducive to the improvement of water quality.the Shannon indices of the surface,middle and bottom layers increased by 3.28%,3.73%and 6.57%,respectively.The Simpson index of the water body decreased by 0.003and 0.0155 in the surface and middle layers,respectively.The ACE index and Chao1index of surface,middle and bottom water bodies increased by 3.55,3.16 and 6.16 times and 2.79,1.51 and 4.97 times respectively compared with the initial period of operation,The metabolic activity of bacteria and microorganisms is strengthened.