Study On Immobilized Aerobic Denitrifiers For Bioremediation Of Black And Odorous Water

Black and odorous water is considered as a kind of polluted water which is difficult to be treated,and its restoration and treatment have aroused widespread attention in recent years.Nitrogen removal by aerobic denitrifying bacteria is thought to be a useful method,but at present,microbial denitrification including biofilm method is confronted with several problems such as low contact efficiency,aerobic denitrifying bacteria is hard to become dominant bacterium,bacterial body is easy to loss and it is difficult to recycle.In this study,aerobic denitrifying bacteria screened and domesticated from the natural environment was immobilized by sodium alginate and activated carbon,then added the immobilized strains to reactor to dispose black and odorous water,investigating its treatment process and effect and study reusable performance of the immobilized strains.The purpose of this study is to provide a theoretical basis for the application of immobilized aerobic denitrifying bacteria aimed at black and odorous water.The main research contents and conclusions of this thesis are as follows:1.Aerobic denitrification strains screened and domesticated from the natural environment were identified and its denitrification performance and the factors affecting the reaction were studied.The nitrate nitrogen removal rates of strains 1-6L and 2-4L were90.2 and 90.01%,the removal rates of total nitrogen were 75.75%and 79.74%,respectively.Two strains are gram negative bacilli,which belong to Pseudomonas sp.The strain can grow and react better in the environment which carbon nitrogen ratio is above 9,temperature of the medium is about 30 degrees and pH is neutral or weak alkaline.2.Aerobic denitrification strain 2-4Lwas immobilized by sodium alginate?SA?and polyvinyl alcohol?PVA?in order to compare the denitrification performance of different immobilized strains,then explored their optimum embedding conditions and environmental tolerance.The immobilized strain of sodium alginate and activated carbon had better nitrogen removal performance.The best embedding conditions of sodium alginate and activated carbon immobilized strain were mass fraction of sodium alginate,activated carbon and calcium chloride were 5%,0.5%and 4%,respectively,with crosslinking time 24h.The mechanical strength and the tolerance to pH of sodium alginate and activated carbon immobilized strains were slightly worse,but their nitrogen removal ability and efficiency were better under different oscillation intensity,temperature and pH conditions,so the sodium alginate and activated carbon immobilized strains were chosen to be the reaction units in reaction system.3.Immobilized reaction system was used to study the treatment process and effect of black and odorous water,and the recyclability of immobilized microorganisms were investigated as well.When using simulated wastewater,the reaction effect reached the best when the density of the suspended reaction units was 100g/L,the removal rate of COD_Crr reached 70.9%,NH₄-N⁺reached 74.7%and TN was 48.5%.Then the actual black and odorous water was treated under the optimum density of reaction units,after 24h,the removal rate of COD_Crr was 70.27%,NH₄-N⁺was 77.39%and TN was 51.19%.The reaction units kept high efficiency of pollutant removal rates after they were taken out to clean and repeat 5 times.It indicated that the sodium alginate and activated carbon immobilized strains could effectively reduce the loss of bacteria and the reaction system could not only guarantee the contact area but also realize the reutilization of the reaction units.