Bioremediation In Polluted River Water Treatment By Simulated River Bioreactor And Analysis Of Microbial Community

With the construction of urbanization and development of industry and agriculture,water resources are becoming contaminated badly,which poses a great threat to drinking water.Based on the investigation of the water quality of Lihe river,the start-up period of simulated river bioreactor operated by enhanced biofilm growing method and the controlling factors for the functioning of bioreactor were studied aimed at removalling nitrogen of Lihe river.The effects of HRTs and temperature on microbial community structure and functional microorganism in bioreactors were conducted in-depth discussions,selection of fillers and optimal operational parameters were determined at the same time,which can remediate the pollutants of Lihe river and provide some scientific basis and technical support for bio-remediation of water pollution in Lihe river,also provide referencing technique for bio-remediation of other similar rivers.The main results were shown below:?1?The performances of start-up period for bioreactors with suspended filler and elasticity plastic filler inoculated sediments and activated sludge respectively were examined.The results showed that the bioreactor with elasticity plastic filler started up earlier than that with suspended filler.In the steady running stage,the removal efficiencies of NH+4-N?COD_Mn and TN in four bioreactors reached 97%?80% and 40%⁵0% respectively.The biofilms attached on elasticity plastic filler has higher activity and more extracellular polymeric substances?EPS?.Aggregation test indicated that EPS of biofilms attached on the elasticity plastic filler was more conductive to aggregation.?2?Based on the stable running of bioreactor,the effects of hydraulic retention time?HRT?,temperature?T?and ratio of carbon to nitrogen?C/N?on removal performances for the functioning of bioreactors were studied.It's shown that the bioreactors had optimum efficiency at the condition of HRT=14.80 h,T=28 °C and C/N=11:1 based on the study of start-up period.The HRTs?11.90h?9.89h?7.99h?on removal performance was examined,the test results indicated that the removal performances of elasticity plastic filler were better than suspended filler in changing HRTs,which showed a stronger resistance to impact load.The biomasses and extracellular polymeric substances?EPS?concentration of the biofilms attached on elasticity plastic filler were more than the ones attached on suspended filler,which indicated that the biofilms attached on elasticity plastic filler had higher activity and more impacted structure due to the reason that hydrophilic functional groups immobilized more functional microbes.The temperature?24 °C?18 °C?10 °C?on removal performance was examined,the test results indicated that the removal performances of elasticity plastic filler still remained at a higher level in changing temperature.Being exposed to lower temperature,the microorganism secreted more EPS to protect themselves and the change of some fluorescence peaks of three-dimensional fluorescence spectrum confirmed this point,influencing the removal performances of biofilms.Also,the stronger fluorescence intensity of EPS from biofilms on elasticity plastic filler showed more substance concentration within biofilms.The C/N?7:1?11:1?16:1?ratio on removal performance was examined.When adding organic carbon resource to be 11:1 C/N ratio into bioreactor with elasticity plastic filler,the removal efficiencies of NH+4-N was remained about 90% and the effluent NO-3-N accumulated to about 2.5 mg/L,while the removal efficiencies of COD_Mn was improved to 90%,which indicated elasticity plastic filler possessed great advantage in denitrification.?3?The high-throughput sequencing from extracted genomic DNA were employed to reveal the similarities and differences of functional bacterium in four bioreactors at hydraulic retention time of 7.99 h.The ammonia oxidizing bacteria and nitrite oxidizing bacteria detected were Nitrosomonas and Nitrospira,the richness of Nitrosomonas in bioreactors inoculated sediments with suspended filler and elasticity plastic filler were 0.29% and 0.35% respectively,the richness of Nitrosomonas were both 0.47%.While the richness of Nitrosomonas in bioreactors inoculated activated sludge with suspended filler and elasticity plastic filler were 0.87% and 1.31%,the richness of Nitrospira were 2.01% and 2.21% respectively.All kinds of denitrifying bacterium were detected,the richness of denitrifying bacterium in bioreactors inoculated with suspended filler and elasticity plastic filler were 1.13% and 1.81%,while the richness of denitrifying bacterium in bioreactors inoculated with suspended filler and elasticity plastic filler were 2.50% and 2.98%.So elasticity plastic filler can immobilize higher proportion of denitrifying bacteria due to strongly hydrophilic groups,which showed a stronger resistance to impact load.There were 12 dominant bacterial community detected in bioreactor at 24 °C and 10 °C When the temperature was dropped from 24 °C to 10 °C,the richness of Nitrosomonas dropped to 0.63% from 1.11% in bioreactor with suspended filler,however,the richness of Nitrosomonas dropped to 0.41% from 0.96% in bioreactor with elasticity plastic filler inoculated river sediments,it can be seen that it still remained a higher proportion at lower temperature of Nitrosomonas due to the hydrophilic groups.However,Nitrospira turned into the dominant bacteria since lower temperature stimulated the growth of Nitrospira.Not surprisingly,the denitrifying process is extremely minus.