Study On Purification Of Polluted River Water By The Mixed Culture Of Simultaneous Nitrogen And Phosphorus Removal Bacteria

River pollution has been a serious problem for a long time in China.Purification of polluted river water with simultaneous nitrogen and phosphorus removal bacteria has the advantages of low cost,high efficiency and eco-friendliness.Simultaneous nitrogen and phosphorus removal bacteria have both nitrogen and phosphorus removal functions under aerobic conditions,which has great application prospect in the purification of polluted water.In this study,simultaneous nitrogen and phosphorus removal bacteria were screened from the river sediments,and high-efficiency functional strains were mixed.The purification performance of the mixed culture and immobilized mixed culture on the polluted river water was studied.In this study,six functional strains with better nitrogen and phosphorus removal performance were successfully screened from the river sediments,using the selected enrichment medium.Among them,strain MC-1 belonged to Alcaligenes,MC-2 and MC-3 belonged to Achromobacter,MC-4 belonged to Thauera,MC-5 and MC-6belonged to Pseudomonas.The analysis of nitrogen and phosphorus removal performance on each single strain showed that the removal efficiency of nitrate by the strains MC-2,MC-3 and MC-6 was higher,which could reach 95.90%-100.00%.The strains MC-1,MC-4 and MC-5 had better removal performance on ammonia and total phosphorus,with removal efficiencies of 74.32%-87.09%and 35.76%-43.27%,respectively.The mixed culture obtained by mixing the six screened functional strains in equal proportions could effectively purify simulated polluted river water.Pseudomonas and Thauera were dominant bacteria,which played an important role.When the COD_Cr/TN ratio of the simulated river water increased from 7.16 to 12.72,the removal efficiencies of the ammonia,nitrate,total nitrogen and total phosphorus by the mixed culture could be significantly increased from 10.38%,82.09%,41.11%and45.78%to 64.26%,100.00%,70.43%and 61.70%.Water purification could be achieved within 72 hours when the dosage of mixed culture was 1.69-16.90 g/m³.The removal rates of total nitrogen and total phosphorus within 36 hours could increase from 0.047 mg/（L·h）and 0.005 mg/（L·h）to 0.091 mg/（L·h）and 0.016 mg/（L·h）.The mixed culture was prepared into an immobilized culture by the carrier binding method.Compared with the biochar,the immobilized culture with zeolite as the carrier had better nitrogen and phosphorus removal performance.The optimized zeolite immobilized culture was obtained by increasing the proportion of the three strains with better phosphorus accumulation ability in the culture.The removal efficiencies of the total nitrogen and total phosphorus by the immobilized culture could increase from 35.39%and 47.64%to 69.10%and 50.44%,respectively.In the three-cycle simulated river water purification experiment,the removal efficiencies of the total nitrogen and total phosphorus by the optimized immobilized culture were63.20%-69.75%and 29.92%-75.38%respectively,which were higher than the original immobilized culture.The optimized immobilized culture had higher relative abundance of the functional microorganisms,including Alcaligenes,Achromobacter,Thauera.This suggested that the immobilized simultaneous nitrogen and phosphorus removal culture in this study had application potential in actual river water purification.