Study On Characteristics Of Microbial Flora And MBR Process Of Tungsten Smelting Wastewater

The large amount of rare and rare earth high-salt ammonia nitrogen wastewater and the difficulty of treatment have become hot topic and difficulties in the field of water treatment.The physical and chemical methods have the disadvantages of high cost and secondary pollution.Due to the influence of salinity,the traditional biological method is difficult to treat it efficiently.MBR has advantages that traditional biological methods does not have,and provides an opportunity to improve the treatment efficiency of high-salt ammonia nitrogen wastewater.In this paper,Tungsten smelting wastewater is taken as the research object,focusing on the characteristics of microbial flora and the influence of pollutants removal in the MBR process of tungsten smelting wastewater.The experimental results show that:（1）Salinity has a great imfluence on conventional activated sludge,which restrains the activity of sludge and affects the nitrification performance.The sludge oxygen consumption rate（SOUR）and sludge specific nitrification rate（SNR）decrease with increasing salinity.At3.0%salinity,SOUR was only 50.6%of that in non-salt environment,and nitrification almost stopped.SEM-EDS analysis shows that the salinity destroys the microstructure of the sludge,the round granular material formed on the sludge surface decreases with the increase of salinity,the C element increases with the increase of salinity,and the opposite of the Si element,which may be related to salinity disrupting the structure of sludge flocs,lysis and characteristic enzyme activity.（2）During the salt-tolerant domestication of sludge,the sludge floc gradually became small and compact.Sludge volume index（SVI）decreased with the increase of salinity,and sludge settling performance improved.Salinity increased from 0 g/L to 30 g/L,and SVI decreased from 111.5 mL/g to 65.3 mL/g.At the beginning of domestication,the removal rate of COD and NH₄⁺-N was greatly affected by salinity.As the microorganisms gradually adapted to the high salt environment,the removal rate increased.The removal rate of COD is86%⁹5%,and that of NH₄⁺-N is 81%⁸5%,NO₂^--N and NO₃^--N concentrations fluctuate greatly due to the effects of salinity.（3）EEM comparison analysis of SMP and EPS of sludge samples before and after salt-tolerant acclimation showed that:salinity increased,the number of fluorescence peaks and fluorescence intensity increased,indicating that microorganisms secrete more SMP and EPS to resist high osmotic pressure.（4）Increased salinity leads to decrease of microbial diversity.Proteobacteria,Bacteroides,Curvularia,Bacillus,Phytophthora,Flora and Phytophthora are the main microbial community structures in the system,Pseudomonas,Paracoccus,Halomonas,Taoer and Nitrosomonas have become the main dominant bacteria.They have good organic matter removal and nitrification or denitrification performance,and show varying degrees of salt tolerance.（5）The removal rate of COD and NH₄⁺-N by the system generally shows that it increase with the increase of HRT and DO values within a certain range.When DO is 2.0 mg/L,the system shows good simultaneous nitrification and denitrification performance.The removal of COD and NH₄⁺-N by the system is not affected by C/N changes,but increasing C/N within a certain range is beneficial to the system denitrification.The response surface method was used to analyze the efficiency of NH₄⁺-N removal,Under the conditions of hydraulic retention time of 20.51 h,carbon-nitrogen ratio of 6.88 and dissolved oxygen concentration of 3.25mg/L,the removal rate of NH₄⁺-N can reach to 90.4%.