Study On The Performance Of MBR In Treating Tungsten Smelting Wastewater And Establishment Of Activated Sludge Model

The rapid development of China’s tungsten smelting industry has resulted in the production of a large amount of tungsten smelting wastewater.Because of its high inorganic salt concentration and low carbonnitrogen ratio,so it is of great significance to study the technology of efficient and stable treatment of tungsten smelting wastewater.Membrane bioreactor(MBR)has the characteristics of small footprint,stable effluent quality and high sludge concentration,which provides the possibility for efficient treatment of tungsten smelting wastewater.The thesis takes tungsten smelting wastewater as the research object,using the gradient domestication method,5.0%salinity MBR reactor is finally established.The characteristics of its microbial flora and the rules of pollutant removal were studied,and a mathematical model of activated sludge suitable for high-salt MBR reactor was constructed based on the ASM1 model.The main conclusions are as follows:(1)Using the MBR reactor,the salt concentration was gradually increased from 3.0%salinity environment,and finally MBR system adapted to 5.0%salinity environment was constructed.The research shows that the increase of salinity makes the sludge flocs small and compact,the protists and metazoans are single,the filamentous bacteria are reduced,and the supernatant liquid is turbid after the sludge settles.The sludge flocs formed a dense and fine nonfilamentous skeleton structure settlement,and the sludge settling speed was accelerated.After the domestication was completed,the mixed liquid suspended solids concentration(MLSS)was 9265mg/L,and the sludge volume index(SVI)was 34mL/g.The removal rates of COD,NH4+-N and TN in the reactor were 90%,78%and 65%.The microbial products were mainly protein and humic acid,and the protein components increased in different degrees during the domestication process,indicating that the microorganisms would secrete more products in order to resist the high osmotic pressure environment.(2)The genus-level microorganisms in the system were mainly Devosia(12.3%)、Luteimonas(8.21%)、Truepera(24.41%)、Azoarcus(7.94%)and unclassified_Rhodobacteraceae(28.07%).Functional genes did not change significantly with salinity.Amino Acid Metabolism and Carbohydrate Metabolism have the highest abundance,which is the main reason why microorganisms can remove pollutants from water.The abundance of Membrane Transport accounts for the highest proportion in the secondary pathway,which also proves that microorganisms require more transport proteins for material exchange in a hyperosmotic environment.(3)Different operating conditions have a significant impact on the removal of pollutants.Based on the results of single-factor experiments,the operating conditions of membrane bioreactors for high-salt wastewater were optimized by response surface analysis method.The response equations for the removal efficiencies of COD(CRR),NH4+-N(ANR)and TN(NRE)were obtained as follows:CRR=91.93+1.71A+1.09B+0.465C-0.152AB+0.3975AC+0.0675BC-3.34A2-2.06B2+0.878C2 ANR=69.2+10.81A+10.59B+3.06C+1.75AB-0.4AC-2.41BC-5.33A2-3.28B2+3.26C2 NRE=44.89+8.77A+20.41B-1.69C+2.39AB+0.225AC-0.635BC+2.01A2-3.88B2+7.2C2 The CRR R2=0.9752,the ANR R2=0.9588,and the NER R2=0.9625.The optimized results were HRT=21.66h,pH=7.98,DO=lmg/L.It is verified by experiments that the actual operating results are close to the response surface analysis results.It shows that it has certain reference significance for the parameter selection of MBR treatment of high-salt wastewater.(4)Based on the ASM1 mathematical model proposed by the International Water Association,considering the actual situation of the MBR reactor to treat high-salt wastewater,the generation and degradation process of SMP and EPS and the corresponding kinetic parameters are introduced.Activated sludge mathematical model ASM 1-MBR suitable for MBR treatment of high-salt wastewater was established and expressed in matrix form.Through sensitivity analysis,parameters with higher model sensitivity are obtained and adjusted and modified.The Runge-Kutta method is used for simulation calculation,and the error is about 1%,and the simulation operation parameters of ASM 1-MBR are finally obtained.The ASM1-MBR model is used to simulate the treatment of high-salt wastewater by the MBR reactor,and the calculated results are in good agreement with the measured values.The average error is less than 5%,and the reliability of ASM1-MBR and parameters has been verified.