Screening Of Dominant Bacteria For Sludge Reduction And Its Application In The Process Of Sludge Reduction

In the sewage treatment,activated sludge process is the mainstream technology for municipal wastewater and industrial wastewater treatment.The formation of microbial micelles is the key to the success of this “Centennial craft”.Micelles can be precipitated by gravity to separate the mud and water.Then the purified water can be discharged after disinfection without filtration.Contrary,a large amount of excess sludge is produced while achieving efficient purification of the sewage.Those excess sludges contain a large amount of toxic and harmful substances.Excess sludges may be harmful to the human living environment if person do not handle properly.The current disposal methods are more rigorous due to the stricter environmental regulations law and cannot meet the requirements of the sewage treatment process.The sludge disposal is getting more and more problematic.In the face of the current situation,researchers have carried out in-depth studies on in situ sludge reduction technology,mainly through metabolic uncoupling,recessive growth,micro animal predation,and other technologies,to achieve the fundamental requirements of sludge reduction.In this work,to solve the problem of a large amount of surplus sludge,the sludge yield was reduced by adding dominant strains in the sewage treatment process in order to better control the sludge source output,with the sludge pre-treatment process was uesed.The application of this method does not change the original sewage treatment process,it is easy to operate,and it is the development trend of sludge source reduction technology.Therefore,this work carried out the following study:1.The strains producing surfactant and extracellular enzyme were screened.According to TSS the sludge reduction index,LD,XLQ and TMQ were the dominant strains for surfactant production.In sludge reduction effect analysis,the LD strain was 7% higher than blank,the TMQ was 4.8% higher than blank while the XLQ 7% higher than blank.Three dominant strains UT2,3-5-1 and 3-10-2 were successfully selected using sludge culture medium,The sludge reduction effect of surfactant producing strain and enzyme producing strain was compared.Finally,it was concluded that 3-10-2 was the best dominant strain,with the highest removal rate higher than 12.2% of blank samples.2.Citric acid was used as a cationic binder to remove the extracellular polymer,and then strain 3-10-2 was added to the sludge to remove the extracellular polymer.The highest sludge removal rate reached 20.1%,higher than the blank 6.5%.The Box-Behnken design was used to analyze the response surface of the three main influencing factors of pH,temperature and time.The optimal reaction conditions were pH=10,temperature 50 °C,time 48 h,and the strain were added under the optimal conditions to further test the reliability of the response surface method where the optimal reduction effect of sludge reached 21.2%,which was higher than the blank group by 6.6%.3.On the optimal conditions,the mechanism study showed:(1)the dominant strain 3-10-2 can produce extracellular enzymes,which can hydrolyze the organic matter in the sludge.The highest content of protease is 0.428 U/mL,which is higher than the blank group of 0.008 U/mL,and the amylase is higher than the blank 0.023 U/mL.(2)The COD solubility increased by 0.53% and 1.8% at 24 h and 48 h respectively.(3)The results of three-dimensional fluorescence spectra and elemental analysis showed that after treatment,the protein and humic substances increased significantly,and the S,C,and N elements decreased respectively.(4)During the sludge reduction process,the polysaccharides and proteins were transformed from tightly bound to loosely bound and dissolved extracellular polymerization.(5)The change of antibiotics was measured during the process of sludge reduction,the initial value of cefortaxime acid in the liquid phase was 45.3 ng/g.Almost all of the samples were completely degraded or transferred with the reaction,the initial concentration of lincomycin in the liquid phase was 38.3 ng/g,was almost degraded in the subsequent reaction.The tyrosine easily migrates from the solid phase to the liquid phase at a high temperature and is partially degraded.The sulfonamides are only sulfadiazine in the water,with an initial value of 12.85 ng/g,which is not contained in the solid phase and is easily biodegradable.The initial values of oxytetracycline in water and solid were 0,99.75 ng/g,respectively.At pH=10,Oxytetracyclin was transferred from the solid to the liquid phase,and the total content was increased.