Research On Enhanced AnMBR Process For Bamboo Products Wastewater By Addition Of Charcoal

In recent years,the industry of bamboo products has developed increasely in China.A large amount of bamboo products wastewater which came from the process of bamboo products,was characterized with high COD concentration and color,and complex components.Therefore,it was great significant to develop the efficient and stable technology for bamboo products wastewater treatment.Anaerobic membrane bioreactor(AnMBR)had been applied gradually in the field of high organic concentration wastewater treatment with excellent performance of pollutants removal and energy recovery.However,unstable operation and serious membrane fouling limited its industrial applications.In this thesis,the enhanced AnMBR systems were developed to treat bamboo products wastewater.The effects of bamboo charcoal(BC)addition and alkalinity in AnMBR,the characteristics of anaerobic membrane fouling and its control mechanism by BC,and microbial community structure of anaerobic granular sludge and membrane deposits were investigated with techniques of scanning electron microscopy with energy dispersive X-ray(SEM-EDX),three-dimensional fluorescence spectroscopy(3D-EEM),confocal laser scanning microscope(CLSM)and high-throughput sequencing.The major results were as follows:1.The influence of BC particles on the removal of pollutants,sludge granulation,gas production and its composition in AnMBR were studied.The results showed that the pollutants removal efficiency was improved in B-AnMBR with addition of BC obviously.The removal efficiency of COD and ammonia nitrogen were 94.5±2.9%and 75.7±2.1%,respectively.Meanwhile,the average mixed liquor volatile suspended solids(MLVSS)increased to 25.3 g/L,and process of sludge granulation was accelerated.At the same time,no acidification occurred in both AnMBRs,and the ORP and effluent VFAs of B-AnMBR were lower than those of AnMBR(without adding BC).The gas production and methane yield were at 13.2±1.2 L/d,0.25 LCH4/g COD in B-AnMBR,respectively.2.The effect of influent alkalinity on the pH,COD removal efficiency and methanogenic capacity in AnMBR were studied.When the influent alkalinity decreased from 4328 mg/L to 549 mg/L,the effluent pH remained above 7.5 in both AnMBRs,which indicated the reactors were running well.The COD removal efficiency,gas production and methane yield in B-AnMBR were higher than those of AnMBR,reached at 89.2%,14.03 L/d,and 0.32 LCH4/g COD,respectively.It was speculated that the consumption of 1 g COD in B-AnMBR would produce 0.19-0.27 g alkalinity which was higher than that of AnMBR,indicating that BC could enhance the performance and steability of AnMBR effectively.3.The results of BC effect on membrane showed that membrane flux in B-AnMBR was significant higher than that of AnMBR(p<0.05),and the membrane resistance of B-AnMBR was 8.41 × 1012 m-1 which was lower than that of AnMBR(5.23×1012 m-1,p<0.01).At the same time,the membrane flux was recovered well after membrane cleaning in B-AnMBR,and its service life was prolonged.The results of SEM-EDX and CLSM illustrated that BC decreased the concentration of dissolved microbial products(SMP)in the reactor,and a loose and porous cake layer was formed on the membrane surface.Furthermore,the metal contents of Ca,Al,Si,Fe and other proteins and polysaccharides had been decreased by addition of BC,which favor the coltrol of pore blocking and increase of membrane flux.4.Analysis of microbial community of granular sludge and membrane deposits in AnMBR showed that the microbial diversity of granular sludge was increased after adding BC,and the methanogenic groups such as Methanosaeta,Methanospirillum and Methanobacterium were enriched in B-AnMBR.At the same time,BC inhibited the enrichment of Bacteroidetes and OP 11 on the membrane surface.In summary,BC particles could enhance the removal of pollutants through adsorption and promote the anaerobic sludge granulation as cores.Meanwhile,BC could reduce the content of SMP in the reactor and optimize the microbial community structure of anaerobic granular sludge,and then improve the functional microbes in the membrane deposits and control of membrane fouling effectively.