Study On Nitrogen Removal Effect Of Membrane Bioreactors And Carrier Enhancement For Mariculture Wastewater Treatment

In recent years, with the rapid development of Chinese marine aquaculture industry,the environmental problems of mariculture wastewater treatment are outstanding.There are rare special technologies for mariculture wastewater treatment. In this paper,dynamic membrane bioreactors (DMBR) and membrane bioreactor (MBR) were usedto treat mariculture wastewater. The effects of dissolved oxygen (DO) and salinityinhibition on CODMnand nitrogen removals were studied. Besides, the microbialcommunity structure of bioreactor was investigated. Morever, the two step ofnitrification-dentriification mathematical model (ASM1-2N) was used to simulate forthe nitrification and denitrification process of the system.The CODMnremoval efficiency of MBR and DMBR could reach above95%under different DO conditions. When DO was0-1mg/L, the TN removal efficiencyof MBR and DMBR was75.8%and71.4%, ammonia removal efficiency was93.9%,89.8%respectively. When DO was2-3mg/L, the TN removal efficiency of MBR andDMBR could reach44.1%and46.3%, ammonia removal efficiency was97.5%,94.8%. First order reaction kinetics model of ammonia removal was set up underdifferent DO conditions; the nitrification rate constant of MBR was slightly higherthan the DMBR. When the DO was2-3mg/L, running period of DMBR was about13days, while MBR was about10days. The effluent of DMBR depended on gravity, sothe DMBR process cost less and reduce energy consumption.The effect of salinity on bacterial community composition of MBR and DMBRfor aquaculture wastewater treatment was investigated via the combination of PCRamplification of16S rRNA gene with denaturing gradient gel electrophoresis (DGGE)analysis. When salinity increased from0to35g/L, ammonia, TN removal efficiencyof MBR decreased from96.92%to91.08%,74.4%to63.9%respectively, ammonia,TN removal efficiency of DMBR decreased from94.32to87.58%,81.4%to61.9%respectively. Shortcut nitrification-denitrification phenomenon took place only whenthe salinity was21g/L and28g/L, TN removal efficiency of MBR and DMBR couldreach above65.2%、68.8%respectively. DGGE profiles of bacterial community demonstrated that transient dynamics of community structure and microbial diversitywould evolve in different periods of reactor operation, salt-tolerant microbe tended togradually dominate in the population. Thiothrix eikelboomii, Pedomicrobiumaustralicum, Paracoccus bengalensis might associate with shortcutnitrification-denitrification phenomenon in MBR when salinity was21and28g/L,besides, Lutibacter litoralis, Paracoccus zeaxanthinifaciens, Ideonella dechloratansmight be the most relevant species in DMBR.The two step of nitrification-dentriification mathematical model (ASM1-2N)was used for model the nitrification and denitrification process, the simulation resultmatched the measurement.A porous polyvinyl formaldehyde (C-PVFM) foam carrier was prepared foraquaculture wastewater treatment. PAC dosage of5%(C-PVFM3) showed the bestbiocompatibility for wastewater treatment.8%(v/v) supplementation of these carriercould enhance the denitrification process of DMBR and MBR, TN removal efficiencyincreased by21.2%,24.0%respectively. Besides, magnet powder was added in thiscarrier for prepareing magnetic carrier. Microorganism respiratory test indicated thatmagnetic might stimulate the biofilm growth, higher magnetic inhibite microbialactivity. When magnetic of carriers was0.2emu/g, the corresponding biologicalrespiration slope is5.8, showed for a thick biofilm and efficient waste removalefficiency.