| AnDMBR replaces the microfiltration/ultrafiltration membrane of AnMBR by using inexpensive microgrids with larger pore sizes as supporting materials for membrane components.AnDMBR has the advantages of good treatment of water quality,low price of membrane materials,small footprint of structures,easy cleaning and regeneration of membrane.However,as a new process,AnDMBR also has certain shortcomings,such as the formation process of dynamic membrane,choice of membrane materials and the optimization of stable operation conditions of dynamic membrane still need to be further explored in order to obtain wider application.It is believed that biogas sparging can strengthen the biomass transfer process and regulate the structure of cake layer,which is conducive to improve the performance of biological treatment and delay membrane fouling.Therefore,in this study,cheap coarse pore microgrid was used as the support material to prepare dynamic membrane components and build a lab-scale biogas sparging AnDMBR process.The research attempts to improve the methane-producing performance of AnDMBR and alleviate membrane fouling by regulating biogas sparging mode.In addition,the COD balance and energy balance of the system were evaluated.The main achievements are as follows:（1）The classification characteristics and chemical composition distribution of particulate matter in domestic sewage were determined by sewage classification experiment and methanogenic potential（BMP）experiment.The sewage used is the actual domestic sewage,COD concentration is about 520 mg/L and suspended solid concentration（SS）is about 140 mg/L.The results show that the main components of COD are protein,polysaccharide and lipid.There are almost no TSS and VSS in the dissolved domestic sewage.The precipitated COD which is difficult to degrade and the dissolved COD（SCOD）which is easy to degrade account for about 10%and 40%of the total COD respectively.TN and TP mainly exist in domestic sewage in the form of dissolved state.The methanogenic potential experiment shows that the methanogenic potential of domestic sewage is 0.32 LCH4/g COD,which can be used to produce methane by anaerobic digestion at room temperature.（2）The stable formation of dynamic membrane under the condition of continuous sparging was explored through batch experiments（self-forming and precoated dynamic membrane experiments with nylon mesh of 200,300 and 400 mesh as the membrane substrate）.The results showed that stable dynamic membrane could not be formed under the condition of continuous sparging.It provides an important basis for the no sparging and intermittent sparging.（3）Based on a lab-scale AnDMBR,the effects of nylon mesh size（200 mesh and 500 mesh）and biogas sparging mode（continuous sparging,no sparging and intermittent sparging）on the wastewater treatment performance of AnDMBR were studied.The results show that the operation cycle of AnDMBR is extended using supporting material of 200 mesh.When the optimized biogas sparging mode（3 h-off and 1 min-on）was applied,the gaseous methane production was optimal and the dissolved methane production was much lower,compared with the non-biogas sparging mode,with the gaseous methane production increased by 15.9%and the dissolved methane production decreased by 46%.The AnDMBR achieved COD removal of more than 80%,suspended solids（SS）removal of nearly 90%,and turbidity removal of about90%.Constant biogas sparging led to sludge particle breaking and cake layer falling off,decreasing the average sludge particle size.SEM-EDX analysis showed that biogas sparging intensity affected the density and thickness of the cake layer.The bacterial community in the bioreactor mainly included Proteobacteria,Chloroflexi,Firmicutes and Bacteroidetes,while the archaea community mainly consisted of Methanoregula,Methanothrix and Methanobacterium.（4）The COD balance and energy recovery under the conditions of the second and third stages were compared and analyzed.The COD conversion and production capacity balance calculation of two-stage AnDMBR systems are carried out.The results show that under the condition of the second and third stages,the net capacity of anaerobic fermentation of 1 m3urban domestic sewage anaerobic treatment can reach0.18 k Wh and 0.35 k Wh respectively,which is higher than the energy consumed by the system and can realize the net energy recovery. |
