| The potential scarcity of water and the decline of water quality have become serious problems.Hence,using an advanced technology such as membrane bioreactor(MBR)for treating and reusing wastewater has emerged.Unfortunately,membrane fouling still poses a major challenge in MBR application.The object of this paper was the control of membrane fouling in submerged MBR.Based on the adsorption mechanism of soluble microbial products(SMP)onto adsorption resin(AR)and the effect of SMP on initial membrane fouling of polyvinylidene fluoride(PVDF)microfiltration membrane,the mechanism of preferential adsorption of SMP between D3520 and PVDF membrane was proposed.Thus,in order to alleviate the evolution of membrane fouling,AR-MBR system was constructed by adding D3520 into MBR.First,the adsorption mechanism of SMP onto AR was studied.According to the result of the batch adsorption experiments,D3520 has the highest adsorption ratio and adsorption capacity in the five kinds of AR.In order to determine the type of adsorption,the adsorption thermodynamic parameters was calculated,and Fourier transform infrared(FTIR)spectroscopy and X-ray photoelectron spectroscopy(XPS)were employed.In order to further clarify the adsorption mechanism of SMP onto D3520,the adsorption kinetics models and adsorption isotherm models were used to analyze the factors of adsorption rate at the adsorption process and the SMP distribution between the liquid phase and the solid phase after adsorption equilibrium.Secondly,the effect of SMP on initial membrane fouling of PVDF microfiltration membrane was studied.According to the batch adsorption experiments,adsorption of PVDF hollow fiber membrane to SMP was investigated by calculating adsorption thermodynamic parameters and applying of adsorption isotherm models.The process of filtering SMP by PVDF microfiltration membrane was investigated based on the dead-end filtration experiment.It was clarified that membrane flux decline mainly resulted from the standard blocking by SMP in the filtration initial stage.Based on the above analysis,through simulation of the intermittent operation of ?suction on-off? of peristaltic pump during the operation of the MBR,the mechanism of preferential adsorption of SMP between D3520 and PVDF membrane was proposed,which provided a theoretical basis for mitigating membrane fouling in MBR.Finally,according to the mechanism of preferential adsorption of SMP between D3520 and PVDF membrane,AR-MBR system was constructed by adding D3520 into MBR,which can alleviate the evolution of membrane fouling.Comparing the treatment effects of MBR and AR-MBR systems on synthetic domestic wastewater,the AR-MBR system has better treatment performance and slower initial trans-membrane pressure(TMP)growth than MBR.Through the study of the membrane fouling resistance distribution,the resistance of irreversible and internal membrane pore blockage of the AR-MBR system were less than of the MBR.Therefore,the fouled membrane has higher the flux of water recovery rate after physical cleaning,which reduced the damage of membrane by chemical cleaning.Moreover,the fouled D3520 can still be added to the MBR through regenerating,which saves increased operating costs due to adding D3520. |
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