Effctiveness And Mechanism Of Water Purification By The Combined Progress Of Coagulation And Modified Gravity Driven PVDF Membrane Filtration

Gravity Driven Membrane(GDM)can achieve a stable flux with no need of backwashing,chemical washing and disinfection.It can simplify system’s maintenance and operation,and also can reduce the operation costs.Now GDM is widely applied in desalination and wastewater treatment.But it low membr ane flux limit the application.Coagulation as a physicochemistry pretreatment process was widely used because of its low cost and simple operation.Combined progress of membrane filtration and coagulation can effectively remove contaminants from water,reduce the formation of disinfection by-products,and also maintain the performance of the membrane.Surface coating as the simplest membrane modification method,can improve the hydrophilicity and anti-pollution properties of the membrane.This article used Fe Cl3·6H2O as coagulant and selected two different coagulant dosing methods ‘Online Coagulation’ and ‘Coagulation-Sedimentation’ as pretreatment and used PAC and PZ to modify the PVDF membrane.Nine different reactors were employed to explore the purification effectiveness and mechanism of GDM.The adsorbent is loaded onto the membrane surface by a peristaltic pump suction and the modified membrane have higher hydrophilicity and then improved the membrane flux.By exploring the turbity,TOC,UV254,Zeta po tential,inorganic cations,EEM,NH3-N,NO2--N,NO3--N of each reactors’ permeate and characterization of cake layers,it was found find that coagulation-sedimentation can effectively reduce the contaminants of water,and the cake layers are significantly thinning and thus we can get better permeate.The GDM can effectively reduce turbity and the concentration of Fe3+ and also can remove some of organic contaminants by biodegradation.PAC modified membrane can remove more organic contaminants because of the adsorption of PAC.We found that lots of Proteobacteria and Actinobacteria on membrane which has a good effect for nitrogen fixation and the removal of organic matter.This paper focuses on the optimization of gravity membrane system operation,and investigated the water purification efficiency and mechanism under different conditions,which provides a theoretical basis for practical application of GDM engineering.