Study On Fouling Mechanism Of RO Membrane Treatment For Leachate And Control Technology

Landfill leachate poses great threat to human living environment, more strictdischarge standards has rendered the membrane process as the main qualifiedtechnology under the standards. However, the membrane fouling problem occurredfrom the complexity of leachate limited the application of membrane by increasing acolossal of sum spent on checking and chemical agents, cleaning and so on.Few researches on control technology of membrane fouling were investigated onthe basis of micro scale while many were done by the judgment on common waterparameters. Therefore, lacking precise theoretical information about the membranefouling mechanism leads to unsatisfactory effect of many control technology.The fouling process of RO membrane using for purifying the leachate treated byMBR was investigated in this study, in order to find useful control technology formembrane fouling which serves as technical support in the fields of leachate treatment,on the basis of research on fouling mechanism, chemical cleaning and pretreatment.①The fluorescence spectra showed that the RO foultants consisted of fulvic-likematter together with the protein-like, low-excitation wavelength tyrosine-like. Theaverage particle size of RO effluent decreased with time, with size distribution100-200nm.②The FRIR spectra showed that obvious absorption band of-OH and-C=O werefound on the surface of membrane as well as other fouling matter containing aromaticand nitric structures. SEM pictures showed that origin membrane was smooth whilemud with some deposits was gradually found on fouled membrane, which went severewith the filtration time.③HCl (0.25%w/v) was found to be best acid cleaning agent, which targetedfoultant with120and360nm particle size. Flux recovery reached74%whenNaOH+SDS (0.2%w/v) was chosen as base cleaning agent rather than single use thanksto their complementary and base cleaning could remove targeted fouling matter sizedabout1200nm and5000nm. The base-acid sequence of cleaing was found to be betterthan acid-base.④The best parameters of electrocoagulation was reaction time45min, currentdensity20mA/cm2, electrode distance30mm, when the performance ofelectrocoagulation was effective with COD removal efficiency64%(2times chemical coagulation) and TP removal more than90%but unsatisfactory effect for TN. When itcomes to combination of RO, with total removal effeiciency of COD over93%,ammonia nitrogen of90%, TP over98%and conductivity over94%, the effluent of bothelectrocoagulation and chemical coagulation met the standard.⑤Molecular weight (MW) distribution result showed removal of small organicmatter (<1k) was achieved by electrocoagulation comparing with chemical coagulation.The results of three-dimensional excitation-emission matrix (3D-EEM) fluorescencespectra showed electrocoagulation have better removal of visible and ultra visiblefulvic-like. It was found that electrocoagulation greatly prevented the RO membranefouling and it could serve as membrane pretreatment.