Identification Of Membrane Fouling Factors And Structure Analysis Of Cake Layer

Membrane Bioreactor, as a new technology for wastewater treatment using membrane filter technology, is under restriction in broad application for high run fee because of membrane fouling. Up to now, lots of researches were made on the membrane fouling and great of developments have been reached. However, former researches focused on the change of membrane flux and trans-membrane pressure, or the qualitative compare of micro structure of cake layer, which lacking for the micro mechanism of membrane fouling and quantitative description of cake layer. In this paper, the hydrophobic polythene hollow fibre membrane was adopted to investigate influence of the membrane fouling factors including concentration and property of active sludge on the membrane fouling, and Fractal theory was used to analyze the micro permeability of cake layer, and the relationship model between membrane fouling factor and Fractal permeability was established.The main research conclusions are summarized as follows:(1) Extracellular Polymeric Substances, as organic matters wrapping around the zoogloea, affected the surface property greatly. With the increasing of the ratio of protein and amylase, the relative hydrophobic was increasing and absolute value of Zeta potential |δ| was inopposition. It was found that the with the change of the relative hydrophobic and Zeta potential of sludge surface, the assemble state between the sludge particle was change which result in the difference of membrane fouling resistance as: R_f = 23.7×R_H - 0.26||δ|- 6.08;(2) The cake layer resistance R_c made up 50%-90% of the total fouling resistance R_t, and required a micro structure analysis;(3) The permeability theory of porous media and fractal theory were combined to deduce apermeability model of porous fractal media as the formula: K₁=[Ï€/8s·d_f/(4-d_f)·λ_max⁴](4) With the help of Scan Electronic Microscopy and date of Image Analysis System, it was found that the pore distribution of cake layer surface was out-of-order and possess Fractal character. However, the theory permeability obtained from the fractal model was relative with the actual permeability of cake layer, and a special Fractal permeability model for the cakelayer was put forwards as:(5) As a membrane fouling factor, the concentration of active sludge affected the Fractal permeability as: K = 0M9e'9xl°5MLSS â– ...