Study On Characteristics Of Membrane Fouling Of Dyeing Wastewater Treatment By MBR

Due to the high COD concentration, heavy color, and low degradability, dyeing wastewater can't be treated efficiently by traditional wastewater treatment methods. An acid hydrolysis-MBR combination system was adopted in this research, which is a perfect combination of the membrane filtration and the activated sludge process. Studies on the membrane fouling in MBR for dyeing wastewater treating are not sufficient so that the characteristics of membrane fouling of dyeing wastewater treatment by MBR was focused on in this research. The system run for 139 days and the experiment was divided into two stages according to whether PVA was added into the influent. Plentiful analyses were made, both of with and without addition of PVA, on the decline of specific membrane flux, the composition and variation of Membrane resistance. The concentration of proteins and polysaccharides in the EPS-containing solution abstracted by disodium EDTA method were measured, and the correlation between the composition of EPS and membrane resistance was discussed. Furthermore, analysis methods, such as SEM, FTIR, GC-MS and spectral scanning, were used to analyze and measure the foulant on the membrane surface. In addition, a pilot-scale device was set up to carry out a filtration experiment of the mixture liquor in MBR. And Hermia lineal filtration model was used to fit the data and discuss the membrane fouling mechanisms. As mentioned above, conclusions were made as follows:(1) The system operated in a long-term under critical condition. During the treatment of dyeing waste water, when HRT reached above 24h, the combined MBR system can achieve a COD removal of over 80% and a color removal of 50%; when HRT increased to more than 3 days, COD removal went up slightly while the removal of color rose up to 80%.(2) The decline of specific membrane flux has a close relationship with the hydraulic factors of the membrane surface. The specific membrane flux shows a more sharply decreasing when the initial membrane flux is higher, because of the severe concentration polarization. The cake layer resistance occupies the major proportion of the total membrane resistance while PVA can rise the percentage of polarization resistance. (3) The concentrations of both SMP and combined EPS keep growing up since the start in the MBR system. In the combined EPS of aerobic sludge, protein shows a higher concentration than polysaccharide and a stronger correlation with membrane fouling. So does the protein in the EPS abstracted from the foulant on membrane surface.(4) With the analysis results of methods such as infrared spectrogram and the spectral scanning, it can be confirmed that foulants on the membrane surface contain characteristic function groups of polysaccharides and polypeptides. SEM analysis of the membrane surface and the cross section indicate that pollution on membrane surface is rather serious than in the inner pore and belt ply.(5) The data collected from the cross-flow filtration of MBR mixed liquor with different crossflow velocities are fitted by Hermia's four blocking laws for filtration. The results show that gel layer formation model obtains the best degree of fitting, of which the Adj. R-Square up to 0.9. The presence of PVA can enlarge the specific resistance of sludge and reduce the function of membrane filtration.