A Study On The Influence Of Effluent Characteristics On Ultrafiltration Performance In Municipal Wastewater Reclamation/reuse

In this study, the secondary effluent of Bei Shiqiao wastewater treatment plant in Xi'an was used to perform bench-scale ultrafiltration (UF) experiments and an integrated understanding of DOM fouling of UF membrane was developed. This study characterized the apparent molecular weight distribution (AMWD) and hydrophobic content of DOM in the secondary effluent, determined the effect of pretreatments on the AMWDs, identified the effect of applicable pretreatment technologies on flux decline and analyzed the data of flux by a model developed by author's research team. The results showed that:(1) The effluent organic matter in the secondary effluent mainly account for the greatest majority in the low molecular weight (MW) fraction of <2k Dalton; along with the season change,the majority of the secondary effluent organic matter was mainly in the low- MW fraction of <2kDalton, but there was a trend that the low-MW DOM reduced with the temperature increase;(2) The AMWDs of the hydrophilic, hydrophobic and unfractionated secondary effluent showed that the overall distributions were similar, suggesting that differences in molecular size would not cause substantial differences in membrane performance;(3) Comparing results of flux decline, unfactionated solution and hydrophobic solution had similar patterns of flux decline, and the rate of flux decline was very rapid for the hydrophilic solution;(4) Coagulation can more effectively remove >100kDalton high-MW organic matter. And PAC adsorption was effective in removing <4kDalton low-MW organic matter. The removal rate of DOC by ozonization-PAC process was much higher than that of PACalone, which reflects the complementarity between ozonization and PAC adsorption in removing organic matter;(5) The rate of permeate flux decline of untreated secondary effluent was the most rapid, the flux decline rate of the PAC and ozonization-PAC pretreatment took the second place, and the flux decline rate of coagulation pretreatment was slowest, which related to the various AMWDs of the water pretreated by various processes;(6) The influence factor a1 and a2 calculated by the model indicated that, a1 of ozonization-PAC and PAC pretreatment was the smallest, which related to low-MW fraction (<4kDalton) decrease after PAC pretreatment. Similarly a2 of coagulation pretreatment was the smallest, which related to high-MW fraction (>100kDalton) decrease after coagulation process.