Study On The Difference And Mechanism Of Controlled Membrane Fouling In MIEX And PAC In Integrated Process

The development of Ultrafiltration (UF) process provides a new direction for drinking water treatment. However, serious membrane fouling limits the use of membrane.As a commonly used adsorption material in water treatment, powdered activated carbon (PAC) and magnetic ion exchange resin (MIEX) combined with membrane technology has also been concerned. But there were a fewer reports about MIEX and PAC for controlling of membrane fouling and mechanism in a long-term running. In this article, integrated MIEX/UF and PAC/UF process were researched, systematically investigated two kinds of processes for controlling of physical irreversible fouling and control mechanism differences in long-term running.The constant pressure cleaning stage operated 45d, integrated MIEX/UF single chemical cleaning cycle average operation time was 13.4d,1.73 times increased compared with integrated PAC/UF process, and chemical cleaning frequency was reduced 66.7%. The regular cleaning stage operated 75d. integrated MIEX/UF process had fewer hydraulic backwashing in single chemical cleaning cycle than integrated PAC/UF process, and transmembrane pressure growth rate was lower. MIEX could better control the irreversible membrane fouling, membrane flux recovery rate of integrated MIEX/UF process was the highest. Integrated MIEX/UF process had more thiner foultant layer after backwashing, and integrated MIEX/UF process chemical cleaning effect was better than the PAC/UF process, which indicated integrated MIEX/UF membrane surface were less residual pollutants and lower degree of fouling. The percentage of physical irreversible resistance accounted for over 90% in irreversible resistance, which was the main cause of membrane fouling.In integrated process, MIEX and PAC controlled membrane fouling was combination of variety of factors. In integrated MIEX/UF process, the effect of MIEX layer accounted for 63%, while liquid organic function was 35%; but in integrated PAC/UF process, liquid organic function played a major role and the proportion was 80%, while PAC layer was 17%. But the MIEX and PAC scraping had no obvious on membrane fouling. The DOC at the membrane surface in integrated MIEX/UF process was slightly lower than PAC/UF process, but the UV254 contents decreased obviously. Low molecular weight organic matters for the physical irreversible fouling in the two kinds of process was the basic consistent, but integrated MIEX/UF process could control membrane fouling caused by high and medium molecular weight organic matters. In the chemical cleaning solution of integratted MIEX/UF process, humic acid, soluble microbial product and fulvic acid redueced 53.4%,28.4% and 20.8% compared to integrated PAC/UF process. MIEX had good removal effect on medium molecular weight organics, but had the same effect with PAC for low molecular weight organic matters. MIEX for protein, humic acid and fulvic acid material removal effect was superior to PAC. MIEX had strong adsorption on irreversible organic matters, which showed MIEX layer on membrane surface could carry on the secondary adsorption to the organic matters, when hydraulic backwashing MIEX could also carry pollutants at the membrane surface, reducing the physical irreversible fouling.