The Effects Of Different Coagulation Patterns On Ultrafiltration Combined Process Operation

Membrane fouling is the main factor restricting the development ofultrafiltration(UF). Pretreatment can control membrane fouling effectively. In practice,coagulation pretreatment is widely used to improve UF fouling problem. Coagulationis the core unit in water treatment technology.As a pretreatment process combined withultrafiltration process, coagulation usually including rapid mixing and slowflocculation part. In this study, flocculant mixed with raw water in the pipeline incogulation integrated with UF process, and flocculation happered directly in membranepool. The new process was compared with conventional coagulation combined withultrafiltration process. Three aspects were studied including effluent quality,membrane flouling speed and flocs properties in membrane system. Currently study ofcoagulation and ultrafiltration technology is mainly about membrane fouling andeffluent quality. There were few research about feasibility of coagulation integratedwith UF process and flocs in membrane system. Understand the relationship amongflocs properties, effluent and membrane fouling through the comparative analysis.During the experiment, optimize the operation parameters at the first step.Membrane fouling speed and effluents were compared for each kind of process after along time and stable operation. The results showed that effluent turbidity and particlenumbers of the two process were very stable with the removal rates more than99%,hardly affected by pretreatment and raw water. Average removal rate of UV254coagulation integrated with UF process and coagulation combined with ultrafiltrationprocess were53.91%and54.35%respectively and average removal rate of DOC were28.51%and29.28%respectively; average removal rate of CODMnwere44.91%and 44.62%respectively. Coagulation combined with UF process works better on solubleorganic matter removal. When raw water SUVA was2.09L/mg m, SUVA in themembrane system were1.42L/mg m and1.43L/mg m respectively. It showed thatflocculation direct in membrane pool had a good removal of hydrophobic organicmatter removal. Floc fractal dimensions of coagulation integrated with UF process andcoagulation combined with ultrafiltration process were1.26and1.39, respectively，instructing more dendritic structure flcs existing in coagulation integrated with UFprocess system. TMP growth rate for coagulation integrated with ultrafiltration processwas0.56kPa/d, while that for coagulation combined with ultrafiltration process was0.44kPa/d. The TMP growth for coagulation integrated with ultrafiltration process wasfaster. From what has been discussed above, coagulation combined with ultrafiltrationprocess under the condition of optimization was better.