Comparison of Fouling Behavior of Ultrafiltration Membranes Under the Influence of Changing Coagulation Parameters

In order to optimize the operating conditions for a combined coagulation-ultrafiltration pro-cess, the main and interaction effects of dose, coagulant type, retention time, and rapid mix-ing speed on hydraulically irreversible and chemically irreversible fouling indices (HIFI and CIFI) are investigated using 100 kDa hollow fiber Multibore PES membranes operated in the dead-end mode. For this purpose, a two-level full factorial design (FFD) is then employed to develop mathematical correlation models for the optimum operating conditions. Two differ-ent types of coagulant chemicals, Ferric Chloride (FeCl3) and Polyaluminum Chloride are used to treat the moderately organic wastewater (TOC 9 mg/l, and Turbidity 1 NTU) effluent of Holzkirchen treatment plant located in 40 kilometers south of Munich. Jar tests and few primary pilot runs are performed to determine the relevant ranges of doses and to compare with plant inline coagulation. The statistical analysis indicates that currently installed rapid mixer has rather detrimental effects and so it is excluded from the rest of the experiments in second phase. In case of PACl coagulant, flocculation retention time is the main effect; low-er retention time is more favorable. Whereas for FeCl3 coagulant, dose is the most signifi-cant factor on HIFI. Higher FeCl3 dose values compounds membrane fouling. Based on HIFI responses, optimum PACl and FeCl3 dosages are 5 ppm and 4 ppm respectively. The differ-ences between these two coagulant processes refer to specific characteristics of chemicals, formed flocs, and consequently the membrane fouling cake. In second phase, the availability and recovery of plant are improved to 93.6% and 93.5% by increasing the process flux and filtration time and the impacts on fouling resistance are ex-amined. Moreover, pH reduction’s positive effect on the process and dissolved organic car-bon (DOC) and SAC removal is studied.