Zhaohui Zhang,Yun Liu,Bin Zhao,Junjing Li,Liang Wang,Cong Ma
In this study, the reductions of long-term irreversible membrane fouling in integrated and separated MIEX-UF processes were explored over a prolonged experimental period. The mechanism leading to the significant difference in membrane fouling behaviors of the two processes was systematically analyzed. The results show that the chemical cleaning frequency and the rate of chemically irreversible membrane fouling formation were decreased by 50% and 49%, respectively, in the integrated process compared to the separated process. Further analysis suggested that MIEX adsorption was unrelated to the different membrane fouling behaviors between the two processes. The effect of the resin layer on filtration and backwashing was the dominate mechanism leading to the more excellent anti-fouling performance of the integrated process. The stronger adhesion force of pollutants-MIEX enable the mixed cake layer formed in the integrated process to maintain good water permeability and easy to be removed by backwashing. The adhesion force of pollutants-MIEX was significantly affected by the saturation level of resin particles and less affected by resin regeneration. During the early period of long-term filtration experiment and the initial stage after every resin replacement, the low saturation degree of resin particles guaranteed the improved effect of the resin layer always existed.
This work investigated the removal of humic acid (HA) as the precursor of disinfection by-product (DBP) using a magnetic ion exchange (MIEX) resin. The Box–Behnken design of response surface methodology (RSM) was used to evaluate the effect of process variables (initial pH, MIEX dose and reaction time) and their interaction for HA removal. Specific ultraviolet absorbance (SUVA) removal was selected as the response value. The analysis of variance (ANOVA) of the quadratic model demonstrated that the model was significant, and the optimum conditions were obtained as pH 2.3, MIEX resin dosage 0.95 mL L−1, and reaction time 59.18 min. At these applied optimum conditions, 39.74% SUVA removal from an initial SUVA value of 10.06 L mg−1 m−1 was achieved. Also the reduction in DBP (chloroform, dichloroacetic acid and trichloroacetic acid) formation potentials was about 76%, 73% and 80%, respectively. The MIEX process was effectively optimized by RSM with a desirability value of 1.0. After the process optimization, the MIEX treatment was proven to be a good option for controlling the DBP derived from HA.
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