加载絮体形态对短流程超滤膜污染影响效应

以聚硫酸铁（PFS）为混凝剂，微砂为载体颗粒，系统考察了采用加载絮凝-超滤联用工艺净化含高岭土、腐植酸和锑Sb（Ⅲ）]的模拟原水过程中，不同PFS和微砂投加量条件下加载絮体形态特性以及其对超滤膜通量衰减、膜污染可逆性和宏观出水水质等的影响，并分析了膜污染机理.结果表明，PFS投加量对絮体形态及膜滤效能和膜污染影响显著，且投加量过少或过多均会产生不利影响，以30mg/L为宜；与不投加微砂的工况相比，加入微砂更易于形成大而结构较为松散的絮体，可有效削弱不可逆膜污染，并获得较为稳定的超滤出水水质；超滤末端膜比通量与絮体平均粒径呈良好的正相关性（R²=0.8774），但因加载絮凝体系中引起分形维数变大的不同类型颗粒（包括小粒径范围絮体和未被加载絮体捕获的微砂）对超滤净水过程产生的影响各异，致使膜通量与分形维数的负相关性较差（R²=0.5760）.

Effect of ballasted floc morphology on membrane fouling during shortened ultrafiltration process

Synthetic water samples containing kaolin, humic acid and antimony(Ⅲ) were purified by combined process of ballasted flocculation and ultrafiltration with using polymeric ferric sulfate (PFS) as coagulant and microsand as ballasting agent. The effects of PFS and microsand dosages on ballasted floc morphological characteristics, ultrafiltration membrane flux decline, fouling reversibility and purified water quality were systematically investigated. Also, the mechanisms of membrane fouling were explored in details. The results showed that the PFS dosage had a significant effect on floc morphology, membrane filtration efficiency and fouling properties; and especially, negative influence could be observed at PFS dosages both lower and higher than 30mg/L. With injecting a certain amount of microsand (1~6g/L), the formation of larger and relatively looser flocs would weaken irreversible membrane fouling and produce quite stable purified-water quality after ultrafiltration. Membrane specific flux and floc average size had a very strongly positive correlation (R²=0.8774), but for floc fractal dimension, a weaker negative correlation (R²=0.5760) was established, possibly due to distinct roles of those particles with higher fractal dimension on ultrafiltration.