预处理对短流程超滤工艺不可逆膜污染影响的中试试验

以东江水为处理对象,进行直接超滤、微絮凝-超滤和絮凝/活性炭-超滤中试研究,探讨预处理对短流程超滤工艺不可逆膜污染的影响.利用扫描电镜形貌观察、三维荧光光谱(EEM)和高效排阻色谱法等手段对不可逆膜污染物进行表征分析,比较预处理对不可逆膜污染物含量和组分的影响,阐述预处理对不可逆膜污染影响的机制.结果表明,在10 L·(m~2·h)~(-1)低通量运行下,微絮凝预处理使不可逆膜污染增长速率从直接超滤的0.32 k Pa·d~(-1)下降到0.16 k Pa·d~(-1),絮凝/活性炭预处理后超滤工艺几乎零污染运行,且当絮凝/活性炭-超滤运行通量增加至17 L·(m~2·h)~(-1)时,仍没有观察到明显的不可逆膜污染增长.东江水中不可逆膜污染的主要组分是蛋白质类和富里酸等腐殖质类物质.微絮凝通过改变膜表面滤饼层的结构(厚度和密实性),提高物理清洗效率,减轻不可逆膜污染的积累;絮凝/活性炭预处理提高对不可逆膜污染物的去除效果,减轻膜污染负荷,控制不可逆膜污染.因此,采用絮凝和絮凝/活性炭预处理工艺,均可有效降低短流程超滤工艺不可逆膜污染积累.

Effects of Pretreatment on Hydraulic Irreversible Membrane Fouling During Ultrafiltration Short Process: A Pilot Study

Pilot-scale performances for ultrafiltration of Dongjiang river water without and with micro-coagulation and coagulation-adsorption-sedimentation pretreatments were conducted to investigate the effects of pretreatments on hydraulic irreversible fouling of ultrafiltration short processes. Scanning electron microscope (SEM) imaging, high performance size exclusion chromatography (HPSEC) and fluorescence excitation-emission matrix (EEM) were employed to identify foulants responsible for irreversible fouling during ultrafiltration with and without pretreatments. The results showed that the hydraulic irreversible fouling rate was 0.16 kPa·d^-1 with micro-coagulation pretreatment at 10 L·(m²·h)^-1, while the rate without pretreatment was 0.32 kPa·d^-1 at the same flux. Meanwhile, the fouling rate with coagulation-adsorption-sedimentation pretreatment was almost zero at the same flux. Furthermore, when the flux increased to 17 L·(m²·h)^-1, the irreversible fouling was not observable with coagulation-adsorption-sedimentation pretreatment (backwashing every 24 hours). Properties of foulants from external membrane and internal membrane after backwashing showed that the protein-like and fulvic-like substances were responsible for irreversible fouling in Dongjiang river water. Furthermore, structural alteration of cake layer resulted in less cake resistance and higher backwash efficiency after micro-coagulation pretreatment, leading to less irreversible fouling. Coagulation-adsorption-sedimentation pretreatment decreased irreversible fouling with higher removal efficiency of protein-like and fulvic substances, which were the foulants responsible for irreversible fouling during ultrafiltration. Both micro-coagulation and coagulation-adsorption-sedimentation pretreatments decreased irreversible fouling during ultrafiltration short process.