超滤处理微污染地表水的膜污染化学清洗研究

针对超滤处理微污染地表水时产生的膜污染,利用电镜扫描和能谱技术分析其膜丝内表面污染物的组份,并考察了几种化学清洗剂对污染膜的清洗效果。试验结果表明,膜丝内表面的污染层是由有机物、微生物和无机物组成,其中有机物覆盖着无机物,以有机污染为主;膜清洗宜先碱洗后酸洗;单一清洗剂中NaOH、NaC1O和H2O2均有较好的清洗效果,但并不能使膜通量完全恢复,而复合清洗剂H2O2+柠檬酸具有显著的清洗效果,膜通量恢复率高达98%。     

接触氧化—超滤膜分离工艺在中水处理中的应用研究

论述了接触氧化—超滤膜分离技术在中水处理中的应用,提出了针对性试验和运行参数,并对不同膜和技术工艺进行了对比。     

粉末活性炭预沉积去除藻类有机物及其对膜污染的影响

以东海原甲藻分泌的藻类有机物（AOM）为研究对象,研究粉末活性炭预沉积和预吸附两种膜前预处理手段对海水中AOM的去除作用,对比分析AOM直接超滤、预沉积和预吸附后再超滤时膜通量、膜阻力分布、膜表面亲疏水性和粗糙度的变化,探讨粉末活性炭孔隙结构、沉积量对AOM去除效果及超滤膜污染的影响.结果表明,活性炭预沉积和预吸附能够提高超滤膜对含AOM海水中DOC和UV₂₅₄的去除率,预沉积对AOM的去除作用优于预吸附,介孔活性炭较微孔活性炭的预沉积效果更好,当介孔活性炭PAC2的沉积量为0.4g/L时,DOC和UV₂₅₄的去除率较直接超滤分别提高了25.1%和33.6%.紫外吸收比指数（URI）分析表明,活性炭预沉积和预吸附对有机物的去除作用具有选择性,AOM中芳香族物质较脂肪族羧基类物质更易被除去.粉末活性炭预沉积下AOM超滤时的滤饼层污染阻力（R_c）和膜孔堵塞阻力（R_p）较直接超滤分别降低了39.6%和81.2%,活性炭在超滤膜表面形成的滤饼层结构将AOM与超滤膜进行了隔离,能够减缓膜污染速率,对于控制膜的不可逆污染亦具有重要作用.     

Ultrafiltration with in-line coagulation for the removal of natural humic acid and membrane fouling mechanism

Experimental and theoretical analysis were made on the natural humic acid removal and the membrane fouling of ultrafiltration （UF） with in-line coagulation. The results showed dissolved organic carbon （DOC） and UV254 removals by the UF with in-line coagulation at pH 7 were increased from 28% to 53% and 40% to 78% in comparison with direct UF treatment respectively. At the same time, the analysis of high performance liquid chromatography showed that UF with coagulation had significant improvement of removal of humic acid with molecular weights less than 6000 Da in particular. Compared to direct UF, the in-line coagulation UF also kept more constant permeate flux and very slight increase oftransmembrane pressure during a filtration circle. Two typical membrane fouling models were used by inducing two coefficients Kc and Kp corresponding to cake filtration model and pore narrowing model respectively. It was found that membrane fouling by pore-narrowing effect was effectively alleviated and that by cake-filtration was much decreased by in-line coagulation. Under the condition of coagulation prior to ultrafiltration at pH 7, the cake layer formed on the membrane surface became thicker, but the membrane filtration resistance was lower than that at pH 5 with the extension of operation time.     

不同组分的有机物对膜过滤通量下降的影响

采用DAX-8、XAD-4、IRA-958型树脂将自来水中有机物分离成强疏水性、弱疏水性、极性亲水性、中性亲水性有机物,以聚偏氟乙烯、聚醚砜、醋酸纤维3种材质的膜对各组分水样进行膜过滤试验,研究不同组分的有机物对膜过滤通量的影响.结果表明,过滤原水时,PES膜、PVDF膜和CA膜的通量分别比初始通量下降了67%、 59%和19%,表明疏水性越强的膜,越容易造成污染.就各种组分对通量的影响而言,过滤中性亲水性组分的通量下降为初始通量的41%～75%,而弱疏水性组分为6%～33%,表明中性亲水性组分对膜过滤通量的影响最大.3种膜中,CA膜对中性亲水性组分的截留率最高,达14.69%,但通量下降程度却最小,说明膜通量下降的程度并不与有机物截留总量正相关.对膜污染机制进行探讨后发现,对于截留分子量较大的超滤或微滤膜,相对分子质量>3×10⁴的中性亲水性组分通过堵塞膜孔内部,从而造成严重的膜污染;而对于截留分子量较小的超滤膜,中性亲水性组分由于无法进入膜孔,主要在膜表面形成滤饼层,从而对膜通量的影响较小.