Membrane filtration technology combined with coagulation is widely used to purify river water.In this study,microfiltration(MF)and ultrafiltration(UF)ceramic membranes were combined with coagulation to treat local river water located at Xinghua,Jiangsu province,China.The operation parameters,fouling mechanism and pilot-scale tests were investigated.The results show that the pore size of membrane has small effect on the pseudo-steady flux for dead-end filtration,and the increase of flux in MF process is more than that in UF process for cross-flow filtration with the same increase of cross-flow velocity.The membrane pore size has little influence on the water quality.The analysis on membrane fouling mechanism shows that the cake filtration has significant influence on the pseudo-steady flux and water quality for the membrane with pore size of 50,200 and 500 nm.For the membrane with pore size of 200 nm and backwashing employed in our pilot study,a constant flux of 150L·m 2·h 1was reached during stable operation,with the removal efficiency of turbidity,total organic carbon(TOC)and UV254 higher than 99%,45%and 48%,respectively.The study demonstrates that coagulation-porous ceramic membrane hybrid process is a reliable method for river water purification.
气升式纳滤装置是一种新型膜过滤装置,具有能耗低、过滤条件温和等优点,在生化产品的分离纯化中应用前景广泛。以杆菌肽水溶液为过滤体系,采用孔径为0.9 nm的TiO2陶瓷纳滤膜,系统考察了曝气量和跨膜压差对气升式纳滤装置过滤性能的影响。结果表明,曝气可有效提升通量和截留率;当跨膜压差为0.3 MPa时,曝气量由20 L h 1增大到100 L h 1,通量和截留率分别提升34.0%和14.5%,在曝气量100 L h 1时两者达到最大,进一步增大曝气量,通量和截留率开始下降;当跨膜压差为0.1、0.3、0.5 MPa时,对应的最优曝气量分别为60、100、140 L h 1。并通过模型计算,分析了不同操作条件下,气升式纳滤装置流体力学性质和能耗的变化情况。
采用化学沉淀法进行盐水精制是氯碱工业的关键过程之一。今采用陶瓷膜脱除盐水中的沉淀物,考察了气升条件下盐水中化学沉淀物(CaCO3、BaSO4、Mg(OH)2)对陶瓷膜过滤过程的影响。结果表明,曝气对三种体系均可显著提高膜的渗透通量,含CaCO3盐水体系的膜通量与含BaSO4体系相当,是含Mg(OH)2体系膜通量的1.5倍;当曝气量大于300 L h 1时,进一步增大曝气量对含CaCO3、BaSO4体系的盐水渗透通量影响不大,但可使含Mg(OH)2体系盐水渗透通量提高50%以上;跨膜压差与通量基本呈线性增大关系,跨膜压差对CaCO3、BaSO4体系通量的影响大于对Mg(OH)2体系的影响;固含量增大,由于体系黏度显著增大,使三种体系的膜通量均呈下降趋势,含Mg(OH)2体系的通量下降最大。对盐水中沉淀物的分析结果表明,方解石相的CaCO3颗粒分散均匀,粒径为16.08μm,表面电势为16.5mV;重晶石相的BaSO4颗粒粒径在2.18μm左右,表面电势为33 mV;而无定形的Mg(OH)2颗粒粒径分布宽,平均粒径1.59μm,表面电势为18 mV。由于粒径与荷电性的双重作用,使得CaCO3、BaSO4体系膜过滤阻力相近,小于Mg(OH)2体系的膜过滤阻力;钙镁离子共沉淀中,随着钙离子量的增大,膜过滤通量增大。
