大型超滤水厂PVC和PVDF膜运行特性差异与优化

超滤技术已广泛应用于城镇给水处理厂,使得饮用水水质得到显著改善。不同材质超滤膜的运行周期、膜通量、跨膜压差(TMP)等的变化规律会有显著的差异,需要根据各自的特点对超滤系统进行运行参数调控与优化,以保证超滤系统的长期稳定运行。分析了山东某大型超滤水厂超滤系统长期运行的特点,对比了PVC膜和PVDF膜孔结构特征、膜通量、跨膜压差变化趋势及膜过滤阻力特性,调控和优化超滤系统运行参数,并进行了长时间的运行验证。结果表明,膜孔径和膜孔结构不同造成的膜污染是PVC膜与PVDF膜过滤特性差异的主要因素,恒定过滤周期运行模式下PVC膜通量加速衰减时段为82~220 min,造成PVC膜通量衰减了9. 14%,并形成了约5%的永久衰减膜通量,而PVDF膜的通量衰减并不明显,使得水厂超滤系统在恒定过滤周期(180min)运行模式下,出现了PVC膜的污染速率明显高于PVDF膜、系统的运行工况出现显著差异的现象。按照恒定过滤阻力模式运行时,PVC膜和PVDF膜的最佳过滤周期范围分别为82~108 min和96~155 min。水厂超滤系统在恒定过滤阻力运行模式下将PVC膜与PVDF膜在高温期和低温期的过滤周期分别调整为110、90 min和150、120 min,TMP的增长速率和化学维护清洗周期均基本一致,超滤系统实现了长期稳定运行。研究成果为我国超滤水厂中不同材质超滤膜的运行参数优化及协同稳定运行提供了参考。

Operation Characteristics and Optimization of PVC and PVDF Membranes in Full-scale Ultrafiltration Drinking Water Treatment Plant

Ultrafiltration( UF) technology has been widely used in various urban water supply treatment plants and the quality of UF permeate is higher than that of conventional drinking water treatment process. The significant differences have been consisted in the operating cycle,membrane flux,transmembrane pressure( TMP) among UF membranes with different materials. According to respective characteristics of UF membranes to adjust the operating parameters is necessary for its long-term stable operation. The long-term operation characteristics of UF system in a full-scale drinking water treatment plant( DWTP) in Shandong was analyzed. The pore structure,flux,TMP and filtration resistance of polyvinyl chloride( PVC) and polyvinylidene fluoride( PVDF) membranes were compared. After adjusting and optimizing the operation parameters of the UF system,the operation verification was carried out for a long time. The results showed that membrane fouling caused by different pore diameter and structure was the main factor for the different filtration characteristics between PVC and PVDF membranes. In the constant filtration cycle operation mode,the flux acceleration decay period of PVC membrane was 82-220 min,which caused the membrane flux to attenuate by 9. 14%,and formed a permanent decay membrane flux of about 5%. While flux attenuation of PVDF membrane was not obvious. Because of these situations,the operation of PVC and PVDF membranes system appeared a significant difference,of which the fouling rate of PVC membrane was obviously higher than that of PVDF membrane. When the UF system operated in constant filtration resistance mode,the optimal filtration cycle range of PVC and PVDF membranes were 82-108 minutes and 96-155 minutes,respectively.The filtration cycles of PVC and PVDF membranes at high and low temperatures were adjusted to 110 min,90 min and 150 min,120 min respectively. At this point,the TMP growth rate and the chemical maintenance cleaning cycle of PVC and PVDF membranes had very good consistency,and the UF system achieved long-term stable operation. Therefore,the research results provide a reference for optimizing operation parameters and keeping cooperative stable operation of different material UF in DWTP.