【作者】 王海燕；

【导师】 顾平；

【作者基本信息】 天津大学 ， 环境工程， 2011， 博士

【摘要】 低压膜分离技术被认为是当今制备优质安全饮用水的重要技术之一,其在饮用水处理领域已得到了普遍的认可。本研究通过中试规模的试验研究,从出水水质及稳定性、有机物去除、系统运行稳定性和经济性等指标,分析论证混凝-沉淀-超滤(简称沉淀-超滤)和混凝-沉淀-砂滤-超滤(简称砂滤-超滤)两种工艺的可行性。为了提高中试膜系统产水率,采用将膜反洗水预处理后回流至调节池的回收方案,并设计安装了两套小试混凝-微滤膜系统,一套处理混配水(预处理后的反洗水与滦河水按1:9的比例混合),另一套作为参比系统处理滦河水。在中试膜系统运行过程中,预氯化加化学强化反洗(CEB)的运行方式对维持系统稳定运行较为有效,两种工艺膜出水水质稳定,处理效果安全可靠,出水水质均满足《生活饮用水卫生标准》(GB5749-2006)的要求。在采用较低浓度次氯酸钠进行预氯化时,并不会对膜出水水质造成安全隐患。沉淀-超滤工艺中膜出水中CODMn、UV254和运行成本均高于砂滤-超滤工艺,但是出水浊度略低。两工艺的产水率分别为88.2%和91.8%。中试膜系统采用预氯化工艺可以延缓膜污染的增长,CEB工艺能够有效地恢复膜比通量。采用草酸进行化学清洗效果较好,铁和溶解性有机物是导致中试系统膜污染的主要因素。两种工艺的膜反洗水中CODMn和DOC浓度均明显高于同时期的滦河水,而UV254较低。膜反洗水中DOC主要分布在MW>30 kDa和MW<1 kDa,UV254主要分布在MW<1 kDa区间。在膜反洗水预处理中单独混凝提高了原水中DOC、UV254和CODMn的去除率。就DOC而言,在混凝/PAC吸附过程中,MW>30 kDa的有机物得到了大幅度去除,但是由于混凝处理增加了小分子有机物含量消耗了部分PAC吸附容量使得MW<10 kDa的有机物去除效果较差。在膜反洗水预处理中,混凝/PAC吸附工艺比单独混凝工艺改善了混配水系统的出水水质。膜反洗水经混凝/PAC吸附预处理后回流对整个膜系统出水水质及膜污染没有明显的影响。反洗水经过预处理后回流能够将中试膜系统的产水率提高至99%左右。更多还原

【Abstract】 Low pressure membrane separation technology is essential for the preparation of safe drinking water and is universally recognized in the field of drinking water treatment. To investigate the feasibility of coagulation - sedimentation - ultrafiltration （CSU） and coagulation - sedimentation - sand filtration - ultrafiltration （CSSU） processes, a pilot-scale of membrane system was set up, and the quality and stability of treated water, removal of organics, stability of system, operation costs of system and other indicators were analyzed and compared. In addition, in order to improve the productivity of the pilot-scale membrane system, a scheme of recovering membrane backwash water （MBW） was applied,which was to pre-treat MBW and recycle the effuent into the equalization tank. Two lab-scale coagulation microfiltration （MF） membrane systems were installed. The raw water of one membrane system was a blend water （pre-treated MBW blended with Luan River water （LRW） in a 1:9 ratio）, and a separate membrane system was used to treat LRW.In the operation process of pilot-scale membrane system, the mode of pre-chlorination plus chemically enhanced backwash （CEB） was more effective to maintain system stability. The quality of treated water from the CSU and CSSU processes was safe and reliable, and met the requirement of the Standards for Drinking Water Quality （GB5749-2006）. The mode of pre-chlorination with a low concentration of NaOCl was not cause security problems. The value of CODMn and UV254 in the treated water and costs by CSU were higher than those by CSSU, but turbidity in the treated water was lower. The productivities of CSU and CSSU processes were 88.2% and 91.8% respectively.Membrane fouling could slow down by pre-chlorination process which the CSU and CSSU process used. CEB could recover the membrane specific flux effectively. The effect of chemical cleaning with oxalic acid was better, and iron and dissolved organic matter were the main factors which leading to the pilot-scale membrane fouling.Compared to LRW, the concentration of DOC and CODMn in the two MBWs from CSU and CSSU processes was higher, but the value of UV254 was lower. Organic matter characterized by DOC in MBWs consisted primarily of compounds with a MW greater than 30 kDa and substances with a MW less than 1 kDa, whereas UV₂₅₄ represented compounds with a MW less than 1 kDa. The removal rate of CODMn, DOC and UV254 in the MBWs was improved due to addition of powdered activated carbon （PAC） in the pre-treatment. In the process of coagulation/PAC, the organics characterized by DOC with a MW greater than 30 kDa was removed substantially, but an increase in the removal efficiency of DOC with MW<10 kDa were not observed due to the enrichment of low MW organic matter during the coagulation process, which adsorbed more efficiently to PAC.Compared to the coagulation pre-treatment, the quality of finished water in the mixed water system had been improved by coagulation/PAC process. There was no obvious difference in water quality of the finished water form two lab-scale membrane systems. And the membrane fouling was not deteriorated after recovering MBW which was pre-treated by coagulation/PAC. The productivity of CSU and CSSU was reached 99% by recovering MBW.更多还原