【作者】 张阳；

【导师】 陈晓国；

【作者基本信息】 武汉理工大学 ， 环境工程， 2010， 硕士

【摘要】 我国水体富营养化现象日益严重,引起蓝藻水华频繁爆发,给淡水生态系统及其功能造成严重破坏,甚至还会威胁人类的健康。在各种治理水华的技术与措施中,絮凝沉降法由于具有快速、有效的优点而被广泛应用,其中天然矿物絮凝法由于粘土来源丰富并且没有二次污染,尤其经过改性后粘土投加量也显著降低,被认为是一种具有发展前景的防治技术方法之一。但是絮凝法处理水华只是将藻细胞从水体中转移到沉积物中,并没有彻底将藻细胞消除。絮凝处理后的藻细胞在沉积物中的死亡分解及藻毒素的释放很可能会对环境产生危害,因此有必要对絮凝处理水华的环境安全性进行研究。本文以水华优势藻类铜绿微囊藻为研究对象,通过模拟絮凝处理水华的过程,研究了铜绿微囊藻经絮凝沉降之后在水-沉积物中的分布和细胞分解过程,以及细胞内微囊藻毒素(MC)在沉积物中的释放和降解规律,进而对絮凝法应急处理水华的有效性及环境安全性进行评价。具体研究内容和结果如下：1.沉积物中MC提取方法的优化沉积物中MC的提取是研究MC在沉积物中迁移转化规律的基础,为了能对MC进行有效提取,对MC的提取方法进行了优化。分别从提取剂甲醇的浓度、提取剂用量、提取时间、提取次数进行优化,最终得到最优的提取方法为：使用浓度为75%的甲醇进行提取,提取剂用量为7 mL,提取时间为20 min,重复提取三次,提取率可达95%以上。2.有氧条件下絮凝处理水华的环境安全性研究以水华优势藻类铜绿微囊藻作为研究对象,通过模拟絮凝应急处理水华的过程,研究了有氧条件下铜绿微囊藻经絮凝沉降后藻细胞在水-沉积物中的分布和细胞分解过程,以及细胞内MC在沉积物中的释放和降解规律。结果表明,PAC、海泡石和PAC/海泡石联用均可有效去除水华藻类,除藻率都可以达到99%以上。其中PAC/海泡石联用不仅能快速沉降藻细胞,还能有效防止藻细胞重悬浮,避免水华的再次爆发。沉积物中的藻细胞经过约28天逐渐死亡分解,而絮凝处理既不会加速细胞的分解,也不会延缓细胞的死亡。MC在经过9天左右的滞后期后,开始缓慢降解,在20-28天左右降低到检测限以下,不同絮凝剂处理对MC的降解规律没有显著性影响。絮凝处理对水相中TOC和TN的变化也没有显著性影响,只是在实验后期(20天左右),水相中TOC和TN浓度会大幅增加,需加强水质的检测与管理。3.厌氧条件下絮凝处理水华的环境安全性研究在完全厌氧的条件下,研究了铜绿微囊藻经絮凝沉降后藻细胞在水-沉积物中的分布和细胞分解过程,以及细胞内MC在沉积物中的释放和降解规律。结果表明,在厌氧条件下,藻细胞生物量经过8天左右的滞后期后开始快速减少,第24天已检测不到藻细胞的存在。絮凝处理及不同的絮凝剂对藻细胞的分解没有显著影响。厌氧条件下沉积物中藻细胞分解较快,这有利于有害藻类的去除。PAC和PAC/海泡石联用在厌氧条件小均可有效抑制藻细胞的重悬浮,对防止水华的再次爆发有较好的效果。MC经过约8天的滞后期后快速降解,第24天降低到检测限以下。厌氧条件下MC在4天时间内可以降解90%以上,说明厌氧条件下沉积物中MC的降解菌活性较强。水相中TOC及TN含量在20天后会大幅增加,需加强检测与管理。更多还原

【Abstract】 The frequency of cyanobacteria blooms has been increasing in recent years in China, which is attributed to the eutrophication of fresh water bodies. Cyanobacteria blooms pose a series of problems on the functions of water body, and even threaten human health. Numerous techniques have been studyed for the control of water bloom. Flocculation is an efficient and inexpensive technique and has been widely used in water treatment. Previous studies showed that it can be used to control water blooms, especially with the natural or moditied clays as flocculator. However, the algal cells are not removed completely from water bodies after flocculation, and they still accumulate in the sediment of water bodies. The decomposition of the algal cells in the sediment, or the release of algal toxin may cause new environmental problems. It is necessary to investigat the environmental safety of water bloom conrol by flocculation. In this thesis, we studied the distribution and decomposition of the Microcystis aeruginosa in the water-sediment phase, and the release and degradation of Microcystin (MC) in the sediment to evaluate the effectiveness and environmental safety of this process by simulating the process of using flocculation in emergent control of algal bloom. The main content and results were as follows:1. The optimization method for extracting MC in sedimentsThe extraction method of MC from sediment is a precondition for the research of MC. In order to extract MC from sediment effectively, it’s necessary to optimize the extraction method. The concentration of methanol, volume of extraction reagent, extraction time, number of extractions was optimized in this study. The result showed that optimal extraction method was:75% of methanol,7 mL,20 min, repeat three times, and the extraction yield could over 95%.2. Research on the environmental safety of water bloom control by flocculation under aerobic conditionsThe distribution and decomposition of Microcystis aeruginosa cells, and the release and degradation of intracellular microcystin under aerobic conditions were investigated through simulation experiments to evaluate the efficiency and environmental safety of this treatment process. Results showed that cells were efficiently removed from water column with polymeric aluminum chloride (PAC), sepiolite or both of them, amd the removal rate were more than 99%. Furthermore, PAC together with sepiolite effectively prevented the recruitment of deposited cells. The cells in sediments decomposed gradually after 24-28 days. Flocculation process neither accelerated cells decomposition nor slowed cell death. MC was degraded to be below the detected limit within 20 to 28 days after nine days delay. Flocculation had no negative effect on the release and degradation of MC, nor the TOC and TN concentration in the water phase. But in the late stage of experiment (about 20 days), TN and TOC concentration increased significantly, it was need more attention.3. Research on the environmental safety of water bloom control by flocculation under anaerobic conditionsThe distribution and decomposition of the cells, and the release and degradation of intracellular microcystin under anaerobic conditions were investigated to evaluate the efficiency and environmental safety of this treatment process. Results showed that cells were degraded to be below the detected limit within 24 days after eight days delay under anaerobic conditions. Flocculation process had no significantly affected on the decomposition of cells. The rapid decomposition of cells favored the removal of harmful algae. Furthermore, PAC and PAC together with sepiolite effectively prevented the recruitment of deposited cells. MC was degraded to be below the detected limit within 24 days after eight days delay under anaerobic conditions. Ninety percent of MC was degraded in four days, demonstrating that the microorganisms can efficiently degrade MC under anaerobic conditions. TN and TOC concentrations in the water phase would increase significantly (after 20 days), it was need more attention.更多还原