胞外物质影响铁盐混凝除铜绿微囊藻的效能与机制

藻及其代谢产物严重威胁着饮用水质的安全.混凝是饮用水处理工艺中去除藻细胞最为重要的单元,而藻细胞的胞外有机物(EOM)是影响藻细胞脱稳和去除的重要因素.本文以铜绿微囊藻为研究对象,对比混凝对原始藻细胞和经离心去除EOM的藻细胞(裸藻)的去除效果.结果发现,在pH为6.0、7.0和8.0的条件下,铁盐混凝对裸藻细胞(去除EOM的藻细胞)的去除率比原始藻细胞分别提高了5.01%、29.24%和27.45%,证实EOM对铁盐混凝除藻具有抑制作用.此外,絮体粒径动态分析表明,在pH分别为6.0、7.0和8.0下,裸藻细胞对应的最大絮体粒径均比原始藻细胞要高.Zeta电位分析表明,裸藻比原始藻的Zeta电位更高,因此,更容易通过压缩双电层脱稳.三维荧光分析结果表明,EOM易与金属发生络合反应,生成螯合物,从而抑制混凝除藻.

Effect and mechanism of extracellular substances on removal of Microcystis aeruginosa by ferric salt coagulation

Algae and its metabolites seriously threaten the safety of drinking water quality. Coagulation is a very important unit to remove algae cells in the drinking water treatment process, and the extracellular organic matter (EOM) of algal cells is an essential factor to affect the destabilization and removal of algal cells. In this paper, Microcystis aeruginosa was used as the research object. It was found that in comparison to that of the original algae cells, the removal rate of naked algal cells (algal cells without EOM) by the coagulation of iron salt increased by 5.01%, 29.24% and 27.45% at pH value of 6.0, 7.0 and 8.0, respectively, confirming that EOM had an adverse effect on the algae cells removal. In addition, the dynamic analysis of floc grain size shows that the corresponding maximum floc size of the naked algal cells at pH level of 6.0, 7.0 and 8.0 is higher than that of the original algae cells. Zeta potential analysis displays that the Zeta potential of the naked algae was higher compared with that of the original algae, so the naked algae is easier to destablize by compressing the double electric layer. The results of the three-dimensional fluorescence analysis demonstrate that the EOM is prone to combine with the metal to form chelate, thus inhibiting the coagulation of iron salts on algae.