高锰酸钾预氧化强化混凝去除绿藻的研究

以小球藻为对象,研究不同高锰酸钾投加量下小球藻胞外有机物分子量的分布、Zeta电位和胞外有机物浓度变化,并观察细胞结构,探讨预氧化强化混凝的机理.研究发现,当高锰酸钾浓度≤2 mg·L-1时,氧化前后藻液中的有机物组成基本不变,胞外分泌物(EOM)部分被氧化;在预氧化初期,EOM在高锰酸钾诱导下释放,胞外有机物浓度升高;藻的表面电位先下降后上升,藻活性由于高锰酸钾氧化受到抑制,但藻细胞结构保持完整,氧化后生成的MnO2附着在藻细胞表面,增加了藻细胞的比重,有利于后续的混凝沉降除藻.高锰酸钾浓度≥3 mg·L-1时,细胞壁被破坏,藻液中出现大分子的有机物,胞外有机物浓度上升,Zeta电位下降,这些都不利于后续的混凝除藻.结果表明,当高锰酸钾投加量为2 mg·L-1,预氧化1h后,PAC投加量为40 mg.L-1时,除藻效率达到92％,去除效果远好于直接混凝除藻.

The study of green algae removal by potassium permanganate pre-oxidation enhanced coagulation

This study investigated the influence of permanganate oxidation on algae cell structure, zeta potential, extracellular organic matter molecular weight distribution and concentration, and explored the mechanisms of permanganate-enhanced chlorella algae removal by coagulation. When the dosage of permanganate was no more than 2 mg·L^-1, the composition of organic matter in suspension kept unchanged and partial extracellular organic matter (EOM) was oxidized. At the beginning of oxidation, permanganate induced the release of EOM from the algae and thus increased the organic content in suspension. The zeta potential experienced an increase after a decrease while the algae activity was dropped by permanganate. However, the structure of algae kept complete and MnO₂ produced after oxidation adhered to the algae surface which increased the algae density and favored the subsequent algal coagulation. When the concentration of permanganate was no less than 3 mg·L^-1, the algal cell structure was destroyed, the high molecular intracellular organic matter was released into the algae suspension, and zeta potential decreased, all of which had negative effects on subsequent algal coagulation. The results showed that the optimal dosage of permanganate was 2 mg·L^-1 and the optimum contact time for permanganate oxidation was 1 h. Permanganate pre-oxidation could enhance algae removal by coagulation with PAC significantly.