水质安全的动态超声波强化混凝除藻水处理试验研究

超声波辐射能够破坏蓝藻气囊,在水处理工艺中达到强化蓝藻混凝沉淀的效果.然而不适当的超声处理会进一步破坏蓝藻细胞,导致胞内毒素大量释放,加重水质污染负荷.本研究为获得水质安全的超声波强化混凝沉淀蓝藻水处理方法,采用频率40~120 k Hz的超声波辐射蓝藻水,考察处理后蓝藻混凝沉淀去除效果及藻毒素释放情况.结果表明,频率68~120 k Hz、能量密度59.1~186.4 W·L-1的静态超声波作用10~15 s后进行混凝沉淀,藻类去除率达98%以上,且频率越高效果越好;然而各频率静态超声波作用5 s以上均会导致藻细胞内藻毒素释放.采用内衬吸声棉及动态超声方式,频率120 k Hz、能量密度38.5~196.6 W·L-1超声波作用7.5~30 s后,可避免胞内藻毒素释放,且能去除水中溶解性藻毒素18.7%~30.7%,混凝沉淀后藻类去除率97.0%以上,其它有机物也降低.

Experimental study on the safe removal of cyanobacteria with dynamic ultrasound enhanced coagulation

Ultrasonic radiation can damage the cyanobacterial vesicles and enhance the coagulation and sedimentation of cyanobacteria in water treatment processes. However, improper sonication would further damage cyanobacterial cells, leading to the release of intracellular toxins and increase of water contamination. In order to get a safe ultrasonic method, both the removal of cyanobacteria and release of microcystins were evaluated for the cyanobacteria-containing water, which was treated by ultrasound combined with coagulation and sedimentation. Results showed that the removal efficiency of cyanobacterial cells was more than 98% after treated by static ultrasound in the frequency range 68~120 kHz and energy density 59.4~186.4 W · L^-1 for 10~15 s, combined with the following coagulation and sedimentation. And the higher the ultrasonic frequency, the higher the removal efficiency. However, static ultrasonic irradiation for more than 5 s in each studied frequency will result in the release of intracellular microcystins. Conversely, after fixed with sound-absorbing cotton in dynamic ultrasonic device, the release of intracellular microcystins could be avoided and 18.7%~30.7% dissolved microcystins could be removed after treated by ultrasound with the frequency of 120 kHz and energy density of 59.4~196.6 W · L^-1 for 7.5~30.0 s followed by coagulation and sedimentation. Besides, the removal efficiency of cyanobacterial cells was more than 97% and other organic compounds were also reduced.