Abstract
Several methods for removal of microcystins from water are investigated. Firstly, the variations of the microcystin concentrations in the water of Taihu Lake and in the tap water of Wuxi city during the summer time are discussed. Secondly, two types of photocatalytic reactors are tested. In the annular-flow photocatalytic reactor with a 6-W blacklight blue fluorescent lamp as a light source, three liters of 1600 ppt microcystin-LR solution was treated and 65 % of microcystin-LR was degraded after 3.5 h and almost 100 % after 20 h. The falling-film photocatalytic reactor was operated under irradiation with sunlight and a rapid degradation of microcystin-LR was observed at an illumination intensity of 60,000-110,000 lx; a degradation of 88 % after 5.5 h. Thirdly, two kinds of activated carbons are tested to remove microcystins by adsorption. In the case of wood-base granular activated carbon, repetitive treatment in a continuous-flow mode removed 99% of microcystin-LR at an initial concentration of 2300 ppt in 50 min. In a batch-recirculation mode, on the other hand, it took about 150 min to achieve the same removal. In the case of bamboo-base activated carbon, only 17.7 % of microcystin-LR was removed even at a very low linear velocity of 0.026 m min-1. Finally, a combined process of the photocatalytic degradation and adsorption by activated carbon is discussed.
