Using hexadecyl trimethyl ammonium bromide (CTAB) modified clays to clean the Microcystis aeruginosa blooms in Lake Taihu, China

Clays are useful in environmental water cleaning because they cause flocculation of the contaminated microorganisms. In order to develop an improved method of mitigating the deleterious effect of harmful algal blooms (HABs) in Lake Taihu, China, we prepared clays from the sediments of the lake and modified the clays with hexadecyl trimethyl ammonium bromide (CTAB). The capability of the modified clays to clean the Microcystis aeruginosa blooms in the lake water was investigated. Using M. aeruginosa collected from the lake, the “jar tests” and sediment resuspension experiments showed that CTAB-modified clays inhibited 92% of the motility of the algal cells at an optimum concentration of 0.3 g/L, and the addition of CTAB greatly enhanced the effect of the clays. Inhibition of cell motility was due to cell aggregation by flocculation as visualized during the experiments. It also caused cell lysis as observed by scanning electron microscopy (SEM). The SEM image of clay-captured cells indicated the irreversible damages of the plasma membranes, which resulted in the disintegration of the harmful algal cells. Our study demonstrated that CTAB-modified clays may be an effective control measure and cleaning media for the water blooms in Lake Taihu. It also could be used to clean other freshwater lakes.