Effective removal of Microcystis aeruginosa and microcystin-LR using nanosilicate platelets

• Nanosilicate platelet (NSP) can selectively inhibit the growth of Microcystis aeruginosa.
• NSP can inhibit M. aeruginosa growth up to higher than 99% at 2.61 × 107 cells mL−1.
• NSP can enhance the settling of M. aeruginosa.
• 500 ppm of NSP can remove more than 99% of microcystin-LR at 100 μg L−1.

Drinking water safety has been threatened by increasing harmful algal blooms (HABs) in water sources. HABs are closely associated with eutrophication in freshwater lakes, e.g. Lake Tai in China, and marine environments as well, e.g. Baltic Sea in Europe. Among all HABs, Microcystis aeruginosa attracted much attention due to its easy proliferation and potent toxins, microcystins. Most of the current control technologies can result in immediate release of microcystins which are hard to remove by drinking water treatment processes. Here we propose to simultaneously remove M. aeruginosa and its toxin, microcystin-LR (MC-LR), using nanosilicate platelet (NSP) derived from natural clay mineral. In this study, NSP showed strong selective growth inhibition and good settling enhancing effects on M. aeruginosa and highly efficient removal of MC-LR. NSP can inhibit the growth of M. aeruginosa (initial cell concentration at 3.00 × 106 cell mL−1) with a LC50 at 0.28 ppm after 12 h exposure. At the dosage of 100 ppm, NSP can enhance settling of suspended M. aeruginosa. Bacterial growth inhibition tests showed NSP had very mild growth inhibition effects on Escherichia coli at high dosage but promoted the growth of Pseudomonas aeruginosa and Bacillus halodurans. For MC-LR removal, at an initial concentration of 100 μg L−1, NSP achieved higher than 99% removal. Thus, the results suggest that NSP could be an excellent candidate for controlling M. aeruginosa-related HABs in water bodies.