Fundamental Structure in Simultaneous Removal for Phytoplankton and Nutrient Salt in Lakes

  • SEKI, Tatsuhiro (Chiba Institute of Technology) ;
  • ISHII, Yuuichi (National Institute for Environmental Studies) ;
  • ISHII, Toshio (Chiba Institute of Technology) ;
  • TAKI, Kazuo (Chiba Institute of Technology)
  • Published : 2009.12.31


The water quality in eutrophic lakes is affected by serious problems, such as abnormal increasing of Cyanobacteria. The purpose of this study was to investigate the possibility of a modified flotation system using a hybrid technique formed by chemical compounds and an electrostatic bridge. Therefore, experiments using the hybrid technique were performed to measure the zeta potential value on the phytoplankton surface and the removal efficiencies of phytoplankton, ammonia nitrogen, nitrate nitrogen and phosphoric acid. The results were as follows: Firstly, the zeta potential of M.aeruginosa was observed to approach charge neutralization due to adhesion of magnesium hydroxide precipitate on the phytoplankton surface in the pH range 10.5 to 11. Secondly, the concentration of chlorophyll-a decreased from about 150 to 20${\mu}g$g/L, with a maximum removal efficiency of 84% due to coagulation with pH values higher than 10. Thirdly, the N$H_4$-N concentration was observed to decrease from 0.62 to 0.54mg-N/L (13%), and the P$O_4$-P concentration, which is a limiting factor to the formation of algae blooms, decreased from 0.27 to 0.02mg-P/L (92%). These findings suggest that the modified flotation system can be applied for the purification of the raw water of numerous lakes containing high phytoplankton populations and elevated pH.


Flotation process;Magnesium compounds;Micro-bubble;Microcystis aeruginosa;Nutrient salt;Zeta potential


  1. Yang, S., Ba, Y., Zhang, H., and Cheng, X., “Characteristic analysis on the toxin of microcystis in life water source of Zhengzhou City,” Wei Sheng Yan Jiu, 36(4), 421-423 (2007)
  2. Rinta-Kanto, J. M., Ouellette, A. J., Boyer, G. L., Twiss, M. R., Bridgeman, T. B., and Wilhelm, S. W., “Quantification of toxic Microcystis spp. during the 2003 and 2004 blooms in western Lake Erie using quantitative real-time PCR,” Environ. Sci. Technol., 39(11), 4198-4205 (2005)
  3. Cyanobacterial toxins: microcystin-LR in drinking-water (Background document for development of WHO guidelines for drinking-water quality), WHO/SDE/WSH/03.04/57, World Health Organization, Geneva, (2003)
  4. Shiga-ken Biwako Kenkyujo, Lake Biwa Research Institute, International Lake Environment Committee, and United Nations Environment Programme (UNEP), Data book of world lake environments: a survey of the state of world lakes, International Lake Environment Committee, Otsu, Japan (1988)
  5. Han, M. Y., Kim, M. K., and Shin, M. S., “Generation of a positively charged bubble and its possible mechanism of formation,” J. Water Supply Res. Technol.-Aqua, 55(7-8), 471-478 (2006)
  6. Amano, Y., Murakami, K., Ishii, T., Matsushima, H., and Taki, K., “Elution of nutrient salts from sediment layer in eurtophicated lake,” Proc. 1st IWA Asian-Pacific Regional Conference, Fukuoka, Japan, vol. 2, pp. 193-198 (2001)
  7. Shin, H. S., and Lee, S. M., “Removal of nutrients in wastewater by using magnesium salts,” Environ. Technol., 19(3), 283-290 (1998)
  8. Mirnezami, M., Robertson, K., Gauvin, R., and Finch, J. A., “Mechanism of aggregation of silica by magnesium ions: A technical note,” Can. Metall. Q., 43(4), 521-525 (2004)
  9. Taki, K., Seki, T., Mononobe, S., and Kato, K., “Zeta potential 999measurement on the surface of blue-green algae particles for micro-bubble process,” Water Sci. Technol., 57(1), 19-25 (2008)