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

• Published in: Environmental engineering research Vol. 14; no. 4; pp. 220 - 225
• Main Authors: SEKI, Tatsuhiro, ISHII, Yuuichi, ISHII, Toshio, TAKI, Kazuo
• Format: Journal Article
• Language: Korean
• Published: 2009
• Subjects: Microcystis aeruginosa; Micro-bubble; Zeta potential; Flotation process; Magnesium compounds; Nutrient salt
• ISSN: 1226-1025; 2005-968X

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.