**Acknowledgements**

*Water Chemistry*

**32**

**4. Conclusion**

**Table 2.**

**Figure 13.**

In the present study, we observed the aquatic ecosystem and investigated the water quality of anthropogenically eutrophied pond between 2006 and 2009. As a result, it was found that in this pond, it was easy for blue-green algae to grow intensively, and it was easy for the pH of the surface water to rise by photosynthesis of the blue-green algae (pH 9.2 ± 0.32, *n* = 24, in 2008). By utilizing these features, we considered to develop a simultaneous recovery system of phosphate ion and blue-green algae using calcium chloride. As the pre-examinations using a growth medium, we observed the phenomenon that the precipitation of calcium phosphate and the coagulation of *M. aeruginosa* occurred simultaneously. The growth medium of 100 mL was filtrated using a prototype sand filtration column which was fabricated to be symmetric for reverse cleaning and to simultaneously recover both phosphate ion and blue-green algae. As a

*Simultaneous removal test of both blue-green algae and phosphate ion from pond water (n = 1).*

*Parts of a simultaneous phosphate ion and blue-green algae removal system. (a) Surface water inlet and pump in pond water bath, (b) side view of surface water inlet, (c) inside of photosynthesis enhancer, (d) lighting of photosynthesis enhancer, (e) calcium chloride injector, (f) piping structure of calcium chloride injector, (g)* 

*reaction bath, (h) structure of sand filtration column, and (i) treated water.*

The author acknowledges Messrs. Mayu Taguchi, Takuto Toshioka, and Tohru Sasaki for the contributions to their experiments in aquatic ecosystem and the present removal system. The author also appreciates Messrs. Naoya Yasue, Tomoyuki Sakamaki, Norio Suka, Jun Kanno, Yuki Ito, Kohei Taguchi, Kyota Suzuki, Daisuke Tokunaga, and other lab members for their contributions and assistances with the experiments in water monitoring. The present work was financially supported in part by grants of collaborative projects in the Tokyo University of Technology.
