The research on control of phytoplankton increase and water purification by artificial running water.

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 14550544
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Civil and environmental engineering
• Research Institution: OKAYAMA UNIVERSITY
• Principal Investigator: KAWARA Osami Okayama Univ., Health & Environment Center, Professor, 保健環境センター, 教授 (90093228)
• Co-Investigator(Kenkyū-buntansha): ONO Yoshiro Okayama Univ., Environmental Science & Technology, Professor, 環境理工学部, 教授 (50152541)
• Project Period (FY): 2002 – 2004
• Keywords: running water / phytoplankton / suppression of increase / water purification / vertical mixing / experiment / field observation

Research Abstract

In this research, the mechanism of suppressing algae increase by running water and application of this phenomenon to water purification were investigated. The main results obtained areas follows.
Based on the experiment using circular tank, the results show that running water suppresses algae increase. The floating chlorophyll-a concentrations were caught by the sand and gravel covering the tank bottom within 2 days. However, the floating algae concentrations increase again. The transmitted light in river water is greatly influenced by water quality and water depth. The transmitted light at the water depth of 50cm decreases by some tens of percent in comparison with the light intensity at the water surface. The running water causes vertical mixing of algae. This vertical mixing reduces available light intensity for algae photosynthesis. In addition, the algae culture is carried out under fluctuated light. The experimental results show suppressing influence in the algae breeding become greater as the fluctuation period of light become longer within the period from 1.2 to 7.6 seconds.