The Mitsui & Co. Environment Fund

Introduction to Grant Projects

Inba Yasai Ikada no Kai

Establishment of a biological purification system

Activity grant

Project Description

This is an initiative to purify the water around Lake Inba, Chiba Prefecture, which, through biological means, has become the nation's worst quality water source. It aims to establish the following methods already verified for use in agricultural canals.
(1) Control the formation of blue-green algae by spurring the growth of water spinach through aeration using a simple raft floating on the water surface.
(2) Remove floating organic matter using freshwater mussels and clams.
(3) Clean the water through a biological purification system combining aquatic plant propagation. In this activity, traditional non-durable wooden rafts are replaced with specially-designed aluminum rafts.

Preservation of biodiversity and ecosystem
Grant year
FY2006 Activity Grants
Grant term
3 years
July 2006 - June 2009
Grant amount
4,000,000 yen
Activity region
Agricultural canals adjacent to Lake Nishi-Inba, Sakura City, Chiba Prefecture, Japan
Harvesting of hydroponically-cultivated water spinach along agricultural canals.

Overview of the Organization

Yasuo Misashima, President
Yasuo Misashima, President
Establishment purpose
Around Chiba Prefecture's Lake Inba, the water temperature increases in the summertime and due to eutrophication, and destructive blue-green algae (fine algae) flourishes causing water vegetation to be on the brink of extinction. In the nation's worst quality water source, this organization aims to use the environmentally friendly "vegetation raft method" in order to regenerate the Lake Inba catchment area for those engaged in agriculture and fishing and, indeed, all citizens. To this end they organize events and are engaged in Lake Inba's water purification and environmental conservation to restore a clean and inviting water source.
Main areas of activity
Agricultural canals around Lake Nishi-Inba, Sakura City, Chiba Prefecture.
1 full-time staff member, 15 part-time staff members, and 150 full members.
Annual operating budget
2.26 million yen in 2005, 3.14 million yen in 2006, 4.99 million yen in 2007.
Recent Activities
  • 1. Water purification using the "vegetation raft method"
  • (1) Through the hydroponic cultivation of water spinach, increase the absorption of phosphorus and nitrogen, thereby suppressing the growth of blue-green algae and encouraging the growth of water vegetation.
  • (2) Through the cultivation of water clams and mussels, facilitate the absorption of floating organic matter, increasing water transparency, allowing the sun to reach the water bed, encouraging water vegetation growth and restoring natural water purification processes.
  • 2. Conduct surveys of fresh water clams and aquatic life.
  • In the Inba catchment area, where freshwater clams and many other kinds of aquatic life are extinct, go out once a month in the rice marshlands and small rivers and conduct surveys of clam and aquatic life populations and work towards the conservation and restoration of aquatic life.
  • 3. Conduct interactive environmental learning.
  • Link up with elementary and junior high schools around the Lake Inba catchment area, teach the children who will be responsible for its future of the importance of the water environment conservation and preservation.
  • 4. Fishing competitions for the fishing out of non-native species.
  • Work towards the conservation of existing fish stocks and restoration activities and the fishing out of introduced species.