A research team led by Masafumi Fujita, Associate Professor of the Department of Urban and Civil Engineering, Ibaraki University, has devised a new treatment system that uses seawater to break down organic matter contained in domestic wastewater. The new system is attracting attention as a low-cost technology for developing nations both because it makes use of tides to allow seawater to fill and then drain from septic tanks, and because it utilizes sulfates contained in seawater to break down organic matter in wastewater and can therefore be used in low oxygen conditions, thus avoiding the generation of sludge.
Public sector facilities, homes, and hotels in the South Pacific atoll nation of Tuvalu are almost all concentrated on the narrow island of Fongafale. Domestic wastewater is treated by combined system septic tanks, pit toilets and other means, but because the tanks and toilets are constructed without bottoms, domestic wastewater seeps into the ground.
Associate Professor Fujita's team has been studying the relationship between coastal water pollution and the growth of foraminifera since spring 2010 at the request of the SATREPS project team led by Professor Hajime Kayanne of the University of Tokyo. Research to date has shown that the bottomless septic tanks are the cause of pollution, with seawater penetrating tank bottoms at high tide and polluted water leaking out to sea at low tide. There is a high likelihood that this pollution is also affecting the growth of foraminifera (the exoskeletons of which become Tuvalu's "star sand").
The research team has also been studying domestic wastewater treatment systems suited to Tuvalu's environment, and has devised and lab-tested a new system that makes use of the bottomless combined septic tanks as they are. The researchers demonstrated that sulfates in the seawater can break down organic matter, and that sulfate-reducing bacteria which contribute to the process are not flushed out together with seawater if supplied with a substrate to adhere to.
Ibaraki University has applied for a Japanese patent for this system, and is holding discussions with private sector entities as it considers further locations in which such a system could be used in addition to atoll nations like Tuvalu. Potential users include developing countries lacking adequate sanitation facilities and coastal regions in Japan.
Research Area: Environment and Energy “Research contributing to adaptation to or mitigation of climate change”
Project Title: Eco-technological Management of Tuvalu against Sea Level Rise “Protecting Tuvalu, Island of Beautiful Coral Reefs and Star Sand, from Sinking”
Tuvalu is a tiny island nation made up of nine atolls and islands. Because it has a very flat topography with a maximum elevation of three meters, Tuvalu is in danger of submerging owing to rising sea levels caused by recent climate change. Two thirds of Tuvalu's land area is composed of depositions of the calcareous exoskeletons of foraminifera and coral, and the sand derived from foraminifera, coral, and other organisms plays a major role in sustaining land formation in Tuvalu. This project aims to elucidate the mechanisms whereby Tuvalu's islands are formed and sustained, develop measures for restoring the ecosystem and preventing coastal erosion, and draw up plans for coastal land management. Research carried out under the project has shown that with population increase and economic development in recent years, local issues such as inadequate waste disposal and domestic wastewater treatment methods, as well as manmade changes to coastal topography, are causing a decline in foraminifera productivity.
This is one of the 87 projects commenced under the co-funding program by JST and JICA called “Science and Technology Research Partnership for Sustainable Development (SATREPS).”
Masafumi Fujita, Ph.D.
Associate Professor, College of Engineering, Department of Urban and Civil Engineering, Ibaraki University
Research Partnership for Sustainable Development Division, JST
Office of Media and Public Relations, Japan International Cooperation Agency (JICA)