UTILIZINGMICROORGANISMSTOPURIFY
WATER
AND ENHANCE PUBLIC HEALTH
A Japanese researcher has been promoting a method called the ecological purification system to purify water
utilizing the activities of small organisms. What is this low-tech but smart solution that produces safe and affordable
drinking water to help protect people’s health?
Ensuring access to safe andaffordable drinking water is oneof the United Nations’ Sustainable
Development Goals (SDGs),
but it has yet to be achieved for 2billion people worldwide.
“In places without safe accessto this vital resource, slight
improvements to water for drinking
and cooking can reduce instancesof diarrhea or dermatologicaldiseases. You’ll then see a change
in people’s health awareness. The
key is promoting sustainable,
do-it-yourself technologies andfosteringawareness,”says
NAKAMOTO Nobutada, Professor
Emeritus of Shinshu University.
As a leading researcher on
biological purification throughslow sand filtration, Nakamoto
has worked to build sustainable
water purification systems in suchdeveloping countries as Sri Lanka,
Bangladesh, Fiji, and Samoa.
Slow sand filtration, a water
purification technique invented
in the U.K. during the 19thcentury, was thought to physicallyremove contamination by slowly

NAKAMOTO Nobutada, who has been disseminating theecological purification system within developing countries, ispictured at the Someya Water Treatment Plant in Ueda City,
Nagano Prefecture, where he has been conducting researchfor decades. The plant uses the ecological purification system(EPS). After 100 years of operation, the plant is still
delivering clean water to citizens. THE ASAHI SHIMBUN

Ecological Purification SystemRaw water
Biological layer
Sand layerWaterflow

The Japanese government is promoting global
health as a priority area of international
cooperation. In the Global Health Strategy set
forth in May 2022, it called for thestrengthening of efforts toward tackling theworld’s water and sanitation problems. JICA
has been encouraging the use of EPS for water
treatment. Nakamoto (right photo, far right)
visited Fiji as a JICA expert and gave direct
guidance to local officials. Since then, 100
Fijian villages have built biofiltration water
purification facilities by using EPS.

Gravel layer
Purified water

filtering water down throughpebble and sand layers. It wasknown that microorganisms in
the upper layer of sand break
down and remove pathogens anddirt, but Nakamoto, an expert
on algae, noticed that algae
also assisted in the process. The
water became tastier when algae
multiplied in copious quantities
at a water treatment plant that had
stopped using algicide. Throughphotosynthesis, the algae createdan oxygen-rich environment inwhich microorganisms accelerate
decomposition.
Nakamoto decided to rename
the “slow sand filtration” process
because of his assertion that theoriginal term is not in fact associatedwith the food chain works as a filter,
and that the actual purification in
biological active layer takes lesstime than one might imagine. His
new term for the process, then,is the “ecological purification
system (EPS),” and he has been
introducing it to the world.
Since the components of EPS
can be constructed without theuse of chemicals or machinery, andsince it features easy maintenanceand high resilience to disasters, theJapan International Cooperation
Agency (JICA) has been working
on transferring the technology
to, and disseminating it within,developing countries. Nakamoto
has cooperated with training
programs in Okinawa Prefecture
for trainees invited from Fiji andSamoa. He said, “It was good tohold the training in Okinawa. The
trainees could drink real filteredwater in a subtropical environment
similar to their own, and realizedthat they could maintain such asystem themselves.” Later, as one of
JICA’s experts, Nakamoto visitedthe two countries to follow up on

the training. There, he provided
guidance to local managers andhanded over simple illustrations
that he had prepared to ensure thatthe technology would remain inuse.
The Clean Water Supply System,
a compact water purification
system that Yamaha Motor Co.,
Ltd. is deploying in developing
countries in Asia and Africa tosolve water-related problems, also
employs the ecological filtration
method. The system has steadily
spread because residents canmanage it themselves. Currently,
45 units have been installed in 15
countries. Having safe, managed
water available nearby will not
only raise awareness of hygieneand prevent epidemics, but also
free women and children from theheavy burden of fetching water.
Japan will continue to makeinternational contributions tobuild societies in which all people
have sustainable access to safewater.