Re-thinking Toilets in Evacuation Shelters:

Plant-assisted Toilets
Introduction

W201905: Shizuoka Prefectural Mishima Kita Senior High School

Thousands of people are forced to stay and live in evacuation shelters every year in Japan due to natural disasters. However, toilet
facilities in local community evacuation shelters are not always ready for use, and this causes inconvenience and threatens the health ofevacuees. I have designed an innovative circulation mechanism that makes use of existing toilet facilities and a water treatment system
assisted by plants. By examining the water treatment ability of different plants and installation costs, and consulting the local community
to meet their needs, I propose plant-assisted toilets with a water circulation system to be fitted in toilets in evacuation shelters.

Research and Proposal
The HandyPod wastewater treatment
system in the Lake Tonle Sap

Typical toilet facilities in community evacuation shelters

CambodiaJapan

Composting

ManholePlastic bags
cover the toilet
to collect waste.

Sawdust treats
waste.

Waste goes tosewer pipes.

Easy to set up.

Less smell.
Expensive.

Disposal

Photos by WaterAidSingle use.
Storage problem.

Photos by Japan
Toilet LaboDirect.
Pipe checks
before use.

1. The waste from the latrine pan above the lakewater is flushed gravitationally into the plant drum
component.
2. Plants in the drum treat the wastewater.
3. Treated water is passed into the lake water.

Existing 6 manhole toilets in Mishima can be modified.

Method and Evaluation
Plant-assisted toilets with water circulation system by making use of existing manhole toilet facilities.
3 plants forhydroponics

Existing manhole toilet facilities

COD (Chemical Oxygen Demand) in eachcontaminated water sample was tested with thePack Test©, three times for a period of one month.
WhiteHyacinth
Pea sprouts
radishsprouts

COD: 100⇒20⇒20(clear)

COD: 100 COD:100
⇒100
⇒100
※ Died in ※ Died in2 weeks.
3 weeks.

Experimenting
water
treatment
ability ofplants

COD: Original state ⇒1 week later ⇒ 1 month later

The crisis management department of Mishima City
was interested in the plant-assisted toilets. Thesystem was highly evaluated as it enables water
circulation, which would help to save precious water
resources in the life of evacuation shelters, instead offlushing water down the sewer pipes.

Hand pump

Designing aplant assisted
toilet andestimating
costs

Treatment drum with plants
Water tank

Sewer pipe

The hand pump enables treatedwater to be used again to flush thewaste.

Consulting thelocal
community for
improvement

Cost to make a plantassisted toilet
Items

Cost

Drum (200L × 2 )¥20,000

Water tank

¥8,000Pipe (×3 )¥2,000Handy pump

¥1,800Total¥35,800

Conclusion
The most outstanding advantage of the plant-assisted toilets I have designed is that the water used in this system recycles and circulates
itself. It enables people to use the toilet facilities with only a limited amount of water needed for flushing. Plants which can be used in allseasons need to be found though. Securing readily usable toilets with good sanitary conditions is essential to saving lives. More attention
should be given to the management of toilets in the time of disasters. I believe the plant-assisted toilets are one possible option.

Reference
Japan Toilet Labo, https://toilet-nippon.heteml.jp/toilet.or.jp/disaster/info_gide2019.pdf（browsed on August 28, 2020)
Water Aid Japan, https://www.wateraid.org/jp/where-we-work/cambodia （browsed on August 28, 2020)
Jack Sim (2019), 『トイレは世界を救う‐ミスター・トイレが語る貧困と世界ウンコ事情』(“Toilets can save the world: Mr. Toilet talks about poverty and toilets in the world”), PHP
Wetlands Work! Ltd. “HandyPod description”, https://wetlandswork.com/products-and-services/handypod/ (browsed on October 10, 2020)