Handwashing Station Design

Course & Project Background

D-Lab: Water, Sanitation, & Hygiene is a course at MIT focused on educating students on these topics and their importance within developing countries. During the course, students also partner with organizations or groups in developing countries on projects relating to those topics. My project was to co-develop a sustainable hand-washing station alongside youth in Culebra, Puerto Rico. The project involved helping design a functional hand-washing station and calculating all the requirements needed to make this project functional. On the right, you can see the final design. Below you can see the design process and all the research and data behind the design decisions.

Ideation & Co-Creation Process

Together with Culebra youth, we engaged in a collaborative ideation and co-creation session. This led to a useful understanding of the needs of the community and the constraints on the design

Design Requirements

Design Challenges

Have a rainwater collection system
Be able to supply enough water for everyone to wash hands
Hands-Free
Integration with garden to supply water for irrigation
Solar Powered

Dry months in Culebra produce little to no rainwater
- Over half the rain falls in just 4 months (August - November)1

Constructible by youth
- Coming up with simple designs
Attractive, incentivizing especially for children to wash hands
- Possibly playing music, possibly having pipes/other mechanisms visible to be attractive for children and others

Preliminary Calculations & Requirements

Power Needs (Estimated Total Operating Time is 1 Hour per Day)

Sensor Operated Faucet and Soap Dispenser - 6V, 1A
Pump - 12V, 4A
LED Light Bulb - 3 Watts
Charge Controller - Neglible Power Needs

Overall Power Needs: 6 Ah per day or about 60 Watts; 9 Ah or 96 Watts including Light Bulb.

Water Storage

100 Gallon tank to store water (50” x 18” x 26”)
Provides enough water for a week if no rainfall

Water Storage Overview: 100 Gallon water tank which can hold a week's worth of water in case of no rainfall.

Power Source/Storage

50W Solar Panel (~3.2 sq. ft.)
12V, 35Ah Battery
Charge Controller (Regulates voltage/current into the battery)

Power Source/Storage Overview: 12 Hours to charge the entire battery using a 50 W Panel, only need 2 hours to obtain the necessary amount of power to operate (6 Ah). About 3 Hours to obtain the necessary power if a light bulb is included, and still uses only 25% of available power.

Water Needs

Since this is a high-volume hand washing station, an estimated 180 hand washes per day for an estimated 20 seconds gives a total of 1 hour of hand washing.

The typical faucet runs at 2.2 GPM, therefore, requiring 132 gallons of water per day
However, the addition of an 0.25 GPM aerator would cause the flow rate to reduce

Overall Water Needs: The addition of a 0.25 GPM aerator means only 15 gallons of water are needed per day or about 100 gallons per week.

Rainwater Collection

About 40.7 inches of rainfall per year-- this is an average of 0.769 inches per week, BUT 21.6 inches fall from August-November (>½ of the yearly rainfall in just 4 months)
About 100 gallons are needed per week
Currently, the roof is 66 sq. ft. which would only produce about 31 gallons of water per week
The roof must be at least 210 sq. ft. to produce 100 gallons of water per week which would be a roof about 18’ x 11.5’ (75-80% increase in roof size)

Rainwater Collection Overview: Need nearly double the roof size in order to collect enough rainwater each week, current roof size and rain condition allow for 54 hand washes per day.