Customer: Fermin Reyegadas, Fundacion Cantaro Azul

Faculty Mentor: Sarah BrownellBackground:Cantaro Azul is a non-profit dedicated to helping people in Mexico access safe drinking water. They provide a community scale ultraviolet disinfection system called the Kiosko Azul to communities in need of water treatment.

Problem:The purpose of this project is to create a system that will first detect failure in the UV chambers. Then signal a safety valve to stop the gravity fed contaminated water supply while simultaneously signaling the operator, both visually and audibly, that the system has suffered that failure.

Concept Selected:-A photo-diode was installed in each chamber to detect the level of UV output, see Figure 7-If the UV output falls below an acceptable threshold the safety system is triggered-The electro-mechanical valves chosen are Weathermatic 12024E-10-H irrigation valves, see Figure 2

- The valves seal by the use water pressure on a diaphragm- Once solenoids are activated the pressure is released, see Figure 2 for exploded view- Valves fail closed and are relatively low cost

-The warn operator system consists of LEDs and sirens for multiple sense warning- These will be mounted in a high visibility location, see Figure 3- Red LED and speaker: System has failed, see Figure 5- Green LED: Failure has been fixed ready for system restart, see Figure 5

-For the operators convince, switches are installed to deactivate the sirens once they realize the system has failed-The ball valves, shown in Figure 2, are a operator interface to prevent premature flow while the UV bulbs heat up to a germicidal UV output

Figure 2: Dual irrigation valve assembly: “Safety Valve System”

Major Constraints:-For proper sterilization, the water must be exposed to the UV irradiance, on average for 20 seconds, this yields a volumetric flow rate of 5.0 +-0.5 liters per minute

- Mechanical controls consist of pipe diameter (1/2” PVC) and overall head (~1.5 meters)

-Correlation between UV output and voltage output form photo-diode-Use of long life parts or parts that would be available at a local hardware store. -UV chamber independence

- If one chamber fails it should not impede the actions of the other chamber

Test Rig/Procedure:-Figure 3 illustrates the test rig created to simulate the kiosk used in Mexico-The “Contaminated water supply” simulates the reservoir on the roof of the kiosk in Figure 1-The water is gravity fed, approximately 5 ft, to the “Safety Valve System”

- The flow is split, (see Figure 2), since this is a dual chamber system, to test chamber independence

-Figure 6 illustrates the cross-section of the solenoid- Activated: the electro-magnet retracts the piston, releasing water pressure- Deactivated: a spring extends piston, preventing pressure release

-The water ascends and enters the top of the UV chambers; for a more controlled flow through the chambers-The chambers then empty into the “Clean water exit”-A push button/dimmer switch was installed at the very back of the test rig to control the PCB and UV chambers

- Push Button: simulates power outage and incomplete circuit related failures- Dimmer: simulate a typical brown-out

Figure 3: Kiosk simulating test rig

Results:-Valves do not impede volumetric flow of treatment system

- Flow is 4.5 liters per minute with a tank depth of 10 inches and overall height difference of 4 feet, which is within the constraint of 5.0+-0.5L/min

-PCB successfully cuts power to the solenoids and activates the alarm system which is highly noticeable to the operator -Brown outs were deemed negligible since a brown out has little effect on the UV lights

- A ballast is used to supply consistent power to the UV bulb as long as there is sufficient energy inputs, if not the bulb is deactivated

-Once the operator realizes the system failure they must close the manual ball valves located just before the irrigation valves

- This is to ensure that when power is restored, the UV bulbs have sufficient time to heat up to proper UV output before contaminated water is allowed through the chamber again

-To allow for chamber independence a separate PCB, power supply and valve system is needed for each UV chamber

Figure 4: Printed Circuit Board (PCB)

Figure 6: Solenoid cross-section (http://www.weathermatic.com/index.cfm?page=Downloads)

Team from left to right: Tyler Josselyn (ME), Evan Hall (EE), Phil Floroff (EE), Matt Switzer (ME, Team Lead).

Figure 1: Kiosk in Mexican village

Figure 5: Operator interface with alarm

Figure 7: Photo-diode position in UV chamber