Water Sanitation


Current Updates:

The quarter has ended, but the projects will continue! We are currently waiting for the Cal Poly craft center to repair their kiln, and we will likely fire the 2nd and 3rd ceramic filters after spring break.


Problem statement: The water in San Pablo is not safe for drinking.

Goals: Our broad view goal is to provide a cheap and effective way to purify water.

Aim: The project in progress is aiming to replace the current method of water sanitation, boiling, by utilizing a more resource efficient method. We plan to match the effectiveness of boiling by achieving a measurably safe level of purity by eliminating harmful contaminants and pathogens. This should be done in a way that matches the needs and desires of the people of San Pablo.

Water in San Pablo:
The above table outlines some coliform testing that has been done in the San Pablo region. The left column specifies the location of the water source, and the Most Probable Number (MPN), or NMP in Spanish, describes the level of contamination.

Group Members:

Carl Petterson – CEPetterson@gmail.com
Meghan Hazlett – mhazlett@calpoly.edu
Matt Schwarberg -mschwarb@calpoly.edu
Anna Yeutter – a.yeutter@gmail.com

For more information about our team select “About Us” in the navigation section to the left, and scroll down to the bottom.

Design matrix:

1-5 (1 being the worst case, 5 being the best)

Importance Slow Sand
UV filtration
UV filtration
Water Treatment
Chlorination Boiling
3 Ease of construction 3 2.5 5 4 4 5 5 5
4 Availability of Mat’ls 3 1/5* 5 1 2.5 2 5 5
4 Cost of Mat’ls 4 3 5 2 2.5 2.5 2.5 4
3 Maintenance/Durability 5 4 5 3 3 3 3 4
5 Performance – Potability 4 4 4 4 3 4 4 4
4 Performance – Palatability 4 4 2 2 3 2 2 2
3 Convenience/ease 4.5 4 1 1 3.5 4 4 2.5
2 Environmental Impact 5 5 5 4 4 2 2.5 3
TOTAL 111.5 94.5/110.5* 106 72 86.5 86 99 104.5

*Ceramic filters will likely be difficult to attain unless we can implement a program in San Pablo that allows sustainable manufacture of these filters.

Technology Fact Sheets:

From the website of the Centre for Affordable Water and Sanitation Technology (a resource of Lifewater International)

Design Matrix Technologies:
HWTS Fact Sheet_Simplified_Biosand Filter_Jul 09.pdf
HWTS Fact Sheet_Simplified_Ceramic Pot Filter_Jul 09.pdf
HWTS Fact Sheet_Simplified_SODIS_Jul 09.pdf
HWTS Fact Sheet_Simplified_UV Disinfection_Jul 09.pdf
HWTS Fact Sheet_Simplified_Chemical Coagulants_Jul 09.pdf
HWTS Fact Sheet_Simplified_PUR_Jul 09.pdf
HWTS Fact Sheet_Simplified_Chlorine_Jul 09.pdf

Other Technologies:
HWTS Fact Sheet_Simplified_Lifestraw_Jul 09.pdf
HWTS Fact Sheet_Simplified_Natural Coagulants_Jul 09.pdf
HWTS Fact Sheet_Simplified_Ceramic Candle Filter_Jul 09.pdf
HWTS Fact Sheet_Simplified_Settling_Jul 09.pdf
HWTS Fact Sheet_Simplified_Kanchan Arsenic Filter_Jul 09.pdf
HWTS Fact Sheet_Simplified_Chulli Pasteurization_Jul 09.pdf
HWTS Fact Sheet_Simplified_Straining_Jul 09.pdf
HWTS Fact Sheet_Simplified_Solar Pasteurization_Jul 09.pdf
HWTS Fact Sheet_Simplified_Solar Distillation_Jul 09.pdf


-Our goal is to create a water sanitation system that will provide an inexpensive, sustainable way of getting clean water to the villagers of San Pablo. We want the system to be easy to maintain and construct by using simply the resources that are readily available in the area. We also want to work together with the inhabitants of this area, to ensure that the end result is something they want and works with their life, which is the most important aspect of this collaboration.


Researching filtration methods and networking with individuals and businesses within the San Luis Obispo region.


  • Jackie Chan: Former Cal Poly student, general guidance and advice on water filtration projects in rural areas
  • Lauren Blomberg: Former Cal Poly student, volunteer with Lifewater, advice on coliform testing
  • William Yee: Current Cal Poly student, advice on slow sand filter construction
  • Rury Velasquez: San Pablo student, member of water/sanitation group, local contact
  • Jerson Velasquez: San Pablo student, member of water/sanitation group, local contact


  • We built a small scale biosand filter to assess functionality and appropriateness/availability of materials.
    • Materials: 5 gallon bucket, 3/4″ pvc piping, small rocks, gravel, 30 grit sand (grain size is .5mm – .3mm), pvc glue, and silicone sealer.
    • Testing: Coliform
      • Unfortunately, our filter was rained out more than once, which delayed the development of the biological layer required to break down contaminants. However, the first coliform test we ran- with Coliscan Easygel- did show promising results though the reduction of the amount of coliform colonies present in the incubated sample despite the absence of a significant layer. We plan to do more testing in the future to determine if this design will function adequately.
    • Photos:

Biosand Filter: pvc array and bottom layer of rocks.
Biosand Filter: the next layer consists of dime sized gravel and is approximately 3″ deep.
Biosand Filter: the last layer consists of sand with grain size .5mm – .3mm and is approximately 9″ deep.

Biosand Filter: the final product with the diffuser plate in place.
  • We also experimented with ceramic filters.
    • Materials: Terracotta clay, rice hulls, coffee grounds, and sawdust.
      • Filter 1: 2lbs clay, 5oz coffee grounds/rice hulls
        • Filter 1 has been fired in the pottery group’s kiln.
        • We have filled it with water for preliminary flow rate testing. Once the filter was saturated, the flow rate was still really slow, on the order of a drop every few seconds, with only an inch of water collected in the bottom bowl over the course of a few hours. Furthermore, the rice hulls did not burn out completely during the firing and were still visible afterwards.
      • Filter 2: 2.5lbs clay, 5oz coffee grounds/rice hulls
      • Filter 3: 3 lbs clay, 2 oz ground rice hulls (we determined that the rice hulls were too large and might make the filters too brittle), 4oz saw dust, 1 oz coffee grounds.
    • Photos:

Ceramic Filter1: wetting the clay to prepare for additives.
Ceramic Filter1: adding the particulates.
Ceramic Filter1: working the clay to prepare for pressing.

Ceramic Filter1: pressing the clay.
Ceramic Filter1: getting some help to press out the clay!
Ceramic Filter1: finally getting it pressed!
Ceramic Filter1: Final product. The filter was fired by the pottery group.

Environmental Impact

  • Materials: Materials used in construction are unknown right now. This will largely depend on what is available in San Pablo.
    • Plastics, concrete, clay, saw dust, …..
  • Production: There will likely be little impact during construction. Firing the filters will probably be the only impact-full step.
  • Whatever we do in San Pablo will most likely be less harmful than using wood stoves to boil the water.
  • The carbon footprint for a bio sand filter is right next to zero if we don’t use plastic buckets and instead only use materials that are available in the area.


  • Cost is an area of concern unless we can set up an income generating process. The people of San Pablo currently harvest wood in a sustainable manner and the cost of new filtering technologies could be a hurdle we need to tackle in the future. How do we make it something that will be a real improvement from their point of view?

Future Directions

  • We know there is great potential for this project.
    • There are numerous organizations that have successfully implemented sustainable water purification systems. (Potters for Peace, Life Water)
    • Water purification is well backed by scientific research.
    • Our preliminary testing was successful.
    • San Pablo is receptive to our project and excited to work with us this summer.
  • We should contact established organizations and see what advice or help they can give us. (Potters for Peace started in Guatemala). Here is the type of system we would love to eventually see on a smaller scale, therefore bringing in income as well as a practical purification method:

  • We would like to look into other water filtration technologies.
    • SODIS is a method that could prove to be effective in San Pablo
    • After further analysis of the materials available in San Pablo we may have a better concept of what purification technology is appropriate.
  • Look into setting up a manufacture and distribution system in San Pablo.
    • We could possibly combine our ceramic filters with the Pottery group’s kilns.
  • Rain water collection?
  • Water testing this summer during Guateca!
    • It is extremely important that we gather adequate information so that an effective system can be implemented. Before we can have something that works, we must first understand the issue.