Prototype Testing

We tested the effectiveness of our filter design by conducting an experiment with water from Strawberry Creek in Berkeley, CA. Water from Strawberry Creek has characteristics similar to the river water collected by families in Tibet: low in turbidity and constantly flowing. Thus we were hopeful in getting relatable results.

Below is our procedure of experiment and lab results, both with takeaways and observations:

Procedure of Experiment

1. Collecting water in a 5 gal. bucket. 1/4 tsp of household 2% bleach is added to the 5 gal of water.

1. Collecting water in a 5 gal. bucket. 1/4 tsp of household 2% bleach is added to the 5 gal of water.

2. Team members Haleemah and Denzil carry the water closer to the labs for testing. Water is mixed while being transported. Water must be in contact with chlorine at least 30 min. for disinfecting to be effective.

2. Team members Haleemah and Denzil carry the water closer to the labs for testing. Water is mixed while being transported. Water must be in contact with chlorine at least 30 min. for disinfecting to be effective.

3. Filter is assembled (we used a simple cotton T-shirt for a fabric filter and duct tape as a fastener since we forgot the rope)

3. Filter is assembled (we used a simple cotton T-shirt for a fabric filter and duct tape as a fastener since we forgot the rope)

4. Water was poured into the system. Time for water to completely run through fabric filter = 30 seconds.

Time for all 5 gallons to run through filter = 1 hour. (this is about the rate of a Brita Filter)

Observations & Takeaways:

-Bamboo charcoal is easy to pour out of PVC pipe during assembly of filter. Possible solution: some kind of mesh on top of PVC pipe to hold in the charcoal.

-Flow rate was good.

Lab Tests & Results

We tested 4 different sample of water: untreated Strawberry Creek water, water after at least 30 min of interaction with bleach, chlorinated water after having run through the fabric filter, and final treated water where water ran through the whole system.

Strawberry creek water samples and chloride test.

Strawberry creek water samples and chloride test.

Below is a table of results:

                       Strawberry creek        bleached          bleach & filter              final treated
pH          8.14                8.4                    8.34                        8.35
EC (micro/cm)               580                  593                    593                            602
DO (mg/L)                 9.55                 9.93                 9.69                           9.65
Turbidity (NTU)             2.1                  2.07                   0.99                       0.87
Chloride test (mg/L)         0                 6.5                    5.6                            5.5

Note: DO measurements aren’t really needed but was measured anyways because it’s a common test in the lab.

Observations & Takeaways:

-From this experiment, assuming turbidity is low enough to conduct disinfection prior to filtration is approximately valid. Disinfection is best when turbidity is less than or equal to 2 NTU.

-Simple fabric filter was the most effective in cleaning the water.

-Bamboo charcoal didn’t prove much filtration of chloride concentration, but the smell of chlorine was greatly reduced!

Conclusion

Bleach works effectively at killing all bacteria and E.coli the water may have. A residual of at least 3 mg/L is the US EPA standard for tap water. Our filter could use less chlorine, the bleach to water ratio could be less. The surface area of bamboo charcoal may not be great enough to have enough contact time with the water. Crushing the bamboo charcoal into smaller pellets could possibly improve filtration by increasing surface area and contact time.

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