Water is a basic requirement for human life. People all over the world are faced with lack of clean drinking water. This project helped us gain insight into water filtration systems. The goal was to better understand how chemistry can support water treatment and clean water initiatives. Our group chose to investigate and evaluate LifeStraw, a lightweight water filter designed for one person. We were impressed that this microfiltration device claimed to filter out almost 99.9999% of all waterborne bacteria and parasites, and that it could filter up to 264 gallons of water, which is enough water for one person for 3 years.
Our group was given one LifeStraw to work with. (Technically, it was a no-name, similar product which was equally as good. For simplicity's sake, I will continue to refer to it as a LifeStraw.) We decided to run a series of tests to see how well the LifeStraw filtered different drinks, and planned to test the taste, as well as the clarity of the filtered drinks. Instead of starting with easy drinks to filter, we jumped right to the most difficult one we could find - hot chocolate made with a mix.
The next step in our process was to take apart the LifeStraw in order to see what was inside. This was a very interesting step. It was much harder to take it apart than I imagined. We tried cutting through the plastic with a box cutter unsuccessfully. We finally had success when we tried heating the blade. Inside we found a number of filtering devices and materials.
Key Materials and Definitions
Within the LifeStraw were two main materials used for microfiltration. Those included:
Hollow Fiber Membrane - Also called HFM. This is a class of artificial membranes with a semi-permeable barrier in the form of a hollow fiber. Usually packed into a cartridge for liquid and gaseous separations. The hollow fibers in LifeStraw have pores that at less than 0.2 microns across. Developed in the 1960's, HMFs are commonly produced using artificial polymers. You can see this in the far left of our photo above.
Carbon Filtering with Activated Carbon - The carbon capsule in LifeStraw is used to absorb contaminates and impurities - natural organic compounds, synthetic organic chemicals, and taste and odor compounds in water. Absorption, which is when pollutant molecules are trapped inside the pore structure of the carbon substrate, is both a chemical and physical process. Various components of this capsule can be seen above - the circular items and black material.
NO iodine - unlike the original LifeStraw with did contain Iodine to kill bacteria, all versions since 2012 no longer contain chemicals.
Reflection
This was a challenging project right from the start. We didn't foresee that testing filtration with hot chocolate mix would be too thick for the LifeStraw. A huge pit we encountered was this clogging up the LifeStraw and making every additional liquid tested taste like chocolate. We tried filtering hot water to clean and unplug it, but this had minimal success. The other difficulty that we dealt with was not being able to skillfully dissect the LifeStraw to see what was inside right away. Luckily we came up with the idea to heat the blade, or our second pit could very well have been failure to open it at all! On the up side, working with a good group of friends was a peak because we communicated well and were supportive of each other. Because of this, we were able to finish in a reasonable amount of time, which is definitely a peak.
I found this project to be a good lesson in how water filtration works. It was interesting to learn that personal water filtration systems life LifeStraw work much the same way as larger filtration systems, minus the chemicals. It is inspiring to know that companies like LifeStraw are helping with clean water issues in third world countries and when natural disasters happen.