1. Introduction

We want to build a straw inspired by The Straw from Waterislife.com which would be cheaper but as effective in filtering the harmful components in water as the orgininal straw - the Straw from Waterislife.com is sold at $10. We want to build a straw which can be sold at a cheaper price and still make a slight profit.

Independent Variable
Our IV is the types of water we are going to use to filter.
They are:
1. Pond Water - from school's school (to be filtered)
2. Collected rainwater - collected by ourselves (to be filtered)
3. Tap water - from the school's toilet and laboratory (as a standard/control)

Dependant Variable
Our DV is the quality of the water after they are filtered.

Constant Variable
The water filtering device we built, the quantity of granular activated charcoal, iodine crystals, silver ion filter and cotton used.

Harmful components in unfiltered water and its effects on humans:
Giardiasis or beaver fever is a zoonotic parasitic disease caused by the flagellate protozoan Giardia lamblia.The giardia organism lives in the digestive tract of humans and animals, including wild and domestic animals. It is one of the most common pathogenic parasitic infections in humans worldwide. Giardiasis causes diarrhea. The parasite is protected with an outer shell and thus it can survive outside and inside the body for long periods of time. Giardiasis can get into water by sewage overflows, spoilt sewage systems, polluted water runoff and agricultural runoff. Wells are more likely to be polluted and contaminated after flooding, especially if the wells have been submerged in flood water for a long period of time or if the well is shallow.  ( Giardiasis. (n.d.). Retrieved March 02, 2016, from http://www.healthline.com/health/giardiasis#Symptoms3)

How the water (of our water filtering device) is filtered:
First, the water passess through the silver ion filter of 10-15 microns and the silver ion filter will filter the particles that are as big or bigger than 10-15 microns would be trapped by the silver ion filter and cotton layer. The silver ion filter traps any dirt, bacteria or particles from entering the straw.

Then, the water will pass through the iodine crystals  (IODINE. (n.d.). Retrieved March 02, 2016, from http://www.chemistryexplained.com/elements/C-K/Iodine.html) which will kill the bacteria/viruses etc. in the water. Finally, the water will pass through the granular activated charcoal which would absorb the odours and chlorine.

3 possible Solutions
We will propose 3 types of straws (using 3 types of membranes), but we will only be doing one straw due to time and money constraints. We decided to vary the filters (as listed below) because different filters have different effects on the water; the membrane filter traps similar things as the silver ion filter but the silver ion filter sterilizes the water while the membrane filter does not; the screen filter only traps dust and particles that can be seen by the naked eye but the silver ion filter and membrane filter traps particles that can be seen by the naked eye and microscopic particles like pollens, bacteria etc. Here are the 3 prototypes (they are all of the same concept except they uses different filters):

  1. Using silver ion filter (5-10 microns)
    1. Traps pollen, bacteria etc. (microscopic particles)
    2. Particles seen by the naked eye (dust etc.)
    3. Sterilized, deodorized and contains silver ions
      1. Prevents fungus or odours from developing
        1. Odours like…
          1. Pet odours
          2. Tobacco odours
          3. Garbage odours
  2. Membrane filter (5-10 microns)
    1. Traps pollen, bacteria etc. (microscopic particles)
    2. Particles seen by the naked eye (dust etc.)
  3. Screen filter  (20 microns)
    1. Traps dust

We used the silver ion filter prototype as we think the silver ion filter will be the most effective filter as it can trap particles of a wide range of sizes. For the screen filter, it generally can only trap large particles, whereas for the membrane filter, it can generally only trap small particles. If the membrane holes are too small, it will be harder for water to pass through and it will take the user more effort to suck up the water. In addition,  it is available in Singapore and the most easy for us to purchase.

Comparing the 2 straws as a whole:
Our concept of the straw originated from the company WaterisLife. Their straw is 1 inch (2.54cm) wide in diameter and 10 inch (25.4cm) long [the length of the straw]. Our straw is 1.5cm wide and 12cm long allowing it to fit better into bags, especially those tightly-packed ones of backpackers and are not as heavy as theirs to carry around, for those people who live in places with little water and/or clean water (desert, Cambodia etc.) Both of our filtering method use Granular Activated Charcoal (GAC) and Iodine Crystals. Their filtering method uses screen filters but we are using silver ion filters which are more durable than screen filters and also, filters smaller particles compared to screen filters.

Pros and/or cons:
Our straw is lighter and shorter, thus making it more portable and has a wider diameter giving the user better grip on the straw, it takes up a shorter space(pros) but takes up a wider space in the bag (cons). Our Straw uses silver ion filters instead of screen filters that filters smaller particles and also are more durable.

which would kill most of the harmful pathogens present in the water.
After that, the  water will pass through the granular activated charcoal (GAC)  (Activated Charcoal: Uses and Risks. (n.d.). Retrieved March 02, 2016, from http://www.webmd.com/vitamins-and-supplements/activated-charcoal-uses-risks) where the GAC absorbs many compounds - toxic and non-toxic - and also removes the taste of iodine. The GAC removes bacteria, chemicals and odours.

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