2. Method

We have decided to built the straw as shown below.


We will use our water filtering device to filter 2 types of water. 
1. Pond water from school pond
2. Rainwater (collected in a bottle)

We will collect 2 sets of water of each type of water listed above and filter them.We will collect some water of the pond water and rainwater before we filterered them and after we filtered them. Afterwards, we will test the quality of the water samples* and using the various sensors: the colorimeter, to test for nitrate, the turbidity sensor, to test the clarity of the water, and the pH sensor, to test for the pH value of the water - which tells us the acididity and alkalinity of the water. We will, also, use agar plates to test for the prescence of the bacteria in the water samples*.

Procedures for building: Detail all procedures for construction of prototype 
Fig 2.1    Fig 2.2
Fig 2.1 shows the real life prototype which we made
Fig 2.2 shows the detailed structure of the straw and how we plan to build the straw.

Devices used to test:
Testing for:
Colorimeter
Nitrate
pH Sensor
pH Value
Turbidity Sensor
Turbidity / Clarity
Agar Plates
Presence of bacteria and microscopic organism


Risk
Assessment
Management
Iodine Crystals are corrosive - evaporate easily  in heat - and would cause eye and/or skin burns if not handled properly.
High
Handle with gloves when disposing and conduct the transferring of iodine crystals in the fume as iodine crystals evaporate easily in heat.
Iodine Crystals are poisonous and cannot be disposed anyhow.
High
Sweep up or vacuum, place in a suitable container for disposal. Wash spill site. Do not allow contamination of drains and waterways.
If not assembled and secured properly, the materials in the straw would fall out.
High
Assemble the materials slightly tightly, living a little allowance between each other, so they do not fly everywhere and tape the silver ion filter (at the bottom and top of the straw) securely.
The Agar plates cannot be handled anyhow.
High
Handle with gloves because our hands can contaminate the agar plate and our results will not be accurate.


Types of water used

  1. Pond water (taken from school) - tested 2 times
  2. Rainwater (collected from rain) - tested 2 times
  3. Tapwater - lab & toilet (as a standard/control)

We are using Pond Water and Rainwater as when people go trekking or camping, they are more likely to come across Pond water and Rainwater for them to filter into clean drinking water.

Procedure of constructing the water filtering device (the straw):

  1. Push the membrane (silver ion) filter to the bottom of the tube.
  2. Push the cotton on top of the membrane (silver ion) filter
    1. Use sterile facial cotton/cotton balls
    2. Half a cotton ball/ 2 quarters of facial cotton
  3. Pour the iodine crystals into the tube
    1. 0.6g of iodine crystals
  4. Repeat step 2
  5. Pour the granular activated charcoal (GAC) into the tube
    1. 0.8g-1g of granular activated charcoal (as long as in the range, it’s fine)
  6. Repeat step 2

(d) Procedures for testing: Detail all procedures for testing of prototype


We used these testing parameters as PUB tests their water based on these tests to conclude whether the water can be consumed by people without having harmful components and the things that are tested for by these sensors may affect the health of the person who is consuming the water.

Filtering Water:

Pour the 250ml of the 2 different types of water (Pond water and Rainwater) into the straw and let the filtered water drip into a clean beaker. (Repeat each type of water one more time, to ensure reliability.)

Steps for testing - Turbidity Sensor

Equipments Needed:
  1. Turbidity Sensor
  2. Labquest 2 (or any other model)
  3. Cuvette
  4. Standard (500 NTU)
  5. Distilled water
    1. For calibration
    2. For rinsing
  6. Lens Tissue
  1. Connect the cable of the testing device to the lab pro
  2. Calibrate the device
  • Rinse the small bottle provided with distilled water.
  • Pour distilled water into the bottle until the white mark.
  • Clean the bottle with a lens tissue.
  • Place the bottle in the turbidity sensor, making the arrow on the bottle and the arrow in the turbidity sensor match-up.
  • Calibrate with the value of 0 NTU
  • Take the small bottle out of the turbidity sensor
  • Clean the small bottle with murky water (provided in the set) with a new lens tissue.
  • Place the 2nd small bottle into the turbidity sensor, again making the arrow on the bottle and the arrow in the turbidity sensor match-up.
  • Calibrate with the value of 100 NTU.
  1. Empty out the 1st bottle with distilled water.
  2. Pour in the water which is to be tested until the white mark.
  3. Clean the bottle with a new lens tissue.
  4. Place the bottle in the turbidity sensor, again making the arrow on the bottle and the arrow in the turbidity sensor match-up.
  5. Read the value on the lab pro
  6. Record results
  7. Repeat Step 2-8 for all the other water.

Steps for testing - Colorimeter
Equipments needed:
  1. Colorimeter sensor
  2. Labquest 2
  3. Cuvettes
  4. Distilled water
    1. For calibration
    2. For rinsing

  1. Calibrate the Colorimeter
  • Press the < or > button on the Colorimeter to select the correct wavelength for your experiment (430 nm, 470 nm, 565 nm, or 635 nm).
  • Allow the Colorimeter to warm up for about five minutes before calibrating. Calibrate the Colorimeter.
  • Open the lid of the colorimeter to reveal cuvette slot.
  • Insert a cuvette, filled with distilled water or other solvent used to prepare your solutions, for your calibration blank (100% transmittance or 0 absorbance). Important: Line up one of the clear sides of the cuvette with the arrow at the right side of the cuvette slot.
  • Close the colorimeter lid.
  • Press the CAL button on the Colorimeter to begin the calibration process. Release the CAL button when the red LED begins to flash.
  • When the red LED stops flashing, the calibration is complete. The absorbance reading should be very close to 0.000 (100%T).
  • Remove the blank cuvette from the Colorimeter.
  • Continue with data collection.
  1. Rinse the cuvettes (which are going to be used) with distilled water
  2. Fill the rinsed cuvettes with the types of water which are going to be tested
  3. Insert the cuvette into the cuvette slot in the colorimeter
  4. Record the results
Steps for testing - pH sensor
Equipments needed:
  • PH probe
  • Labquest 2

  1. Calibrate the PH sensor if needed
  2. Rinse the sensor with distilled water
  3. Put the probe in the waters needed to be tested
  4. Record the results
  5. Rinse the probe with distilled water

(Using Agar plates) - Test for bacteria

Equipments needed:
  • Agar Plates
  • Parafilm
  • Spreader
  • Micropipette
  • Micropipette tips
  • Tissue
  • Marker
  • Biohazard bin
  • Incubator

  1. Wear gloves
  2. Wipe off the condensation on the agar plate and label it
  3. Use the micropipette and attach the tip by pushing the front of the micropipette into the tip
  4. Set the micropipette to 100 microlitres
  5. Press the plunger of the micropipette
  6. Release the water into the agar jelly
  7. Dispose the plunger in a biohazard bin
  8. Use a spreader to spread the water (gently)
    1. Important: Hold it by the handle
  9. Close the agar plate and seal it with parafilm
  10. Incubate for a day
  11. Take picture of results the next day
    1. Against a black or dark background


The picture below shows:

        Fig 1 Fig 2

(Above) Fig 1: Equipments used to construct the straw.

Equipments Used:
  1. Plastic straw
  2. Cotton wool
  3. Iodine Crystals (not shown - see in link)
  4. Silver ion filter
  5. Granular Activated Charcoal
  6. Rubber gloves - 2 pairs
  7. Small spatula - scoop iodine crystals
       
(Above) Fig 2: Equipments used

Equipments Used:
  1. Agar Plates
  2. micropipette
  3. Tips
  4. Plate spreader
  5. Parafilm
  6. Bio-hazard dustbin
(Above) Fig 3: Colorimeter
(Above) Fig 4: pH sensor        (Above) Fig 5: Turbidity Sensor

Fig 3: Equipments needed to test for the prescence of nitrate (using the colorimeter)

Equipments needed:
  1. Colorimeter sensor
  2. Labquest 2 (or any other model)
  3. Cuvettes (at least 2)
  4. Distilled water
    1. For calibration
    2. For rinsing

Fig 4: Equipments needed to test for the pH value - acidity and alkalinity of the water
  (Using the pH Sensor)
Equipments Needed:
  1. pH Probe
  2. Labquest 2 (or any other model)
Fig 5: Equipments needed to test for the clarity (using the turbifity sensor)

Equipments Needed:
  1. Turbidity Sensor
  2. Labquest 2 (or any other model)
  3. Cuvette
  4. Standard (500 NTU)
  5. Distilled water
    1. For calibration
    2. For rinsing
  6. Lens Tissue
Risk Assessment Table

Data Analysis

The water is much cleaner after filtering through the straw. From all the tests (turbidity, pH, Colorimeter), we can conclude that the water quality has improved after filtering through the straw. In addition, from the results we collected from the Agar plates, there was much more bacteria cultivated on the agar plates before the filtering rather than after. When we compared our results to Singapore’s tap water, we realised that the quality as well as the amount of bacteria after filtering the water was about the same as Singapore’s tap water. This means that the water is consumable. Thus we conclude that our experiment was a success and our straw can be used by backpackers or travellers.

*Water samples refer to:
1. Filtered pond water   (set 1&2)
2. Filtered rainwater      (set 1&2)
3. Original pond water  (set 1 &2)
4. Original rainwater     (set 1 &2)
5. Tap water from laboratory - used as a standard/control
6. Tap water from toilet - used as a standard/control

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