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The Effects of Chlorine on Harmful Bacteria. Group 1-010 Leow Shawn Tao (1A413, Leader), Sow Jeng Wei (1O220), Justin Soh (1P111), Soh Yee Kiat (1P127). Overview Materials and Methodology Results and Discussion Conclusion. Contents. - PowerPoint PPT Presentation
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The Effects of Chlorine on Harmful Bacteria
Group 1-010Leow Shawn Tao (1A413, Leader), Sow Jeng Wei (1O220),
Justin Soh (1P111), Soh Yee Kiat (1P127)
Contents
OverviewMaterials and MethodologyResults and DiscussionConclusion
Rationale
To test the ability of chlorine as an disinfectant while also suggesting an alternative to chlorine, in which is Silver Nanoparticles for our case.
Hypothesis
Chlorine water is ineffective in killing common harmful bacteria.
MATERIALS AND METHODOLOGY
Variables
Controlled Dependent Independent
Dilution of bacteria and silver nanoparticles
Colonies of bacteria left
Type of disinfectant used
Amount of bacteria
Area of collection of water
Materials
Agar PlatesSterile SwabsChlorine Water (Collected from HCI swimming pool)Pipette & MicropipetteCentrifuge TubesNutrient Agar & Nutrient BrothMeasuring CylinderDe-ionized waterE.coli
Materials
METHODOLOGY
DAY 1Pre-Experimental Procedures
Water Collection
Water was collected using centrifuge tubes from the HCI Swimming Pool at the times of 7.50am, 2.30pm and 5.00pm.
Broth and Agar Preparation
For broth, 3.25g were displaced into a bottle and mixed with 250ml of de-ionized water.
For agar, 14g were displaced into a bottle and mixed with 500ml of de-ionized water.
Broth and Agar
DAY 2Preparation
Synthesis and Dilution of Silver Nanoparticles
1. 30ml of sodium Borohydride is poured into a small beaker. This small beaker is then placed into a larger beaker. Ice is placed into this larger beaker. Stir for 20 minutes.
2. 2ml of silver nitrate is then dropped into the sodium Borohydride. 1.28g of polyvinyl alcohol is then added into the mixture and heating is carried out.
Agar Spreading
Using our agar, the agar was displaced onto Petri dishes to half the Petri dishes height. They were then left to solidify for approximately 15 minutes.
Overnight Culture
1. 10ml of our nutrient broth was displaced into 4 centrifuge tubes each.
2. Then, using a bacteria streaking rod, bacteria was displaced into the tubes. The centrifuge tubes were then placed in the shaking incubator for 1 day.
DAY 3Experimentation
Dilution
1. Our aim was to reach 1 x 10-⁶ of bacterial dilution. We filled 6 centrifuge tubes each with 9ml of nutrient broth.
2. Using a micropipette, we displaced 1ml of the bacterial broth from the overnight culture into a centrifuge tube labeled 1 x 10-¹. This procedure was repeated on the tubes labeled 1 x 10-²to 1 x 10-⁶.
Bacterial Spreading
1. The plates were labeled accordingly to their content. Triplication was carried out. Also, 3 controls involving sterile water instead of silver nanoparticles or chlorine water was set up.
E.g.: First plate consisting of 2.30pm water will be labeled as: 2.30pm, C.Water, 1.
Bacterial Spreading
2. Next, according to the labels, 50 microlitres of bacteria and 50 microlitres of silver nanoparticles or chlorine water accordingly was displaced onto the agar dish with a micropipette. This mixture was then spread and sealed with Parafilm, before being kept in the incubator at 36 Degrees Celsius.
RESULTSDAY 4
Chlorine Water
Controls 7.50am 2.30pm 5.00pm
Dish 1 27 N/A 15 33
Dish 2 16 29 15 35
Dish 3 22 26 8 23
Average 21.67 27.5 12.67 30.34
Results of Chlorine Experiment
7.50am 2.30pm 5.00pm Control05
10152025303540
No. of Bacterial Colonies
No. of Bacterial Colonies
Results of Chlorine experiment
7.50am 2.30pm 2.30pm05
101520253035
No. of Bacterial Colonies
No. of Bacterial Colonies
Silver Nanoparticles
Controls Silver Nano 1x10-4
Dish 1 18 9
Dish 2 21 3
Dish 3 21 7
Average 20 6.34
Q&A
Biblography
http://aem.asm.org/content/44/4/972.short
https://mrsec.wisc.edu/Edetc/nanolab/silver/
http://www.medicalnewstoday.com/articles/68511.php
http://natsci.edgewood.edu/wingra/wingra_bacteria.htm
http://www.cbc.ca/news/health/story/2009/07/02/f-ecoli-recall-food-safety.html
http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_p013.shtml
http://proquest.umi.com.libproxy.nlb.gov.sg/pqdweb?index=9&did=2037658811&SrchMode=1&sid=2&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1332762445&clientId=13402
Thank You!