The Effects of Chlorine on Harmful Bacteria

1. 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)

2. Overview • Materials and Methodology • Results and Discussion • Conclusion Contents

3. To test the ability of chlorine as an disinfectant while also suggesting an alternative to chlorine, in which is Silver Nanoparticles for our case. Rationale

4. Chlorine water is ineffective in killing common harmful bacteria. Hypothesis

5. MATERIALS AND METHODOLOGY

6. Variables

7. Agar Plates • Sterile Swabs • Chlorine Water (Collected from HCI swimming pool) • Pipette & Micropipette • Centrifuge Tubes • Nutrient Agar & Nutrient Broth • Measuring Cylinder • De-ionized water • E.coli Materials

8. Materials

9. METHODOLOGY

10. DAY 1 Pre-Experimental Procedures

11. Water was collected using centrifuge tubes from the HCI Swimming Pool at the times of 7.50am, 2.30pm and 5.00pm. Water Collection

12. 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 Preparation

13. Broth and Agar

14. DAY 2 Preparation

15. 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. Synthesis and Dilution of Silver Nanoparticles

16. 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. Agar Spreading

17. 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. Overnight Culture

18. DAY 3 Experimentation

19. 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. Dilution

20. 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

21. 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. Bacterial Spreading

22. RESULTS DAY 4

23. Chlorine Water

24. Results of Chlorine Experiment

25. Results of Chlorine experiment

26. Silver Nanoparticles

27. Q&A

28. 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 Biblography

29. Thank You!