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Sewage design lab

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Kaleem Atchia February 15th, 2009 SBI3U7-AA (Grade 11 IB Biology) Mr. Pourkhatai Sewage Treatment Design Lab Disinfectants and E. coli Research Question: How can you determine which method of disinfection is most effective in eliminating E. coli within water? Introduction: At the tertiary treatment of sewage, nitrogen and phosphorus compounds are removed but the water is also disinfected to kill all micro-organisms to make sure no pathogens are released in nature. In this experiment, a harmless strain of E. coli (HB 101) will simulate the presence of bacteria in water. Different methods of disinfection such as boiling, UV light exposure and chlorination will be used. The physical methods which are primary disinfectants only, will be compared to each other. Likewise the chemical methods which also have a residual effect will be compared to each other. After treatment, a Colilert testing kit will be used which would detect the presence of coliforms in water by a colour change to yellow. ...read more.


2. The approximate number of E. coli bacteria will be somewhat controlled. 2 mL of the E. coli culture will be placed in 10 mL of water. 3. The volume of solutions added for the chemical methods will be constant. 2 mL of the solutions will be added to the appropriate trials. 4. The time the chemicals are allowed to act unaffected will be 5 minutes for each trial. After that time, the Colilert reagent will be added. 5. The testing for bacteria will be the same for all trials. 10 mL of the Colilert reagent will be added to each trial. 6. The time allowed for Colilert test to act in incubation. 24 hours, same for all trials. Materials: * Beakers * Graduated cylinder * Pipets * Retort stand * Ring clamp * Thermometer * Stopwatch * Heating plate * Waterproof marker * Spectrophotometer * Distilled water * E. coli culture * Incubator * Colilert Test kit * Sodium hypochlorite * Calcium hypochlorite * UV lamp Procedure: 1. ...read more.


Heat the water until it boils, check temperature with thermometer. Set retort stand and ring clamp to hold the smaller beaker. 8. Repeat step 3 and place the beaker in the clamp 9. Lower the beaker with the clamp into the bath and time 30 seconds with the stopwatch before removing it and adding 10 mL of Colilert reagent. Label the beaker accordingly and place it in the incubator. 10. Repeat steps 8 and 9 but time 2 minute and 8 minutes for each trial. 11. Repeat step 3 and place it on the table. 12. Shine the UV lamp upon it for 15 seconds. Then add 10 mL of Colilert reagent before labelling it and placing it in the incubator. 13. Repeat step 11 and 12 but time 2 minute and 8 minutes for each trial. 14. Come back in 24 hours. Remove the control and place a sample through the spectrophotometer, setting the wavelength as the baseline value. 15. Take a sample of each trial and place it within the spectrophotometer, recording the readings carefully. ?? ?? ?? ?? Page 1 of 2 ...read more.

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