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. By the use of a spectrophotometer, the percentage transmittance relative to a positive test from a control will give quantitative data to determine which method was most effective in killing the E. coli.