Science Buddies: "Ask an Expert"

my science fair project is comparing two different type of water treatments and how efficient each one is through comparing the bacteria growth by swatching samples of both treated water and untreated water. But I just did my first trial yesterday, and found that once once the first bacterias appeared (at around 24 hour mark) the bacterias grew rapidly and every 2 hour interval which is the time for me to check up, the number triples and it grew clumpier. pretty much at 30 hours I wouldn't be able to count since its too plumbed together. how would I compare this, and put it onto graph? would it be about how fast the first speck of bacteria appeared? and graphed on the time at which first colonies are formed?

When you say that the bacteria appeared in both treated and untreated water. Well, that is result in itself. Do you have access to a Spec 20, used to determine concentrations of solutions? If you do, it would be much easier to grow the bacteria in tubes, and simply read the absorbance every 2 hours and absorbance correlates with bacteria concentration. This would also be very easy to graph. If you need more help, feel free to email me.

More on your question...You would begin as soon as you saw the first bacterial colony. I'd like to know how you are treating your water, and what you are growing them on.

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