Science Buddies: "Ask an Expert"

Change of plans. I want to test different brands of bottle water to see if they are really safe. What could i test for and how could i preform the tests? thanks for your help.

Hi Justin,
That's quite an interesting topic, and also an extremely complicated one. There are many, many regulated drinking water contaminants. Here is a list of the ones regulated by the Environmental Protection Agency:
http://www.epa.gov/safewater/mcl.html#mcls
Many of the analyses for these potential contaminants are very expensive

One approach you could take would be to focus on a particular contaminant for which you are able to find a cheap analysis method. Microbes and nitrate are some of the more popular tests which are available in some commercial kits (try google for "nitrate test kit").

Thanks for your help on my project. now can send me the amount of those things that are safe to have in the drinking water.

I'm happy to help.
Can you clarify your second sentence?
"now can send me the amount of those things that are safe to have in the drinking water."
I'm not sure what you meant.

what are the safe amount of the chemicals, particles and other things in the link from above that you sent me. thanks

On that web page, next to the name of each contaminant, there are two columns. The number on the left is the suggested highest concentration in drinking water, which is not a legal guideline. The number on the right (often the same value as on the left) is the legal Maximum Contaminant Level. These are the most commonly used guidelines in the US for drinking water. However, keep in mind that "safe" is a relative term, and doesn't have much meaning in a scientific context. The EPA chooses those values based on this sort of risk analysis:
"The risk estimate is based on the possibility that exposure, at some level, will cause one additional cancer per . . . one million people over a lifetime of 70 years. EPA generally sets an acceptable (negligible) risk level at one in a million."
http://www.ces.purdue.edu/extmedia/WQ/WQ-5.html

What can i use for review of the literature, And what would be your hypothesis? Mine would be that the more expensive brand of water would be better than the cheaper brand. does this sound like a good hypothesis? What can i say in my discussion part? thanks for ur advice.

help me out here. i need some research papers on this topic.

Justin,
Have you figured out how you are going to do this experiment? What sort of data are you going to collect? For a science fair experiment, you probably can't quantify which water is "better" so you will have to choose some specific type of data, and then figure out how you are going to collect that data. Keep in mind that measuring low concentration contaminants (lead, mercury, etc.) can be very difficult and/or expensive. A simple quantification of microbial populations in bottled water is a possible cheap alternative.

For references, here is a page that lists a online articles:
http://www.sciencecases.org/bottled_wat ... _notes.asp
You should also try using a search engine like Google to search for more specific topics.

Good luck!

Ok i have tested the Nitrate, Phorpus, PH, turibity, and coliform. The coliform test showed postive on all of my samples but i can't find out for sure about the amount of each. i am colecting the data as a chart. I have six samples of various brands of water. to get my results i have used a testing kit from the game and fish.

Here are my results:

Nitrogen 1.1 mg/L, 1.4 mg/L, .7mg/L, 1.6mg/L, 1.2mg/L, 1.4mg/L How can i cange the Mg/L units to PPM units

Phosphate: .5 ppm, 1.5ppm, 1.5ppm, .5ppm, .5ppm, 1ppm

pH: 7.5, 7, 8, 8.5, 7, 8.5

Coliform: All was postive

Trubity: 2FRU, 2, 0, 1, 0, 1 How can i cange the FRU units to PPM

Also when those are converted to PPM are they at a safe level. What is a safe level in PPM for the tests that i have done.

Hi Justin,

Although I am unable to answer all of your questions, the easiest one (for me!) to address is the conversion from mg/L to ppm. For aqueous solutions, the conversion is very simple: 1 mg/L = 1 ppm. Try doing a Google search on mg/L ppm conversion and see what you find. There are several excellent websites that give very good explanations as to the how and why.

Basically, there are one thousand grams of water in a liter. Your milligram measurement is one-thousandth of a gram. Therefore, 1 mg = 0.001 g (i.e. 1 thousandth of a gram). Since you don't just have one gram of water, you have one thousand (that is, one liter), the concentration is one-thousandth of a gram in one thousand grams of water. The key factor here is one thousandth of a gram in one thousand grams. Thus, if you have 1 mg/L, (that is, 0.001 g in 1000 g) this converts directly to 1 ppm (1,000 x 1,000 = 1,000,000).

Hope that isn't too confusing! Have a look online and see what articles you can find.

Good luck!
Geoff.

Justin,
Here is some info about turbidity units:
http://www.hannainst.com.au/GEN/Turbidity.pdf

Phosphate, pH, and turbidity are usually not a major concern in water quality. The water would typically become foul tasting before it became dangerous to drink.

Nitrogen can be in the form of ammonia, nitrite, nitrate, or other molecules, and each one will have a different toxicity. Probably, yours is mostly in the form of nitrate, though there's no way to know for sure without testing for nitrate. For nitrate, the EPA enforces a Maximum Contaminant Level of 10 ppm.

Coliform is a general category of bacteria and includes many strains that are non-toxic. It can indicate that there may be a problem with other pathogenic microbes, but, by itself, it does not indicate whether water is safe to drink. However, take a look at that EPA web page that I posted earlier and you'll see that there are standards for detections of coliform bacteria in drinking water.

I know that nitrate and phospate may not be a major factor for safe drinking water but what is the safe amount of each in Parts Per Million (PPM) Also i only have 4 days left to put together my board and project. can you give me some tips on doing that to make it stand out and be a outstanding looking project. i really need help, on whats the safe amount of each Ni. Phosphate, pH, Coliform, Trubity. thanks for your help but i need some help on finding out those things. also, where can i get some research papers on my title, how safe is drinking water.

Justin,
I would recommend asking your quesion about putting together your board and project in the "Preparing for the Science Fair" part of this forum. Let people know your The more detail you can provide on your thought process and your progress to date, the more the experts there will be able to help you.

For research papers, try using Google to search for topics of interest like "how safe is drinking water" or "is bottled water safe." You'll find pages like this:
http://www.nrdc.org/water/drinking/qbw.asp
Let us know what you find and then let us know how we can help from there.

Regarding "safe amounts" I don't have any values in PPM aside from what I've already given you. For Turbidity and Coliform, I do not think it is possible to specify a "safe amount." Turbidity and coliform are indirect indicators of water quality and they do not tell you what is actually in the water. For example, turbidity tells you how cloudy the water is. The turbidity of milk is very high, but that doesn't mean it is unsafe to drink. Likewise, there are many species of coliform bacteria, and only a few (such as E. Coli) that make us sick. Without knowing what type of coliform you have, there is no way to know for sure whether a sample of water is safe to drink or not.

Thanks alot guys i got 4th place and $60

Congratulations! Enjoy the prize.