A viewer asked this question on 6/23/2000:
I am trying to find out what data I need to collect and exactly how to do it in order to measure water pollution on the River Wandle in South London before and after the sewage works discharges its effluent. I am doing an A-level independent study. I'm also wanting to ask if you know of any names of books I could get on this subject. Of what I know, I know that I would like to measure the dissolved oxygen content, (I don't know where to get a device, maybe I could borrow it from an organisation, my college doesn't have very good resources) temperature, pH, the presence of pollution sensitive organisms, (I'm not very sure how to do that) and that's it I think... I managed to get a thermometer, litmus paper and a net from my school so far.
Well I am not sure if you needed that information, but it might help.
Thank you very much!
JesseGordon gave this response on 6/27/2000:
You've got the right list. That's the same list of 4 tests I've used -- the organism to test for, however, should be e. coli. They're not "pollution sensitive" in the sense that they are sensitive TO pollution; they are indicators OF pollution. E. coli is a bacteria that comes only from mammalian feces. Hence its presence is the indicator that sewage is in the water. You can test for it by growing colonies from water samples.
If you're doing the sampling and testing yourself, you're taking on a huge project! You'd have to measure them over a period of a few months, and under different conditions. The most relevant condition is the level of rainfall in the preceding few hours or up to a day upstream. If it has rained a lot, feces get washed into the river from nearby cow fields, for example. To account for that, you'll need to have many samples, so you know which are the "base level" and which are only high because of a recent rain event.
Good luck -- read details of how I handled the same thing at http://www.brsf.org/bnr_econ/d_pol.htm
A viewer rated this answer:
Thank-you again for your
I may ask some follow up questions later(?)
A viewer asked this follow-up question on 6/28/2000:
Do you know more about the method you would use for obtaining and observing the pollution indicator organisms in the water?
JesseGordon gave this response on 6/29/2000:
I haven't done colony growth samples is a very long time; I got the data in the study above from the National Park Service. So forgive anything that's out of date, but here's the basics. Also, please forgive the American dialect -- translate "toilets" as "WCs" but I don't know what you'd call "stoppers." All of this is in a first-year biology lab course, so ask the teacher for that course for assistance:
1) Pick a few points along the river that you can visit on a regular basis. Don't pick places where people often go, because that will skew your results by what the people there happen to do that day. Especially, pick places where there are no toilets nearby (like, avoid a campground which has a bathroom, and avoid even more a campground which does NOT have a bathroom).
2) Bring some clean test tubes and stoppers and go out 2 or 3 times a week to the same spots and collect a test tube full of water. Label them with the place and the date and keep them at a reasonable temperature until you can get them to a lab. If you have a picnic cooler (the Styrofoam kind), that's perfect -- get some crushed ice and stick a test tube rack into the ice while you're out. The thing you're trying to avoid here is letting the bacteria grow while you're collecting other samples and getting back to the lab. At room temperature, E. coli reproduce every 20 minutes or so, which means your colony count will be off by a factor of 8 if you keep the water sample at room temperature for an hour.
3) Back at the lab (or at your home), put a fixed amount of water (say 1 ml) from each sample onto its own "agar plate." Agar is a bacterial growth medium -- you can use anything that readily supports the growth of E. coli. Your lab attendant will know what's appropriate. You'll need a couple for each sample for each day -- it's best if you do it twice for each sample.
4) Cover the agar plates and "incubate" them in a 40-degree Celsius room for a few hours, or overnight if that's convenient. If you don't have a 40-degree room available, you can do it at room temperature; it'll just take longer to grow the colonies. You haven't waited long enough if you can't yet see any colonies. You've waited too long if the colonies merge together so you can't tell how many there are any more. The amount of time isn't critical; being able to count the colonies is.
5) Count the colonies. That just means, look at them and write down how many you see. If the count is too low (like, under 3 or 4 per plate), then use more water (say, 5 ml) in step 3. If the count is too high to conveniently count (like, over 50 per plate) then use less water (say, 1/2 ml) in step 3. At first, try different volumes of water until you get a good count, then use that amount consistently. The goal is to get the number of colonies per ml -- that's how you report your results.
6) Repeat that process for a couple of weeks. So the total number of counts is:
3 or 4 runs per week X 3 or 4 river sites X 2 plates per site X 2 weeks = 50 or 60 plates.
That's the minimum for a decent collection sample. Do more if you have the time.
7) I assume you know about "sterile technique." If you don't know how to keep the plates and transfer tools sterile, you'll get bad counts. You'll need a couple lab sessions for practice to learn that. I also assume you know about "control data." If not, take a couple more bio labs and learn that. An appropriate control here would be to run a sample of distilled water and/or tap water with each batch. The colony count on those should be zero! A second control would be to run a sample of water which you know is contaminated with feces. You can find a stagnant pond near your school, preferably one near a sewage line, the stinkier the better; that's sure to have fecal contamination. The purpose there is to check your technique. If you get zero counts on your river samples, explore your technique with more sewage samples as controls.
Good luck -- is this your first biology project? I'm not sure what "A-level" means -- how old are you? And how many biology lab courses have you taken? You can ask me as many follow-ups as you like, but the only way to get this stuff right is to do it, with enough lab experience behind you that you don't mess it up.
A viewer asked this follow-up question on 6/30/2000:
Thanks, your answer was very helpful.
This project is not so much biology as it is geography, so I might not have to go in to or have the time to get very detailed data collection, although I'm doing biology as well. I could mention it as one of the limitations. A(advanced)-level in England is about equivalent to what you would do in college in America I think. It's not yet complete university standard. This is one of the first projects I'm doing.
JesseGordon gave this response on 6/30/2000:
It's a very biological subject for a geography project. I suppose to make it more geography than biology you could take samples over a very wide area, and then only have to do it once or twice. That way you could map pollution levels against the length of the river and its tributaries. You'd still need to grow e. coli colonies to get the counts, but you could do the whole thing in two weekends that way. You'd likely find a correlation between e. coli counts and population centers and/or farms which have animals near the river (higher just downstream from each).
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