Turbidity

[deleted-68184]

Hi,
For school, students were assigned to figure out a science fair topic, do the background research, and create the research plan prior to the start of school. I basically have a topic in mind on which I'm going to research. I want to test what is the best way to decrease the tubidity in water. I'm planning on basically getting turbid water from an university lake. I will make a tubidity tube to measure its turbidity(the website shows how I plan on making it http://www.cee.mtu.edu/sustainable_engi ... e_Shaw.pdf). Then I'm planning on testing various filters(cheap, inexpensive, easy to access) to see which one filters the water the best. Of course I will use the turbidity tube to measure the turbidity level of the water after it has been filtered. My purpose is that after I decrease the turbidity in water, the same water is solar disinfected. That way those in underdeveloped nations have a way to clean their water even if it is highly turbid. I'm curious if this project seems suitable for a student in a 10 grade honors class? What are possible ways I can make this expreiment more challenging/difficult? What are some possible ways to figure out which filters to test? Any suggestions would be greatly appreciated. Thanks.

[donnahardy2]

Hi,

Welcome to Science Buddies! I really like this topic because it focuses on one important problem of water purification, the turbidity, and it has a practical application, providing safe water in underdeveloped countries. And, you have a method of measuring turbidity so you will able to present quantitative results.

When does school start? For a 10th grade honors class, I recommend that you start by doing background reading from scientific sources and find out what causes turbidity in water and all about water filtration. You will need to know how water is filtered in water purification plants currently so you will have an idea what to do to make your project unique. You could make this more challenging by using analysis methods, such as microscopic observation or perhaps bacterial plate counts. To add to the challenge, you could test the method that you identify as the best method with a variety of water samples. Or, you could scale up your lab-scale filter and show how your idea would work on a larger scale. Your background reading will give you more ideas about how to make the project more challenging. Your idea to use solar treatment on the water is a good idea, but it sounds like a second project idea to me. Perhaps you could save that idea for 11th grade.

The Wikipedia article actually gives a good overview of the problem caused by high water turbidity, and includes references for standard methods of analysis.

http://en.wikipedia.org/wiki/Turbidity

Here a method to measure turbidity. This site has a photograph of a standard filtration laboratory device that you could use with various filtration materials for your project:

http://www.ecy.wa.gov/programs/wq/plant ... /4tss.html

Here’s another method for measuring turbidity in the field:

http://serc.carleton.edu/microbelife/re ... idity.html

You will need to do a similar search to learn all about filters that are suitable for filtering water. You need to know the approximate size of the particulates in water so you will know what porosity of filter will be needed. Since this is a project for underdeveloped countries, you need the least expensive option and materials that are readily available.

I am having trouble finding scientific papers on this topic. It might be a good idea to contact your local water company and ask to talk to someone who is familiar with this problem, or ask for a referral to another source. If you are close to a university, you could contact the geology department and ask for information on water turbidity and filtration techniques.

Here is information on the Science Buddies website which includes a step-by-step guide for doing a science project:

https://www.sciencebuddies.org/science- ... ndex.shtml

I hope this helps you get started. Please let us know if you need for information about proceeding with your project.


Donna Hardy

[deleted-68184]

Thank you so much for your help. I’m currently working on my project with a ceramic and a slow sand filter. I would like to have another filter to test, but despite my best efforts, I am unable to find/think of any other cheap inexpensive filters. Any suggestions? Also does the bacterial plate count method use soy agar plates?

[donnahardy2]

Hi,

It sounds like you are making progress on your project. You could also consider adding a layer of charcoal to a sand filter. That would give you 3 types of filters to test.

http://www.wildwoodsurvival.com/surviva ... ation.html

Turbidity will be your main measurement to assess the quality of the water. Here is a description of a homemade turbidity meter from the Science Buddies website.

https://www.sciencebuddies.org/science- ... p032.shtml

Testing for total bacteria could be done with soy agar plates. Testing for coliforms, a group of bacteria that inhabit the intestines of animals and humans is also commonly done as an indication of the presence of potentially pathogenic bacteria. Here is a website that describes several different tests including the coliform test.

http://www.lifewater.ca/Section_16.htm

Before you order any microbiological media, however, please read the following guidelines for projects involving potentially hazardous biological agents from the Science Buddies website. To grow unknown bacteria, you would need to get prior approval from your teacher and you local scientific review committee and you would need to have access to a laboratory. To do the testing at home, you would need to order media

https://www.sciencebuddies.org/science- ... ents.shtml

There are other possible tests that you could do. Here is a list of tests that are relatively easy to do and that you would not need prior approval for. You should do an internet search on these tests and decide what you have the time and resources to include in your project. Also, you could consider working on a water to filter that would solve a particular contamination problem, such as iron or manganese contamination. I would not recommend doing all of these tests; just pick 2-3 tests, such as pH, temperature, and conductivity, in additional to the turbidity that you could do on every sample of water that you filter.

total dissolved solids
temperature
conductivity
hardness
dissolved oxygen
pH
nitrate


https://www.sciencebuddies.org/science- ... p013.shtml

https://www.sciencebuddies.org/science- ... _p013.shtm

Donna Hardy

[deleted-68184]

Thank you so much for your help. I have just one more problem that needs to be resolved before I can begin the actual experimenting. From the resources I have found, clay pot filters are made with crushed pieces of clay and organic material. Basically I add water and shape the mixture into a clay pot. The problem is, after these steps I am suppose to put the pot in an open fire. I do not have access to create and open fire. Would it be possible to use an oven instead? If not are there other alternatives? Thanks

[donnahardy2]

Hi Aisho101,

What kind of organic material are you mixing with the crushed pieces of clay? If it would not be flammable when heated in the oven, then I would go ahead and try using the oven. You might have to experiment with the temperature.

Another possibility would be a charcoal grill. Do you have access to an outdoor cooking grill? That would work like an open fire.

Donna Hardy

[deleted-68184]

I was going to mix grass and leaf pieces. For safety reasons, I must ask, a gas grill is out of the question? Thank you

[donnahardy2]

Hi,

I agree that the oven would be the best option then. You could use a low heat, and watch it carefully.

Donna

[deleted-68184]

Sorry for all the questions, but I was wondering would it be fine if I used, used tea grounds (similar to used coffee grounds) in the place of organic material. There would be no safety hazard in the oven? Thanks so much

[donnahardy2]

Hi

I think that either tea or coffee grounds would work well for this. In my experience, if anything catches fire in the oven, all you have to do is shut the door to extinguish it, so I think this will be safe enough to do. If you are not experienced in using the oven, then make sure there is an adult at home to help with this step. I assume the tea grounds are going to be embedded in layers between the clay pot fragments and that you won't have a large quantity of organic matter that you will be cooking in the oven. I think the purpose of this step is to convert the organic material to charcoal, which makes an excellent way to remove organic impurities from the water.

This is not an easy topic to search on the internet, but here is one source that recommends using a slow oven with the organic material sealed from oxygen, so it won't turn to ashes.

http://painting.about.com/od/artsupplie ... arcoal.htm

Try it and let me know what happens.


Donna Hardy

[deleted-68184]

Hi,
I made my clay filter, and I let it dry for a couple of days. I wrapped it in heavy duty aluminum foil and placed it in the oven for approx. an hour at 300 degrees. There was no change at all in the pot, so I experimented with the temperature up until it was 450 degrees. In the end the pot was exactly like it was before I placed it in the oven, except for the fact it smelled of wet clay afterwards. Any suggestions? My father says he may be able to create a small fire if all else fails.

[donnahardy2]

Hi,

Here is some information from one of the references in the link from my last post:

“The basic principal of charcoal is incomplete combustion. When wood is heated to a temperature of about
259 degrees Celsius (482 degrees Fahrenheit) or higher, it quickly decomposes to form gases, vapors and
solids. If heating takes place in the presence of sufficient air, combustion is complete or nearly so and the
only residue is ash. If, however, the air supply is restricted, combustion is incomple
te, the volatile elements are driven off as "smoke" and charcoal and ash remain as solid residue.”

So heating in the 450 F oven with the filter wrapped in aluminum foil to restrict the air should have allowed the tea leaves to be converted to charcoal. Did you see any smoke coming from the filter? There should have been a small amount. Can you see the tea leaves in the filter? They should be black. If the tea leaves are black, then you do have charcoal; if not them maybe you just need to bake at 450 F for another hour or two.

Donna Hardy

[deleted-68184]

Thanks I finished my ceramic filter and was able to perform the filtering, but it collapsed soon afterwards. Perhaps in the future I might bake it for more than 2 hours. Thanks again.

[donnahardy2]

Hi,

Thanks for letting me know what happened. You can learn all kinds of interesting things when you actually do something. I agree that baking for a longer time would probably help prevent a filter collapse, but it sounds like you were able to get some results before it collapsed. When you write up your science fair board, you should include a description of what you would do differently next time to change your results. The science fair judges always appreciate knowing that you can analyze the problem and that you have ideas for improving the experimental design.

Donna Hardy