Bio-Filtration Systems
| 28 April 2009
What do a bucket of sand, some wetland plants, and a bunch of tap water have to do with each other? They’re all part of a bio-filtration system that we constructed in class a couple of weeks ago to remediate city water that has been treated with the chemical chloramine. Although municipal water folk will tell you that “treating” water with these chemicals is necessary for public health, the presence of such persistant compounds in our water presents numerous challenges, and any aquarium owner will assure you that our tap water will kill their fish in no time. Do you still want to take that sip?
Anyhow….We crafted these bio-filtration systems to get rid of choramine. They consist of some PVC pipes with small holes drilled on the underside, on top of which is about 2-3 inches of gravel, and then sharp sand, into which is placed water-loving plants like taro, wasabi, and chocolate mint, as well as native wetland species found in a local SF area marsh. The idea is that you can pour tap water into the open top of the bucket, and as it filters through the plants, sand, gravel, and finally the pipes, it comes out the attached spigot in a pure, non-chlorimine state. The wetland plants are able to break apart the chloramine into ammonia and chlorine, and after using the ammonia for their nutrients, the free chlorine evaporates out of the H20.
So, being the bucket-toting gal that I am, I took one of these (extremely heavy) contraptions home to Berkeley. I filled it with water, and wated for the magic to begin. Well, right off the bat one of the plants died…. Everything else seemed to do pretty well, and I happily went to a local pet and aquarium store in search of an aquarium test strip kit to test for the presence of chlorine/chloramine in the water. I returned home, and dutifully tested the water: it turns out Berkeley’s water isn’t as full of chemicals as the SF water supply. However, it was still showing the presence of some chemicals--about .5 ppm of chloramine.
Two weeks later, I’ve let the water have some good “residence time” in the bucket, filling and flushing it a little every 4-5 days. Today I went out to my bio-filter and tested the water that came out of the spigot. I took a reading with my test strips, and got a 0 ppm reading on free chlorine, and 0 ppm on the total chlorine. That means there is no chloramine, either!
I’m going to see what happens if I flush the whole system, fill it up again, and test in a week. I’d like to know how long it takes the bio-filter to eat up all that nasty chloramine!
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written by Jim Eagan, May 01, 2009
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written by eengineer, May 11, 2009
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written by David Cody, September 16, 2009
This is not mis-informative. Plant do in fact remove chloramines from water by using up the ammonia that has bonded to the chlorine(chlormines are ammonia and chlorine bonded together).
The point of this is not to remove chloramine from water for drinking purposes. The point is to remove it for garden uses. Chloramine AND chlorine kill fish and the bacterias which we want in our garden. We know chlorine is easy enough to remove by waiting for it to flash out, but chloramines will not flash by simply sitting in the sun (at least not very fast, Hetch Hetchy is in full sunlight and still has chlormine in it).
In fact, you know how when you go to a public pool and it smells VERY strongly of chlorine? That is in fact chlormaines you smell. Chlorine will bond with ammonia if the ph is below 7. What happens is the chlorine applied during pool maintenance bonds with the ammonia from human urine in the pool and forms chloramine. Chloramines will form in nature if you add chlorine to a nitrogen (ammonia) rich body of water. If you added chlorine to most any duck pond, you would get chloramine.
You will need some strategy for chloramine removal if you want to make compost teas for your garden. This strategy will work.
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written by unholysf, October 23, 2009
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written by David Cody, October 24, 2009
And while "worm tea" is a wonderful amendment to any garden soil, it is not the same as an aerobically aerated compost tea.
Here is a link to a PDF by Elaine Ingham, one of the leading soil scientists concerning soil mocrobial life:
http://www.soilfoodweb.co.nz/linked/why use compost tea.pdf
We don't pass all of our water through a wetland system before application to the garden, but if it was an option I certainly would try it out. But for making a compost tea, you have no way of doing it without removing the chloramines from the water first. Chloramines, and regular chlorine for that matter, kill the bacterial life we are going for. If that is true, I wonder what it does to the flora in my body.
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You could does them with some compost tea, or the super easy way would be a little urine. Just pour some in with some frsh water, let sit for a few days or so, then maybe flush the whole system and refill. Not sure how long it will take the plants to take up the nutrients, that's another bit of data that is good to know.