Bio-Filtration Systems

Bio-BucketWhat 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.

BioSplashTwo 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!