Today we visited one of Charlotte’s waste water treatment plants (Mallard Creek), and did some water testing at Reedy Creek Nature Preserve!
The waste water treatment plant was all about going to “away”. When you flush things down the toilet or pour something down the drain, you are sending things away. Well here at the treatment plant, there is no away. Everything has to be sorted and dealt with (from diamond rings to latex condoms–lots of latex condoms.)
Aerial View ( I took all plant photos)
First the inflow comes to the bar screens where large pieces of debris and various other things (condoms, tampons, toilet paper, plastics) are raked out. The plant screens out the solid objects or grit, after allowing the water to settle in the settling tank
Then the water, still a murky brown, goes to a primary clarifier. Here the oils and greases float to the top, and the solids condense at the bottom as sludge. It’s sludge, not poop.
Next the water goes to the aeration basin. Here the plant has a “farm” of microbes and bacteria that consume the organic matter. The basin is constantly aerated to supply the microbes with oxygen, and sometimes the nearby Cheerwine plant with give the plant their waste sugar water to feed the microbes. On days like that, you better believe that denitrification is working.
The plant CAN deal with up to 12 MGD (millions of gallons a day), but they average around 8.5.
Fun Fact: If you fell in the aeration basin, you would sink to the bottom and drown. Do you know why? ….
because the DO (dissolved oxygen) is so high that the water is too light for our dense bodies.
Next, the water goes through some secondary clarifiers (which look identical to the first), and finally, to be filtered and disinfected before reentering the stream. The disinfecting process is done with giant UV lamps that sanitize the water; the lamps destroy any pathogen’s/bacteria’s/organism’s genes beyond reproductive potential, so it’s safe! (Safe for the stream…not drinking.)
Here's the process outlined
Meanwhile, the sludge goes to an anaerobic digestor, where the methane is burned off, and the remaining solid (known as cake) is sent to animal farms for crop fertilizer.
After the treatment plant, we went to Reedy Creek and tested the waters in Dragonfly Pond. The pond did not have particularly high numbers in general (a fairly low DO and a fairly low nitrate/phosphate level). We took tests on pH, temperature, and fecal coliform presence. Fecal coliform is bacterium that comes from feces (poop), and it’s important in water sanitation. Many people were walking their dogs around the pond, so it’s no surprise that coliforms were present; furthermore, the phosphate/nitrate level makes sense considering there is no farm or lawns to runoff their fertilizers into the pond. Lastly, without a fountain to mix oxygen into the pond, it was free standing, so the low DO makes sense as well. It is important to remember that our sample was taken at the edge of pond, where the temperature is warmer; thus the do is lower. Had we taken a sample fifteen feet underwater in the center of the pond, we would probably have a much higher sample.
After the fun “hands-on-stuff”, we had to trek back indoors and listen to a park naturalist. She explained the values of Bio-indexing. Basically, the organisms living in a body of water indicate the health of that water. If there are lots of organisms that are very sensitive that pollutants, then the water must be relatively untouched (otherwise those organisms wouldn’t survive). On the other hand, if a body of water only contains organisms that are very resistant to toxins, then you have a problem on your hands. Next, we looked at pictures/descriptions of aquatic bugs.