PDS AP Environmental Science 5th Period 2011-12

*Note: This is a guest post by RayS in the other class, scribe for our all day field trip.

Today we visited one of Charlotte’s waste water treatment plants, 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

First the inflow comes to a big grate 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.

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.

Primary Clarifier

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.

Aeration Basin

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!

UV disinfectant

Here's the process outlined

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 the pond was free standing, so the DO makes sense as well.

After the fun “hands-on-stuff”, we had to trek back indoors and listen to some lady. 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.

AHHH!

This 18-minute video was made by me a few years ago. While it is a bit grainy, it covers the major field research techniques I try to show students at Davidson each year. A good review if you have the time:

You can also check out MattP’s post that reviews our day.

*Note: The Internet filter at school will not let you view YouTube videos, so you have to watch it at home.

Note: This is a guest post by Matt from the other class.

At Davidson we learned how to conduct out-door experiments through use of a line transect, quadrats, sweep nets, drift fences, and cover boards.

To take random samples of detritus from the forest floor, we had to represent the area as a grid to use a method called a line transect. Next we used a random number generator to decide which part of the grid we would choose samples from. The random number generator was a piece of paper with numbers randomly placed across it. Someone would close their eyes and point to a number. We would then measure the distance of the chosen number and repeat to get a measurement to the right or left. We did this because humans naturally are going to choose a place that is out in the open and easy to get a sample from. That is not the goal. We want samples from anywhere in the given  are, and that includes briar patches or any other hard to get to place. So to be fair we use the random number generator.

Random Number Generation

After we chose the spot we placed a quadrat on the ground and collected all detritus within it.  We repeated until we had seven samples, which was roughly ten percent of the area we were sampling. Always aim to collect ten percent of the target area.

Line Transect and Quadrat

We also learned how to collect samples of bugs. We used the same random number generator and line transect to choose an area to use a sweep net. Once you choose the spot, you walk ten steps forward swing the net back and forth evenly with each pace to beat the plants and collect the bugs clinging to them. Then dump the nets on a mat and bottle the samples.

Sweep Netting in a Field

The way to sample reptiles and amphibians starts with a drift fence. It is a silt fence place near a water source. As amphibians approach the water source they hit the fence and walk along it until they hit one of the pitfall traps. A pitfall trap is a bucket buried right at surface level. When they amphibians fall in, it is too steep to get out. For reptiles it is similar. They hit the fence and walk along until they hit one of the wood boxes with inward slanting chain-link fence on each side. They slide in but can not figure out the way out. They are trapped until people come and collect the samples.

Checking Pitfall Traps on a Drift Fence

The last way we learned to collect samples was by using a cover board. Place a board of plywood on the ground and leave it there a few days. Many types of bugs like to live under things like that. Then collect the bugs that have gathered underneath the board.

Checking a Coverboard