Monday, November 16, 2015

Rainwater Samples

So it finally rained last week. Even though it was not a downpour I was amazed at how quickly the barrel filled. It really is an excellent example of how large the volume of rain runoff is from a non-absorptive surface (the problem with flooding from shopping mall parking lots, etc). So, anyway, it probably filled somewhere around Tuesday or Wednesday. Saturday morning I siphoned off 5 samples of unchlorinated rainwater to use as the control blank (always use an odd number so there is no chance of a "tie") for background chlorine levels or for microbial cultures. Then it was time for bleach. Now, we based the majority of our calculations on what we thought was the most common strength of commercial bleach, sodium hypochlorite 5.25%. The store shelves now also carry "concentrated" bleach of 8.25%. We did do a table of calculations using this strength just in case. So, on Saturday morning, I look under my cabinet at my bleach - all of it is 8.25%. Figuring I really want to do this as close as to what we will be doing down in Panama I went down to Hannaford to try to find some 5.25% stuff. Good luck with that - every last bottle was 8.25%. Oh well, you gottta work with what you got, so, back home. I drained the barrel down exactly to the 55 gallon mark and added the bleach. The volume of bleach is quite minuscule - 5.8 ml or slightly more than a half a teaspoon full - and you don't just squirt it in directly. The correct procedure is to siphon off a half gallon or so from the barrel then add the 5.8 ml of bleach to that, thoroughly shake it around, then add that solution to the main barrel. All of this was done just so; I left it to sit for 45 minutes then went out and stirred it for several minutes with a broomstick and let it sit for 45 more minutes. Finally, 5 more samples were drawn off, capped and placed in specimen bags. Delivered to Mike Saturday night, then went to the hockey game. Yesterday, I drained and rinsed the barrel and set it up again to wait for the next rain in case we need to repeat the test.

Now, all we do is wait for the results which I will post as soon as I get my hot little hands on them. Fascinating stuff, huh? Science really is like this.

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