More Partially Explained

I ferried the water samples up to RPI and met Frank, Kyra and Jonathan at the MRC lab and we headed down to the basement where the EWB chapter has been granted some primo real estate. That is sarcasm. The place kind of reminds me of being backstage at some very old theater - rooms sectioned off by lumber and fencing and such. All kind of creepy. Anyways, this is where we had the testing equipment stored so it would have to do. I will spare the boring details and cut to the chase. After checking the 4 different specimens (0, 1x, 10x and 100x) it looked like 1x was not enough but 10x was too strong; by making serial dilutions we were able to get a rough idea that our bleach doses needed to be 1.25 to 2.5 times larger than we had calculated. Much better than my original 100 fold estimate of error and fairly close to being within the ballpark.

Had a long talk with Chip Kilduff on the drive home and we both agreed that the main value here is: 1. We will definitely need to carry out  same determinations as soon as we get the system set up on the island; and 2. That we will need to have a number of different dosing tables for a range of chlorine doses pre-made and select those best suited to the chlorine demands imposed by the islands water. Fine tuning this will require at least one more set of rainwater tests and I have already started the siphon to drain the barrel and reconnected the diverter hose. Once the next rain comes I will repeat the tests using bleach strengths of 1x (5.8 ml bleach per drum), 1.5 x, 2x, 2.5x, 3x maybe up through 5x (29 ml per drum). With this info we can generate dosing charts and be ready to go.

Very satisfying - all in a days work.

Lastly, a big hello to everyone in South Korea reading this - I hope you are enjoying it and hope the English slang expressions I use are not too confusing. Yell if you need help.

Partially Explained

As I laid in out in yesterdays posting I have (so far) taken samples from the barrel with no bleach, 5.8 ml of bleach and 58 ml of bleach; currently the barrel has been dosed up to the max of 580 ml of bleach and it is equilibrating. I tested the samples of the first three doses with the high sensitivity/low threshold dipsticks from dialysis. My prediction was that it would be pointless to even test the maximal dose as the threshold should be met or exceeded by the third sample (58 ml or ten times our predicted dose). The samples behaved as predicted.

The level that dose our calculation was predicted to produce was 2.5 mg/L; this batch again shows it somewhere in the range of 0.02 - 0.05 mg/L or 1/100th of expected. When the bleach dose was increased tenfold (58 ml in the barrel) the threshold of the test strips, 0.2 mg/L, was exceeded (as predicted). I bet that using different scaled strips it would fall somewhere in then range of 0.2-0.5 mg/L. The whole thing is off by 100 fold and I have a feeling it has something to do with the base assumption of the bleach strength expressed as a % (ie, 8.25%). Our calculations are based on the assumption that 8.25% means 8.25 grams of Sodium hypochlorite in 100 grams of water. This may be an incorrect assumption. However, in the absence of a better explanation the new empiric value rules and it would work out to something on the order of either ~ cups of 8.25% or ~3 cups of 5.25% bleach per 55 gallon drum.

I will finish up the last set of samples (580 ml - which should yield the target range of 2.5 mg/L) and cart them up to Frank for definitive testing. I also have a 4 gallon tank (blue) of untreated rainwater for him to use in anything he sees fit.

If anyone reading this finds it tedious, I apologize. Just thought you might want to know...

More Glitch

I have not been able to reconcile the discrepancy between the negative results obtained from the rainwater samples and our calculations. I checked with Frank and he ran the samples promptly.To try to get better insight into the problem I went down to the dialysis unit and spoke with Joey Schoonmaker, the water technician for the unit. He is, literally, a walking encyclopedia with regards to the water treatment system in the dialysis unit. He provided me with a pretty quick and in-depth overview of how the water is processed before it is safely utilized in the dialysis process for patients. Unlike our need for chlorination theirs is the exact opposite - they want no chlorine in the water being used for dialysis so they test for chlorine residuals at the lowest end of the spectrum. Still, the test strips they use could be used to at least let me know if our dosing discrepancy was a fluke or a reproducible error. Unfortunately, it appears to be the latter.

Joey gave me a handful of test strips to bring home and I set up a counter top chemistry lab.

 In the photo below the actual unused test strip is at the lower left and the chart for interpreting values is in the center of the photo. If you can make out the markings, from left to right, as the colored ovals progress from yellow to blue, the values go from 0 to 0.2 mg/L. The World Health Organization set 2.5 mg/L as the target level for chlorine residuals in treated water.

 

The fact that these test strips are off by one full order of magnitude does not render them useless. For starters, I can mix a batch of rainwater on a smaller scale to the same concentration as I would in the barrel, just scaling back the amount I add proportional to the size of the batch I am making then test. If our calculations are correct, and there are no other errors in either our assumptions or our methods, then the sample should overshoot the test strip and it should turn it dark blue. Bad if we are doing dialysis; good if we are disinfecting water for drinking purposes. So, following this reasoning, I mixed up a fresh batch of water, using a TB syringe to add 0.15 ml of 8.25% bleach to 2.65 L of water. This mixture is actually rather rich and should produce a chlorine level of between 4 and 5 mg/L. After letting it stand for a few minutes I

lowered in the dipstick, swirled it a bit, drew it out and read the results. Take a look.

The reading should be a robust blue of a shade equal to, or darker, than the last oval on the right. As you can see, it clearly is not. It reads right on 0.05 mg/L. What is interesting about this error is that it is numerically correct, only that it is off by two orders of magnitude (factor of 100x). This leads me to believe that somewhere in the calculations is a unit conversion error, but I will be damned if I can find it. I have re-run the numbers more than once and don't see it.

On the up side, though, is that I have a plan for tomorrow. I will first add 5.8 ml of bleach to the barrel and take samples; then I will add another 52 ml (for a total of 58 ml) or 10 times as much and take samples; then finally, I will add 520 ml of bleach (for a total of ~580 ml of bleach) or 100 times as much and again sample. If it is simply a unit conversion error in our calculations this should reveal it. I am, however, leery about this as it would entail adding a liter of bleach to every 55 gallon drum. This seems to fly in the face of more conventional doses that I have found online at the WHO and other websites that start with 1% stock solutions and add amounts on the order of 20 ml to a 45 gallon drum. Something just is not adding up and we need to rectify it quickly.

Glitch

Okay. On Tuesday I reported here on the sample chlorination using rainwater that I did last Saturday. I traded emails with Frank Sokolowski who ran the samples and none of them showed any chlorine residual at all (neither free nor total). It's a good thing I refilled the barrel on yesterdays rainfall as we definitely need to do it again. Here is the error analysis I submitted to Frank.

Error Analysis – Potential Sources

1.       I have rechecked our calculations to make sure there are no unit conversion errors. I can find none and both of our calculations were performed independently and agree.

2.       The bleach I used was of uncertain age. It certainly wasn’t new. Loss of efficacy? Seems unlikely, but I will buy new bleach.

3.       Chlorine consumption/decomposition due to delay in testing? I don’t know when you did the testing and how long the samples sat. Chip Kilduff can shed some light on the time dependent aspect of chlorine degradation.

4.       Routine chlorine demand of rainwater at my house exceeds our calculations. Again, Chip is our resource.

 So, the plan is to repeat the procedure on Sunday with a bottle of new bleach and bring the samples directly up to Frank for prompt testing to eliminate those factors. I will also bring up a 4 gallon tank of untreated rainwater for Frank to use. I'll make a point to throw in some photos then. We shall see.

On another note, the blogs administrative area includes a statistics section that provides me with various breakdowns of readership. Over the past two weeks there has been a bit of a surge in views from South Korea and Japan. Now, I have no idea why folks over there would have any interest in this blog but I certainly want to reach out and say "annyeonghaseo" and "kon'nichiwa". God bless Google Translate, that's all I can say. Thanks for reading and I hope I don't bore you. Who knows, maybe you need this for some class project or something.

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.

The New Team

As I previously wrote, the preliminary team was Me (Assistant Construction Lead) and Chip Kilduff (Quality Assurance Lead) as mentors, with Mike Kubista as student project lead and 4 students to be added. The final lineup has been announced and here's how it looks:

Mariana Cintron - Translator
Elizabeth Kwon - PMEL Lead
Mike Kubista - Construction Lead
Tim Andrews - Assistant Construction Lead
Frank Sokolowski - Education Lead

January 4th is less than two months away. For me it means getting through the holidays and taking the extra on-call so I can be away for much of January. Much less packing as most of my stuff from last year was neatly stored away for easy use; all the first aid kit was restocked. For the students it means the last 6 weeks of the semester with finals and all of the stuff that comes with being a student.

On the plus side, I am going back a veteran and have a much clearer view of the things I would like to do. The scope of the project is smaller and should require a little less of the hands on that I gave last year. I want to take lots more photos and get them posted up to the blog really quickly this time - none of this after the fact stuff. I really want to spend more time with the people in the community and get to know them better and have a little fun with them. I would like to try to get them to understand the value of clean drinking water and improved hygiene but I don't have a clear plan for that as of yet. We should definitely challenge them to volleyball.

It is gently raining out now and the experimental tank is slowly filling - hopefully by the morning it will be full and I can dose it with bleach and mix. We'll see how good those paper calculations turn out!

The Hurley Rainwater Research Center

Last week it occurred to me that, while we have carefully done the calculations to determine the amount of bleach to be added to each 55 gallon drum to achieve a level of chlorine that will kill bacteria yet not leave an unpleasant taste (WHO  recommends 2.5 mg/liter, US EPA less than 4 mg/liter) it might be nice to see if our calculations are on the mark. Not only would it validate our calculations it would give us experience using the system and doing real-world chlorine residual tests. I ran it by the major honchos (Mike, Frank and Chip) and all thought it was a pretty good idea. Chip also added that different water sources pose different chlorine demands depending on level of bacterial contamination. I figured I was in a pretty good position to at least do a rainwater sample as my downgutters are equipped with diverters for rain barrels. Borrowing an empty 55 gallon drum from dialysis (and thoroughly rinsing it out) the Hurley Rainfall Research Center was born. Following the next sizable rain the protocol states to add 9.1 ml of regular strength (5.25%) commercial bleach to the barrel.

Now, to wait for the next rain event. Unfortunately, according to the National Weather Service we are looking clear for the next 5-7 days. I'm sure it will rain sometime between now and January.