Thursday - D3P2 , in which Daniel gets a new name and we check some bleach

The new first flush was an engineering marvel to be sure, but still had some significant kinks to be worked out, in particular, the issue of draining the air out of the horizontal pipe as it was locked in by the upright "Y" connector. Note that this would not have occurred with ether the "T" connector or the inverted"Y" connector. Still, it could be solved with a bit of tinkering. This discovery, by the way, was once again the result of Frank's sharp eye and analytical mind.

So we continued on with other parts of the project. Getting back to Frank; since we had touched down he had set up his chlorine testing equipment on the left hand corner of the work table up on the platform and been mixing various solutions of bleach in various containers to determine the amount of bleach needed for various vessels based on size or material. This is surprisingly more complex than one might expect as the variables include the concentration of the bleach, the chlorine demand of the container the water is held in, and the chlorine demand of the water itself. To start with, we bought two bottle of commercial "Chlorox" style bleach off the shelf the day we arrived in Bocas del Toro and brought them with us, both for experimentation and for general housekeeping. In the US, the concentration of sodium hypochlorite (the active ingredient in bleach) is either 5.25% or 8.25%. (In the US, we also now make "splash free" bleach which cannot be used for water chlorination as it contains soaps and surfactants which minimize the surface tension of water which leads to splashing. They are non-ingestible). We had based several pages of calculation on one of those two values, but also knew that we might have to deal with other concentrations, so we were prepared for this. Frank's water lab was ready to deal with it and Frank had made great strides in his understanding of water chemistry. For example, the meter tests total chlorine as well as the"free" fraction. Why are those two different fractions important; well, as an example, standing pond water may have a large component of dissolved organic (carbon) matter from plants and animals, as well as ammonia from animal life. When these combine with chlorine two sets of chemical families can be formed, trihalomethanes and chloramines. These not only do not contribute to the bactericidal function of the chlorine, they can be toxic in and of themselves, what we refer to as '"disinfection byproducts" or "dibs". In municipal water supplies, these must be accounted for and controlled. In theory, this should be a minimal problem using rain as a sourcewater. Proof of this would be found if the free fraction and the total fraction nearly agreed indicating there was little organic or nitrogen in our rain water. Now, stepping back one place, we discovered that commercial bleach available in the islands of Bocas del Toro were all 3.5%, considerably weaker than what we had developed our guidelines for. This however, was neither unexpected, nor a problem. If anything, the weaker concentration meant that a slightly larger volume had to be used for any dosing regimen and it is actually easier (and more accurate) to measure a larger volume with any given measuring devices, than a smaller one.  Proof came in that, after adding the calculated dose of 2.5 mg/L, (The WHO approved standard), the free and total chlorine concentrations were reproducibly in the 1.4 - 1.8 mg/L (PPM) range, exactly where we wanted them. This applied to plastic drinking water bottles and 5 gallon painters buckets. As we were still letting the 40 gallon drums dry out from their cleaning we had not yet tested them. Results in those barrels might be very confusing owing to the possibility of any residual glop interacting with the chlorine. We could only hope that Frank and I had really gotten them clean.

Chip working near water testing area (blue box).

Frank drawing off water samples from the main tank

Chip hard at work.

Thinking Deep Thoughts

When all was said and done, we came in with an interesting and very useful dosing schedule. Back home in Hurley, we needed about 8 ml of 8.25% bleach added to a 55 gallon drum to get chlorine residuals of about 2.2 mg/L (PPM). (This is really a bit higher than needed but completely safe). On the island we found that using 10 ml of 3.5% bleach in a 40 gallon barrel reliably produced chlorine residuals in the range of 1.4 - 1.8 mg/L (PPM). Number one, the numbers add up and compare very neatly with our home values. Number two, that 10 ml is a "nice" number to work with - easy to remember, easy to see on the side of the syringe or beaker, easy to divide if, say, they are only chlorinating 20 gallons (5 ml). And the proximity of the free to the total fraction meant we were dealing with a good water source without significant contaminants. As long as these measures held up in the 40 gallon barrels we would have one sticky problems solved.

Now, on a lighter note, on last years visit I had been introduced to Daniel. I was told that he was the "president of the school". And he is. The community is very hierarchical and every one of the various institutions on the island (the schools, the water system, the restaurant, the tourist board) all have a president and board of governors. It takes quite a while to learn all of this as an outsider and can be

 

quite confusing to the uninitiated. Daniel is sweet, soft and gentle with a warm sense of humor. And while he is certainly willing to work damn hard (especially with cement) he can be a bit lazy and a bit of a mooch. He always has his hand out. His recognized call is heard every day at midday when he yells out to me - "Paulo - Lonche?" (Lunch break?). Which is usually fine; if anything, his work is usually finished, and anyhow, I am not his boss. It's just funny because it reminds of union highway crews.("9:00 o'clock - Coffee!"). So I usually shout back, "Si, Daniel, lonche". Then I tease him with something like, "5 minutes and back to work", or "No lonche today - manana". Big laugh.

Well, the thing about Daniel is has last name. Viagra. Daniel Viagra. Or so I was told last year. I asked the students at that time if they didn't think it was funny that his last name was the name of an erectile dysfunction drug, but they hadn't really paid attention. Well, at one point on this trip, Mike pointed out to me that the correct spelling of Daniel's last name was "Villagra" (pronounced 'Veelyagra') which makes entire linguistic sense to me. Thank God they just send me to an out of the way island where my offenses do little damage. I am not ready for the ambassadorship!