Less than three and a half weeks until we leave and we still have not established the correct bleach dose. I have been using 60 ml plastic specimen containers to collect the water and then bringing it up to the lab at RPI. I have usually done the dosing and sampling the day before so that the samples have sat for 24 or more hours in the containers before being tested. Last week I had done the bleach dosing on Tuesday then went up to campus on Wednesday night and we ran the levels using dipsticks. The effective dose seemed between 12 and 15 ml per barrel and we were hoping to confirm this using a colorimeter. Chip and Frank found the one in the basement and I ordered a used on on Ebay (as well as reagent kits for it and several bottles of 5-in-1 test strips). Frank went back a couple of days later and rechecked the levels. The previously robust sample ranges (12-15 ml) were now reading zero. This can be explained by either adsorption of chlorine to the plastic or reactivity of the chlorine (oxidation) with the plastic itself. Given the 24 hour delay between sampling time and testing, this calls into question the validity of these ranges. It may be much lower bleach dose is needed and that means we need to do more testing.
The new plan involves a two-arm experimental plan: One is a real time dose-titration, the other a time-stability study. Now that I have all of the necessary equipment at my house I can test immediately after I have made each dose titration. I will start at the 6 ml of 8.25% bleach, do a fresh sample using both dipstick and colorimeter and then pull off two samples - one stored in plastic and the other stored in glass (these are for the time-stability portion). I can add bleach in any increment I choose then add smaller increments as I start to get readings on either dipstick or colorimeter until I get overshoot. Hopefully, once and for all, this will give us the best correct bleach dose. Once that portion is complete I can then do a daily check on the stored plastic and glass container samples to see if the chlorine degrades faster in the plastic containers.If there is degradation of chlorine level I don't know if this data will be sufficient to distinguish the mechanism between adsorption to the sides of the container versus oxidation of the plastic by the chlorine. That would be a function of the reaction rate kinetics. Chip can hopefully shed some light on that aspect.
I have picked up two more 55 gallon drums to hook to the downgutters so I have enough water to repeat tests if I need to. Fortunately, I don't anticipate much packing as most stuff is all packed up neatly from last year. As soon as I get some of the testing done (hopefully Sunday afternoon) I will post the results here. Lastly, it looks like my loyal reading base in South Korea has been looking in. I wish you all gyejeol-ui insa. I am trying to say "Seasons Greetings" and I am totally depending on Google Translate for this. If am wrong, please, someone correct me and let me know the correct way to say it. Also, there seems to be a bunch of folks in Russia reading; to all of you I send sezony privetstviya. Again, if wrong, please me a comment and correct me.
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