We revived our chlorine tests this week and found the following:
1. The non-return valves we installed about a month ago are working properly—we no longer see chlorine contamination in our water reservoir!
2. After dropping our starting chlorine concentration to 0.06% and closing our IV regulator halfway, we finally started seeing downstream chlorine concentrations that made sense given our setup. (~0.25 ppm average across three or so trials) These numbers are also closer to the model that the prototyping team has been developing based on Bernoulli’s principle.
To maintain our improved consistency (25% error or less) in future tests, we have determined that we should:
1. Flush out our system with DI water at the beginning of each testing session.
2. Discard the first 4 strokes for each trial. This effectively serves as a “re-priming” step between trials.
3. Collect 1 L samples (instead of ~100 mL samples) to account for the possibility of poor mixing inside the pump, where the concentrated chlorine first comes into contact with the water source.
Now that we’ve determined our current setup (IV = 1/2 open, starting Cl conc. = 0.06%) provides decently reproducible results, our next goal is to use this setup to compare the tube-in-pipe concept with the venturi to finally settle on one prototype for on-site installation in the summer. We will eventually modify our chosen starting concentration of chlorine to yield a final dose within our target range (1.0 +/- 0.5 ppm), but for now the goal is to verify the reproducibility of our promising findings so that we can be confident in whichever prototype we choose.
Stanford Dhaka Water Project | Bangladesh 