Yoshika and I have spent the past two weeks field testing our prototype at a hand pump in Dhaka! We quickly discovered that the field conditions here are quite different from the conditions that we had created in the lab at Stanford, and have had to make a couple of changes to our device.
First, we noticed that the pressure at the hand pump we are testing at in Dhaka is much higher than the testing setup we used in the lab. This higher pressure has meant that the same volume of water flowing through the pump receives a much higher chlorine dose than what we saw in the lab. To correct this, we have reduced the concentration of chlorine in our chlorine feed and dialed down our flow regulator to a lower dosing level.
Also, when we initially installed our all-plastic prototype on the hand pump, it raised the height of the hand pump significantly and made the hand pump quite wobbly. To fix this, we have changed the pipe section that we are installing back to metal and removed both large non-return valves. It turns out that the large non-return valves were only necessary to maintain chlorine consistency in the lab to prevent chlorine back flow into the testing water. In the field, we found that removing the large non-return valves has no affect on consistency. Which is great news for us, because it reduces that cost of our device by about $25/each, bringing the total capital cost of our device down to about $5!
We’ve also have seen good accuracy of our device at the one hand pump that we been testing it at, and have been able to meet our chlorine dosing range at a number of flow regulator settings. Our next step is to try it out at other hand pumps, particularity those with lower pressure, and see if we can repeat the results.
All-in-all, we’re quite happy with the results of our testing over the past few weeks!