This week, we acquired a store-bought non-return valve. Good news: it was only $15, it fits our pipe, and it seals really well in one direction without causing a noticeable inhibition of flow in the other. Unfortunately, we found that the use of the non-return valves have been the reason we were seeing such low doses of chlorine in our outflow, despite the fact that we have been using our highest starting chlorine concentrations to date (0.66%).
We noticed that fully opening our IV regulator and even varying the height of the chlorine reservoir relative to the aspirator did little to increase chlorine doses past 0.01 to 0.04 ppm in our outflow. However, as soon as we took out the non-return valve, we started seeing overdosing of our water, to the point where our colorimeter was being saturated and reporting “Error 2” or “Error 3.”
Therefore, in our next round of tests, we’ll likely leave our IV regulator only 1/4 open (versus fully open, as in this set of tests). We’re also considering installing 2+ IV regulators in series in order to fine-tune our dosing capabilities and finally hit the desired 1 ppm goal. The big challenge however, will be to develop a method for accurately measuring the dosing capabilities of our aspirator while accounting for residual chlorine in our holding tank due to back-flow from our pump. More on this later…and in our draft of the second deliverable!