Hello again,
Last Friday, Dr. Perreault (my faculty host) showed me how to set up and operate the membrane distillation system. We ran it with DI water for a few hours to test it. We had sort of a very leaky start, but it flows just fine now. Thank goodness we’re working with water and not some crazy dangerous chemical, because we practically flooded our side of the lab! I’m in charge of writing up a protocol for others to reference when they try to set up the same system. Here’s what it looks like:
My men
tor, Ana, and I were discussing the problem statement we were discussing in the meeting this morning. I’m still in the process of writing it, but our goal is to characterize the scaling in the conventional MD system. Then, in the future (We do not think we will have time during my stay, but who knows!) we will compare with solar MD.
There are three components to this work: 1) Equilibrium modelling of the change in solubility as the solutes are concentrated on the feed side of the membrane. 2) Running a bench-scale MD system and monitoring change of permeate flux over time to quantify the impact of scaling on the membrane performance. 3) Analysis of the membrane surface to identify what deposited
on the membrane and how much of it is there.
Essentially, tomorrow we’re going to do our first run with the NEWT Standard brackish water recipe. Which, by the way, took a little time to figure out, since it was so concentrated that our salts kept crashing out of solution. A couple of the salts have inverse solubility, so when we autoclaved (heated to kill biological contaminants) it, it only made the salts precipitate more. We ended up making stock solutions for each individual salt and will combine them into one brackish water solution as needed. We also nixed the autoclave since our system isn’t sterile anyway. This seemed to majorly alleviate most of the problem and our little brackish water solution is sitting happily on its stir plate overnight. Tomorrow we’re running it through the MD system for about 8 hours and seeing how long it takes before it crashes. Every hour, we’ll be taking samples to measure the water conductivity. Dr. Perreault and Ana are both leaving for a 10 day seminar on Thursday, so I’ll be on my own for a bit soon. Wish me luck!