Salt Recovery & Enhanced Evaporation (how we achieve zero liquid discharge)

This week (so far) we have focused on on the final piece of our technology: salt recovery and enhanced evaporation. As mentioned on an earlier blog, we can achieve up to 98% recovery and we are expecting at least 95% recovery. This means that there is 2-5% of the initial volume and all of the salts removed in the process leftover. Our plan is to mix our two EDM concentrate streams together. One is rich in calcium salts and the other is rich in sulfate salts. When mixed, calcium sulfate (gypsum) is precipitated and the remaining fluid contains sodium chloride (table salt). The gypsum can be used by farmers to mix into their soil and improve its quality (more calcium relative to sodium can increase water infiltration). The sodium chloride can be used in the ZDD system, but it needs to be concentrated first. To accomplish this step, we are using a deconstructed evaporative cooling system (those in the desert will recognize the media we are using). The solution is pumped to the top of six evaporative tank/media systems and water evaporates. Over time, the concentration will increase enough that we will be able to use the salt solution to minimize salt purchases. So, we will produce two water streams (irrigation and drinking water), a solid byproduct (gypsum), and a liquid byproduct (sodium chloride). No liquid waste will leave the site. Pretty neat, right? I'm including a few photographs and a video below.

Salt Recovery / Enhanced Evaporation System Installed in Tegucigalpa, Honduras (picture credit: Clara Borrego)

We finished with an all female team since Victor has class in the afternoons (picture credit: Clara Borrego)