More troubleshooting and some thoughts on how to solve problems

In between our participation in two seminars/tours and waiting on container repairs, we have continued to operate our system and attempt to get data. Also, we had a final report due to our funding agency (USAID ) on August 15.

We are continuing to have problems related to the particulates from the Los Almendros well. Particles, like sand and other things, are common with wells. The Los Almendros well is able to produce much more flow than what our pilot needs, so we are cycling the well multiple times per day to fill a tank which feeds our system.Wells aren't normally cycled like this, or, if they are, a sand strainer is installed prior to a membrane system. We didn't know about the particles prior to our arrival, so we don't have this level of pre-treatment. The particles seem to be causing problems in our the RO/NF and EDM systems (here's a link describing our process if this is the first post you have read). We will need to change out our cartridge filters much more often than what is normally done with a brackish well water pilot. This is a fair amount of work and Clara and I, try as we might, just can't get the housings loose all the time.

Cartridge filters and evidence of particles from the well. From top left, going clockwise:
1-Clara and I trying to get the cartridge filter loose (failed). 2-Bottom cartridge filter vs new filter. 3. Three filters showing 1 week's worth of particle filtration, 2 day's worth of particle filtration, and a brand new filter for comparison. 4. sample of the water in the cartridge filter housing with particles rejected by the filter. 5. Scale and particles in the EDM feed manifold.

The high level of alkalinity (Wikipedia describes it pretty well) present in the Los Almendros well has caused precipitation to occur without acid pre-treatment or a lot of water for dilutions. In previous pilots with high alkalinity, acid pre-treatment or substantial dilutions to the concentrate stream were implemented to prevent scale. We have attempted to operate without both of these because increased dilutions reduce the overall recovery and the Desal Prize and piloting objectives prioritized less chemicals. However, sulfuric acid is a common chemical and is relatively easy to procure and use safely. The minimum recovery with dilutions alone will be determined in the coming weeks. Acid pre-treatment will also be attempted to show the maximum recovery possible.

Water samples from pilot. Having solids precipitate is uncommon from the UTEP team's experience (especially precipitation within 4-6 hours!)

The high level of silica and higher than expected rejection by the RO/NF is causing scale in the RO/NF. It is possible that the particles (possibly iron, or sand with iron) from the well are enhancing this problem. We will test operations with a silica bleed (send a partial stream of RO/NF reject to drain) to see if the problem is mitigated. We cleaned the RO/NF and installed a bleed on the RO/NF to test whether it will help with reducing scale buildup. We will attempt to identify the minimum waste flow to protect the RO/NF and estimate the additional evaporation capacity necessary to maintain the zero liquid discharge aspect of the system.

Our container will be repaired over the next few days, so we will have our system off. We expect to be up and running for the next several weeks and hope to have good news to report based off our findings thus far.