The major highlight this week was that the phrase “THMs are a DBP caused by TOC levels, sodium hypochlorite, and bromide from raw water”  actually makes sense to me now. (It didn’t make sense at first).  And I also got to use a THM analyzer and I completed THM profiles of the building where we work.

So I am discovering that the vernacular of water science is starting to make sense.  When I did the Chandler water plant tour, they had a process that used “ballasted floc”.  At the time, all I understood was that a ballasted floc system took up less space, processed water faster, and needed sand.  Then it dawned on me a couple days later, the sand is ballast and the floc sinks faster so they called it “ballasted floc”.

The same thing happened with the THMs.  The most common one is chloroform (there’s three others).  To me, chloroform was just a name of something in water.  And then I saw the formula: CHCl3.  Hey, I know what that is; it’s trichloromethane from organic chemistry.  It’s like tricholorethane that I researched in college, and it’s similar to carbon tetrachloride and other chlorofluorocarbons like freon.    Making that connection, I now have a better feel for THMs and why we don’t want them in out drinking water.  So from my background knowledge of similar chemicals, I can predicted that THMs will be volatile, they are linked to  cancer, they will have low water solubility, they are weakly polar, they probably contribute to global warming and ozone depletion, and they might form radicals.

FYI,  DBP stands for disinfection by-products, TOC stands for total oxidizable carbon, THM stands for Trihalomethanes, and FYI stands for for your information.

So this week I used a THM analyzer.  It’s new so I wrote up a brief user guide with pictures.  I started by analyzing the water in the ISTB4 building where we are doing the internship.  I found THMs every place I checked.  I’m not sure what numbers are significant or not, but I found a 20% difference on different floors of the building and I found a 20% difference depending on the day of the week, and I found about a 20% difference depending on the time of day.  Let’s just say that I recommend that you fill your water bottle up on Friday, just after lunch, in an active kitchen.  FYI, every reading was within water quality specs.

Richard

The highlight of my first week as an RET was a tour of the Chandler Water Plant. My mentor, Dr. Sinha Shahnawaz, was going there to find a location for one of his other water quality projects and thought it would be beneficial for me to see how a water treatment plant works. He was right. The tour gave me the background and implications for the THM project I am working on, it gave me a chance to ask a lot of basic questions (thank you Vickie, Anupa, and Chris for your patient answers), we obtained a few gallons of unprocessed raw water for future experiments, and we got the current processing parameters to replicate.

This is a settling pond.  The design minimizes turbulence so denser solid pieces (floc) sink to the bottom.  About 30 million gallons flow through this pond every day.

They add Alum (aluminum sulfate) and polymer directly into the pipe so it rapidly mixes with the water creating floc with what we want removed from water.

The tanks on the right are filled with salt water.  Inside this building, Chandler uses the salt water to create chlorine (bleach) using electrolysis.

The concrete pillars mark the location of the underground tank holding the clean drinking water ready to be sent to Chandler residents.

Richard