Have you ever wondered where your water comes from or what happens to it? If you’re like most people then probably not. If you live in the Orange County/Los Angeles area though, you know this area is famous for not having enough water and needing to import it to provide their ever growing populations.
So how do they do it (besides importing water)? That’s where the Orange County Water District (OCWD) comes in. My geography class went on a field trip there and got to see how sewer water is treated to become purified/recycled water that is in fact so pure (no minerals) that they have to add the minerals back. And yeah, I drank the purified water. It tasted like, well, water.
The OCWD has public tours every first Friday of the month. If you want to see it for yourself just make a reservation. For our tour, we started off by getting a general explanation of where California gets its water and its water project history. Some sources are imported, groundwater, storm water, water transfers, desalination and water recycling. The water projects mentioned were the Central Valley Project (1931), State Water Project (1960s), Los Angeles Aqueduct (1913) and the Colorado River Aqueduct (1939).
When it comes to purified/recycled water, there is this negative image attached. A problem Los Angeles had was with the not so nice term “toilet to tap”. Fortunately for the OCWD, their commitment to transparency has allowed the public to see that recycled water is not only a good way to save water but also safe. It’s only natural to feel uneasy about recycled water (I did at first too) but through educational tours like the OCWD provides, one can see just how their water is being made clean and safe.
OCWD’s main goal is groundwater replenishment. They manage the recharge basin underneath the north and central part of Orange County (OC). The southern part unfortunately doesn’t get the benefits of this water source. Not only do they recharge the basin, but they also inject treated water into the aquifers to prevent seawater intrusion.
On the tour I was able to get a recording of the general explanation, which you can listen to here. Our tour guide only touched on the main processes because she explained it during the walk around, and since it was too noisy to record during that time, I’ll discuss it here.
(Note: the audio has been edited. These things have been removed: time doing a survey and getting safety information-wearing hard hats, etc.).
The water comes from Orange County Sanitation District (OCSD), which is right next door to the facilities my class visited. Then it goes through a three step process: microfiltration (MF), reverse osmosis (RO) and exposure to ultraviolet light (UV). (Note: explanations mostly come from an information brochure I received during the tour.)
Bundles of hollow polypropylene fibers are used to remove particulate contaminants. There are minute pores (about 0.2 microns) where the water is drawn through by a vacuum. The suspended solids, protozoa, bacteria and some viruses are strained out. This process includes doing a backwash every 22 minutes, which keeps pressure from building up and a full chemical cleaning is done every 21 days.
This process involves using long sheets of semi-permeable polyamide membranes (they look like big, thick pieces of plastic covered paper) that are rolled tightly into bundles and placed in long pressure vessels. Microfiltered water goes through at one end and passes through the layers of polyamide to the center where purified water collects and exits. The water that exits here is the water that is so purified that it needs minerals added back. What’s left behind after this process are dissolved salts, organic chemicals, viruses and pharmaceuticals.
This final process uses high intensity ultraviolet light and hydrogen peroxide to disinfect the water. It destroys any remaining low molecular weight organic compounds. This is done to make sure that any unwanted biological materials and organic chemical compounds are removed or destroyed. Our tour guide also said that the water is exposed to the UV light for about 10 seconds. The tubes of UV light are inserted into a larger pipe where they shine onto the water, but the actual UV tubes are covered by a plastic-like tube so that the UV tubes are not directly touching the water.
There you have it, the water treatment process! Well, it’s of course a lot more technical and complicated than what I’ve written but that is the gist of it.
At the end of the tour there were three sinks of water each showing it at the three stages of treatment. Our guide cautioned us to not drink from the ones that looked like ice tea, but we could drink from the clear one. That one was the fully purified water. Everyone in our group tried it. Some even went back for seconds. After all, as one person joked, we’re not going to get to taste water that pure again anytime soon.
And of course what tour is complete without free souvenirs. Water flavored chap stick and mints anyone? (Joking, it was actually spearmint and peppermint, respectively.)