Let’s be real about “Toilet to Tap”

by on December 9, 2007 · 1 comment

in Environment

Written by SS

Toilet to tap, indirect potable reuse, reservoir augmentation, whatever you want to call it, our City Council finally took up the issue and showed some balls. The vote was five in favor, three with no vote or against. Of course our local councilman from Point Loma voted against the override. At least five of the eight had the “cojones” to bring more water to San Diego, a coastal desert.

It is certainly a controversial issue although I am not sure why. It has been going on for a number of centuries. If you assume there is a finite amount of water in the world that would mean we have just been recycling it since the beginning of time.

Let’s examine the natural cycle. It rains and water falls from the sky onto the earth. It drains into streams and lakes and sinks into the ground. From there the water flows into the oceans. Along the way the water is evaporating and going back up into the sky. This evaporation process is taking place in all of the water bodies with the exception of ground water. Water falls from the sky as rain, it gets used and it evaporates back into the sky where it all starts again, a first class water recycling plant. Of course it is the middle part, the use, that starts to mess things up, that is where civilization gets involved. Civilization uses water for industry, cleaning, crops, flushing and numerous other uses, all of them life supporting. We can’t live without water and the more we, civilization, use it, the more we have to conserve it and treat it.

At the dawn of civilization, settlement only occurred where there was water. People took the water out for use and then put it back in downstream of where they took it out, then further down stream the next settlement did the same. The river did the cleaning as the water flowed over the rocks and the sun used its ultraviolet rays to purify the flow. This method continued even as civilization learned how to move water uphill and could settle in other places that didn’t have a natural water source. Water is used and the next person downhill uses it again. That brings us to our location San Diego.

San Diego, as we all know, does not have a very good natural water source. We have the San Diego River and several other rivers in the area. The San Diego River did an okay job of supporting the early settlers and the native population. Since we know how to move water up hill we have been able to tap other water sources that are not so local, like the Colorado River and the Sacramento River Delta. Our forefathers have done a pretty decent job of supplying our region with water from the other side of the mountains, but all that water we get from the other side of the mountains has been used by others. They drank it, bathed in it and flushed it then the next city did the same thing. Finally it ends up at the end of the line. Then we get it and pump it over the mountains and treat it again before drinking it. This process sure sounds like toilet to tap to me!

Congratulations and thank you to the five City council members for having the “huevos” and the smarts to realize that San Diego needs water. Orange County our neighbor to the north has taken steps to turn its toilet water into drinking water. Counties on the east coast where it rains have been doing it for a 20+ years. Technology is available, but at a price of course. It makes sense that that cost would escalate if you are bringing water to a desert. The City already recycles wastewater for irrigation and other uses by treating the wastewater but it still wastes approximately180 million gallons (mg) a day of highly treated wastewater to the ocean. But let’s not talk about what it wastes because the City can treat and try to reuse approximately 45 million gallons at its two reclaimed water treatment plants. This water is treated and then sold for irrigation or industrial use. This water is distributed in purple pipes. There are not many miles of purple pipe in the ground. There is no doubt more reclaimed water could be produced and sold if the purple pipe distribution system was in place. Now while this reclaimed water is treated to a high level it is not the level that it would be treated if it were going to be placed in a drinking water reservoir. But that is not the real problem for San Diego and its reclaimed water for irrigation system. The real problem is the distribution system.

To distribute reclaimed water (RW) a system of purple pipes needs to be installed. They don’t really need to be purple but that is the color that someone decided to differentiate between reclaimed water that is almost potable and potable water. It just avoids confusion. Right now the City of San Diego has approximately 3280 mile of potable water pipes and about 79 miles of purple pipes in the North City area. In the South Bay area of the reclaimed water is sold to another water provider who distributes it to their customers. There are no purple pipes in the older parts of San Diego but there are lots of old water pipes. This is where the real advantage to toilet to tap comes in to play. The distribution system exists and this avoids the need to dig up all the streets and place new pipe in the ground.

If the City could produce water to the advanced tertiary level, then pipe the water to a reservoir where it could sit until needed, it would follow the same treatment and distribution that all the imported water from the Colorado River and Northern California follows. The quality level of that water would be as good if not better as the water we are treating today.

Next time we can look at the difference in treatment that is demanded for regular reclaimed water and advanced tertiary treated water. After all what do the astronauts drink?

{ 1 comment… read it below or add one }

avatar Deb December 10, 2007 at 5:15 pm

Thanks for this informative article. It certainly puts our H2O woes into perspective.

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