Chloride in the Santa Clara River — Part I

In Santa Clarita, California, we are considering a sewer rate hike. If passed, sewer fees will more than double over the next few years. The reason for the hike is the reduction in chloride levels in the discharge. Three key questions arise on this issue:
(1) What is the source of the chloride?
(2) How can we treat water to remove chloride?
(3) Why is the chloride content important?
Today, we will address the first two questions, and tomorrow we’ll complete the discussion. And a relatively short (12 page) report from the County Sanitation Districts of Los Angeles County, provides an excellent summary of the situation: http://apps.santa-clarita.com/ViewFile.aspx?Type=Agenda&ID=9743
First what is the source of the chloride? A look at today’s figure tells the story. Nearly two-thirds of the chloride comes from the source water. In a way, it can be considered “natural.” However, since slightly more than half the water used in Santa Clarita comes from the State Water Project, there is an unnatural aspect to much of the source water.
And it is this imported source that is the real culprit. The water in Lake Oroville and in the Sacramento River has virtually no chloride. But when this water meets the Pacific Ocean in the Sacramento River Delta, the chloride level increases dramatically. Chloride is the largest single component of the oceans, after water itself. The concentration of chloride in sea water is about 19,000 milligrams per liter. The water leaving the Delta has had chloride levels approaching 200 mg/L at times – especially during low-outflow periods, such as during droughts. The average chloride level is around 100 mg/L.
Is this level a problem? More on that in tomorrow’s blog, but for today, recognize that the Regional Water Quality Control Board is imposing a limit on the CSDLAC discharge into the Santa Clara River of … 100 mg/L!
This brings us to our second question: how do we remove chloride? And this leads to an important follow-up question, what is the cost of such treatment? Chloride is a dissolved solid in water, and dissolved solids are, by far, the most difficult and costly to remove. There are very few technologies that are even capable of this feat, with ion exchange, reverse osmosis, and distillation being the only real options. And reverse osmosis is the most viable option at present.
The cost of reverse osmosis is about ten times as high as the normal treatment cost of wastewater. Fortunately, to meet the chloride standard, only about one-half of the plant flow would require this level of treatment. But obviously, operating costs will skyrocket; hence, the proposed rate increase.
But an even more troubling aspect of RO technology is this: when something is removed from the water, where does it go? For this plant, I estimate that the RO waste would total about 500,000 gallons per day – perhaps even more. At 5,000 gallons per tanker truck, that’s 100 truck loads per day – going exactly where (on crowded freeways)? This is not even close to viable. So the plan is to build a 40-mile pipeline to the ocean to dispose of this salty waste there. I’m pretty confident that NO environmental organization would allow this to happen without decades of law suits.
So where does that leave us? More tomorrow!

One Response to Chloride in the Santa Clara River — Part I

  1. avatar Kevin D. Korenthal says:

    Excellent analysis Steve. I hope you will be participating in the debate on the May 25th and 27th. See our event page here: http://www.facebook.com/home.php#!/event.php?eid=119602928079972&ref=ts

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