No one is arguing that we can conserve our way out of the water crisis — although that is where we must start.  But if we move to the next tier, what does that look like?  Call it water reuse, recycling, indirect potable reuse (IPR), reservoir augmentation, even the rather simplistic but catchy toilet-to-tap. 

However you label it, the concept is simple: treating sewage to a level that’s cleaner than our current drinking supplies, using the same technology as desalination plus a few steps to make the result even more pure. There has been a huge outpouring of support for taking water out of the ocean and treating it to a level suitable for drinking. But that’s exactly where our slightly treated sewage is currently being disposed of — in the ocean. And make no mistake; our sewage is not treated to federal standards before disposal. 

It makes much more sense to treat sewage directly rather than dumping it in the ocean, then pulling it out a few miles away for treatment. IPR uses reverse osmosis, the same process involved in desalination. The problem is that desalination involves ocean water, which is four times more saline than sewage.  Reverse osmosis requires far more pressure to treat the higher salt content of ocean water, the main reason for the energy (and cost) discrepancy between IPR and desalination.

From a purely economic standpoint, IPR makes sense. That’s why businesses, trade associations like BIOCOM, and the San Diego County Taxpayers Association support it. Using the same state-of-the-art technology as desalination, but at a lower cost and without as much environmental impact, makes IPR the best choice for planned recycling.  

In Orange County, the water district provides its ratepayers with drinkable treated wastewater at half the cost of imported water and half to a quarter the cost of desalinated water. One economic argument used against IPR in San Diego is that local governments would have to build the infrastructure. Desalination is a commercial enterprise, which means no up-front expenditure by local government. But therein lies the fallacy — there’s no such thing as a free lunch. If a private corporation is willing to build, it must be profitable, and the ratepayers (you and I) will have to pay for it down the road. Our locally proposed plant, in Carlsbad, is tied to the cost of imported water.  The plant’s owners are betting that the cost of that water is going to go up, meaning they can charge more for their water and eventually be profitable. 

If the city of San Diego built a full-scale IPR project, or several satellite projects, it would save ratepayers money in the long run, given IPR’s lower than desalination or imported water costs. The IPR hurdle isn’t public support or technology; it’s a failure to take the long-view.


Leave a comment

We expect all commenters to be constructive and civil. We reserve the right to delete comments without explanation. You are welcome to flag comments to us. You are welcome to submit an opinion piece for our editors to review.

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.