skip compact fluorescents – recycle wastewater

An interesting article has recently been published in an open-access journal called “Environmental Research Letters.”  I’m torn on open-access journals: people should have access to research results, but the quality of publication suffers without higher quality reviewers.  That said, this article seems pretty informative.  The authors attempted to quantify the energy used in the US in 2010 for treating and delivering water, and they found a whopping 12.6% of energy consumption in the US is due to water.

I found this figure instructive, showing the difference in energy requirements for various types of water sources and treatment levels.  Note the difference between desalted water and normally treated water is large, but the difference between desalted water and the California State Water Project water (which is pumped from the Bay-Delta to southern California) is small.  No wonder southern Californians are getting more excited about seawater desalination and water recycling, assuming that cost scales with the  energy intensity of the water source.

energy consumption for water supply

With some pretty complicated flow diagrams, the authors come to one very striking conclusion:

We estimate that 5.4 quads of this primary energy (611 billion kWh delivered) were used to generate electricity for pumping, treating, heating, cooling and pressurizing water in the  US, which is approximately 25% more energy than is used for lighting in the Residential and Commercial sectors [40]. (Despite this equivalency, much more policy attention has been invested in energy-efficiency for lighting, rather than reducing hot water consumption or investing in energy-efficient water heating methods, even though the latter might have just as much impact.)

In other words, reducing hot water consumption or investing in energy-efficient water heating methods could have a similar impact to switching our personal lightbulbs to compact fluorescents, yet there has been no policy push to educate people on this aspect.

Results like these are fascinating and instructive.  Once we know where the energy is going and how much our water really “costs”, we can make adjustments that make sense without revamping the whole system.  You and I can be more energy efficient by taking shorter showers and turning water off while lathering up with soap and shampoo.  California can promote water recycling in southern California instead of desalination and increasing imported water, which would save on energy without cutting off the State Water Project.  I’m sure many more examples of efficiency improvements are available — we just have to think a little outside the box.

Preview of Hetch Hetchy removal?

The city of Monterey’s water supply is in transition.  Apparently the dam upon which they have relied for years, the San Clemente Dam, is filling with sediment and has been subjecting the Carmel River to accelerated erosion since 1921 (erosion is a balance between sediment coming in and sediment washing away, and the dam blocks the sediment coming in, leading to net washing away of the riverbanks).  The dam is in the process of being removed, while the city debates a new water supply – a combination of desalination, aquifer storage and recovery, and conservation.  The California Coastal Conservancy has also been involved in removing the dam and restoring habitat for steelhead trout and the California red-legged frog.  But between environmentalists and citizens of the Monterey peninsula, people aren’t that happy.

Environmentalists are disappointed that the city is headed towards desalination, an energy-intensive process that could possibly damage the environment through the discharge of its waste brine (the verdict is still out over how best to manage the wastes from desalination).  There’s already a desalination plant in Marina that sits idle because of high energy costs, and state utilities regulators rejected the Environmental Impact Review for the new desalination plant.  Recently, dozens of residents near the San Clemente Dam protested the use of a local roadway as the key access point for large trucks and other heavy equipment in connection with the $83 million project. Dam removal has been delayed by a month.

Is this a harbinger for how Hetch Hetchy removal would proceed?  I wouldn’t be surprised.  The Hetch Hetchy is a larger system, with estimates of $1-10 billion for its removal.  The San Francisco Public Utilities Commission has presented a series of facts to rebut some of the aspects to appear in the November ballot measure to study removal of the Hetch Hetchy reservoir.  Among other things, SFPUC notes that there is no good way to replace the storage capacity of the Hetch Hetchy (bigger than the other 5 drinking water reservoirs in the San Francisco Bay supply system combined) or the 500 MW of power from the O’Shaughnessy Dam.  Plus, the idea has been studied many times before in the past 20 years.  Furthermore, the cost would be prohibitive — as much as $700 to $2800 more per year for the average customer.  Sounds to me like a bad idea…

Plus, we have this example from Monterey that even when being removed, people find new ways to protest the dam/reservoir in question.  What a headache.  If it ain’t broke, don’t fix it?

future water supplies

Long term water supplies in California are quite limited if we continue to use water at present rates and the population grows.  The engineers and regulators know this, and theoretically so do the farmers and politicians.  We’ve already overallocated the Colorado River, such that it vanishes into the sediments at its mouth, no longer flowing directly into the Gulf of California.  And wet years for the Sacramento-San Joaquin River watershed doesn’t mean as much for the river flowrate as it does for the downstream farmers in the Central Valley who want to irrigate as much of their land as possible, or for the southern California utilities who want to store the extra water for drought conditions.

On top of expected in trends in population growth, climate change could potentially decrease the precipitation and/or streamflow in most of the southwest.  Furthermore, environmental concerns are pushing water regulators to scale back the allotted flows in the California and Colorado River aqueducts.  If you were the water manager for the city of Los Angeles, what would you do?  The net balance of your inflows is likely to decrease, while the delivery people demand is increasing…

There are a couple of options for new water supplies.  One is to build massive desalination plants, at a high energy cost and a high environmental cost for the disposal of brine waste.  In California you also run into the problem that necessary locations on the shoreline have really high property values and a bunch of neighbors screaming NIMBY.  Another is to look for temporary solutions like underused groundwater basins or watersheds.  Las Vegas is in the process of shipping groundwater from a remote valley of ranchers along the Nevada-Utah border to its water supply.  There’s also a project to mine a groundwater basin in the Mojave Desert in California, between Joshua Tree and Death Valley, for water supply to the L.A. basin.

But to me, the most reliable long-term option is indirect water reuse, which is already in place in Orange County, a relatively conservative portion of southern California.  I am slightly skeptical of direct reuse of wastewater effluent, even when treated beyond normal potable water standards, just because of the lack of a buffer or factor of safety if anything goes awry at the wastewater/water treatment plant.  But indirect potable reuse makes a lot of sense: treated wastewater is injected into a storage basin, most often an aquifer, and then after some flow distance, it is re-extracted as raw water for drinking water supply (i.e., it gets treated again after extraction).  During its travel in the subsurface, the water is filtered naturally by the soil and mixes a little bit with the native groundwater.  Quite a few cities employ this system with lakes, notably Las Vegas, Milwaukee, and Berlin (Germany), but there’s a lot more mixing and dilution in lakes than in groundwater.

To be honest, the indirect reuse in Europe, which has been working in some cases for over 120 years (see Berlin), is very convincing to me.  Water recycling could regenerate roughly 50% of the water supply of the entire L.A. basin (a lot of water is lost to outdoor uses like pools and lawns), and would make water supply as reliable as the wastewater supply.  An odd concept, perhaps, but in the case of Los Angeles this would be less wasteful than all the treated wastewater currently discharged to the ocean.  Given the right geology, water recycling would also require far less infrastructure than desalination plants or large water pipelines.

Would the public go along with this, if properly informed?  Sydney, Australia provides an example of the PR gone wrong – after a contentious public debate, they built a massive desalination plant.  But again, Orange County is already employing this successfully, so we should be able to point to them as a model.  As Orange County goes, so goes the country?  It’s not something I would normally expect to hold.