Milton N. Burgess P.E.

San Diego Business

Ocean Water is Really Good to Drink

What is Water Independence?
By Milton N. Burgess P.E.
Posted on Fri, Mar 27th, 2009
Last updated Fri, Mar 27th, 2009

Out of bed, into the shower and what? Nothing happens when the showervalve is turned on! A bad dream? No, a real possibility for San Diego County residents where 90% of the water we use is imported. But sometime after the Spring of 2012, those living in Carlsbad are assured the water will flow from the shower head, and the day can begin. They will be water independent. No imported water.

How is this possible? After five years struggling to get through the regulatory process, all of the permits are now in place. Construction of Poseidon's Desalination Plant will begin September this year in Carlsbad. This plant will produce 50,000,000 gallons per day of pure drinking water made from 100,000,000 gallons per day of ocean water from SDG&E's Encino Power Plant discharge water. Carlsbad's entire water needs will be met 100% by the new plant, with capacity to spare. Water costs to Carlsbad's residents will not be higher than they are paying now for imported water.

Quality of the water at 80ppm contains less than one third of the mineral content of the water currently delivered to San Diego County homes. By drinking water standards it is considered "soft", and it meets all of the strictest Federal, State and local drinking water standards. I had a drink of it and it tastes really good. That was possible because the pilot plant can produce 30,000 gallons per day. None of the pilot plant water goes into the municipal water system. When the pilot plant is operating, except for small amounts for sampling and drinking, the water is piped back into the lagoon from whence it came. On March 25, 2009, I was part of a tour of the pilot plant with the local chapter of the American Society of Mechanical Engineers set up by member Mark Shin.

Without getting into eye-glazing technical stuff that only engineers find both interesting and fascinating, it may be instructive to know something about why we can drink water made from ocean water. Osmosis is a term used occasionally when someone doesn't seem to "get it", and is encouraged to hang around in the hope they can absorb new information. It actually is a technical term describing a process akin to gravity. When salt water is put in a container with a vertical dividing membrane that only tiny, invisible water molecules can penetrate, with regular tap water on the other side of the membrane, the volume of the salty side increases. The mechanism that causes the tap water side to become so friendly with the salty ocean water is called osmotic pressure. In the human body, if we eat too much salt, there is a tendency to gain "water weight" -- same process.

To make tap water out of ocean water, the process is reversed by overcoming the osmotic pressure, forcing the water molecules to go backwards through the membrane, leaving the minerals behind. Hence the term for the process, reverse osmosis. Osmotic pressure is very high, In the order of 35 times atmospheric pressure, or over 500 pounds per square inch. That is more than 10 times ordinary automobile tire pressure. So the plant operates well in excess of 850 pounds per square inch to produce drinking quality water. For a 50 MGD (50,000,000 gallons per day) plant, approximately two tons per day of sludge is produced and hauled away to a landfill.

There are various energy saving devices used in the plant. The bottom line is the completed plant will require electrical power capacity of 25 megawatts (25,000,000 watts). For comparison, a standard photo-voltaic electrical solar system currently being installed on homes around San Diego is around five kilowatts, or 5,000 watts. So the power required for the 50 MGD plant would service about 10,000 homes. It takes approximately 12 kilowatt hours to produce 1000 gallons. Using an average consumption of 300 gallons per day, the plant will provide water to about 170,000 residents, which is about twice the current population of Carlsbad.

The Carlsbad Plant is being built entirely with private financing, i.e., no government funds. The only subsidies involved are through the Metropolitan Water District (MWD) which incentivizes water districts to produce their own water supplies. Why would the MWD be interested in a water competitor like the Poseidon Plant?

Nine water utilities in the Greater San diego Area depend on receiving water from two sources -- the Sacramento River Delta and the Colorado River. The Delta water is entirely dependent on the snow pack in the Sierras. The Colorado River is dependent upon the the snow and rain falling in the seven states that use the river water. Regardless of whether or not global warming is caused by humans or not, climatologists agree that current modeling, based on historical river flows, predicts the Colorado River will be flowing at a rate 20% less than current flows. For an excellent analysis of the Colorado, read "Dead Pool, Lake Powell, Global Warming, and the Future of Water in the West by James Lawrence Powell. By 2020, he predicts the Glen Canyon Dam will be at "Dead Pool". That is a technical term meaning the water flowing into Lake Powell, flows out without providing storage or electrical generation.

Damage to the Sacramento Delta is a current topic in the Governor’s Delta Vision Blue Ribbon Task Force. Earthquake liquifaction of the levees (like patting a wet mud cake) that separate ocean water coming up the Sacramento River and snow water coming from the Sierras, will destroy Delta water brought south by the California Aquaduct.

Water independence for Southern California through recycling sewage for reservoir augmentation (like Orange County currently does) and additional desalination plants is dependent upon whether or not our elected public officials have the political will to make it happen. There is no "Plan B".

About the author: Milt Burgess is a Registered Professional Mechanical Engineer in several states and a licensed California contractor with experience in all phases of mechanical construction and consulting spanning several decades.
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Comments

Posted by James	Mon, Jul 6th, 2009
Such as this article. Let people to know that there is Plan A. I believed city of Long Beach is start doing something with Ocean water. thank you for your article. James

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