Desalinization plant outage listen11/10/09 Mark Anderson
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The Tampa Bay Waters desalinization plant was shut down last weekend after a power outage occurred in Apollo Beach. The abrupt shutdown damaged the troubled water supply plant.
The desalinization plant had another problem last weekend, when several pipelines burst, forcing an extended shutdown for repairs. The damage was caused by a condition known as “water hammer,” which can result if high pressure water in motion is forced to stop suddenly, creating a pipe-breaking pressure surge. The power failure created the water hammer condition at the plant.
The plant is the largest in the United Statues, and treats bay water that is far more salty than normal sea water. But the plant has had a troubled past. It went on line 5 years late, and cost $40 million over budget. During the delay, major modifications were made because mollusks and impurities were clogging the plant up. Since going on line after a multi year redesign process, its record has been spotty. Tampa Bay Water’s Chuck Carden noted that the plant reliability has improved greatly and has been operating at 25 million gallons per day, its original design capacity, for several months.
Tampa Bay Water produces around 160 million gallons per day from 3 source: well and river pumping, and desalinization. Currently most is pumped from wells, with some supplied from local rivers, and the desalinization plant. During the rainy season, excess water production is sent to the giant C.W. Bill Young reservoir, which is used to supplant production in the dry winter months. The water utility is under orders from the Southwest Florida Water Management District (SWFWMD) to reduce well production to an average of 90 million gallons per day by December. To comply with that, the utility plans to increase the use of river water and maintain desalinization production at its maximum levels. The balancing of sources is expected to be worse for two years, starting in 2012, when repairs are being made to the reservoir. Carden noted that the repairs might not require draining the reservoir.
One little understood aspect of the desalinization process is energy usage. The Apollo Beach plant uses a relatively efficient technology known as reverse osmosis, where salt and impurities are filtered out of seawater at high pressure. Even with this technology, desalinization can take up to 10 times more electricity that the conventional sources, well and river pumping. Under full production, the Apollo Beach plant uses about as much electricity as 10,000 homes, and generating the needed electricity adds about 7500 tons of carbon dioxide to the atmosphere monthly. Carden noted that Tampa Water recognizes the high costs of desalinization, but has little choice in running the plant at high levels.
The next challenge for the utility is to run the plant at full capacity continuously for 4 months. Upon meeting this benchmark, SWFWMD will make its final payment of $21.5 million to the utility for the construction of the plant.