Jan 18 2012
California Desalination Report With MoreThan A Grain Of Subjectivity Part 2
Is desalination affordable for Californians? The PI report indicates that one of the major reasons for California desalinations immaturity is its lack of affordability. Currently, the price of desalinating seawater in California is relatively higher than that of traditional low-cost water sources (groundwater and river water) and water reclamation and reuse for irrigation and industrial use. Indeed, the price of traditional local groundwater water supplies in a few areas of the state is as little as $0. 5/1, 000 gallons ($160/acre foot [AF]). However, the amount of such low-cost sources is very limited (less than 30 percent of water resources statewide). For instance, notwithstanding that over 40 percent of the current Orange County water supplies have been in this category, that countys water agencies have embarked on exploring seawater desalination because practically all available fresh aquifers currently delivering this low-cost water are tapped-in and over-drafted. Most of the utilities in southern California currently purchase imported water from the Bay Delta and Colorado River at a rate of $1. 5 to at least one. 8/1, 000 gallons ($500 to $600/AF) and the price of these water supplies is very more likely to increase by 10 to 15 percent in the next five years due to additional expenditures needed to conform to more stringent normal water quality regulatory requirements recently promulgated by the US EPA. In line with the 2006 California Water Charge Survey published in July 2006 by Black Veatch (http: //www. bvaeservices. com/news/articles/jul06/ca_ survey_businesswire. htm), the common residential monthly charge for 1, 500 cubic feet of normal water was $36. 39 ($3. 24/ 1, 000 gallons or $1, 058/AF). The survey also indicates that the price of residential water supply has increased by 16. 7 percent since 2003. Meanwhile, the price of desalinated water has been decreasing steadily over the last 10 years and a lot of the projects contained in the California desalination initiative, declared premature by the PI report, are projected to make water at a cost of $2. 6 to $3. 7/1, 000 gallons ($850 to $1, 200/AF). These costs are estimated based on an asset life of 30 years and unit power costs of $0. 08/kWh to $0. 11/kWh. Therefore, if we follow the gem of advice in the PI report that, cost comparison must be made on comparable basis, then a costs for production of desalinated seawater would be similar to the future total costs for delivery of new incremental water supplies to a lot of areas of the state, especially to municipalities and utilities in southern California depending on imported water supplies. The PI report uses the argument that desalinating seawater and brackish water is normally more expensive compared to the production of reclaimed water and the implementation of water conservation measures. This argument however, is fatally flawed by the fact water conservation and reuse do not create new sources of drinking waterthey are only a rational tool to maximize the beneficial use of the available water supply resources. Under conditions of prolonged drought when the available water resources can’t be replenished at the rate of these use, aggressive reuse and conservation will help but may not completely alleviate the necessity for new water resources and water rationing. Simply put, if your backyard well is dry you cannot resolve your household water supply challenges by reusing or conserving more of the well water there is no need. A real-life example may be the period of prolonged drought in California in the early 90s, which created the necessity for emergency fast-track implementation of several water desalination projects, despite the fact that some municipalities, such as the City of Santa Barbara, had reduced their water use by nearly 40 percent by aggressive conservation measures. While the relatively high cost of seawater desalination ($4. 6 to $6. 1/1, 000 gallons or $1, 500 to $2, 000/AF) and the available low-cost reclamation and reuse measures combined with an interval of several wet years following that long drought marginalized the benefits of seawater desalination at that time, the water conditions, costs and challenges California faces today are extremely different. The primary differences stem from the significant reduction of the expense for seawater and brackish water desalination over the last 10 years and the incrementally higher costs related to achieving dramatic increase in water reuse and conservation statewide following the initial group of low-cost/high-effect water reclamation and conservation measures are implemented. While in the early 90s extensive conservation and reuse were uncommon for a lot of the municipalities in California, the prolonged drought during this period forced many utilities to implement lowcost water reuse and conservation measures that now constitute 5-15 percent of these water portfolios. Utilities which curently have comprehensive water reuse and conservation programs won’t be in a position to squeeze another 10 or 15 percent of water savings via the same low-cost reuse and conservation measures. Implementing the next tier of more sophisticated equipment and technology-intensive reuse and conservation measures to achieve water-saving goals of an additional 20-25 percent comes at a price which, in some instances, may approach that of desalination. Additionally, seawater desalination cost benefits extend beyond the production of new water supplies. If desalination is replacing the usage of over-pumped coastal or inland groundwater aquifers, or is eliminating further stress on environmentally sensitive estuary and river habitats, then a higher costs of this water supply alternative would also be offset by its environmental benefits. Similarly, desalination provides additional benefits in the time of drought where traditional water supplies may not be reliable and their scarcity may increase their otherwise relatively low costs. Will desalination break the rear of Californias power supply system? Desalination is more power intensive than traditional treatment of fresh water sources because it requires additional energy to overcome the naturally occurring osmotic pressure exerted on the reverse osmosis water filtration (RO) membranes by the saline water source (ocean or brackish water). Table 1 presents the energy use related to various California water supply alternatives. The table does not incorporate the expense related to raw water treatment of the surface water imported from the Colorado River project and supplied by the state Water Project and product water delivery costs for any of the listed alternatives. It is interesting to see that the PI report contains several factual inaccuracies which indicate the authors superficial comprehension of the factors affecting the energy demand related to seawater desalination and the contribution of power expenditures to the overall cost of water production. Based on mention of energy use of projects in Israel, the middle East and Spain, where ocean water has approximately 20 percent higher salinity compared to the Pacific Ocean across the California coast, the report concludes that even though most useful available technologies are used, the power demand for production seawater desalination will be 12 kWh/1, 000 gallons (3, 912 kWh/ AF). In fact, since the Pacific Ocean has lower salinity compared to the referenced locations, the energy needed to produce desalinated water ranges between 8. 6 and 11 kWh/1, 000 gallons (2, 800 to 3, 600/ kWh/AF). The PI report remains silent concerning the outstanding efforts of the Californiabased Affordable Desalination Collaboration (ADC) which recently completed a report to demonstrate what the now available state-of-the art desalination technology can perform to lessen energy use for seawater desalination. ADC is really a non-profit organization consists of leading companies and public agencies involved with seawater desalination. The expert-reviewed results from over twelve months of operation of the ADC seawater desalination demonstration facility located at the US Navys Desalination Research Center in Port Hueneme, California validate the energy consumption values contained in Table 1 as well as indicate that in the not-so-distant future the power use for seawater production can be reduced even more (see www. affordabledesal. com). The PI report contains another inaccuracy with important implications concerning the viability of seawater desalination in California. Without normalizing data from foreign desalination plants for the site-specific conditions in California (labor, construction, equipment costs, etc.) the report stipulates that electricity is the reason 44 percent of the total water production costs of a typical membrane seawater desalination plant and 60 percent of costs for thermal water desalination. In fact, due to site-specific differences, the power costs for seawater desalination in California would contribute only 20-30 percent of the total costs of water production. The PI report draws the erroneous conclusion that the fluctuations in international fuel markets could have a dramatic influence on the viability of desalination; in addition, it misses the purpose that energy cost increases will even have the same incremental influence on all water supply alternatives in California. Based on a written report prepared by the California Energy Commission, the current power demand of the water sector in California (including both water and wastewater conveyance and treatment) totals 13, 341, 000 mWh. Assuming a conservative unit energy use for seawater desalination of 11 kWh/1, 000 gallons, the total energy needed to produce 450 mgd of normal water is 4, 950 mWh, which will be just a 0. 037 percent increase of the current California water sector energy demand. Based on these facts, it is erroneous to conclude that the current desalination initiative would break the rear of the California energy supply system, nor could such be objectively used as a valid argument for rejection of the viability of seawater desalination in California. This assessment also diffuses the PI reports claim that, desalination facilities exacerbate climate change with their large use of energy, and that it, can contribute to greater reliance on fossil fuels. It should also be remarked that a target analysis of the energy use for seawater desalination should take into consideration that while the energy use for production of desalinated water is projected to diminish further (by 10-20 percent within the next five years, as a result of advancements in membrane and energy recovery technologies), the total energy demand for conventional water treatment would increase (by 15 to 20 percent) in the same timeframe due to the energy demand linked to the additional treatment (such as micro- or ultra-filtration, ozonation, UV disinfection, etc.) which would be needed to be able to meet the most recent regulatory requirements for production of safe normal water.
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