Economics of Desalination

Cost estimation for industrial plants is usually performed with the assistance of aggregated data and estimates by knowledgeable bodies. Younos (2010) discusses the many factors that affect desalination<!–[if supportFields]> XE “desalination” <![endif]–><!–[if supportFields]><![endif]–> plant cost and evaluates their impact on total cost. In addition, he describes several cost estimation models that are used for desalination plants. Costs are broken into one time construction costs, including both direct and indirect costs, and recurring operation and maintenance costs. The primary factors that determine the magnitude of these costs are feedwater salinity<!–[if supportFields]> XE “salinity” <![endif]–><!–[if supportFields]><![endif]–>, plant capacity and the location of the plant. One of the more costly aspects of plant location is brine removal as coastal plants can use cost effective surface water disposal while inland plants must use more expensive alternatives. Younos concludes based on aggregated desalination plant cost estimates that fixed costs play a large role compared to maintenance costs, and that brackish water treatment only differs from seawater treatment in energy costs.—Erin Partlan
Younos, T., (2010). The Economics of Desalination. Journal of Contemporary Water Research and Education 132, 39–45.

Younos defined the following costs pertinent to the construction and operation of a desalination<!–[if supportFields]> XE “desalination” <![endif]–><!–[if supportFields]><![endif]–> plant. The direct construction costs of implementing a desalination plant include costs for land, production wells, surface water intake structure, equipment (i.e. for water treatment), buildings and brine disposal. Indirect costs include construction overhead such as labor costs and tools, owner’s costs such as administrative fees, freight and insurance costs, and resources reserved for contingency. The recurring operations and maintenance costs are separated into fixed insurance and amortization costs and all other costs, including energy, equipment replacement and cost of chemicals. For each site, these costs will be based on the quality of the feedwater, the plant capacity, the location of the plant, and any regulation requirements that may exist. For example, low salinity<!–[if supportFields]> XE “salinity” <![endif]–><!–[if supportFields]><![endif]–> feedwater will cost less in terms of energy usage, large capacity plants cost more initially but are more efficient in the long run, and costs associated with water intake, pretreatment and brine disposal will depend on the plant surroundings. Younos points out that brine disposal plays a large role in desalination plant design due to its dependence on site location and regulations. In addition, there are multiple options for brine disposal including surface disposal, disposal with wastewater plant effluent, deep well injection, on-land dispersal such as evaporation ponds, spray irrigation, percolation, and zero liquid discharge. For coastal plants, surface disposal to large bodies of water is common and cost effective. However, this is generally not an option for inland plants. Options for inland plants depend on the characteristics of the plant location and techniques such as deep well injection and zero liquid discharge can be costly.
Younos also describes three cost estimation models that are particularly useful for evaluating desalination<!–[if supportFields]> XE “desalination” <![endif]–><!–[if supportFields]><![endif]–> projects. WTCost, a model from the Bureau of Reclamation, includes thorough and detailed plant cost estimates for the following desalination technologies: reverse osmosis (RO)<!–[if supportFields]> XE “reverse osmosis (RO)” <![endif]–><!–[if supportFields]><![endif]–>, mechanical vapor compression (MVC), multiple effect distillation (MED), multi-stage distillation (MSF), nanofiltration (NF), and electrodialysis reversal (EDR). The the Desalination Economic Evaluation Program (DEEP)<!–[if supportFields]> XE “Desalination Economic Evaluation Program (DEEP)” <![endif]–><!–[if supportFields]><![endif]–> developed by the International Atomic Energy Agency (IAEA)<!–[if supportFields]>XE “International Atomic Energy Agency (IAEA)” <![endif]–><!–[if supportFields]><![endif]–> is a model for evaluating the effects of various energy sources on a desalination plant, particularly looking at nuclear sources versus other alternative energies. However, this model was not intended for industrial use and is not as detailed in non-technical costs. The third model is the Reverse Osmosis Desalination Cost Planning Model, a product of Water Resources Associates (WRA)<!–[if supportFields]> XE “Water Resources Associates (WRA)” <![endif]–><!–[if supportFields]><![endif]–>, which includes 33 different parameters for desalination plants and is similar to WTCost. While Younos did not perform the cost estimation himself, Sandia National Laboraties aggregated the work of others who have used such methods to estimate the costs of desalination plants. Based on this report, which differentiated estimates by both technology and feedwater quality (brackish vs. seawater), Younos concludes overall that fixed costs are actually a large component, equipment replacement is actually relatively small, and that the only major difference between brackish water and seawater desalination is the cost of energy.

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