Considering location, compliance, and storage in decisions on brackish water resource development

摘要

In the past, brackish water resources have often been dismissed due to concerns over the cost gap between desalination and conventional treatment, but this simple comparison neglects several important factors that should be considered when making water supply development choices. Although desalination is more expensive than conventional treatment, the costs of delivering potable water are also linked to source location (relative to users) and steps needed to maintain regulatory compliance and supply reliability, factors largely unexplored in previous cost comparisons. This work describes an approach to more comprehensively evaluate the costs of developing and using brackish surface water and groundwater resources, then compares these to similar costs for freshwater supplies. Freshwater and brackish water supplies are compared in terms of the "total cost of supply and treatment," which includes the costs of raw water acquisition, storage, conveyance, treatment, and residuals disposal. Results show that brackish resources become economically competitive under a wide range of circumstances when these other cost factors are considered. This is especially true for smaller systems, and economies of scale can play an important role in determining the circumstances under which a brackish resource is economically preferred. Results are most sensitive to variation in the capital costs of membranes and conventional treatment, as well as the recovery rate of desalination processes.