Application of salinity thresholds in Spanish brine discharge regulations: Energetic and environmental implications

Abstract

This paper reviews the application of salinity thresholds in the Environmental Impact Statements (EIS) in Spanish desalination plants. Lower salinity thresholds than those recommended by the scientific community for the protection of the Posidonia oceanica meadows were established in the EIS in 2005, whereas after this year thresholds more consistent with scientific recommendations were established. In addition, as a case study, the energy consumption of these lower thresholds was analyzed using the brine discharge of the Alicante desalination plants. The threshold of 38.3 psu was easily exceeded, which resulted in increased dilution ratio and higher energy consumption. The cost of the dilution was more than 600,000 kwh and €50,000 for a six-month period. The dilution ratio and energy consumption would have been considerably decreased without any negative environmental effects on marine environment if the applied value was 38.5 psu as it has been suggested. Therefore, it is recommended to unify the salinity thresholds in the applied Spanish regulations for the protection of P. oceanica meadows based on the best available scientific evidence to avoid additional energy-economic costs.