3D physical modelling in a wave flume of brine discharges on a beach

摘要

The seawater desalination process is a strong bet for developing regions like the Spanish Mediterranean, to satisfy the increasing fresh water demand, or the Canary Islands, being the desalination the most important artificial water resource. The main characteristic of the waste brine disposal resulting from the desalination process is its high salinity, and consequently, its higher density in comparison with that of the environment. Therefore, the discharge of the concentrated effluent into the sea may cause a negative impact in the sea water quality and its ecosystems, specially regarding the sea grass meadows that cover the Mediterranean coast. In order to make the development of the desalination plants sustainable, the Spanish Ministry of the Environment and Rural and Marine Affairs agreed to invest in Experimental Development Projects within its National Plan for Scientific Research, Development and Technological Innovation. The project entitled "Development and implementation of a methodology to reduce the environmental impact of brine discharges from desalination" has been approved and supported as a part of the Plan. This project is being carried out by the University of Cantabria in collaboration with the Spanish Centre for Experimentation on Public Works (CEDEX). The aim of this study is to find which discharge devices produce the biggest brine dilution, to make the environmental impact on the biocenosis as low as possible. Under this perspective, the behaviour of different jets and discharge devices were investigated in physical models. To this purpose, different instrumentation has been using to measure the conductivity and velocity in the near and far field of the effluent, including a micro scale conductivity and temperature instrument or a doppler velocity profiler. Part of the experiments have been performing in a wave flume of 30 m long, lm wide and 2 m high, simulating a 3D superficial discharge from a beach with a fixed slope. In this flume different simulations, changing the wave variable (height and period, in an irregular JONSWAP train wave), have been testing. The results obtained with the performed physical model will be presented in this communication.