Set-up of a mid-field model to investigate the recirculation of effluents in the Mirfa power and desalination plant

The Mirfa power and desalination plant was built in the Abu Dhabi Emirate, United Arab Emirates, in the early 1990s. Plant capacity is16.5 MGD. It was decided to increase the plant’s capacity to satisfy rapid urban and industrial development in the Emirate. A comprehensive study was carried out to investigate the recirculation of salinity and temperature from the plant outfall to the intake, which determines the feasibility of extending the plant’s capacity. The study was carried out by a two-dimensional numerical flow model, which was calibrated and verified with field data obtained from the plant’s vicinity. The set-up of the model and the model calibration are presented. The effect of the plant’s extension on recirculation of effluents is discussed.

The tidal flow in the Arabian Gulf is the main hydrodynamic forcing dispersion and diffusion of the plume, which is developed at the outfall of the Mirfa power and desalination plant. A twodimensional hydrodynamic model was developed to determine the recirculation of salinity and temperature at the plant intake. The model was calibrated with the available field measurements and is capable of correctly reproducing the hydrodynamic forces and transport of effluent discharges. Model runs were carried out to determine the recirculation of salinity and temperature at the plant intake due to a capacity extension of 65 MGD. Computations were carried out for the spring neap tidal cycle, which presents the most “aver- age long-term” seasonal variation and for different wind conditions obtained from the wind rise in the area. The recirculation of salinity and temperature was computed by the model for the present condition without and with the proposed extension, and the effect of the new extension was investigated. The computations show that the capacity extension increased the recirculation of temperature and salinity (on average) by 0.2°C and 0.25 ppt compared to the present situation. These values are within the admissible values from the recirculation point of view. The output from the hydrodynamic model will be coupled with a water quality model to investigate the effect of the capacity extension on water quality within the plant vicinity and to evaluate the effect of the plant’s extension on the habitat living in the vicinity.