Numerical Prediction of Background Buildup of Salinity Due to Desalination Brine Discharges into the Northern Arabian Gulf

Abstract

Brine discharges from desalination plants into low-flushing water bodies are challenging from the point of view of dilution, because of the possibility of background buildup effects that decrease the overall achievable dilution. To illustrate the background buildup effect, this paper uses the Arabian (Persian) Gulf, a shallow, reverse tidal estuary with only one outlet available for exchange flow. While desalination does not significantly affect the long-term average Gulf-wide salinity, due to the mitigating effect of the Indian Ocean Surface Water inflow, its resulting elevated salinities, as well as elevated concentrations of possible contaminants (such as heavy metals and organophosphates), can affect marine environments on a local and regional scale. To analyze the potential effect of background salinity buildup on dilutions achievable from discharge locations in the northern Gulf, a 3-dimensional hydrodynamic model (Delft3D) was used to simulate brine discharges from a single hypothetical source location along the Kuwaiti shoreline, about 900 km from the Strait of Hormuz. Using nested grids with a horizontal resolution, comparable to a local tidal excursion (250 m), far field dilutions of about 28 were computed for this discharge location. With this far field dilution, to achieve a total dilution of 20, the near field dilution (achievable using a submerged diffuser) would need to be increased to approximately 70. Conversely, the background build-up means that a near field dilution of 20 yields a total dilution of only about 12.

Unconfined Dense Plunging Jets Used for Brine Disposal from Desalination Plants

“…To estimate the increase of dissolved oxygen for a typical plunging jet, the following estimates of the parameters were used as typical for a brine discharge offshore of Kuwait [45]: , yielding…”

Spatial and temporal variation patterns of Total Suspended Solids around the coastal areas of Bahrain, a water quality guideline

“…One of the most commonly used indicators of seawater quality is TSS (MacDonald et al, 2000 andRossi et al, 2013). Consequently changes in the TSS have a direct (physical, biological, and ecological) and indirect (toxicological) impact on the surrounding ecosystems (Chebbo, 1992;Rossi et al, 2005;Sikorska, 2012;Taylor and Owens, 2009;Walling, 2005;Yang et al, 2011;Mackinnon et al, 2012 andBai et al, 2015). Reviews of the effects of these activities provided by (Zainal et al, 2012;Price, 1993;Al-Sayed, 2000 andAbahussain et al, 2005).…”

Desalination Brine Management: Effect on Outfall Design

“…For this choice of θ 0 , the impact point dilutions in deep and shallow (and vertically mixed) conditions are given by Eqs. (1) and (2), respectively [11,13].…”

“…These design parameters do not minimize the total cost as they require a large capital cost. Specifically, in locations with very small bottom slope, such as the Arabian Gulf [2], the capital cost can be several orders of magnitude larger than the pumping cost and the total cost can be very high. To reduce the capital cost, it is beneficial to achieve the desired dilution with smaller ambient depth by reducing the port diameter or to employ a multi-port diffuser.…”

“…Thus, brine is usually discharged as a dense submerged jet which provides rapid mixing with ambient water. However, at locations that are characterized by shallow water depth and mild tidal currents, such as the north-western Arabian Gulf [2], diffusers with multiple jets are preferred as they can generate the required amount of mixing in smaller water depths.…”