Confined Plunging Liquid Jets for Dilution of Brine from Desalination Plants

Abstract

Confined plunging jets are investigated as potential outfalls for the discharge of desalination brine. Compared to offshore submerged outfalls that rely on momentum to induce mixing, plunging jets released above the water surface utilize both momentum and negative buoyancy. Plunging jets also introduce air into the water column, which can reduce the possibility of hypoxic zones. In contrast to unconfined plunging jets, confined plunging jets include a confining tube, or downcomer, around the jet, which increases the penetration depth of the bubbles and can provide better aeration. However, the presence of this downcomer can hinder mixing with surrounding water. Therefore, laboratory measurements of dilution are reported here and compared to the dilution of unconfined plunging jets. In addition, qualitative observations of bubble penetration depth are also used to discuss aeration potential. For designs that increase the bubble penetration depth as compared to unconfined plunging jets, results show that dilution decreases as the depth of the downcomer is increased. However, it is shown that confined plunging jets can be designed with a short downcomer to provide higher dilution than unconfined jets. The effect of the diameter of downcomer on dilution is also investigated and a non-monotonic effect is observed.

Sensitivity Test of Jet Velocity and Void Fraction on the Prediction of Rise Height and Performance of a Confined Plunging Liquid Jet Reactor

“…They are of great use in aerobic wastewater treatment plants, in froth flotation, and can also be used in desalination outfalls [4]. Recently, a group of researchers from Kuwait University and MIT explored the idea of utilizing such technology (both confined and unconfined) as a brine dispenser and for oxygen dissolution [5,22]. Another application of using this technology is using an airlift column that surrounds the confining tube (Figure 2).…”