Non-interfering multiport brine diffusers in shallow coastal waters

Multiport brine diffusers are capable of handling large brine flow rates and producing relatively high dilution ratios, and thus are gaining popularity nowadays. A key design issue of the multiport brine diffuser is the selection of the proper discharge port diameter (D) and number of ports (N), i.e. the D-N combination, to meet the design objectives. In the present study, semianalytical solutions for the optimal D-N combination of non-interfering multiport brine diffusers are derived, including both the full submergence scenario as well as scenarios in shallow coastal waters whereby surface contact is permitted. The semianalytical solutions illustrate how the challenges of a wide operation flow range with a low Q(min)/Q(max) ratio, a high species protection level and a shallow cover water depth impose on the diffuser design. The influence of these dominant factors can be quantified using the equations obtained, and case studies are provided as practical examples. Additionally, the results also show that the 30. inclination and surface contact scenarios are recommended for shallow receiving waters, since they lead to a significant reduction of the number of ports and/or the length of the outfall pipe, which can in turn reduce the capital cost of the desalination plant. The D-N diagrams for this configuration are provided which can be used to estimate the optimal D-N combination.