Brine Recirculation and Other High Recovery SWRO Process Innovations Utilizing Isobaric Energy Recovery Devices

The Recovery Rate (Recovery) of a Reverse Osmosis (RO) system is defined as the ratio of permeate to total feed flow. The recovery is a key design parameter which, for a given plant production capacity, will help define both: the infrastructure and equipment sizing as well as expected energy and chemical consumption. These factors relate directly to the desalination plant capital expense (CAPEX) and operating expense (OPEX) respectively and ultimately to the production cost of product water. Generally speaking, higher recoveries are more CAPEX efficient while lower recoveries reduce OPEX. This relationship implies that a desalination plant design, given a host of other factors, most notably water quality and power cost, will have an optimum recovery which minimizes overall water production costs. Over time the seawater RO industry has standardized the main RO process to that of a single stage operating at recoveries between 40 and 45%. The purpose of this paper is to show how innovation in SWRO systems configuration using isobaric energy recovery devices (and state of the art RO membranes) will perfectly allow working at high recovery rates, providing to the plant designer with much more flexibility to find the perfect CAPEX/OPEX balance demanded by its particular project structure and technical constraints. Different configurations will be presented in the research section and the results section will include the specific energy consumption evaluation along with the advantages and disadvantages for each case. Finally in the conclusion section, we will present the findings of this study and will open the discussion on the high recovery SWRO and their likeability of implementation by the designers in new plants.

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