Water. Desalination + reuse
Issue link: https://fhpublishing.uberflip.com/i/86284
Time to upgrade Carlsbad SWRO design to NF-SWRO Hybrid ? _________ Dr Ata M Hassan, Blue Revolution Foundation, USA ___ Editor's Note: The Carlsbad seawater reverse-osmosis (SWRO) desalination plant in California has been endeavoring to get started for more than a decade. During this wait, which now looks as if it could end this summer, has technology passed it by? Engineering proposals are now being invited for the similar plant at nearby Huntington Beach. The author puts forward a novel proposal that San Diego County would get a better deal from Carlsbad THE PRESENT design for the desalination plant at Carlsbad, California, USA, is a conventional seawater reverse-osmosis (SWRO) designed to produce 50 MGD (189,000 m3 combines nanofiltration (NF), SWRO and thermal components to produce a hybrid design yielding substantial increases in fresh water from two processes: the SWRO permeate, plus multi-effect distillation (MED) of the SWRO reject, which had not been possible prior to the invention of this NF hybrid. The added NF pretreatment also has two distinguishing properties: l Reduction of the seawater feed total dissolved solids (TDS) salinity from 33,500 ppm down to 23,400 ppm or lower. This TDS reduction allows for the application of an MED process to the SWRO reject for additional product yield This article outlines an alternative design which /d) of drinking water. It can be concluded that the upgrading of SWRO to NF-SWRO hybrid yields much more water output than that normally achieved from the traditional SWRO design. For example, compared with the design permeate of 50 MGD (189,000 m3 l Reduction of scale-forming ions and salts to no scale value. percentage SWRO water recovery in the NF-Hybrid process from 70% to 50% will decrease output correspondingly from 63 MGD (238,500 m3 45 MGD (170,000 m3 /d). /d) to /d), gradual reduction of the with the upgraded performance of a nanofiltration- SWRO hybrid with the reject treated using multi- effect distillation (MED). This RO/MED hybrid idea is under development by several groups, including Saline Water Conversion Corporation, Leading Edge Technologies, Sasakura and Water Reuse Promotion Center. The merits of the idea for Carlsbad or Huntington Beach would require evaluation of availability of steam for the MED process. the permeate of which will correspondingly increase from 16.2 MGD (61,000 m3 (102,000 m3 The SWRO reject can be treated using MED, /d) up to 27 MGD This design approach has been demonstrated by the author at various existing/planned seawater desalination plants in countries across the world. These plants work with seawater TDS salinity varying from 45,000 to 20,000 ppm or even less. This new approach has only so far been considered for plants in the Gulf states where both SWRO and thermal(MSF/MED) exist at the same site. The purpose of this article is to evangelize this process to other regions of the world where existing or planned SWRO plants can achieve tremendous increases in their output with the introduction of NF pretreatment combined with an MED post-process. /d). DUAL NF-HYBRID SEAWATER DESALINATION PROCESS The Saline Water Conversion Corporation (SWCC) was established by the Saudi government in 1974 and followed nine years later by the Saline Water Desalination Research Institute (SWRDI) in Al-Jubail City in 1983. As a result of this strategic decision, Saudi Arabia is considered among the global leaders in R&D for seawater desalination processes and implementation of this technology. This resulted in the invention in 1997 at SWRDI, by the author with various SWRDI May-June 2012 | Desalination & Water Reuse | 17 | PROJECTS