Analysis of High Recovery Brackish Water Desalination Processes using Fuel Cells

Abstract

The production and supply of potable water and the disposal of wastewater are among the major challenges of the 21st century. Inadequate supply of potable water, coupled with increasing water demand in developing countries due to rapid population growth and industrialization are among the major reasons for the worsening water situation (1). Desalination of brackish water by reverse osmosis (RO) and nanofiltration (NF) are the leading technologies used in supplying potable water. Typically, these plants operate at 75% product water recovery so that 25% of RO feed water is wasted as concentrated brine. However, the recovery can be increased by processing the primary RO reject water with the aid of selective membrane processes such as a secondary RO or NF unit. Hybrid RO/NF processes were modeled using the membrane manufacturer's software for various membranes and for two specific brackish waters studied (total dissolved solids, TDS = 1700 and 3700 mg/1). The analyses show that 90% product water recovery is achieved for the low TDS feed water and 88% recovery is achieved for the high TDS feed water using simple, state-of-the-art hybrid membrane systems, and with minimal feed water chemical pre-treatment. It is also shown that the specific energy consumption of the RO system is reduced when it is powered by a stand-alone, on-site fuel cell power plant.

Keywords:

• Brackish water
• desalination
• fuel cells
• high recovery
• reclamation
• RO/NF

View correction statement:

Corrigendum: Analysis of High Recovery Brackish Water Desalination Processes Using Fuel Cells

Notes

∗Brine feed data is PRO/BW-PRO concentrate at 75% recovery based on Hydranautics membrane projections.

^#PRO = Primary RO; SRO = Brine recovery RO; SNF = Brine recovery NF.

∗SRO/SNF feed is PRO (III) reject. BW-SRO feed is BW-PRO (III) reject.

∗∗Hydranautics TFC membranes. Membrane age = 3 years.

^∧Two-stage array: (A) Six (20 cm dia) spiral-wound modules/vessel; (B) Four (10 cm dia) spiral-wound modules/vessel.

Single-stage array: (C) Six (10 cm dia) spiral-wound modules/vessel.

^&PWR = Product water recovery.

∗∗∗System Overall PWR = [PRO product flow rate + SRO product flow rate]/PRO feed flow rate, e.g. (17 + 2.8)/22.5 = 88%.

⁺Total dissolved solids.

^$Net power is PRO (III) + SRO, or PRO (III) + SNF.

^$$Net power is BW-PRO (III) + BW-SRO. RO pump motor η = 90% and RO pump η = 80%.

^@Specific energy consumption = Net power/Product flow rate.