Optimization of Reverse Osmosis Networks with Spiral-Wound Modules

Abstract

An optimization of reverse osmosis (RO) networks for seawater desalination with spiral-wound modules (SWM) was presented in this work. The membrane transport model, which was based on the mass and momentum transport equations, took into consideration the longitudinal variation of the velocity, the pressure, and the salt concentration in the membrane modules. The pressure exchanger (PX) was included in the RO superstructure, and salinity increase caused by volumetric mixing in the PX was considered. The results obtained from the presented model were compared with the actual plant operational data from literature and found to be in good agreement with relative errors of 0.81%∼2.15% and 0.01%∼0.09%, in terms of water recovery and salt rejection, respectively. The optimum design problem was formulated as a mixed integer nonlinear programming (MINLP) problem. The variation of feed salinity was studied using the RO networks model. For the feed concentration higher than 32 kg/m 3 , one-stage RO system is favored. When the feed concentration is below 28 kg/m 3 , two-stage RO system is the better choice. The unit product cost increases with the decreases of permeate concentration requirement. For the looser permeate concentration requirement (0.30 kg/m 3 ), one-pass configuration can meet the required quality of desalted water. When the lower permeate quality requirement of concentration is from 0.050−0.20 kg/m 3 , a two-pass system is more suitable. The influence of system recovery rate on the plant performance was discussed. Finally, sensitivity analysis showed that the total annualized cost is highly sensitive to the feed flow rate, the operating pressure, and electricity cost, while the energy consumption is highly sensitive to the operating pressure, the feed salinity, and the feed temperature.

How RO membrane permeability and other performance factors affect process cost and energy use: A review

“…However, over the last two decades, two-stage RO ( Fig. 5) has become to be applied to the RO system instead of single-stage RO to minimize the specific energy consumption, especially for seawater desalination [22,26,[31][32][33][34][35][36][37]. In two-stage RO, concentrated brine from the first stage is further pressurized, to overcome the osmotic pressure of concentrated brine, and then provided to the second stage [26,31,32,[34][35][36][37].…”

Simulation of full‐scale reverse osmosis filtration system for the removal of N‐nitrosodimethylamine from wastewater

“…The rapid growth of RO membrane technology in wastewater treatment is attributed to a number of factors including high packing density, minimum thermal damage, do not involve phase change, and lower energy consumption with its simplicity of operation and maintenance . Furthermore, spiral‐wound RO modules are known to be relatively easy to clean with a lower fouling possibility …”

“…1,2 Furthermore, spiral-wound RO modules are known to be relatively easy to clean with a lower fouling possibility. 3,4 Nitrosamine and specifically N-nitrosodimethylamine (NDMA) is an organic compound, which has been detected in chlorinated water and addressed as a probable human carcinogen. The removal of NDMA from water is becoming a real challenge due to low-molecular weight of NDMA with high hydrophilic properties.…”

Synthesis of reverse osmosis desalination network under boron specifications

“…Any RO network design is therefore affected by water demand quality. Sensitivity analysis of different seawater streams and permeate product quality were studied in order to analyze the RO network final layout [15,16]. The study assumed a superstructure which is composed of RO passes, high pressure pumps, and energy recovery units.…”