Energy Consumption Optimization of a Brackish Water Reverse Osmosis System
Author | : Leili Abkar |
Publisher | : |
Total Pages | : 392 |
Release | : 2015 |
Genre | : Brackish waters |
ISBN | : |
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Clean water and energy are two key concerns in today's world, and climate change is making both of these issues even of more significant importance. Desalination, a process that removes salt from saline water to produce fresh water, is a solution for the worsening water scarcity issues. Many different desalination technologies are available and applied around the world, including thermal-based technologies, which include multi-stage flash (MSF) and multiple effect distillation (MED), as well as membrane-based technologies such as reverse osmosis (RO) and also electrodialysis reversal (EDR). Reverse osmosis is the most commonly used membrane-based technology, capable of eliminating a wide range of contaminants to produce clean water. There are two different types of RO systems, Brackish Water Reverse Osmosis (BWRO) and Seawater Reverse Osmosis (SWRO), which are applied based on the characteristics of the feedwater. In inland regions, groundwater, surface water, and river water are considered brackish water. In the state of New Mexico for instance, brackish water is the available feedwater source, and therefore BWRO is applied to provide fresh water. Due to a water shortage crisis in the Southwest USA, one of the major goals is to optimize the BWRO process to minimize energy consumption and simultaneously increase the water recovery rate. By increasing the recovery rate, a higher percentage of the feedwater is converted into fresh water; therefore, less feedwater is required to produce a given quantity of fresh water, conserving water resources. In this research, energy consumption optimization for BWRO systems has been investigated. The key control factors for minimizing BWRO energy consumption include feed flow rate, pressure, and temperature, as operating conditions, feed concentrations, and membrane type (representing membrane permeability). The effect of each of these control factors on energy consumption is evaluated, and presented. A full factorial design has been done with mixed level for different factors. In this research, pressure has six level in the range of 50-175 psi by the 25 psi step, Flow rate 3-6 LPM with the step of 1 LPM, temperature has two level of 30 and 40 centigrade, and salinity varies from 2,000, 2,500, 3,000 ppm to cover the middle range of brackish water. Each experiment has three replication. Using linear regression method makes it possible to determine relation between input variable (feed flowrate, salinity, pressure and temperature) and response variable (energy, recovery and specific energy consumption). The empirical model developed to predict the energy, recovery and specific energy consumption of the reverse osmosis system in the specified range and finding the sweet spot to run the system to produce the minimum energy cost for 1 cubic meter of water.