Comparison of Configurations for High-Recovery Inland Desalination Systems

• Published in: Water (Basel) Vol. 4; no. 3; pp. 690 - 706
• Main Authors: Qiu, Tianyu, Davies, Philip A.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 17.09.2012
• Subjects: Brackish water; Capital costs; Desalination; Design; Drinking water; Efficiency; energy; Energy consumption; energy recovery; Environmental impact; Groundwater; pumps; reverse osmosis; Salinity; Seawater; specific energy; Water conservation; Water shortages; Water supply; United States > US; Texas
• ISSN: 2073-4441; 2073-4441
• DOI: 10.3390/w4030690

Desalination of brackish groundwater (BW) is an effective approach to augment water supply, especially for inland regions that are far from seawater resources. Brackish water reverse osmosis (BWRO) desalination is still subject to intensive energy consumption compared to the theoretical minimum energy demand. Here, we review some of the BWRO plants with various system arrangements. We look at how to minimize energy demands, as these contribute considerably to the cost of desalinated water. Different configurations of BWRO system have been compared from the view point of normalized specific energy consumption (SEC). Analysis is made at theoretical limits. The SEC reduction of BWRO can be achieved by (i) increasing number of stages, (ii) using an energy recovery device (ERD), or (iii) operating the BWRO in batch mode or closed circuit mode. Application of more stages not only reduces SEC but also improves water recovery. However, this improvement is less pronounced when the number of stages exceeds four. Alternatively and more favourably, the BWRO system can be operated in Closed Circuit Desalination (CCD) mode and gives a comparative SEC to that of the 3-stage system with a recovery ratio of 80%. A further reduction of about 30% in SEC can be achieved through batch-RO operation. Moreover, the costly ERDs and booster pumps are avoided with both CCD and batch-RO, thus furthering the effectiveness of lowering the costs of these innovative approaches.