RO concentrate minimization by electrodialysis: Techno-economic analysis and environmental concerns

http://dx.doi.org/10.1016/j.jenvman.2012.04.020

Abstract:This paper presents a systematic techno-economical analysis and an environmental impact evaluation of a reverse osmosis (RO) concentrate treatment process using electrodialysis (ED) in view of environmental management of brine discharges. The concentrate originates from a secondary effluent treated by RO. Without any treatment, the concentrate would have to be discharged; this is compared in this study to the costs and benefits of an effective treatment method in a pilot scale ED plant. A technical analysis was done both on lab scale and pilot scale for the determination of operational and maintenance costs for the ED installation at the required conditions of process performance and safety. Subsequently, an economical analysis was done to calculate the cost of the different parts of the ED system. It was shown that an operational cost of 0.19 EUR m⁻³ can be achieved, assuming that the ED concentrate is to decarbonated at pH 6.0 to prevent membrane scaling. Finally, environmental impact issues were calculated and discussed for the overall system. Results imply that if renewable energy is applied for the ED power source, CO₂ emission from membrane processes can be much less than from the conventional treatment methods.

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Highlights

► Lab scale ED can be used to demonstrate pilot ED.
► A linear correlation with applied current/flow rate predicts salt removal.
► Environmental impact was calculated (CO₂/H₂ emission, salt and organics discharge.

Fig. 1. Schematic diagram of (a) current wastewater treatment and infiltration process (WWTP and Torreele, respectively), (b) proposed ED process for recycling of RO concentrate.

by Yang Zhang^a, Karel Ghyselbrecht^b, Ruben Vanherpe^a, Boudewijn Meesschaert^{b, d}, Luc Pinoy^{a, c}  and Bart Van der Bruggen^{a, ,}  

^a Department of Chemical Engineering, Laboratory for Applied Physical Chemistry and Environmental Technology, KU Leuven, W. de Croylaan 46, B-3001 Leuven, Belgium 

^b Department of Industrial Sciences and Technology, Katholieke Hogeschool Brugge-Oostende, Associated to the KU Leuven as Faculty of Industrial Sciences, Zeedijk 101, B-8400 Oostende, Belgium 

^c Department of Industrial Engineering, Laboratory for Chemical Process Technology, KaHo St.-Lieven, Associated to the KU Leuven as Faculty of Industrial Sciences, Technologie Campus, Gebroeders Desmetstraat 1, B-9000 Gent, Belgium 

^d Department of Microbial and Molecular Systems, Centre for Surface Chemistry and Catalysis, KU Leuven, Kasteelpark Arenberg 23, B-3001 Leuven, Belgium 

Journal of Environmental Management via Elsevier Science Direct www.ScienceDirect.com  

Volume 107; 30 September 2012; Pages 28–36
Keywords: Techno-economical analysis; Electrodialysis; RO concentrate; Environmental impact