Desupersaturation of RO concentrate and gypsum removal via seeded precipitation in a fluidized bed crystallizer. (15th February 2021)

• Record Type: Journal Article
• Authors: Choi, Jin Yong; Kaufmann, Florian; Rahardianto, Anditya; Cohen, Yoram
• Is Part Of: Water research. Volume 190(2021)
• Publication Date: 2021-02-15
• Subjects: RO desalination -- concentrate treatment -- membrane mineral scaling -- gypsum precipitation -- fluidized bed crystallizer -- high recovery RO; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.116766
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: RO brine gypsum desupersaturation achieved in a seeded fluidized bed crystallizer Seeds size, loading and solids handling are critical for crystallizer operation Solids purging and replenishment established via simulations and experimental tests Stable crystallizer desupersaturation demonstrated from gypsum SIg ~2.5 to SIg ~1.1 Salt harvesting up to 3.6 kg/m 3 RO concentrate feasible at up to 96% recovery Abstract: The feasibility of a continuous chemically-enhanced seeded precipitation (CCESP) process was evaluated for desupersaturation of primary reverse osmosis (PRO) concentrate generated from RO desalting of inland agricultural drainage (AD) water with high gypsum scaling potential. The CCESP approach, comprised of partial lime treatment (PLT) followed by gypsum seeded precipitation (GSP), was assessed via laboratory and field tests, along with model simulations. PLT effectiveness was confirmed for residual antiscalant removal from the PRO concentrate, which otherwise would suppress gypsum crystallization. GSP was carried out in a fluidized bed crystallizer (FBC) demonstrating the feasibility of continuous PRO concentrate desupersaturation with suitable solids management. FBC operation was stable, with respect to desupersaturation performance, when operating over a sequence of periodic solids purge-only mode with intermittent seeds replenishment. The study suggests that CCESP integration with primary and secondary RO desalting (i.e., PRO-CCESP-SRO) can provide for significant enhancement of product water recovery for inland water of high gypsum scaling propensity. For example, source water of high salinity (14, 347 mg/L total dissolved solid) AD water, nearly saturated with respect to gypsum, could be desalted up to a recovery of 88-96% (relative to merely 66% recovery feasible via PRO desalting. Moreover, net salt harvesting of 2.6-3.6 kg per m 3 RO concentrate (with concentrate recycle) can be obtained from high recovery desalting of the above PRO concentrate. Graphical Abstract: Image, graphical abstract