Pilot studies on high recovery BWRO-EDR for near zero liquid discharge approach

A hybrid process combining reverse osmosis and electrodialysis has been shown to be effective in recovering 97–98% of brackish water as product water with chloride levels of 200 mg/L or less. Potential for scaling on the brine side of the electrodialysis unit was prevented by acidification, operating the electrodialysis in a reversal mode (EDR), and a side loop crystallizer which prevented buildup of scaling components. Settlers, inline microfiltration, and side-loop ultrafiltration kept suspended solids from returning to the EDR unit. This process was demonstrated in a series of more than eighty batch experiments of 1.5 to 1.8 m3 of RO concentrate of raw brackish groundwater from the Negev Highland, Israel. Each batch could be processed within a single day. The feed-water was concentrated from 0.3% to over 10% TDS super-concentrate while producing the water that could be recycled to the RO permeate. This super-concentrate from the EDR unit was further concentrated in a wind powered WAIV unit that brought final brine TDS to N 30%, and showed promise as a method to recover mineral byproducts such as magnesium salt. Initial economic estimates show that this hybrid process is competitive with conventional RO and other enhanced recovery processes for inland desalination requiring use of evaporation ponds. © 2010 Elsevier B.V. All rights reserved.

This work summarizes the long term studies made on BWRO desalination of raw brackish water from the Negev Highlands, Israel Table 2 Unit Treatment costs for RO/EDR hybrid with 98% total recovery for a 100 m3/h plant (feed flow rate). RO step recovery RO Processing Costs 75% 83% 88% Unit Feed and pretreatment (at 0.16 €/m3 feed at 100 m3/h for all cases)@ RO Power and capital (0.13 €/m3 product) RO permeate Annual RO cost Total EDR costs* Total RO/EDR Costs Brine disposal# Total Costs Sp. RO costs (feed, power, capital) Total product costs Base Case costs Israel Water Tariff 124,484 124,484 124,484 € 76,869 85,068 90,193 € 591,300 201,353 140,418 319,999 16,556 336,555 0.341 654,372 209,553 115,763 308,441 16,556 324,998 0.320 693,792 214,677 99,689 298,857 16,556 315,413 0.309 m3/y €/yr €/yr €/yr €/yr €/yr €/m3 0.436 0.491 0.730 0.421 0.491 0.730 0.408 0.491 0.730 €/m3 €/m3 €/m3 *) From Table 5-A. #) Taken from Table 4 in [18]. @) From Table 1-A.