Hybrid BWRO/FO system for high recovery in-land brackish water desalination: techno-economic assessment

Abstract

Several hybrid Forward osmosis (FO) systems for seawater and brackish water desalination have been developed in recent years. This study investigates two approaches of integrated systems comprising brackish water reverse osmosis desalination (BWRO) and forward osmosis (FO) systems. These approaches aim to minimize the environmental effect of inland reject brine disposal while enhancing total water recovery. Experiments were performed using different draw solution (DS) concentrations of KCl and MgCl2.6H2O (0.5, 1, 1.5 and 2 Molar) to reach maximum recovery. In scheme (A), feed water is directed to BWRO with recovery 45% and 97% rejection, while the brine water is directed to the FO system as FS stream. In scheme (B), the feed water is divided into two streams, one of which is directed to the BWRO with recovery 75% and 98% rejection and the other stream is sent to the FO unit as FS stream. KCl DS displayed higher flux rate of an average 28.5 L/(m2.h) using 2 M concentration, while MgCl2.6H2O 2M solution shows an average flux of 23.5 L/(m2.h) during the first 100 min of operation. Scheme A shows 81% total system recovery, while scheme B shows 78% total system recovery. The cost indicators for desalination system with small capacity of 10 m3/d showed that scheme (A) has lower capital cost 55,732$ for scheme (A), while total capital cost was 59,400 $ for scheme (B).