A new concept to concentrate seawater up to 200 g/kg for producing vacuum salt using a reverse osmosis (RO) system hybridized with an electrodialysis (ED) system is presented. The RO system operates up to pressures of 120 bar and concentrates seawater up to 120 g/kg with the ED system concentrating RO brine to 200 g/kg. A parametric analysis to minimize the specific cost of brine concentration was conducted. Parameters varied were: the degree of RO-ED hybridization, ED current density, electricity prices and water prices. Optimal hybrid RO-ED designs reduced brine concentration costs by 33-70 % over standalone ED systems, with revenue generated from water co-production further subsidizing costs by 1-6 %. Optimizing ED current density reduced costs the most. Including a crystallizer, the total reduction in production cost over a standalone ED-crystallizer system was 19-55 %, with the production cost for a typical case being $111/tonne-salt. The proposed RO-ED-crystallizer (REC) systems were found to be techno-economically feasible in Cyprus, Japan, Kuwait, Saudi Arabia, and the USA. At a road transportation distance of 735 km, REC based seawater vacuum salt was competitive with conventional vacuum salt. REC systems may open up the potential of small-scale decentralized salt production.

There is an increasing need for the desalination of high concentration brine (>TDS 35,000 ppm) efficiently and economically, either for the treatment of produced water from shale gas/oil development, or minimizing the environmental impact of brine from existing desalination plants. Yet, reverse osmosis (RO), which is the most widely used for desalination currently, is not practical for brine desalination. This paper demonstrates technical and economic feasibility of ICP (Ion Concentration Polarization) electrical desalination for the high saline water treatment, by adopting multi-stage operation with better energy efficiency. Optimized multi-staging configurations, dependent on the brine salinity values, can be designed based on experimental and numerical analysis. Such an optimization aims at achieving not just the energy efficiency but also (membrane) area efficiency, lowering the true cost of brine treatment. ICP electrical desalination is shown here to treat brine salinity up to 100,000 ppm of Total Dissolved Solids (TDS) with flexible salt rejection rate up to 70% which is promising in a various application treating brine waste. We also demonstrate that ICP desalination has advantage of removing both salts and diverse suspended solids simultaneously, and less susceptibility to membrane fouling/scaling, which is a significant challenge in the membrane processes.

Despite its attractive features for energy saving separation, the performance of forward osmosis (FO) has been restricted by internal concentration polarization and fast fouling propensity that occur in the membrane sublayer. These problems have significantly affected the membrane performance when treating highly contaminated oily wastewater. In this study, a novel double-skinned FO membrane with excellent anti-fouling properties has been developed for emulsified oil-water treatment. The double-skinned FO membrane comprises a fully porous sublayer sandwiched between a highly dense polyamide (PA) layer for salt rejection and a fairly loose dense bottom zwitterionic layer for emulsified oil particle removal. The top dense PA layer was synthesized via interfacial polymerization meanwhile the bottom layer was made up of a zwitterionic polyelectrolyte brush - (poly(3-(N-2-methacryloxyethyl-N,N-dimethyl) ammonatopropanesultone), abbreviated as PMAPS layer. The resultant double-skinned membrane exhibited a high water flux of 13.7 ± 0.3 L/m2.h and reverse salt transport of 1.6 ± 0.2 g/m2.h under FO mode using 2 M NaCl as the draw solution and emulsified oily solution as the feed. The double-skinned membrane outperforms the single-skinned membrane with much lower fouling propensity for emulsified oil-water separation.

A zero brine discharge seawater desalination concept integrating reverse osmosis (RO), electrodialysis (ED) and crystallizer into a single system (REC) is presented. Analytical models were used to optimize parameters and minimize water production costs. Parameters varied were: the ratio of seawater to RO brine in the ED diluate channel, ED current density, ED diluate outlet salinity, electricity and salt prices, and RO recovery by adding high pressure RO (HPRO). Using only RO brine instead of only seawater in the ED diluate channel reduced water production costs by 87% from 27 to 3.5 $/m 3 while increasing salt production costs 26% from 135 to 170 $/tonne-salt. The former was best for brine minimization, and the latter for salt production.Optimizing ED current density reduced REC costs by another 14% to 3.0 $/m 3 while increasing specific energy consumption 26% to 12.7 kWh e /m 3 , corresponding to a Second Law efficiency of 18%. Adding an HPRO stage was uneconomical as it increased specific costs 21%. A salt price of 104.5 $/tonne-salt will justify the cost of adding an ED-crystallizer. REC systems may be economically feasible in parts of the Middle-East. Producing other products such as Mg(OH) 2 or Br 2 may further improve economics. , "Cost and energy needs of RO-ED crystallizer systems for zero brine discharge seawater desalination," Desalination, online

Carbon-based nanocomposite membranes have recently drawn tremendous attentions among membrane scientists due to their excellent chemical, mechanical stability and antifouling properties against oil deposition/adsorption.

The effects of operating conditions including a novel downcomer geometry on the gas/air entrainment rate, Qa, were investigated for a local vertical confined plunging liquid jet reactor (CPLJR) as an alternative aeration process that is of interest to Kuwait and can be used in various applications, such as in wastewater treatment as an aerobic activated sludge process, fermentation, brine dispenser, and gas–liquid reactions. Operating conditions, such as various downcomer diameters (Dc = 45−145 mm), jet lengths (Lj = 200–500 mm), nozzle diameters (dn = 3.5–15 mm), and contraction angles (Ɵ =20–80°), were investigated. A newly designed downcomer with various mesh openings/pores (Dm = 0.25ʺ (6.35 mm)–1ʺ (25.4 mm)) was also investigated in the current study. The air entrainment results showed that these were the primary parameters for the measured air entrainment rate in confined systems. The highest gas entrainment rates were achieved when the ratio of the downcomer diameter (Dc) to the nozzle diameter (dn) was greater than approximately 5, as long as the liquid superficial velocity was sufficient to carry bubbles downward. Furthermore, a downcomer with mesh openings (Dm) less or equal to 0.5ʺ (12.7 mm) provided a higher entrainment rate than that of conventional downcomer (without a mesh).

Laboratory experiments were conducted to measure entrained air bubble penetration depth and dilution of a dense vertical unconfined plunging jet to evaluate its performance as an outfall to dilute brine from desalination plants as well as a means to aerate water column. Experiments involved neutrally buoyant or dense plunging jets discharging in quiescent receiving water. The density difference between effluent and receiving water, the plunging jet length (height above water surface), and the receiving water salinity were varied in the experiments. Observed penetration depth for neutrally buoyant jets was somewhat greater than previously reported, and increased modestly with jet density. Increasing density also resulted in an increasing number of fine bubbles descending together with the dense plume. These observations can help guide the design of plunging jets to mitigate anoxic conditions in the water column when brine is introduced to a receiving water body, as with seawater desalination.

Forward osmosis (FO) and assisted forward osmosis (AFO) mass exchangers are currently receiving considerable attention for their potential use in a variety of dilution and concentration applications in resource extraction, fertigation, and pharmaceutical process streams. In this work we develop analytical expressions for parallel and counterflow FO and AFO exchangers which can be used to quickly and accurately estimate the membrane area required for these applications in addition to determining the performance of existing exchangers. Unlike previous models, our analytical model accounts for internal and external concentration polarization in system scale exchangers with overall average errors of less than 10% against a numerical model and less than 35% validated against data from the literature. The performance of FO and AFO exchangers is compared, and an osmotic fertilizer dilution (fertigation) case study is investigated in which the trade-off between energy and membrane area requirements is quantified. We find that AFO exchangers yield a higher recovery relative to FO exchangers for a given energy input especially when the inlet draw-to-feed osmotic pressure ratio is low. Diminishing returns in recovery ratio are attained for increasing membrane area and increasing draw-to-feed mass flow rate ratio. We also find that for the same brackish feed water and recovery ratio, reductions in area of up to 40% relative to FO can be realized with 2 kWh/m 3 of energy input into an AFO system in the fertigation case study.