Brine Disposal Costs Research Articles

How split-feed osmotically assisted reverse osmosis (SF-OARO) can outperform conventional reverse osmosis (CRO) processes under constant and varying electricity tariffs

Improving the recovery of desalination processes can have economic benefits, as feed and brine volumes are minimised. Furthermore, brine volume minimisation (BVM) simplifies brine treatment prior to disposal and hence, alleviates potential environmental concerns. However, BVM is not widely applied, as it is generally more energy intensive and costly. This may change in the future, as new high-recovery membrane processes, such as split-feed osmotically assisted reverse osmosis (SF-OARO), can potentially lower the required operating pressure and the energy consumption associated with brine dewatering via osmotic counterbalance. In addition, the added flexibility of OARO integrated systems may further reduce the unit water cost (UWC) in regions with varying-electricity tariffs. To verify these hypothesised advantages of OARO, this study explores the economic and technical viability of SF-OARO. Under constant electricity tariffs, the results indicate that the optimized SF-OARO process can achieve a higher process recovery (65% versus 50%) while operating at a 4.1% lower UWC than conventional RO (CRO), when assuming an intermediate brine disposal cost of 0.3 $/m3. This cost advantage of SF-OARO further expands under operation with varying-electricity tariffs. In summary, the presented results indicate that the SF-OARO process is the preferred and cheaper choice once the brine disposal cost exceeds 0.21 $/m3 of brine.

Novel dynamic and cyclic designs for ultra-high recovery waste and brackish water RO desalination

There is a drive for ultra-high recoveries in waste and brackish water RO desalination due to high brine disposal costs. In this work, two novel dynamic and cyclic designs (i.e. feed reversal and retentate recycle with a time-varying ratio in stage 3, as well as stage rotation between 1 and 3) are proposed to achieve a 90% recovery while alleviating scaling potential. The designs are conducted following FilmTec's guidelines and are simulated using validated models published previously. It is shown that retentate recycle suppresses concentration polarization, despite a higher pressure drop. Feed reversal leads to a quick drop of salt concentration due to mixing of fresh feed and brine. However, if the feed reversal is applied to the same stage, the salt concentration on the other end may be higher than brine concentration for a short period of time. Such a behavior is not observed during rotations between stages 1 and 3, whether the feed is reversed or not. Interestingly, the designs at 90% recovery demand only a few percent more energy than traditional two-stage designs operated at 80% recovery. Moreover, cycle-to-cycle salt build-up in batch-type ROs is absent in both dynamic designs presented in this work.

Can capacitive deionization outperform reverse osmosis for brackish water desalination?

Abstract Capacitive deionization has received significant attention as an energy-efficient technology for brackish water desalination. The capacitive deionization suffers from lower water recovery and high electrode discharge time, that hampers its economics. The low recovery ratio increases the brine disposal cost and is also environmentally polluting. In this paper, the feasibility of capacitive deionization as a brackish water desalination technology is studied. The capacitive deionization performance is first optimized and is later compared with the state-of-the-art reverse osmosis. Both modeling and experimental studies are carried out to optimize the performance of capacitive deionization. A new cost correlation as a function of the capacitive deionization system size is proposed. By optimally designing the system, the treated water cost for capacitive deionization is reduced by 36%. A feasibility map for capacitive deionization is generated and compared to reverse osmosis as a function of brackish water concentration and different brine disposal options (see the graphical abstract). Compared to reverse osmosis, capacitive deionization economics are sensitive to the feed concentrations but becomes superior for salt concentrations less than (a) 70 ± 15 mM (surface brine discharge), (b) 65 ± 13 mM (deep well injection), and (c) 43 ± 10 mM (evaporation pond). For zero liquid discharge, the CDI is not economical compared to RO regardless of salt concentrations. Based on the feasibility map generated in this paper, the optimal technology for desalination can be selected as a function of brackish water concentration and brine disposal.

Advances in seawater membrane distillation (SWMD) towards stand-alone zero liquid discharge (ZLD) desalination

Abstract Seawater membrane distillation (SWMD) is a promising separation technology due to its ability to operate as a stand-alone desalination unit operation. This paper reviews approaches to improve laboratory-to-pilot-scale MD performance, which comprise operational strategies, module design, and specifically tailored membranes. A detailed comparison of SWMD and sea water reverse osmosis is presented to further analyze the critical shortcomings of SWMD. The unique features of SWMD, namely the ability to operate with extremely high salt rejection and at extreme feed concentration, highlight the SWMD potential to be operated under zero liquid discharge (ZLD) conditions, which results in the production of high-purity water and simultaneous salt recovery, as well as the elimination of the brine disposal cost. However, technical challenges, such as thermal energy requirements, inefficient heat transfer and integration, low water recovery factors, and lack of studies on real-case valuable-salt recovery, are impeding the commercialization of ZLD SWMD. This review highlights the possibility of applying selected strategies to push forward ZLD SWMD commercialization. Suggestions are projected to include intermittent removal of valuable salts, in-depth study on the robustness of novel membranes, module and configuration, utilization of a low-cost heat exchanger, and capital cost reduction in a renewable-energy-integrated SWMD plant.

Brackish water desalination for greenhouse agriculture: Comparing the costs of RO, CCRO, EDR, and monovalent-selective EDR

Greenhouses are a rapidly growing agricultural sector that uses desalination systems. However, the desalination requirements of the greenhouse industry and an economic evaluation of desalination technologies for greenhouses have not been reported previously. Several greenhouse operators in North America using desalination systems were interviewed to identify key design specifications. A detailed cost comparison was conducted for key technologies: reverse osmosis (RO), closed circuit RO (CCRO), electrodialysis reversal (EDR) and monovalent selective EDR (MS-EDR). Capital, energy and membrane replacement costs, savings in feedwater costs from operating at higher recovery, and potential savings in fertilizer from using MS-EDR, were calculated. For <10-hectare greenhouses, RO was the most cost-effective technology. For >10-hectare greenhouses, alternatives can be considered. MS-EDR is economically competitive if it can retain at least 20% of the calcium and magnesium needed for growing and if membranes last 7 years. CCRO is competitive if the sum of feedwater and brine disposal costs are >$0.24/m3. If this cost was $0.32/m3, additional investment over RO for CCRO, EDR and MS-EDR, could pay itself back in 2.4, 3.4 and 2.1 years. In Ventura county where municipal water costs $1.05/m3, RO, CCRO, EDR and MS-EDR had payback periods of 7.1, 8.4, 7.8 and 8.2 months.

Porous hydrophobic-hydrophilic composite membranes for direct contact membrane distillation

Direct contact membrane distillation (DCMD) for desalination is attractive for high salt concentrations if low-cost steam/waste heat is available and waste brine disposal cost for inland desalination is factored in. A number of innovations have taken place in DCMD in terms of the structure of the porous hydrophobic membrane. Composite membranes are of increasing interest. Composite membrane structures of great interest include a thin hydrophobic porous layer over a porous hydrophilic layer of polyvinylidene fluoride (PVDF) or a thin porous hydrophobic layer over a more conventional hydrophobic porous membrane. These membranes can be in the form of an integral composite or a stacked composite or a laminated composite. A facile method of fabricating such integral composite membranes is plasma polymerization under vacuum. A class of such membranes yielding quite high water vapor fluxes have been characterized using a variety of characterization techniques: Contact angle, liquid entry pressure (LEP), bubble-point pressure, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM). Stacked composites of a hydrophobic ePTFE membrane over a hydrophilic PVDF membrane or a hydrophobic PVDF membrane over another hydrophobic PVDF membrane were also studied. Novel conditions created lead to very high water vapor fluxes compared to those from conventional hydrophobic membranes supported on a mesh support.

Prevention and management of silica scaling in membrane distillation using pH adjustment

Membrane scaling by silica is a major challenge in desalination, particularly for inland desalination of brackish groundwater or geothermal water, which often contain high concentrations of silica and dissolved solids. Adjustment of feed pH may reduce silica scaling risk, which is important for inland facilities that operate at high water recoveries to reduce brine disposal costs. However, water recovery of reverse osmosis is also limited due to increased osmotic pressure with feed water concentration. Membrane distillation (MD) is a thermally driven membrane desalination technique that is not limited by increased osmotic pressure of the feed. In this investigation, pH adjustment was tested as a strategy to reduce silica scaling risk in the MD process. With feed water pH less than 5 or higher than 10, scaling impacts were negligible at silica concentrations up to 600 mg/L. Scaling rates were highest at neutral pH between 6 and 8. Cleaning strategies were also explored to remove silica scale from membranes. Cleaning using NaOH solutions at pH higher than 11 to induce dissolution of silica scale was effective at temporarily restoring performance; however, some silica remained on membrane surfaces and scaling upon re-exposure to supersaturated silica concentrations occurred faster than with new membranes.

Pushing desalination recovery to the maximum limit: Membrane and thermal processes integration

The economics of seawater desalination processes has been continuously improving as a result of desalination market expansion. Presently, reverse osmosis (RO) processes are leading in global desalination with 53% share followed by thermally driven technologies 33%, but in Gulf Cooperation Council (GCC) countries their shares are 42% and 56% respectively due to severe feed water quality. In RO processes, intake, pretreatment and brine disposal cost 25% of total desalination cost at 30–35% recovery. We proposed a tri-hybrid system to enhance overall recovery up to 81%. The conditioned brine leaving from RO processes supplied to proposed multi-evaporator adsorption cycle driven by low temperature industrial waste heat sources or solar energy. RO membrane simulation has been performed using WinFlow and IMSDesign commercial softwares developed by GE and Nitto. Detailed mathematical model of overall system is developed and simulation has been conducted in FORTRAN. The final brine reject concentration from tri-hybrid cycle can vary from 166,000ppm to 222,000ppm if RO retentate concentration varies from 45,000ppm to 60,000ppm. We also conducted economic analysis and showed that the proposed tri-hybrid cycle can achieve highest recovery, 81%, and lowest energy consumption, 1.76kWhelec/m3, for desalination reported in the literature up till now.

Recycling brine water of reverse osmosis desalination employing adsorption desalination: A theoretical simulation

Intake, pretreatment and brine disposal cost of reverse osmosis sea water desalination systems represent about 25% of total cost of the desalinated water. The present study investigates effect of reverse osmosis brine recycling employing adsorption desalination on overall system desalinated water recovery. The adsorption desalination produces dual useful effects which are high quality potable water and cooling effect. Reverse osmosis desalination is simulated by engineering equation solver (EES). The brine leaving reverse osmosis system is fed to adsorption desalination system. The adsorption desalination is driven by a low temperature heat source such as solar energy. The adsorption desalination system has been simulated by MATLAB. Results show that the proposed combination system recovery increases and permeate salinity decreases. In addition to system performance improvements, a cooling effect is generated and can be utilized for cooling applications.

Implementation of Brackish Groundwater Desalination Using Wind-Generated Electricity: A Case Study of the Energy-Water Nexus in Texas

Growing populations and periodic drought conditions have exacerbated water stress in many areas worldwide. In response, some municipalities have considered desalination of saline water as a freshwater supply. Unfortunately, desalination requires a sizeable energy investment. However, renewable energy technologies can be paired with desalination to mitigate concern over the environmental impacts of increased energy use. At the same time, desalination can be operated in an intermittent way to match the variable availability of renewable resources. Integrating wind power and brackish groundwater desalination generates a high-value product (drinking water) from low-value resources (saline water and wind power without storage). This paper presents a geographically-resolved performance and economic method that estimates the energy requirements and profitability of an integrated wind-powered reverse osmosis facility treating brackish groundwater. It is based on a model that incorporates prevailing natural and market conditions such as average wind speeds, total dissolved solids content, brackish well depth, desalination treatment capacity, capital and operation costs of wind and desalination facilities, brine disposal costs, and electricity and water prices into its calculation. The model is illustrated using conditions in Texas (where there are counties with significant co-location of wind and brackish water resources). Results from this case study indicate that integrating wind turbines and brackish water reverse osmosis (BWRO) systems is economically favorable in a few municipal locations in West Texas.

Desalination of the Colorado River water: A hybrid approach

Membrane scaling constrains the operation of Reverse Osmosis (RO) forcing low water recovery, increasing brine amount and disposal cost. A high water recovery hybrid system (without antiscalants) was designed and simulated for desalination of Colorado River (CR) water (TDS = 941 mg/L) at the same capacity as the Yuma plant (96 Mgpd). The hybrid system incorporates ion exchange (IEX) water softening of Primary RO (PRO) retentate before the water is sent to Secondary RO (SRO). pH adjustment and heating of the concentrate from SRO is done before it is sent to an optional Tertiary RO (TRO). IEX treatment helped remove the scale causing precursors like Ba 2 + , Ca 2 + and Mg 2 + while pH adjustment and heating partially alleviated the problem of silica scaling allowing a maximum recovery of 96.4% with the PRO-IEX-SRO-Heat-TRO sequence. Use of concentrate from the last RO for IEX regeneration eliminates need for regeneration chemicals. Optimal RO configurations that minimize total annualized cost were determined by formulating the design as a mixed-integer nonlinear programming (MINLP) problem. Optimal process schemes were identified for different brine disposal costs. Reductions in product water cost of 75% and 50% were attained at high and low brine disposal costs, respectively.

Simulation of ion exchange water softening pretreatment for reverse osmosis desalination of brackish water

Prevention of membrane scaling in reverse osmosis (RO) desalination may require operation at low recoveries, which increases the amount of brine, increasing brine disposal costs and creating environmental hazard. Ion exchange (IEX) pretreatment removes Ca2+ and Mg2+ ions to limit scaling of salts. Use of concentrated water from RO process for regeneration of the IEX column eliminates the need for regeneration chemicals. Detailed simulations of the process were done. Optimal IEX/RO configurations were developed to avoid precipitation and minimize brine disposal cost.Simulations were done for Ca2+ rich and Ca2+ poor brackish water, in which relative composition of different ions mimics real brackish water source and sea water respectively. For the Ca2+ rich feed considered (TDS=12,000ppm), RO operation without either IEX pretreatment or anti-scalant predicted 36% recovery before precipitation occurred. In comparison, RO simulations after IEX pretreatment predicted recoveries as high as 90% with no precipitation in RO modules. IEX/RO operation at higher recoveries decreased the cost of product water by 75% when brine disposal costs are high and by 20% when brine disposal costs are low. Simulations showed IEX pretreatment was not beneficial for the Ca2+ poor feed, which did not precipitate.

Design of dual‐purpose membrane desalination systems

AbstractReverse osmosis (RO) and nanofiltration (NF) membrane plants are used extensively for brackish water desalination and industrial water purification. The operating range of RO plants is 60–80% product water recovery depending on the quality of raw water and feed water pretreatment. Typically, these plants operate at 75% recovery. The disposal of RO reject streams (20–40% of plant feed water) containing high concentration of salts is becoming an environmental problem. To reduce brine disposal costs and to increase product water recovery, several high‐recovery energy‐efficient membrane processes were analyzed. Generally speaking, a balance is required between brine volume reduction, capital and operating costs, energy consumption, and process simplicity. The analyses showed that up to 90% product water recovery can be achieved for low to medium brackish feed waters using RO/NF membrane systems with minimal feed water chemical pretreatment. The benefits of hybrid membrane systems integrated with fuel cell alternate energy systems are discussed. © 2009 American Institute of Chemical Engineers Environ Prog, 2010

Integrated membrane systems for seawater desalination: energetic and exergetic analysis, economic evaluation, experimental study

Currently over 12,500 industrial desalination plants, with an average production rate of 22.8 million m 3/d, are operating worldwide to alleviate water shortage problem. In this contest, pressure driven membrane operations are today largely utilized. They compete successfully with the more traditional thermal systems due to their lower energy consumption. However, critical issues still remain open: improvement of water quality and plant global recovery factor, reduction of desalted water cost and brine disposal problem. Recent developments make realistic to affirm that integrated membrane systems might offer one of the most reliable solution to solve these problems and also a sustainable development of desalination processes. Integrated membrane processes represent an attractive opportunity because of the synergic effects that can be reached, the simplicity of these units, the possibility of advanced levels of automation and remote control. In this logic well fit in also temperature driven membrane operations, such as membrane distillation and membrane crystallization: they allow increasing fresh water recovery factor, recovery of the crystals naturally present in the concentrated streams of the desalination plants, reduction of brine disposal cost and its negative environmental impact. In this work seven flow sheets for seawater desalination have been proposed, analysed and compared. In each of them different membrane units have been integrated in pre-treatment and post-treatment stages for reaching the process intensification goals, overcoming the limits of the single units and, thus, improving the performance of the overall desalination process.

Comparison between Compact Accelerated Precipitation Softening (CAPS) and Conventional Pretreatment in Operation of Brackish Water Reverse Osmosis (BWRO)

Preliminary tests have previously been conducted on compact accelerated precipitation softening (CAPS) as a pretreatment for membrane processes operating on various natural and industrial waters. In the present study, we compare CAPS efficacy for desalting brackish groundwater from the Negev region of Israel (original pH = 7.8) to that for conventional pretreatment, namely, dual media filtration (DMF) with acid or antiscalant. Samples of groundwater (400 L) were pretreated alternately by CAPS and conventional means and concentrated >8-fold in a batch desalination experiment with 2.5 in. x 40 in. spiral low-pressure reverse osmosis (RO) elements. The pure water flux of the membrane element was preserved in an experiment reaching nearly 90% recovery from CAPS-treated water adjusted to pH 7.6, whereas it declined to 30% of its original value after desalting the brackish groundwater treated by dual media filtration and adjusted to the same pH. In runs comparing CAPS pretreatment and conventional pretreatment with the supplemental use of antiscalant or acid, membrane processes operated with a CAPS-treated feed stream required less antiscalant and acid than those operated with conventionally pretreated water. In addition, the membrane modules required no cleaning at the end of the experiments, whereas membranes operated with conventionally pretreated water required significant cleaning to restore the pure water flux obtained at the beginning of each run. A comparison is made of the chemical requirements and brine disposal cost associated with each type of operation.

Investigation into alternative water treatment technologies for the treatment of underground mine water discharged by Grootvlei Proprietary Mines Ltd into the Blesbokspruit in South Africa

Grootvlei Proprietary Mines Ltd is discharging between 80 and 100 Ml/d underground water into the Blesbokspruit. This water is pumped out of the mine to keep the underground water at such a level as to make mining possible. The water is of poor quality because it contains high TDS levels (2700–3800 mg/l) including high concentrations of iron, manganese, sulphate, calcium, magnesium, sodium and chloride. This water will adversely affect the water ecology in the Blesbokspruit, and it will significantly increase the TDS concentration of one of the major water resources if not treated prior to disposal into the stream. Therefore, alternative water desalination technologies were evaluated to estimate performance and the economics of the processes for treatment of the mine water. It was predicted that water of potable quality should be produced from the mine water with spiral reverse osmosis (SRO). It was demonstrated that it should be possible to reduce the TDS of the mine water (2000-2700-3400-4500 mg/l) to potable standards with SRO (85% water recovery). The capital costs (pretreatment and desalination) for a 80 Ml/d plant (worst-case water) were estimated at US$35 M. Total operating costs were estimated at 88.1c/kl. Brine disposal costs were estimated at US$18 M. Therefore, the total capital costs are estimated at US$53 M. It was predicted that it should be possible to produce potable water from the worst-case feed water (80 Ml/d) with the EDR process. It was demonstrated that the TDS in the feed could be reduced from 4178 to 246 mg/l in the EDR product (65% water recovery). The capital costs (pretreatment plus desalination) to desalinate the worst-case feed water to potable quality with EDR is estimated at US$53.3M. The operational costs are estimated at 47.6 c/kl. Brine disposal costs were estimated at US$42M. Therefore, the total capital costs are estimated at US$95.3 M. It was predicted that it should be possible to produce potable water from the mine water with the GYP—CIX ion-exchange process. It was demonstrated that the feed TDS (2000–4500 mg/l) could be reduced to less than 240 mg/l (54% water recovery for the worst-case water). The capital cost for an 80 Ml/d ion-exchange plant (worst-case water) was estimated at US$26.7M (no pretreatment). Operational costs were estimated at 60.4 c/kl. Brine disposal costs were estimated at US$55.1 M. Therefore, the total desalination costs were estimated at US$81.8 M. The capital outlay for a SRO plant will be significantly less than that for either an EDR or a GYP—CIX plant. The operating costs, however, of the RO plant are significantly higher than for the other two processes. Potable water sales, however, will bring more in for the RO process than for the other two processes because a higher water recovery can be obtained with RO. The operating costs minus the savings in water sales were estimated at 17.2; 6.7 and US$8.6 M/y for the RO, EDR and GYP—CIX processes, respectively (worst case). Therefore, the operational costs of the EDR and GYP-CIX processes are the lowest if the sale of water is taken into consideration. This may favour the EDR and GYP-CIX processes for the desalination of the mine water.

Optimized brackish water desalination plants with minimum impact on the environment

Mekorot's activities and achievements in the implementation of RO technology to solve water supply and quality problems were reviewed. Two design concepts were applied: optimal usage of basic resources for large capacity systems, and simplicity in design and operation for small systems at remote locations. Special efforts are directed to minimize negative impacts on the environment. Existing systems of both large and small capacities, along with systems under design are being reviewed, including cost breakdown and analysis. The large capacity systems are characterized by high product recovery and low specific energy consumption. In two specific cases brine disposal cost has a negative value. In one case, the brine is used for raw seawater blending for a SWRO plant, and in another case, concentrating the brackish source via desalination facilitates the solution of an environmental problem.

Engineering development of hyperfiltration with dynamic membranes Part IV. Economic analysis

Cost estimates have been prepared for 5 mgd dynamic membrane reverse osmosis plants for desalting brackish water. Parameters included in the estimates were fluxes from 50 to 160 gal/ft 2· day and velocities from 5 to 15 ft/sec. The module used in the plant design contained 72 ft 2 of porous support area in a tube 4 in. in diameter and 12 ft long which, at a flux of 100 gal/ft 2· day, would result in a volumetric productivity of 8850 gal/day per cubic ft of module. Feed was assumed to be a high-hardness low-salinity water typical of those found in much of the mid and southwest United States. The results of the analysis indicate water costs in the range 49 to 60¢/kgal exclusive of brine disposal costs. These may be compared with costs in the range 44 to 58¢/kgal, exclusive of brine disposal costs obtained by Fluor Corporation in a recent economic study in which spiral and hollow fine fiber membrane modules were used.

Effect of brine disposal cost on hyperfiltration plant optimization

Parametric studies of hyperfiltration were carried out: (1) to determine optimal flow conditions and relative water costs when waste brine disposal costs are included in the economic model and (2) to further investigate tapered plant geometries. Relative water costs were computed at optimum flow conditions by use of a Fortran computer program (“HYPFIL”) which deals with a single-stage hyperfiltration system with tubular membranes under turbulent conditions. It was found that, for the conditions investigated, the optimum permeability of an ion exchange type membrane which gave the minimum relative water cost decreased with increased brine disposal cost. As expected, the optimum water recovery increased with increased disposal cost. The effect of brine disposal costs on relative water cost for a membrane with a permeability of 0.5 gpd ft -2 atm -1 and the characteristics of cellulose acetate resulted in higher optimum water recoveries as expected and increased the relative cost of water by a much higher percentage when the feed concentration was near the inherent rejection ability of the membrane to produce product with satisfactory salinity.