Seawater Reverse Osmosis Plant Research Articles

Energy Recovery in SWRO Desalination: Current Status and New Possibilities

Reverse osmosis (RO) technology requires high energy input in order to extract freshwater from seawater. Improvements in RO technology have led to seawater RO (SWRO) becoming the dominant form of large scale desalination around the world. However, the specific energy consumption (SEC) of SWRO remains substantially higher than that for surface water treatment and indirect potable recycling, making SWRO less cost effective than other alternatives for producing potable water. Furthermore, where non-renewable energy sources are used to supply SWRO energy demand, higher levels of greenhouse gas are emitted compared with lower energy alternatives. The purpose of this paper is to review the RO process configurations currently available and their impact on reducing SWRO energy consumption. This paper highlights the main factors contributing to SWRO energy consumption and presents some of the commonly adopted approaches to reducing SEC in SWRO plants. The use of energy recovery devices (ERDs) in SWRO is explored and the relative effectiveness of the various types of ERDs in reducing SEC presented.

Highly concentrated HCl and NaOH from brines using electrodialysis with bipolar membranes

Electromembrane technologies, such as electrodialysis with bipolar membranes (EDBM) have been widely proposed for the treatment and valorization of seawater reverse osmosis (SWRO) concentrated streams. The EDBM technology applied to brines produces acids (HCl) and bases (NaOH) with just two inputs: electric energy and brine. Thus, the reagents self-supply to the SWRO plant could be achieved, which definitively fits the principles of the Circular Economy. However, previous works have shown low concentration values of the produced acids and bases by EDBM, which undoubtedly hampers the possibility of its use in the SWRO plant.Therefore, the aim of the present work is to demonstrate the viability of a new strategy to valorise SWRO brine producing commercial HCl at 35 wt.% by means of the integration of EDBM technology under constant (galvanostatic, equivalent to the use of electrical energy from the grid mix) and variable current intensity (equivalent to the use of PV solar energy) and azeotropic distillation. Concentrations of HCl and NaOH up to ~3.3 mol·L−1 and ~3.6 mol·L−1 are obtained respectively, which are almost 50% higher than any other reported in the literature so far using this technology. The specific energy consumption of the EDBM unit was in the range of 21.8 kWh·kg−1 of HCl and 43.5 kWh·kg−1 of HCl, being dependant on the average applied current density. These HCl concentrations, although being acceptable for internal use in the SWRO plant, did not reach commercial levels (35 wt.% of HCl), so a further concentration stage using distillation has been evaluated through simulation. Minimum values of the overall EDBM plus distillation process specific energy consumption (SECOV) was between ~40 kWh·kg−1 and ~60 kWh·kg−1 of HCl.Moreover, the environmental burdens associated with the energy consumption are quantified in terms of the carbon footprint (CF). Although the SECOV is slightly higher, the use of PV solar energy instead of the grid mix let the process to provide a better environmental performance. The renewable alternative provides values between 1.61 kg CO2-eq.·kg−1 of HCl (full PV solar energy) and 6.97 kg CO2-eq.·kg−1 of HCl (PV solar energy and steam).

Innovative seawater uranium recovery agent based on low-cost polyacrylonitrile fibers

An innovative seawater uranium adsorbent was prepared from the low-cost and commercially-available polyacrylonitrile (PAN) fibers. The optimum condition to synthesize the adsorbent was to irradiate the PAN fibers with 100 kGy gamma ray, amidoximate in 3 (w/v)% hydroxylamine hydrochloride solution for 75 min at 75 °C, yielding the PAN nitrile group conversion of approximately 60%. At 100 kGy, the degree of crystallinity of the irradiated fibers was also highest at 79.1%. The performances of the adsorbent in seawater samples were excellent. By submersion in the seawater sample spiked with 250 ppb of uranium for 4 weeks, the prepared fibers exhibited the adsorption capacity of 32.28 mg/g adsorbent. By submersion in seawater samples spiked with 76.5 ppm of uranium for 1 week and 945 ppm of uranium for up to 4 weeks, the fibers exhibited the adsorption capacities of 111.25 and 200.07 mg/g adsorbent, respectively. The adsorbent showed a uranium adsorption capacity of 0.11 mg/g adsorbent for 8 weeks of soaking in brine concentrate from a seawater reverse osmosis plant. The kinetics of seawater absorption by the adsorbent was quite rapid, reaching the equilibrium swelling ratio of approximately 300% in 5 min or less. Another important finding was that the prepared PAN fibers exhibit the characteristics of a superabsorbent material (equilibrium swelling ratio in DI water of 5,550%). The low cost and the ease of preparation of the fibers offer a novel environmental remediation process to adsorb uranium ions released into seawater following a nuclear accident.

Determination of optimal design factors and operating conditions in a large-scale seawater reverse osmosis desalination plant

A large-scale seawater reverse osmosis (SWRO) plant was designed with a capacity of 10 million imperial gallon per day (MIGD) and to optimize design factors and operating conditions of the plant, various evaluations were undertaken. These involved pretreatment investigations, split partial simulations, evaluation of the final water quality with respect to production capacity, and a performance comparison with other SWRO plants using the normalized specific energy consumption (SEC). As a result, the turbidity and silt density index values of the pretreatment permeates were not affected by the productivity of the plant during the operation period. Additionally, the optimum split partial ratio of the RO membranes was determined to be 4.5:5.5 which satisfied the final produced water quality and energy consumption requirements. Based on the split partial ratio, the total dissolved solids (61–280 mg/L) and boron (0.1–0.9 mg/L) concentrations of the final permeate satisfied the Korean standards at all capacities (5.7, 8.0, 10 MIGD). In particular, the total SEC of the 10 MIGD train was estimated as 3.66 kWh/m3, which is greatly lower compared to that of other SWRO plants with similar capacities. Thus, these specific performance evaluations will be useful in determining the optimal design factors and operating conditions for other large-scale SWRO plants.

Securing future water supply for Iran through 100% renewable energy powered desalination

Iran is the 17th most populated country in the world with several regions facing high or extremely high water stress. It is estimated that half the population live in regions with 30% of Iran’s freshwater resources. The combination of climate change, increasing water demand and mismanagement of water resources is forecasted to worsen the situation. This paper shows how the future water demand of Iran can be secured through seawater reverse osmosis (SWRO) desalination plants powered by 100% renewable energy systems (RES), at a cost level competitive with that of current SWRO plants powered by fossil plants in Iran. The optimal hybrid RES for Iran is found to be a combination of solar photovoltaics (PV) fixed-tilted, PV single-axis tracking, Wind, Battery and Power-to-Gas (PtG) plants. The levelised cost of water (LCOW) is found to lie between 1.0 €/m3 – 3.5 €/m3, depending on renewable resource availability and water transportation costs.

Economic Assessment Based on Energy Consumption on the Capacities in Seawater Reverse Osmosis (SWRO) Plant in Korea

Objectives The production cost of reverse osmosis (RO) seawater desalination plant is determined by the CAPEX (Capital expenditure) and OPEX (Operating expenditure). In detail, CAPEX and OPEX are composed of direct cost, overhead cost, electricity cost, and other O&M costs. However, CAPEX and OPEX may vary by country and region. Therefore, this study tries to estimate the production cost by calculating the construction and maintenance costs depending on production capacities based on the operation results such as TDS concentration and the energy consumption from a seawater desalination plant in Korea. Methods A two-stage RO based seawater desalination plant with a capacity of 10 MIGD (45,000 m3/d) was used in this study. The plant consists of a 2 MIGD (9,000 m3/d) unit having DABF (Dissolved air bio-ball filter) and UF (Ultrafiltration) as pretreatment processes, and another 8 MIGD (36,000 m3/d) unit having DABF and DMF (Dual media filtration) as pretreatment processes. To estimate the production cost, construction and maintenance costs were calculated by using GWI's Desaldata cost estimator. CAPEX (Capital expenditure) was calculated based on production capacity, recovery rate, TDS concentration and temperature of seawater, while OPEX (Operating expenditure) was calculated based on production capacity, country, energy consumption, and electricity unit price. Results and Discussion The energy consumptions from EMS (Energy Management System) were 5.48 kWh/m3 at SLC (9,000 m3/d) and 3.4 kWh/m3 at MLC (45,000 m3/d), respectively. In the CAPEX, MLC was reduced by 395,954 ￦/m3 compared to SLC, and the LLC was lower by 192,019 ￦/m3 than MLC. Overall, CAPEX decreased as the production capacity increased. The CAPEX of small plants with production capacity between 10,000 and 50,000 m3/d was significantly different; however, there was no significant difference in larger plants having a capacity above 100,000 m3/d. The OPEX for the annual production capacity showed a sizable difference with 742.3 ￦/m3, 636.5 ￦/m3 and 580.3 ￦/m3 for SLC, MLC, and LLC, respectively. The electricity cost was a substantial portion of OPEX. Also, the production costs based on the interest rates (3% and 5%) were 1,326-1,384 ￦/m3, 1,163-1,209 ￦/m3, and 1,023-1,070 ￦/m3 for SLC, MLC, and LLC, respectively. The results were consistent with 1.0 US$/m3, which is the average production costs presented from other references. Conclusions The production cost estimated using the Desaldata cost estimator based on the CAPEX and OPEX tends to decrease as the capacity increases. However, when the capacity increased over 50,000 m3/d, the production cost decreased by an average of 40 ￦/m3. Thus the decrement of production cost reduced. From these results, the production cost of tap water through seawater desalination was estimated between 1,023 ￦/m3 and 1,070 ￦/m3 above 100,000 m3/d. Therefore, it is difficult to introduce a large-scale desalination plant in Korea, because the average tap water price was 834.6 ￦ in Korea in 2017. However, It is expected that the seawater desalination will be introduced as an alternative water source whenever drinking water price rises, or when the quantity of available drinking water sources reduce due to climate change and water pollution, or whenever energy consumption is reduced as a result of the steady development of the component technologies such as the reverse osmosis membrane, high-pressure pump, and energy recovery device. Key words: Reverse osmosis seawater desalination plant, Water price, Capital expenditure, Operating expenditure, Energy consumption

Assessing pretreatment and seawater reverse osmosis performance using an ATP-based bacterial growth potential method

Various bacterial growth potential (BGP) methods have been developed recently to monitor biofouling in seawater reverse osmosis (SWRO) systems such as assimilable organic carbon and bacterial regrowth potential. However, the relationship between these methods and biofouling in SWRO desalination plants has not yet been demonstrated. In this research, an attempt is made to investigate if a correlation exists between BGP of SWRO feed water and the chemical cleaning frequency in SWRO plants using an ATP-based BGP method employing an indigenous microbial consortium. Using ATP-based BGP method at 5 different seawater locations showed low variations of bacterial yield.The BGP method was applied to assess the pretreatment performance of three full-scale SWRO plants with different pretreatment processes. Dual media filtration (DMF) showed the highest BGP removal (>50%) in two SWRO plants. Removal of BGP and hydrophilic organic carbon in dissolved air floatation combined with ultrafiltration was similar to the removal achieved with DMF in combination with inline coagulation. For the three SWRO plants investigated, a higher BGP in SWRO feed water corresponded to a higher chemical cleaning frequency. However, more data is required to confirm if a real correlation exists between BGP and biofouling in SWRO plants.

Advanced coagulation using in-situ generated liquid ferrate, Fe (VI), for enhanced pretreatment in seawater RO desalination during algal blooms

Harmful algal blooms (HABs) are considered a major threat for seawater reverse osmosis (SWRO) plants. The presence of HABs in the raw feed water can cause increase of chemical consumption within the desalination plant, increase membrane fouling rate and might lead to plant shutdown. The removal of Algal Organic Matters (AOMs) during the pretreatment will help in increasing the membrane lifetime, reduce operation cost and increase the plant reliability. In this study, the efficiency of liquid ferrate and ferric chloride during coagulation on the removal of AOMs was investigated. The liquid ferrate was generated in-situ by wet oxidation of ferric iron using hypochlorite in a caustic medium. Two seawater models were employed, the first one contains 10 mg c/L of sodium alginate and the second one contains also 10 mg c/L of Chaetoceros affinis algae (CA). During the advanced coagulation, liquid ferrate proved to be more effective in removing AOM than ferric chloride, with an overall DOC removal of 90%, enabling 100% algal removal and the inactivation of 99.99% of the microorganisms. The results presented in this study highlights the efficiency of liquid ferrate as seawater pretreatment during the HABs events.

Environmental assessment of intake alternatives for seawater reverse osmosis in the Arabian Gulf

The study carried out an environmental assessment for two seawater reverse osmosis (RO) plants located within the Arabian Gulf considering subsurface intake alternatives and differing energy source options. The study used life cycle assessment to quantify the environmental impacts for open intake pretreatment vs. subsurface intake pretreatments of two plants with operating capacities of approximately 175,000 m3/d and 275,000 m3/d respectively. For both RO plants, electricity and chemical inputs were considered. Significant energy reductions of 30% were observed with subsurface intakes for extraction and pretreatment, resulting in a plant-wide energy saving of 6%. Open intake pretreatment had higher environmental impacts compared to subsurface intake across all impact categories, although in some impact categories significant differences existed between the two similar plants due to differences in chemicals used. The study further established that the renewable PV power generation resulted in the lowest global warming potential (GWP); however, a significant trade-off occurs with this energy source since it had the highest impact relative to both ozone and abiotic depletion potentials and was also worse than natural gas for both marine and human toxicity potentials. The GWP reductions achievable using a subsurface intake for the larger of the two plants is equivalent to 58,000 tons of CO2 per year, or more than 12,000 cars, making subsurface intakes a worthy alternative to conventional open intake systems in the Arabian Gulf region. Marine aquatic eco-toxicity potential was identified as the most significant normalized environmental impact, which should be best managed through using natural gas as an energy source.

Chemical-free scale inhibition method for seawater reverse osmosis membrane process: Air micro-nano bubbles

One of the major problems of seawater reverse osmosis (SWRO) process is the formation of inorganic scales (calcium carbonate, CaCO3) and calcium sulfate, CaSO4)) on the membrane surface, which degrades the filtration performance. Antiscalants have been applied to SWRO plants to overcome the scaling problem. In this study, we used the air micro-nano bubbles (MNBs) as a chemical-free scale inhibition method to improve the overall membrane performance in the comparison with the commercially available antiscalants. During four days of continuous experiments with MNBs, the permeate fluxes declined to 86.5(0.4)% and 83.0(0.5)% with CaCO3 and CaSO4 containing feed solutions, respectively. These values were higher than those obtained with the use of antiscalants in the feed water (CaCO3–63.5(0.4)% and CaSO4–55.8(1.0)%). Membrane fouling characterization results showed that the MNBs efficiently controlled the scaling development on the membrane surface without any chemical addition.

Design and analysis of a solar photovoltaic powered seawater reverse osmosis plant in the southern region of the Gaza Strip

Design and analysis of a solar photovoltaic powered seawater reverse osmosis plant in the southern region of the Gaza Strip

ATP measurement in seawater reverse osmosis systems: Eliminating seawater matrix effects using a filtration-based method

A direct method for measuring adenosine-triphosphate (ATP) in seawater was developed recently, in which commercial reagents are added directly to seawater. However, calibration is required if seawater quality changes (such as changes in salinity, pH, Mg2+, Fe3+) as the seawater matrix interferes with ATP measurement. In this research, a 0.1 μm filtration process is introduced to eliminate such interferences. In addition, a filter rinsing step with sterilized artificial seawater is proposed to eliminate interference of free ATP.The ATP-filtration method is fast (<5 min), reproducible (VC = 7%), six times more sensitive than the direct ATP-method and correlates (R2 = 0.72, n = 100) with intact cell concentration. Microbial ATP concentration measured using the ATP-filtration method and the ATP-direct method were comparable. Microbial ATP measured along the treatment train of a full-scale seawater reverse osmosis (SWRO) plant decreased from 530 in the raw seawater to 10 ng-ATP/L after pre-treatment and to 0.5 ng-ATP/L in the SWRO permeate. The method was also applied to monitor bacterial growth potential (BGP) across the pre-treatment train of a (pilot) seawater desalination plant, where the removal of BGP through the media filtration and ultrafiltration was 44% and 7%, respectively.

Genome-resolved metagenomic analysis reveals roles of microbial community members in full-scale seawater reverse osmosis plant

Biofouling of Reverse Osmosis (RO) membrane is a significant issue for the water treatment industry. In this study, we apply the metagenomic shot-gun sequencing technology to characterise the composition and functional potential of the microbial community in a full-scale RO plant, at different stages of seawater treatment. We find Proteobacteria, Bacteroidetes and Planctomycetes to be the most abundant bacterial phyla. The genetic potential of the RO membrane microbial community shows the enrichment of genes involved in biofilm formation, representing the selective pressure of the biofilm formation process. We recover 31 metagenome-assembled genomes (MAGs) from intake (raw seawater), fouled RO membranes (leading and middle RO module) and brine reject water. A total of 25 MAGs are recovered from the biofilm samples (leading and middle RO modules), with 9 of them (36%) belonging to Planctomycetes. We investigate all 25 MAGs for genes (pili, flagella, quorum sensing, quorum quenching and nitrate reduction) that play an important role in biofilm formation and sustenance of cells. We show that Planctomycetes contain genes for the formation of flagella and pili, and the reduction of nitrate. Although genes for quorum sensing are not detected, quorum quenching genes are identified in the biofilm MAGs. Our results show that Planctomycetes, along with other microbes, play an important role in the formation and sustenance of biofilms on seawater RO membranes.

Techno-Economic Feasibility Study of a Hypersaline Pressure-Retarded Osmosis Power Plants: Dead Sea–Red Sea Conveyor

In this study, three pressure retarded osmosis (PRO) power plants are proposed to be built on the Red Sea–Dead Sea (RSDS) water conveyance project, to generate power from the salinity gradient between two water streams at different salt concentrations. The first two proposed plants are to be built after sea water reverse osmosis (SWRO) desalination plants, where Red Sea water and the rejected brine from SWRO plants are used as feed and draw solutions, respectively. In the third proposed plant, Red Sea water and Dead Sea water will be used. Results showed that the three proposed plants are technically feasible while the third plant is the only one that is economically feasible with a 134.5 MW capacity and a 0.056 $/KWh levelized cost of electricity (LCE). The power generated from the third PRO power plant accounts for about 24.7% of the power needed for the RSDS project that can be used to power SWRO-2 in order to reduce the electricity consumption by 49.3%. If the generated power from the proposed PRO plant is sold to the Jordanian national electricity grid at the current selling price in accordance with Jordanian prices of electricity, a saving of about 21.2% can be attained. It is found that using the power generated by the current proposed plants for desalination project purposes will significantly reduce the price of desalinated water produced from SWRO desalination plants.

Systems-level thermodynamic and economic analysis of a seawater reverse osmosis desalination plant integrated with a combined cycle power plant

This study includes thermodynamic and economic analyses of a seawater reverse osmosis (RO) plant integrated with a small-scale combined cycle natural gas (CCGT) plant ranging from 36–71 megawatts (MW). These analyses model electricity produced by the CCGT plant as power for the RO plant or for sale to the power grid. These analyses consider the coolant flow rate, carbon intensity, and capital and operating costs of the CCGT plant. For a case where the RO plant is sized according to the rated capacity of the CCGT plant, the maximum flow rate of coolant for the CCGT plant is only 8–10% of the total rate of seawater intake for the RO plant. Thus, no additional intake capacity is needed for the CCGT plant. The carbon intensity of the CCGT plant varies from 802-885 pounds per megawatt-hour (lb/MWh) compared to an average carbon intensity of 1285 lb/MWh for the Texas power grid. The economics of the integrated facility are evaluated using a levelized cost of water (LCOW) framework, which accounts for the capital cost associated with the CCGT plant and electricity sales to the grid. Results indicate that integrating an RO plant with a CCGT plant reduces LCOW by 8–10% compared to an RO plant powered by electricity from the Texas power grid. Citation: Reimers AS, Webber ME. 2018. Systems-level thermodynamic and economic analysis of a seawater reverse osmosis desalination plant integrated with a combined cycle power plant. Texas Water Journal. 9(1):82-95. Available from: https://doi.org/10.21423/twj.v9i1.7065.

Photocatalytic inactivation of Vibrio fischeri using Fe2O3-TiO2-based nanoparticles

Biofouling is a major problem in water membrane processes, especially in seawater reverse osmosis plants. Inactivation of Vibrio fischeri (a well-known marine bacterium forming biofilm) through photocatalysis via visible light was investigated in this work using active Fe2O3-TiO2 nanoparticles. Five Fe2O3-TiO2 photocatalysts with different weight percentage of Fe2O3 (0–5 wt%) were synthesized using an ultrasonic-assisted co-precipitation method. The photocatalysts were characterized by powder X-ray diffraction (XRD), BET surface area, transmission electron Æ (TEM) plus selected area electron diffraction (SAED) patterns, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and diffuse-reflectance spectroscopy (DRS). Based on the design of experiments, the synthesized photocatalysts were tested for inactivation of V. fischeri under visible light irradiation at different temperatures (25–35 °C) and different photocatalyst dosage (0.1–2 g/L). The photocatalytic microbial inactivation experiments were performed in artificial seawater appropriate for growth of the marine bacterium. The results revealed that the highest inactivation efficiency of V. fischeri was achieved when 1 g/L of 2.5 wt% Fe2O3-TiO2 were used, at 35 °C. Photocatalytic inactivation of microorganisms using visible light-driven Fe2O3-TiO2 photocatalysts, could introduce an innovative green method in pretreatment units of reverse osmosis plants to control the membrane biofouling.

Role of Seawater Desalination in the Management of an Integrated Water and 100% Renewable Energy Based Power Sector in Saudi Arabia

This work presents a pathway for Saudi Arabia to transition from the 2015 power structure to a 100% renewable energy-based system by 2050 and investigates the benefits of integrating the power sector with the growing desalination sector. Saudi Arabia can achieve 100% renewable energy power system by 2040 while meeting increasing water demand through seawater reverse osmosis (SWRO) and multiple effect distillation (MED) desalination plants. The dominating renewable energy sources are PV single-axis tracking and wind power plants with 243 GW and 83 GW, respectively. The levelised cost of electricity (LCOE) of the 2040 system is 49 €/MWh and decreases to 41 €/MWh by 2050. Corresponding levelised cost of water (LCOW) is found to be 0.8 €/m3 and 0.6 €/m3. PV single-axis tracking dominates the power sector. By 2050 solar PV accounts for 79% of total electricity generation. Battery storage accounts for 41% of total electricity demand. In the integrated scenario, due to flexibility provided by SWRO plants, there is a reduced demand for battery storage and power-to-gas (PtG) plants as well as a reduction in curtailment. Thus, the annual levelised costs of the integrated scenario is found to be 1–3% less than the non-integrated scenario.

Reducing specific energy consumption of seawater desalination: Staged RO or RO-PRO?

Specific energy consumptions (SECs) in seawater RO desalination employing staged RO and RO-PRO with energy recovery devices are investigated using systematic mathematical methods. The SECs in both configurations are minimized by solving a constrained nonlinear optimization model which optimally selects operating conditions and allocates membrane area between different membrane units. It is shown that both staged RO and RO-PRO are noticeably advantageous over single-stage RO only if a dimensionless parameter γtotal=AtotalLpπ0/Q0 is sufficiently large. The RO-PRO outperforms staged RO when internal concentration polarization is not severe, water recovery is low (e.g., 30%) and/or membrane area is abundant (e.g., γtotal ≥ 1.6). The staged RO is likely to excel at a high water recovery (e.g., 60%) even though the high-salinity brine enhances the driving force for osmotic energy recovery in the RO-PRO. Both configurations have comparable SECs based on water recoveries of 40% and 50% and a γtotal of 0.8, a representative value in industrial seawater RO plants.

On thermoeconomic analysis of a single-effect mechanical vapor compression desalination system

The current study is focused on thermoeconomic analysis of a single effect mechanical vapor compression (MVC) desalination system operating with and without brine recirculation. For this purpose, first- and second-law analyses are carried out to estimate the energy consumption and second-law efficiency of the plant. A single stage seawater reverse osmosis plant is also presented for the sake of comparison. For thermal systems, a detailed heat exchanger design is provided to calculate an overall heat transfer coefficients, heat transfer areas, and the pressure drops on the cold- and hot-sides of the heat exchangers. Besides, the product cost is calculated and compared by using two different cost estimation methods. Moreover, it is demonstrated that the cost-flow method of economic analysis is more elaborative and useful because it enables the component level cost optimization. The calculations reported the values of specific energy consumption (SEC), second law efficiency and product cost to be 10 to 13kWh/m3, 8 to 9% and 1.7 to 2.3$/m3, respectively. Furthermore, it is shown that the input parameters like cost index factor, electricity cost, compressor efficiency and the heat transfer areas have a remarkable influence on the product cost and must be selected carefully for accurate cost estimation.

An optimization model for the allocation of water resources

Critical water shortages, triggered by increasing demands and decreasing supplies, are growing in frequency and spatial extent pausing major challenges for water resources managers around the world. This paper presents an integer linear programming decision support model for the optimal treatment and allocation of water resources. The model seeks to minimize the total water cost which includes the economic cost of treatment and distribution, as well as the associated environmental costs. The model is unique in its ability to account for spatially distributed water supply and demand nodes, as well as multiple water supply (seawater, surface, ground and wastewater) and demand (irrigation, potable, and industrial) types and qualities. It accommodates various treatment technologies, different energy recovery levels, and resource availabilities or capacities. The optimal solution yields volumes of water transported from each supply source to each treatment plant and treated by an appropriate technology in order to satisfy multiple water demands at different required water qualities with the lowest overall economic and environmental costs. The model is applied to a case study. Results showed that the distance of brackish water sources and the environmental cost, observed in terms of carbon savings only, had limited impact on the optimal solution with the demand for the base case being met through a combination of conventional water and wastewater treatment and brackish water reverse osmosis. Sensitivity analysis is performed to determine the effects of variations in demand/supply volumes as well as variable distances and environmental cost. Sensitivity analysis showed that increased demand under limited resources can be met through the introduction of seawater desalination plants, initially through multi effect distillation combined with residual thermal energy then augmented with seawater reverse osmosis plants with further increase in demand.