Alternative Source Of Fresh Water Research Articles

The contribution of coastal land subsidence to potential sea-level rise impact in data-sparse settings: The case of Ghana’s Volta delta

Deltas are highly valuable environmental systems, ensuring various livelihoods through their ecosystem services. However, human impact and climate change stressors are impacting deltas immensely. Consequently, many deltas, including Ghana's Volta Delta, are facing increasing risks, especially as hazards are increasing in magnitude and impacting coastal livelihoods. To provide a better understanding of coastal hazards in the Volta Delta, this study assessed the Delta's subsidence regime and its consequences for the potential impact of sea-level rise (SLR). Using the Interferometric Synthetic Aperture Radar (InSAR) technique and Global Navigation Satellite System (GNSS) surveys, vertical land motion (VLM) was documented. Interferograms of Sentinel-1 data from 2016 to 2020 indicated subsiding rates of up to −9.2 mm/yr. By combining local VLM information with recent SLR projections and elevation data, this study updates those projections and provides local assessments of potential Relative SLR (rSLR) impact. According to these locally improved scenarios, up to ∼45 % of the Delta will fall below local sea level by 2100, of which close to 10 % is explained by the integration of local VLM data alone. Depending on the climate change scenarios used, land subsidence will increase the deltaic area at risk by 4.31 % (96.27 km2) to 10.18 % (227.64 km2) and consequently exacerbate its exposure to coastal inundation. To avert the projections, the study recommends robust monitoring regimes; alternative freshwater sources to groundwater; reduced sediment trapping and river obstruction; and the need to stall ongoing oil and gas prospecting and subsequent extraction in the Voltain Basin.

Improving Atmospheric Water Harvesting in Carbon‐Based Sorbents Through CO2 Activation

AbstractAtmospheric water harvesting (AWH) can serve as an alternative fresh water source in regions with scarce access to drinking water. While many techniques are geographically or seasonally limited, sorbent‐based AWH shows the potential for wider application. Low‐cost, carbon‐based sorbents named nanoporous sponges (NPS) are recently developed, exhibiting fast and repeatable water uptake of 0.14 g g−1 at 90% relative pressure. While useful from a cost and daily water yield point of view, there is room for improvement. This article presents an improved production process combining pyrolysis and activation under CO2 in a single step, yielding improved NPS capable of reproducibly reaching a water uptake of 0.47 g g−1 at 95% relative pressure while maintaining fast sorption rates. The NPS show significant endurance and are able to maintain stable performance over numerous humidity cycles. An unexpected time‐dependant sorption behavior is also identified for NPS produced with a modified synthesis formulation, due to an increase in sodium carbonate residual content.

Removal of Base Metals from Mine Tailings in Chloride- and Seawater-Based Media Followed by Solvent Extraction

The high volume of mine tailings generated during mining activities poses significant worldwide storage risks. However, these tailings often contain valuable metals that can be recovered. Therefore, reprocessing mine tailings has emerged as a crucial strategy to assess secondary metals resources and mitigate storage risks. Furthermore, the mining industry’s extensive use of freshwater necessitates exploring alternative water sources. In this study, the leaching of base metals from mine tailings in chloride-based media was investigated. Approximately 52% Cu, 73% Zn, and 100% Pb were leached from the sample in the presence of HCl and NaCl. The substitution of freshwater with seawater yielded comparable results, demonstrating the potential of seawater as an alternative freshwater source that does not compromise leaching effectiveness. Additionally, 77% of Pb precipitated as PbSO4 from the pregnant leach solution. Through solvent extraction, approximately 100% Cu was recovered using LIX 984 as an extractant, and 71% Zn with D2EHPA. The use of Fe0 significantly reduced the co-extraction of Fe in the Zn recovery step. Overall, this study provides a potential route for reprocessing mine tailings, ensuring maximum leaching and efficient recovery of metals from sulfide mine tailings.

Cyclic zinc capture and zeolite regeneration using a column method, mass transfer analysis of multi regenerated bed.

Treatment of wastewater and reuse of purified water in an industrial process can provide an alternative source of fresh water as well as reduce pollution load by discharging a lower quantity of wastewater. When adsorption is used for treatment, the regeneration of the used adsorbent may also account for a large portion of the operational cost and cause secondary pollution. This problem may be solved by cyclic repetition of adsorption/regeneration cycles using a column method. In this paper, a total of nine successive cycles of zinc capture and zeolite bed regeneration using a column method have been investigated. The derived form of the breakthrough curve was used for analysing mass transfer in the column. For that purpose, the Dose-response, the Thomas, the Bohart-Adams, the Yoon-Nelson and the Wolborska models were used for modelling the breakthrough curve by nonlinear regression analysis. Simulation results and mathematical similarities between the models were discussed. This is the first study that used derived form of Dose-response model to analyse the inflection points of the breakthrough curve and mass transfer during nine consecutive sorption-regeneration cycles of zinc ions on natural zeolite. Obtained peak shape rate profiles were analysed for all cycles. Optimal operation conditions were evaluated with respect to the inflection point, the model parameters, and the residence time.

Utilizing the Harvesting of Rainwater to Provide Safe Road Transportation Efficiency and Increase Water Resources in the Context of Climatic Change

This research investigates the effect of heavy rain on highway traffic volume and average speed, and proposes a recharging well harvesting system as an alternative freshwater source in the context of climate change. The Cairo Autostorad highway was taken as a case study. The highway climate data were collected, and traffic was measured using Metrocount equipment during the period from 2008 to 2020. The results show that the studied road is about 12 km long, and about 40 water ponds exist along the route. Each pond has an estimated water volume of 300 m3, and a 30 cm recharging well, with a maximum recharging capacity of 25 m3/h with satisfactory performance, is recommended to be constructed for rainwater harvesting. The recharging wells will clear the ponding volume within 2.5 to 3.5 h after the rainfall has stopped. The design incorporates a 1.2 safety factor against blockage inside the well. In addition, a model was established between the average rainfall depth and the average measured highway speed for the period (2008–2020) during rainy months, indicating an exponential function with a determination factor R2 = 0.7076. The present rainfall (2020) and the representative concentration path (RCP) for 4.5 and 8.5 emissions scenarios were used to simulate the rainfall for future years: the 2040s, 2060s, 2080s, and 2100s. The results show that in the winter season for the current scenario (2020), the average rainfall depth was 45 mm, and the highway speed was 78 km/h. For the RCP 4.5 emission scenarios for the 2040s, 2060s, 2080s, and 2100s, the rainfall depths were 67.8, 126.4, 131.2, and 143.9 mm, and the corresponding reductions in the highway speeds were 23, 34, 35.3, and 36.9%, respectively, compared to the baseline scenario (2020). On the other hand, the RCP 8.5 emission scenarios show a reduction in the highway speed of 23, 34.5, 36.9, and 36.9% for the years 2040, 2060, 2080, and 2100, respectively, due to rainfall depths of 68.7, 128.4, 143.9, and 143.9 mm, respectively. This study helps policymakers to make wise decisions regarding sustainable water resource management and highway traffic problems related to rainwater depths in the context of climate change.

Investigating the pilot-scale performance of a hydroponic nutrient solution as potential draw solution for fertilizer drawn forward osmosis and hydroponic agriculture of lettuce

The objective of this research is to test the feasibility of a large-scale application of fertilizer drawn forward osmosis using a concentrated hydroponic nutrient solution as the draw solution. This large-scale application will help to mitigate the ever-growing issue of freshwater resources, by providing an alternative source of freshwater for agriculture. This method can then be used to grow crops hydroponically in arid regions that have access to both brackish groundwater and freshwater. The nutrient solution was prepared by dissolving industrial-grade fertilizer salts in dechlorinated tap water and was tested as a draw solution (DS) on a pilot-scale forward osmosis membrane module. The feed solution (FS) for the process was NaCl dissolved in dechlorinated tap water, in a 10 g/L (10% w/w) NaCl concentration to represent the salinity level of brackish groundwater. The performance of the draw solution was measured based on the water flux, water recovery, specific solute flux, and salt rejection. Two hydroponic basins were utilized to hydroponically grow lettuce. The first basin was grown using a commercial hydroponic nutrient solution, while the other basin was grown using the diluted draw solution from the pilot-scale. The growth of the lettuce in both basins was compared based on wet and dry weights of the stem, percent reduction in weight by drying, total length, stem length, and the ratio between stem and total lengths. Results showed that average water flux on the pilot-scale was found to be 1.11 L/m2/hr (LMH), while it was found to be 7.7 LMH in previous research on the bench-scale; this is in line with previous experiments conducted on both bench-scale and pilot-scale forward osmosis. The highest value specific reverse solute flux on the pilot-scale was found to be 7.48 g/m2/h for the K+ ion, which is also comparable to the results obtained on the bench-scale. Finally, salt rejection was found to be high, the lowest value was 90.7%, indicating high membrane selectivity against feed ions. The lettuce grown hydroponically using the resultant diluted draw solution from the pilot-scale was comparable to the lettuce grown using a commercial nutrient solution, with the draw solution lettuce being 16.23% less in terms of weight than the commercial lettuce, and 27.18% in stem length. This decrease in size and weight of the lettuce grown with the diluted draw solution can be attributed to the ratio of macro- and micro-nutrients in the Resh Florida/California solution not being optimized for the species of lettuce grown (loose leaf). It was concluded that concentrated hydroponic nutrient solution is a valid draw solution for large-scale fertilizer drawn forward osmosis, and this application mitigates some of the drawbacks of fertilizer drawn forward osmosis and increases the feasibility of large-scale application of forward osmosis as a desalination technology.Graphical abstract

Indirect charging of carbon by aqueous redox mediators contributes to the enhanced desalination performance in flow-electrode CDI

Reversible electrochemical separation based on flow electrodes (e.g., flow-electrode capacitive deionization (FCDI)) is promising to desalinate brackish water, a reliable alternative source of freshwater. The deployment of redox mediators (RMs) in FCDI offers an energy-efficient means to improve the process performance, but the nature of the RMs-mediated charge transfer remains poorly understand. We therefore systematically investigated commonly-used RMs including sodium anthraquinone-2-sulfonate (AQS), 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), hydroquinone (HQ) and ferricyanide ([Fe(CN)6]3−). Results showed that the desalination rate could be increased by over 260% with the addition of 10 mM [Fe(CN)6]3−. The lowest efficiency of AQS among the RMs should be ascribed to its reduction potential of −0.84 V (vs. Ag/AgCl) exceeding the potential (−0.48 V) of the negatively charged current collector at 1.2 V. While aqueous TEMPO and HQ could facilitate salt removal, their loss of efficiencies upon sorption onto the carbon surface indicated the insignificant pseudocapacitive contribution to ion migration. In-situ cyclic voltammetry measurements demonstrated the crucial role of the indirect charging of the flowable carbon materials to enhance the desalination performance in RMs-mediated FCDI. To sum up, results of this work pave a way to understand the RMs-mediated charge transfer and ion migration in FCDI, which would serve the purpose of design and optimization of the flow electrode systems for wider environmental applications.

Effect of anion-exchange membrane type for FCDI performance at different concentrations

ABSTRACT Brackish water was an important alternative source of freshwater. Desalination using flow electrode capacitive deionization (FCDI) needs to explore the role of ion exchange membranes (IEM) of FCDI. In this study, brackish water was desalinated using FCDI, and anion exchange membranes with different characteristics were used in the FCDI cell to investigate their influence. The result showed that the membrane polymer matrix was the main influencing factor for ion transport. Ion exchange capacity (IEC) has a huge impact that low IEC made the various ion transport priority. Low IEC not only limits ion transport but also leads to ion leakage in seawater. Resistance had a significant blockage to the effect with weak intensity.

Atmospheric Irrigation with Wind Turbines

In this paper, atmospheric irrigation with wind turbines is proposed. This technology addresses the problem of water scarcity by enhancing the natural water circuit in the atmosphere with wind turbines. There are three different operating modes conceivable for this technology. In two of these the wind turbines interact with the ground in their near wake. The third operating mode is the one which is discussed in this paper, and it aims at transporting water potentially over long distances. The basic working principle, the utilized physical phenomena and the basic design of the technology are introduced. The equations governing the hydraulic and the hydrological effects are presented. The goal of this paper is to quantify the necessary power and the necessary amount of water when wind turbines humidify a certain volume of air in the atmosphere. For this purpose, the power and water demand are assessed, both in a generalized manner and for a realistic scenario. It is concluded that the proposed system can achieve the objective in most wind speed conditions. However, the required amount of water is substantial. Therefore, an alternative source of fresh water has to be found when the system is used on a comparably large scale.

Response of Soil and Crop to Mixed Irrigation Using Brackish and Reclaimed Water

HighlightsMixed irrigation with brackish water-reclaimed water was introduced.IBRv2 was used to evaluate the effects of mixed irrigation on the soil–crop system.Reclaimed water could be used as an alternative source of freshwater to mix with brackish water, and the suitable mixed proportion should be 1:1 based on IBRv2.Abstract. To explore the reasonable utilization of brackish water in areas where freshwater is scarce, we used pot experiments to study the physical, chemical, and biological properties of soil and crop yield characteristics under mixed irrigation using brackish–reclaimed water at different ratios. There were six treatments, including brackish water irrigation (T1); mixed irrigation using brackish–reclaimed water at 1:1 (T2), 1:2 (T3), and reclaimed water irrigation (T4); pots with plants irrigated with freshwater (CK2); and pots without plants irrigated with freshwater (CK1) as the control. The salinity of the brackish water was 3 g L-1 (6.1 dS m-1). The results indicated that compared to T1, with the increase in the proportion of reclaimed water in the mixture, the water and salt contents in the soil gradually decreased significantly; the K+, Ca2+, and SO42– contents demonstrated an increasing trend; the Na+, Cl–, HCO3–, and Mg2+ contents showed a descending to ascending trend; and the soil water drop penetration time decreased first and then increased slightly. At the same time, the soil organic matter displayed an opposite trend, and the chlorophyll content of leaves and crop biomass both changed with an “N”-style curve. Differences existed in the responses of soil enzyme activities to different mixed water mixtures. There was a slight decrease in the enzyme activity, except for sucrase under T2 and T3. The Integrated Biological Response Version 2 (IBRv2) scored 3.97 in T2. Therefore, considering the characteristics of the soil and crop and the limits of reclaimed water, reclaimed water could be used as an alternative source of freshwater to mix with brackish water, and the suitable mixed proportion should be 1:1 based on IBRv2. Keywords: Brackish water, IBRv2, Reclaimed water, Repellency.

Application of GIS in Rainwater Harvesting Research: A Scoping Review

The spatial and temporal variability of quantity and quality of water are important aspects of water resources management. Water demand has been increasing across the globe, but the fresh water supply is limited. Rainwater harvesting (RWH) systems are increasingly being embraced as an alternative freshwater source. This study reviews the dynamics of global research on RWH that utilises geographic information systems (GIS). It is found that the interest and use of RWH utilising GIS have increased over the recent years. However, the full potential of GIS in large scale RWH is yet to be untapped. We make recommendations for future research on RWH based on GIS. This includes new software and model development that links RWH with GIS to plan and design large scale RWH and automated building footprint extraction for estimating RWH potential. GIS can play a bigger role in achieving Sustainable Development Goals (SDGs) by incorporating GIS with RWH since GIS can handle large spatial data efficiently, which can help in locating areas that are suitable for rainwater harvesting.

Production of concrete using reclaimed water from a ready-mix concrete batching plant: Life cycle assessment (LCA), mechanical and durability properties

This study investigates novel methods and more sustainable techniques that have been developed to minimize the environmental damage of concrete production. The use of reclaimed water and supplementary cementitious materials in concrete can be a solution to the problems of water scarcity and excessive CO2 emissions. In this context LCA, mechanical and durability properties of concrete containing silica fume as a supplementary cementitious material (SCM) and reclaimed water as an alternative source of fresh water are studied. First several properties of concrete such as consistency, compressive strength, electrical resistance, chloride ion penetration and water penetration under pressure were measured. Then, the LCA of concrete using LCA web tool was evaluated and the global warming potential (GWP) emission rates along with air pollutants such as lead, volatile organic compounds, CO, NOX, PM10 and SO2 were determined. The results show that adding a certain level of silica fume is desirable in terms of environmental issues, cost and mechanical and durability properties of concrete. In concrete containing 5, 8 and 11% of silica fume, GWP emissions decreased by 4.9, 8 and 11.2%, respectively. On the other hand, the production of lead, volatile organic compounds (VOCs), CO, NOX and PM10 decreased by 2–12%, while SO2 production increased by 4–10%. According to the obtained results, the manufacture of concrete with the mixing ratios presented in this research in a large-scale ready-mix concrete batching plant that produces 576 tonnes concrete per year (240,000 m3/year) will lead to a reduction of GWP about 3900–8700 tonnes CO2-eq per year.

Treated Wastewater Irrigation—A Review

As the most important resource for life, water has been a central issue on the international agenda for several decades. Yet, the world’s supply of clean freshwater is steadily decreasing due to extensive agricultural demand for irrigated lands. Therefore, water resources should be used with greater efficiency, and the use of non-traditional water resources, such as Treated Wastewater (TW), should be increased. Reusing TW could be an alternative option to increase water resources. Thus, many countries have decided to turn wastewater into an irrigation resource to help meet urban demand and address water shortages. However, because of the nature of that water, there are potential problems associated with its use in irrigation. Some of the major concerns are health hazards, salinity build-up, and toxicity hazards. The objectives of this comprehensive literature review are to illuminate the importance of using TW in irrigation as an alternative freshwater source and to assess the effects of its use on soil fertility and other soil properties, plants, and public health. The literature review reveals that TW reuse has become part of the extension program for boosting water resource utilization. However, the uncontrolled application of such waters has many unfavorable effects on both soils and plants, especially in the long-term. To reduce these unfavorable effects when using TW in irrigation, proper guidelines for wastewater reuse and management should be followed to limit negative effects significantly.

Assessment of a pilot solar V-trough reactor for solar water disinfection

Rural and isolated communities of low-income countries suffer the lack of access to safe drinking water. Harvested rainwater (HRW) is becoming an alternative source of freshwater in many areas of the world. Nevertheless, its quality usually doesn’t meet drinking water standards, posing a health risk for human consumption. Solar water disinfection – SODIS – is a low-cost household intervention used to disinfect water. In this work, we investigate a new solar photoreactor based on V-trough mirrors as alternative to the most used Compound Parabolic Collector (CPC) geometry at pilot scale (54 and 32 L per batch), with the aim of reducing costs and reactor surface’s footprint. An experimental assessment of two key parameters as water recirculation and mirror geometry was carried out. For this study several water-pathogens commonly found in HRW were used, Escherichia coli, Enterococcus faecalis, Salmonella enteritidis and Pseudomonas aeruginosa. Best results were obtained with the V-trough reactor in static condition, where>5-LRV (log-reduction value) for all bacteria tested were reached with a solar-UVA dose of 254 kJ m−2 (90 min). At this operational condition, a total volume of 162 L (3 batches) of water were treated in one full sunny day in Spain (300 min of effective treatment time). A comparison between CPC and V-trough mirrors resulted in similar disinfection efficiencies even if the actinometric results showed that CPC collects 1.58 times more photon flux than the V-trough in the solar-UVA region. These results show the great performance of the V-trough mirror for this application, which is cheaper to produce than CPC and permits treating higher amounts (66% more) of water for the same collector area and same treatment time.

Wastewater Reclamation in Major Jordanian Industries: A Viable Component of a Circular Economy

Water scarcity remains the major looming challenge that is facing Jordan. Wastewater reclamation is considered as an alternative source of fresh water in semi-arid areas with water shortage or increased consumption. In the present study, the current status of wastewater reclamation and reuse in Jordan was analyzed considering 30 wastewater treatment plants (WWTPs). The assessment was based on the WWWTPs’ treatment processes in Jordan, the flowrates scale, and the effluents’ average total dissolved solid (TDS) contents. Accordingly, 60% of the WWTPs in Jordan used activated sludge as a treatment technology; 30 WWTPs were small scale (<1 × 104 m3/day); and a total of 17.932 million m3 treated wastewater had low TDS (<1000 ppm) that generally can be used in industries with relatively minimal cost of treatment. Moreover, the analysis classified the 26 million m3 groundwater abstraction by major industries in Jordanian governorates. The results showed that the reclaimed wastewater can fully offset the industrial demand of fresh water in Amman, Zarqa, and Aqaba governorates. Hence, the environmental assessment showed positive impacts of reclaimed wastewater reuse scenario in terms of water depletion (saving of 72.55 million m3 groundwater per year) and climate change (17.683 million kg CO2Eq reduction). The energy recovery assessment in the small- and medium-scale WWTPs (<10 × 104 m3/day) revealed that generation of electricity by anaerobic sludge digestion equates potentially to an offset of 0.11–0.53 kWh/m3. Finally, several barriers and prospects were put forth to help the stakeholders when considering entering into an agreement to supply and/or reuse reclaimed water.

Impacts of saline water stress on livestock production: A review

Limited freshwater resources and climatic change are major challenge face animal production industry, especially in the arid and semiarid regions. Climate changes are reflected in global warming and rainfall reduction, which in turn may increase the salinity of both soil and water. Within the reclamation strategy, groundwater will be the main source of used water in cultivated desert lands in Egypt. However, the groundwater has high salinity and the cost of desalination is expensive. This review gives an overview of the impact of using saline water as an alternative source of fresh water to avoid water scarcity effect on the performance, carcass traits, and meat quality of farm animals. The ability of animals to tolerate saline water depends on the animal species, salinity level and the type of salt minerals in water. Some studies indicated that the animals' performance improved in low levels of salinity, but the performance decreased when the salinity levels was increased. In conclusion, this study implies that the saline water containing high concentrations of minerals mainly sodium chloride can largely affect the livestock productive aspects.

Groundwater as a social-ecological system: A framework for managing groundwater in Pacific Small Island Developing States

Groundwater in Pacific Small Island Developing States is a critical source of freshwater for island ecosystems and human communities. Groundwater systems face challenges from growing populations, climate change and climate variability. Many groundwater systems in the region have been inappropriately managed, with increasing occurrences of groundwater pollution and saltwater intrusion. This limits the availability of freshwater, increases the likelihood of contracting water borne diseases, and the cost of access to alternative freshwater sources. In this paper, we argue that groundwater systems are social-ecological systems, where anthropogenic activities and groundwater conditions are linked through dynamic, non-linear processes. We also argue that groundwater management failures in the region, are associated with traditional command and control approaches to management, which ignore the systemic nature of coupled social and ecological groundwater systems; and assumes that groundwater resources, and the dependant human communities can be managed independently. Recognising the linkages and feedbacks between groundwater and dependant social communities is important for the long-term sustainability of groundwater in these regions. Conceptual frameworks are useful tools to order phenomena and material, revealing patterns and processes, and enabling the joining of multiple areas of understanding into a single conceptual-empirical structure. We propose a framework to manage groundwater as a social-ecological system. The framework is comprised of three building blocks: complex adaptive systems, resilience thinking and strategic adaptive management. We discuss how the application of the framework in the Republic of Nauru may alter decades of groundwater mismanagement and steer the resource towards a sustainable path.

Drinking seawater: Investigations into desalination

Water is essential to living organisms, yet only 0.02% of this natural resource is accessible as a direct source of fresh- and drinking water. South Africa, being a coastal country, is an ideal candidate for the use of treated sea water as an alternative source of fresh water. Desalination is the process in which dissolved salts are removed from saline water, forming fresh water. However, desalination processes are costly and are often energy and water intensive. This project considers the economic feasibility, environmental feasibility and viability of a differed distillation column that can be used as a desalination unit. A laboratory-scale distillation column was modified to provide energy to the unit with the purpose of decreasing the cost, time and energy requirements of the desalination (distillation) process. Current technologies such as Reverse Osmosis and Multi staged flash distillation are costly, time and energy intensive. In this work, the proposed desalination unit is a findenser in place of the traditional Liebig condenser to provide an environmentally friendly and cost effective alternative. It is also compact and portable which makes it favorable for domestic use. The small scale experiments performed using the Liebig condenser showed an average water recovery of 1.38 x 10-3 L/min and the scaled-up experiments show an average water recovery of 3.53 x 10-3 L/min, which resulted in an efficiency of 91% and 93%. Removal of salt water using the lab scale distillation unit requires 2 hours and 13 minutes to distil 500 mL. The salt solution reaches a maximum temperature of 105°C. The findenser is the more favourable cooling method due to its portability and conservation of water. Our results further show that the maximum capacity of this lab-scale unit is 3 liters of fresh water per day, over a 12 hour operational period.

The Use of Desalination Technologies to Alleviate Water Shortages in Sub-Saharan Africa (SSA): Challenges and Recommendations

<p><em>Water scarcity is a major and growing problem in SSA. A SSA country (South Africa) has adopted desalination as a strategy for dealing with water shortages; while the construction of new desalination plants have been proposed in some others (Ghana, Namibia and Cape Verde). </em><em>This review paper </em><em>examines the use of desalination technologies for augmenting supplies in sixteen SSA countries, using data derived mainly from published literature. Results reveal that the usage of desalinated freshwater to augment supplies in the region is relatively recent; however the usage is on the increase, especially in countries with arid climate. Several factors including massive failures of </em><em>public water supply systems, increases in the demand for freshwater, rapid and high rates of urbanization, population growth and the reoccurring droughts</em><em> account for increases in the demand for desalination technologies in SSA.</em><em> </em><em>Many critical issues and constraints make the desalination option</em><em> neither the most feasible nor a priority for</em><em> water supplies within the humid parts of SSA. </em><em>The paper recommends that for quality and sustainable service delivery to be attained in the region</em><em>, governments should develop alternative freshwater sources,</em><em> address infrastructural decay, employ new management strategies in the water sector and distribute water infrastructure equitably. </em><em></em></p>

Modelling saltwater intrusion processes and development of a multi-objective strategy for management of coastal aquifers utilizing planned artificial freshwater recharge

The need for freshwater is emerging as the utmost critical resource issue facing humanity. In several arid and semi-arid parts of the world, groundwater resources are being used as an alternative source of freshwater. Excessive and/or unplanned groundwater withdrawals have a negative impact on the aquifer. Groundwater withdrawn from coastal aquifers are susceptible to contamination by saltwater intrusion. This study investigates the efficiency and viability of using artificial freshwater recharge (AFR) to increase fresh groundwater pumping from production wells for beneficial use. A three dimensional (3D), transient, density dependent, finite element based flow and transport model of an illustrative coastal aquifer is implemented using FEMWATER code. First, the effect of AFR on inland encroachment of saline water is quantified for existing scenarios. Specifically, groundwater head and salinity concentration differences at monitoring locations before and after artificial recharge is presented. Second, a multi-objective management model incorporating groundwater pumping and AFR is implemented to control groundwater salinization in an illustrative coastal aquifer system. To avoid computational burden and ensure computational feasibility, the numerical flow and transport simulation model is substituted by the new support vector regression (SVR) predictive models as approximate simulators in the simulation–optimization framework for developing optimal management strategies. The performance evaluation results indicated that the SVR models were adequately trained and were capable of approximating saltwater intrusion processes in the aquifer. Multi-objective genetic algorithm (MOGA) is used to solve the multi-objective optimization problem. The Pareto-optimal front obtained as solution from the SVR–MOGA optimization model presented a set of optimal solutions needed for the sustainable management of the coastal aquifer. The pumping strategies obtained as Pareto optimal solutions with and without freshwater recharge wells showed that saltwater intrusion is sensitive to the AFR. Also, the hydraulic head lenses created by AFR can be used as one practical option to control saltwater intrusion in coastal aquifers. The developed 3D saltwater intrusion model, predictive capability of the developed SVR models and the feasibility of using the proposed linked multi-objective SVR–MOGA optimization model makes the proposed methodology potentially attractive in solving large scale regional saltwater intrusion management problems.