Non-conventional Water Sources Research Articles

Wind-Powered Desalination on Islands: A Review of Energy–Water Pathways

Water scarcity is a global problem that particularly affects islands located in arid regions or regions with limited water resources. This issue has prompted the development of non-conventional water sources such as fossil fuel-powered desalination systems. Concern about the high energy and environmental costs associated with this type of facility has created the ideal framework for the proliferation of desalination projects powered by renewable energies, especially wind energy due to the multiple advantages it offers. This article provides a bibliometric analysis to identify the advances made in wind-powered desalination on islands. While many studies explore wind-powered desalination, none compile references specific to islands. This paper analyses islands’ desalination needs and showcases wind-powered systems, exploring their types and uses. Firstly, the most relevant international scientific journals are identified to allow the subsequent selection and quantitative and qualitative analysis of articles directly dealing with wind-powered desalination systems. A total of 2344 articles obtained from the Scopus database were analyzed, of which 144 including 181 case studies were selected. Among the results of this study, an increasing year-on-year trend is observed in the number of published studies tackling wind-powered desalination. Finally, this paper presents a series of maps showing the most relevant facilities, projects, and data in this field, and provides an overview of the lessons learned in the decarbonization of desalination.

The Performance and Feasibility of Solar-Powered Desalination for Brackish Groundwater in Egypt

With a deficit of about 20 BCM in 2022, Egypt faces a severe water shortage due to rapid population growth (109.3 million in 2022). Egypt launched a program to utilize non-conventional water sources, like treated wastewater, agriculture drainage water, and desalination. Egypt is expanding its non-conventional water resources, boosting desalination capacity from 86,000 m3/day in 2015 to 680,000 m3/day in 2022, with plans to reach 1,250,000 m3/day by 2025. Despite the improvements in desalination technologies and cost, its high energy use and environmental impacts are still limiting its use. Egypt’s desalination relies on grid electricity, but renewable energy is crucial for remote areas where no electricity grid exists. Scaling up renewable energy in desalination faces challenges like land availability and high costs. GIS was used for optimal site selection for a brackish groundwater solar desalination plant in the Western North Nile Delta. Factors like solar radiation, groundwater quality, aquifer potentiality, geology, and seawater intrusion were carefully assessed. An evaluation of a sustainable 1000 m3/day solar-powered RO desalination pilot plant’s economic and technical viability is provided, along with its performance assessment. Limitations, challenges, and potential improvements are discussed. The study finds that RO–PV desalination for brackish groundwater is technically mature, with competitive Capex costs (USD 760-USD 850/m3) and low Opex (USD 0.55–USD 0.63/m3). Solar desalination for brackish groundwater with salinity less than 23,000 ppm can reduce energy consumption to 3.6–4.2 kWhr/m3. Water storage and hybrid systems with solar and conventional energy are suggested to enhance efficiency. This implies a growing market for small- to medium-scale RO solar-powered desalination in remote areas in the near future.

Wastewater irrigation and Trichoderma colonization in tomato plants: effects on plant traits, antioxidant activity, and performance of the insect pest Macrosiphum euphorbiae

The scarcity of freshwater for agriculture in many regions has led to the application of sewage and saline water for irrigation. Irrigation with non-conventional water sources could become a non-harmful process for plant cultivation, and the effects of their use on crops should be monitored in order to develop optimal management strategies. One possibility to overcome potential barriers is to use biostimulants such as Trichoderma spp. fungi. Tomato is a crop of great economic importance in the world. This study investigated the joint effects of Trichoderma afroharzianum T-22 on tomato plants irrigated with simulated unconventional waters. The experiment consisted of a control and three water treatments. In the control, the plants were watered with distilled water. The three water treatments were obtained by using an irrigation water added with nitrogen, a wastewater effluent, and a mixed groundwater-wastewater effluents. Potted tomato plants (variety Bobcat) were grown in a controlled growth chamber. Antioxidant activity, susceptibility to the aphids Macrosiphum euphorbiae, and tomato plant growth parameters were estimated. Trichoderma afroharzianum T-22 had a positive effect on plant growth and antioxidant defenses when plants were irrigated with distilled water. Instead, no significant morphological effects induced by T. afroharzianum T-22 on plants were observed when unconventional water was used for irrigation. However, inoculation with T. afroharzianum T-22 activated a stress response that made the colonized plants more susceptible to aphid development and increased their fecundity and longevity. Thanks to this study, it may be possible for the first time to open a new discussion on the practical possibility of using reclaimed wastewater for crop irrigation with the addition of a growth-promoting fungal symbiont.

FLOT-ART: An integrated plant optimization tool for the flotation of copper and copper–gold ores

Conventional flotation plant optimization procedures for copper and copper–gold ores have served the industry well over decades. But with the present trend in declining ore grades along with increase in metallurgical complexity, many flotation operations are experiencing significant challenges in sustaining design or operational budgeted recovery and concentrate quality targets. The need to use non-conventional water sources like brackish, sea water, and recycled process water has exacerbated the problem. Also with the emergence of various large mechanical cells and new non-mechanical flotation technologies, the ongoing use of traditional plant operational strategies is further adding to the challenges.This paper discusses an integrated plant optimization tool for the flotation of complex copper and copper–gold ores in addressing the present challenges, branded as FLOT-ART (Flotation Advanced Recovery Technology). This includes a cohesive flotation plant optimization approach starting with a mineral surface preparation step in grinding followed by advanced mineral-specific electrochemistry and cell hydrodynamics based circuit operation. This approach then allows an ore-specific grade-recovery control strategy for optimum flotation performance. This development is based on extensive greenfield projects, brownfield plant expansion studies along with operational optimization programs involving bench and plant campaigns. Principles of the FLOT-ART optimization system will be presented in this paper along with some commercial applications in the flotation of copper and copper–gold ores.

Research on water supply model, technology, and management mechanism for villages in China

China's village drinking water has poor protection of water sources, water purification technology and equipment, water supply pipeline network leakage rate, the high risk of secondary pollution, operation and management mechanism, and other issues. How to enhance China's village drinking water through the whole process of the amount of water and the ability to ensure water quality has become the current problem to be resolved urgently. The study summarizes China's village water supply model selection, conventional and non-conventional water sources of water supply key technologies and applications, as well as long-term management measures, and through the application of China's northwestern Gansu's Huanxian and southeastern Zhejiang's Shangyu District, summarizes the success of the experience of the different regional characteristics, and strengthens the leading demonstration. Relevant countermeasures and suggestions are put forward to realize the long-term operation of rural safe drinking water projects.

Optimizing bilinear multi-source water supply systems using mixed-integer linear programming approximations: An analysis of the Israeli seawater desalination array

Decision support systems (DSSs) in water resources management often use optimization models to make decisions. Therefore, the quality of these models is crucial for the success of DSSs. However, optimization models can struggle with reaching global optima, resulting in inconsistent and untrustworthy results for decision-makers. Additionally, current solution methods can be slow and inefficient, hindering real-time interaction with the DSS. This study addresses the optimal regional Multisource Water Supply Systems (MWSS) management using efficient global optimization techniques. The MWSS problem is formulated as a nonlinear optimization program due to using bilinear terms, which can result in multiple local optima. To overcome this challenge, four Mixed Integer Linear Program (MILP) formulations are proposed, which can be globally solved in a computationally effective manner using readily available MILP solvers. Our proposed formulations are tested on the Israeli Water Supply System (IWSS), which presents a unique challenge due to the inclusion of the seawater desalination array. In addition, this system must balance conventional and non-conventional water sources with varying qualities and characteristics. The results show that the proposed formulations provide a computationally efficient solution for the IWSS problem, allowing for the optimal utilization of different water sources in the IWSS.

Proposing a Wetland-Based Economic Approach for Wastewater Treatment in Arid Regions as an Alternative Irrigation Water Source

Point and nonpoint wastewater sources have a detrimental, negative effect on agriculture, soil, surface, and groundwater supplies. In this research, a wastewater treatment system made up of a sedimentation tank, a horizontal subsurface flow constructed wetland (HSSF-CW), a vertical subsurface flow constructed wetland (VF-CW), and a storage tank was proposed, designed, and cost estimated. Small populations in underdeveloped nations with dry and semi-arid climates can use the treatment system as an affordable construction, maintenance, and operational solution for wastewater treatment. The system will protect agricultural lands and groundwater from pollution. The system can service 6000 capita and has a wastewater discharge of 780 m3/d in the developing arid region in El-Moghra Oasis western desert of Egypt, where the 1.5 million acres used for the land reclamation project based on groundwater irrigation. The relaxed tanks in a series model based on the areal loading rates and background pollutants concentrations (P-K-C*) was utilized to size the HSSF and VF-CWs. The results indicated that the HSSF-CW design treatment surface area was 2375 m2, and the hydraulic surface loading (q) and hydraulic retention time (RT) were 0.33 m/d and 0.55 d, respectively, and utilizing Phragmites australis and Papyrus for the biological treatment. The expected overall cumulative removal efficiencies were 96.7, 70, and 100% for the biological oxygen demand (BOD), total phosphors (TP), and fecal coliforms (FC), respectively. The VF-CW indicates that there was a 2193 m2 design treatment surface area, q = 0.36 m/d, and RT of 0.63 d. The expected BOD, TP, and FC removal efficiencies were 75, 33.3, and 92.7%, respectively. In order to simplify the design stages and the cost estimation, design and investment cost curves were established for a population range from 500 to 9000. The total monthly water loss due to evapotranspiration for the HSSF and VF-CWs indicates a range from 3.7 to 8.5%, respectively. The total investment cost analysis for the proposed system corresponding to 780 m3/d wastewater discharge of indicates a total investment cost of EUR 146,804 and EUR 24.46/per-capita equivalent (P.E). This approach can be used by decision makers in the Mediterranean region and Middle Eastern countries to improve the water quality using social and economic criteria, leading to the effective implementation of ecological restoration projects as a low-cost treatment system and adding a nonconventional water source that can be used in irrigation.

Use of Wild Rice (Zizania palustris L.) in Paddy-Scale Bioassays for Assessing Potential Use of Mining-Influenced Water for Irrigation.

The online version contains supplementary material available at 10.1007/s10230-022-00908-0.

Fluidized–bed homogeneous granulation for potassium and phosphorus recovery: K-struvite release kinetics and economic analysis

BackgroundThe last few decades have seen the critical role of global cattle industry in agricultural development. However, while giving prosperity and significant benefits to the countryside, the industry also produces wastewater streams, that cause eutrophication in water bodies. The streams, if treated effectively, could act as a valuable nonconventional water source to help address the global freshwater crisis. Moreover, resources recovered from these wastewater streams, e.g., potassium (K) and phosphorus (P), could be converted to valuable commodities such as fertilizers. We, therefore, propose to use a continuous K–struvite granulation process as an effective method for the treatment of swine wastewater (SW) and recovery of K–struvite. Results show that the P and K were efficiently removed and that wastewater-derived K–struvite is a promising green chemistry agent for a slow–release, reinforcing a promising pathway to global P and K conservation. MethodsThe fluidized-bed homogeneous granulation (FBHG) has recently emerged as an advanced metal recovery technology with high efficiencies for several metals and low moisture products. Based on the principle of chemical precipitation, FBHG technology requires less chemicals while producing insignificant amounts of sludge, thereby alleviating burden on sludge management often encountered in conventional chemical precipitation and others. Significant findingsHerein, we investigate the potential use of FBHG technology for simultaneous recovering K and P while treating swine wastewater. The recovered products are in the form of K–struvite pellets having a studded quasi-spherical form with a rough surface and sharp spikes that resemble sea urchins. The pellets are almost free of heavy metals, which make them promising candidates for use as fertilizer without significant harm. We observed that the release of K was faster than that of P. The formation, size, morphology, purity, and crushing strength of the pellets greatly affected the up-flow velocity value condition. The FBHG could potentially be scaled up for more extensive nutrient recovery.

Nitrate removal in saline water by photo-reduction using natural FeTiO3 as catalyst

As climate change progresses, there is an increasing interest on the use of non-conventional water sources such as brackish or saline waters. Nowadays, the main threat in Europe detected in these waterbodies is nitrate contamination. Within the multiple available methods studied for nitrate reduction, photocatalysis presents promising results, but this technology has not yet been tested in saline water. This work tackles the elimination of nitrate ([NO3−] =50 mg/L) in brackish and saline water ([sea salt] = 5–33 g/L) using ilmenite as photocatalyst and oxalic acid as an environmental-friendly reducing agent. The main challenge when working in saline water is to overcome oxalic acid scavenging by Ca2+ present in the water matrix. This can be solved either working at over stoichiometric concentrations of oxalic acid (≈300% stoich. dose) or acidifying the reaction media. The addition of hydrochloric acid ensures the protonation of oxalic acid, reducing drastically its precipitation as CaC2O4. Working at [C2O42−] = 180 mg/L, [FeTiO3] = 450 mg/L and [HCl 37%] = 13 mM, 73% total nitrogen (TN) elimination was reached after 420 min. Reaction temperature was also evaluated in the range of 20–80 °C, which allowed to calculate the Ea=9.8 kJ/mol. Finally, the effect of dissolved O2 on the TN reduction was assessed. Overall, photocatalytic nitrate reduction presents itself as a feasible technology regardless of the water salinity.

Soil Salinity Prediction Using Remotely Piloted Aircraft Systems under Semi-Arid Environments Irrigated with Salty Non-Conventional Water Resources

The effects of climate change on food security have been unfavorable, particularly in the area of Murcia where there is a water shortage. To satisfy crop needs, farmers combine several irrigation water sources, such as brackish groundwater, desalinated water, reclaimed water, and desalinated water. Good agricultural and irrigation practices are essential for preventing soil salinization and production losses, and remote sensing might be used to evaluate these practices. This research, performed in an experimental field under greenhouse conditions and in an open-air commercial lettuce field irrigated with non-conventional water sources, determined that the Salinity Index (SI) applied to bare soil is a useful spectral index, providing an R2 range of 0.40 to 0.83. The other metric used to the bare soil, the Normalized Difference Salinity Index (NDSI), exhibited poor correlations, with R2 values as high as 0.49. Moreover, the thermal camera did not operate well within the greenhouse, but it performed in the commercial plot, where the canopy temperature was linearly correlated, with an R2 value of 0.50. The second analyzed vegetative metric, the Normalized Difference Plants Index (NDVI), was exclusively applied to the vegetation and showed minimal relationships with the soil salinity. In the visual evaluation of the maps, the temperature patterns of the canopy were strikingly comparable to the electrical conductivity of the soil, which was not the case for the other analyzed indices. The use of non-conventional moderately saline irrigation water sources negatively impacts the lettuce development by decreasing the fresh head weight and increasing the sodium and chloride leaf concentrations.

Constructed Wetland for Sustainable and Low-Cost Wastewater Treatment: Review Article

There is a growing need for more sustainable wastewater treatment technologies to provide non-conventional water sources. Constructed Wetland systems (CW) are viewed as a low-cost treatment technology with proven treatment efficiency. CWS can treat a variety of contaminants using low energy and natural systems by altering various design parameters. There are two configuration types of constructed wetlands: vertical (VF) and horizontal flow CW (HF). Both configurations have been widely adopted in both large and pilot scale studies with proven records of reasonable wastewater treatment efficiency. The current article reviews the recent development of CW technology and highlights the main achievements and successful applications for wastewater treatment at various locations. The review has indicated that a considerable removal efficiency is attained while using engineered CW systems with variable treatment rates for various pollutants. The treatment efficiency is a function of various parameters including wastewater type, scale dimensions, applied plant and the retention time. The review compared the treatment efficiency for both VF and HF and has revealed that various removal rates of BOD, COD, TSS, TN, TP and NH₄ was attained using both configurations. Yet, the removal efficiency in the case of VF was slightly higher compared with the HF with an average treatment level of 77% and 68% was achieved in both systems, respectively. The review revealed that the CW is an effective and sustainable technology for wastewater treatment with the initial influent level, microbial biofilm, detention time, plant species and configuration among the most dominating parameters that are directly controlling the removal rates.

An IUWM incorporated model to improve water supply reliability in intermittent and no service areas

Water supply reliability is an increasingly important aspect of water system design, especially in regions with unreliable water supply. Most water systems initially designed as continuous supply systems are affected by constraints such as limited freshwater supply, infrastructure inadequacy and insufficient expansion, poor operations and management, contributing to Intermittent Water Supply (IWS) or no services in some regions. IWS is a common condition in developing countries like India. Many approaches have been developed to address water availability and quality challenges, including Integrated Urban Water Management (IUWM). The main principle of IUWM is to incorporate non-conventional water supply sources, such as stormwater, rooftop rainwater and recycled wastewater, to augment water supply and provide fit-for-purpose water. However, in developing countries, IUWM principles have not been sufficiently investigated to understand how they can improve water supply reliability in regions with IWS or no centralized water supply. In this study, an IUWM incorporated model was developed to understand how supply reliability can be improved in areas with IWS or no services, with Bangalore city in India, as a case study. Five different supply configurations to incorporate IUWM principles were analyzed and compared to identify the most efficient way to incorporate non-conventional water sources. The analysis identifies potential supply issues in the area under the current centralized water supply. The results show that the traditional water supply system can not meet the minimum water demand. The reliability can be improved from <50% to 100% with the incorporation of non-conventional water sources.

Circular economy and payment for ecosystem services: A framework proposal based on water reuse

Water scarcity forces the use of non-conventional water sources, to satisfy water demand, such as the effluent of wastewater treatment plants (WWTPs). Water reuse helps to close the urban water cycle and reduce pressure on available water resources, providing a bases for circular economy in the water sector. Under an ecosystem services (ES) point of view, if water reuse is considered the best management option in water scarcity areas, WWTPs are responsible for the ES of provisioning. One of the main requirements for the ES of provisioning is to guarantee the reclaimed water quality due to this water being discharged back into the ecosystem. Hence why removing pollutants, such as pharmaceutical and personal care products (PPCPs), is necessary to reduce the environmental impact of reused water. Considering the lack of legislation about PPCPs in effluents, this study proposes the use of the Payment for Ecosystem Services (PES) approach as an innovative solution to provide reclaimed water without PPCPs considering both the environmental and institutional context and the importance of WWTPs as non-conventional water sources. This study contributes to consider the PES as a water cycle management tool and its suitability to be used to remove PPCPs is highlighted, with the purpose of promoting water reuse in water scarcity areas under circular economy approach.

Municipal Wastewater Reuse: Is it a Competitive Alternative to Seawater Desalination?

Water scarcity is becoming a global challenge to attempts to narrow the water demand–supply gap. To overcome this problem, it is sensible to consider alternative technologies that can exploit non-conventional water resources. The choice of such technologies should be, however, carefully analyzed, because any choice might be unfeasible from an economic point of view. In this work, a methodology to select the most appropriate non-conventional water resource, out of municipal wastewater and seawater, was proposed. Specifically, we attempted to determine which alternative provides cheaper water supply and production costs for domestic uses, depending on the wastewater treatment system used and the water plant capacity. The production of water under three scenarios was analyzed: (i) a city that has a conventional wastewater treatment plant (WWTP); (ii) a city that uses primary treatment and submarine outfalls to treat municipal wastewater; (iii) seawater desalination. The proposed methodology was tested in Chilean cities that are located in areas where water is a scarce resource. The results showed that the reuse of municipal wastewater represents a cost-competitive alternative to seawater desalination, mainly when municipal wastewater is treated in a conventional WWTP and when water flow demand is higher than 1500 m3/d. In contrast, seawater desalination becomes more profitable than wastewater reuse when the treatment of municipal wastewater is based on the use of submarine outfalls. This study provides a useful economic tool for promoting municipal wastewater reuse as a non-conventional water source for supplying water to cities that suffer from water scarcity in Chile and in similar areas of the world.

A Novel Idea for Improving the Efficiency of Green Walls in Urban Environment (an Innovative Design and Technique)

The advantages of low-impact development approaches, such as green walls in an urban environment, are numerous. These systems can be applied for managing stormwater, saving energy consumption, decreasing noise pollution, improving runoff quality, improving life quality, and so forth. Besides, atmospheric water harvesting methods are considered a nonconventional water source. There are many studies about the analysis and advantages of green walls and atmospheric water harvesting conducted separately. However, the use of a combined system that uses fog harvesting in the irrigation of green walls has received less attention in previous studies, and therefore in this research, the feasibility of a novel green wall platform was investigated. At first, the potential of using green walls and atmospheric water harvesting in different climates was analyzed. Then a new combined system was proposed and explained. The study results determined that atmospheric water harvesting can be applied as a source of irrigation for green facilities, particularly in the dry season and in periods with lower precipitation. In the Mediterranean climate, summer fog harvesting yields 1.4–4.6 L/m2/day, and the water consumption of green walls is about 4–8 L/day/m2. This can improve one issue of green walls in an urban environment, which is irrigation in summer. Furthermore, the novel system would protect plants from severe conditions, improve buildings’ thermal behavior by decreasing direct sunlight, and increase conventional green walls’ efficiency and advantages.

A Low-Impact Development–Based Multi-Objective Optimization Model for Regional Water Resource Management under Impacts of Climate Change

Under the urgency of rational water resource allocation and effective urban flooding control, a multi-objective interval birandom chance-constrained programming (MIBCCP) model is developed for supporting regional water resource management under multiple uncertainties and climate change in this study. Two objectives were included in this model, which are the minimization of total system costs and the maximization of total pollutant-treatment amounts, respectively. The major advantage of proposed MIBCCP model is that it realized the effective combined utilization of conventional and nonconventional water sources under complexities and uncertainties through incorporating compromise programming (CP), birandom chance-constrained programming (BCCP) and interval linear programming (ILP) within a general framework. This way effectively overcome water-shortage issue and reduced urban flood frequency under climate change. A water supply management system of the educational park in Tianjin was used as a study case for demonstration. A variety of adaptive water allocation alternatives and construction schemes for LID projects under RCP4.5 and RCP8.5 (representative concentration pathway 4.5 and 8.5) scenarios were obtained to deal with possible changes arising from increasing rainfall and runoff in the future. It is concluded that proposed MIBCCP model provided the effective linkage between the utilization of nonconventional water resources and urban flood prevention, and offered insights into the tradeoff between economic benefits and environmental protection.

Evaluation of ozone-based oxidation and solar advanced oxidation treatment of greywater

Reclaiming non-conventional water sources such as greywater is gaining more attention in the light of current and expected water shortage due to the global trend of continued population growth, urbanization, and the impact of climate change. In this work, the degradation of organic matter measured as total organic carbon (TOC) and biochemical oxygen demand (BOD5) in real greywater samples using different ozone-based oxidation and solar advanced oxidation treatments was investigated in a custom-built glass tube reactor combined with a concentrated parabolic collector (CPC). The evaluated processes included ozonation (O3), solar ozonation (O3/solar irradiation), hydrogen peroxide oxidation (H2O2), hydrogen peroxide under solar irradiation (H2O2/solar irradiation), peroxonation (H2O2/O3), and solar peroxonation (H2O2/O3/solar irradiation). Combining different treatment methods with/without exposure to solar irradiation enhanced overall treatment efficiency. The efficiency of the examined processes followed the order: solar peroxonation > solar ozonation > peroxonation > ozonation, while the other processes showed a negligible effect. The highest TOC reduction (58.6 %) was observed using solar peroxonation at 41.7 mg O3/min and 0.2 H2O2/O3 molar ratio; the highest BOD5 reduction (29.4 %) was observed using solar peroxonation at 41.7 mg O3/min and 0.4 H2O2/O3 molar ratio. We conclude that low-cost advanced oxidation technologies can be effective to remove organic materials providing efficient greywater remediation for reuse applications.

Effect of the chloride content of seawater on the copper solvent extraction using Acorga M5774 and LIX 984N extractants

In recent years, the application of non-conventional water sources, such as seawater in metal extraction industries located in arid and semi-arid areas have been increased. In this study, the integration of seawater in the solvent extraction of copper hydrometallurgical operation was investigated. Accordingly, two commercial copper extractants, Acorga M5774 and LIX 984N were used in extraction of copper from a sulfate–chloride solution containing seawater. The results showed a higher concentration of copper in the pregnant leach solution (PLS) as a result of using seawater; however, the concentration of Fe and the impurities that are associated with seawater, i.e., Cl, Na, Mg, Ca, K were also increased. The presence of the chloride ion resulted in a higher copper extraction at pH values below 1.5. Synergistic system of LIX 984 N and Acorga M5774 (1:1 vol mixture 15% v/v) was found more efficient in extraction of copper at pH values below 1.5 in comparison to sole LIX 984 N and Acorga M5774. Similarly, the extraction of impurities (Na, Mg, K, and Cl) were observed less when a mixture of extractants were used. The results showed that increasing the chloride concentration had a negative effect on copper extraction as the organic to aqueous ratio was decreased. The copper extraction mechanism was also studied using single LIX 984N, Acorga M5774, and a 1:1 vol mixture of these two extractants at chloride concentrations of 0 and 40 g/L. Increasing the chloride concentration resulted in the involvement of more organic molecules.

Challenges and Opportunities for Sustainable Management of Water Resources in the Island of Crete, Greece

Crete, located in the South Mediterranean Sea, is characterized by long coastal areas, varied terrain relief and geology, and great spatial and inter-annual variations in precipitation. Under average meteorological conditions, the island is water-sufficient (967 mm precipitation; theoretical water potential 3425.89 hm3; and total water use 610 hm3). Agriculture is by far the greatest user of water (78% of total water use), followed by domestic use (21%). Despite the high average water availability, water scarcity events commonly occur, particularly in the eastern-south part of the island, driven by local climatic conditions and seasonal or geographical mismatches between water availability and demand. Other critical issues in water management include the over-exploitation of groundwater, accounting for 93% of the water used in agriculture; low water use efficiencies in the farms; limited use of non-conventional water sources (effluent reuse); lack of modern frameworks of control and monitoring; and inadequate cooperation among stakeholders. These deficiencies impact adversely water use efficiency, deteriorate quality of water resources, increase competition for water and water pricing, and impair agriculture and environment. Moreover, the water-limited areas may display low adaptation potential to climate variability and face increased risks for the human-managed and natural ecosystems. The development of appropriate water governance frameworks that promote the development of integrated water management plans and allow concurrently flexibility to account for local differentiations in social-economic favors is urgently needed to achieve efficient water management and to improve the adaptation to the changing climatic conditions. Specific corrective actions may include use of alternative water sources (e.g., treated effluent and brackish water), implementation of efficient water use practices, re-formation of pricing policy, efficient control and monitoring, and investment in research and innovation to support the above actions. It is necessary to strengthen the links across stakeholders (e.g., farmers, enterprises, corporations, institutes, universities, agencies, and public authorities), along with an effective and updated governance framework to address the critical issues in water management, facilitate knowledge transfer, and promote the efficient use of non-conventional water resources.