A Review of Water Stress and Water Footprint Accounting

Analysing spatial variability in drought sensitivity of rivers using explainable artificial intelligence

Hydrological drought can have a severe negative impact on aquatic ecosystems and human living standards. Therefore, being able to predict and gain more insights in the spatial variability in drought sensitivity of rivers is of relevance for water managers. The drought sensitivity of a river is in this study represented by four drought metrics, of which three are relative towards the ecological minimal flow. Statistical and machine learning methods were evaluated to predict these metrics for rivers in the Flanders region of Belgium based on catchment characteristics and data on human interferences. XGBoost had the best performance, with an explained variance of 80 % to 90 %. After applying explaining AI on these models, insights were obtained in the spatial variability of the drought metrics. Irrigation is the most important variable, a high percentage of irrigation leads to a higher drought sensitivity. If there are a lot of human interferences, there is a higher drought sensitivity. Many of the observed dependencies can be explained by the differences in soil infiltration capacity and transferability of water for sandy versus clay soils. No clear dependence with the amount of forest or agriculture was observed, implying that the impact of forest and agriculture on the drought sensitivity of a river is complex.

Implementation of the water footprint as a water performance indicator in industrial manufacturing units located in Greece: challenges and prospects

Global water resources are under great pressure, so sustainable water and wastewater management is essential for every industrial unit. The water footprint (WF) is a multidimensional indicator of volumetric water use and pollution and is applied throughout the production cycle from the supply chain to the end user. The state-of-the art method of calculating the direct (operational) WF requires detailed records of water consumption and wastewater production per process, that are usually not available. In order to effectively implement the indicator, modifications to the standard calculation method are usually necessary, to meet the requirements and characteristics of each production unit. The present study focuses in three production units in Greece (i.e., cement, brewery, and natural cosmetics) and analyzes the modifications and assumptions required for the operational WF assessment, calculated for each production process where possible and for the whole unit. The WF assessment performed for the three case studies showed that both water consumption rates and operational WFs are within the lowest values (4.7 hL water/hL beer for brewery case study and 0.155 L/kg cement for cement case study) of the ranges reported in the international literature (4-8.8 hL water/hL beer and 0.14-0.413 L/kg cement). The total operational WF of the brewery after applying mass balances was calculated at 23.8 hL water/hL beer with virtual grey WF contributing at 79.7% and blue WF at 20.3%. For the cement manufacturing unit, using estimations from the plant operators and data from international literature, the total operational WF of the plant was assessed at 0.159 L/kg cement with blue WF contributing at 95.8%, green WF at 1%, and virtual grey WF at 3.2%. For the natural cosmetics unit, after modifying the system boundaries properly, the total operational WF was assessed at 81.6 L/kg bulk with virtual grey WF contributing at 88.8%. Through WF assessment, strategic actions could be identified to reduce water consumption and a benchmark could be provided to assess water performance between companies of the same branch.

Evaluation of the impact of water reclamation on blue and grey water footprint in a municipal wastewater treatment plant

Sustainable water management is one of the research areas that is gaining importance worldwide today. In this work, water footprint assessment was conducted in a wastewater treatment plant before (called as WWTP-C for the year of 2018) and after (called as WWTP-WR for the year of 2021) adding the water reclamation unit, using the method proposed by Water Footprint Network (WFN). Additionally, the impact of water reclamation on blue water footprint (WFblue) and grey water footprint (WFgrey) was investigated from an environmental sustainability point of view. Water footprint of WWTP-C and WWTP-WR was evaluated as 2.2 m3 and 2.3 m3; respectively. While energy consumption and sludge treatment were determined as the major components for WFblue, total nitrogen (TN) and total phosphorus (TP) were the most limiting pollutants for WFgrey. Environmental benefit of water reclamation to reducing the WFgrey was determined as 44 % for the year of 2021. The sensitivity analysis results showed that high variability in the values of maximum allowable concentration of pollutants by national regulations has significantly affect the sustainability of WFgrey.

Water consumption by rinse-off cosmetic products: The case of the shower

OBJECTIVE

This article measures and discusses the effects of different shower gels on the consumption of water used during a shower.

METHODS

A sensory panel was created for quantifying water consumption associated with the use of shower gels. Fifteen French panellists were recruited (age: 59 ± 7, height: 163 cm ± 9 and weight: 68 kg ± 20) and trained to assess rinsed skin in a standardized way. Effective panellists were then asked to assess 25 shower gels covering the variety of existing products on the market.

RESULTS

Results showed that the average volume was 4.77 L for heating the water and wetting the body and 4.15 L for rinsing the shower gel off the full body. We observed a significant shower gel effect (p < 0.0001) with the water volume needed to rinse the 25 shower gels ranging 3.21 L to 5.65 L.

CONCLUSION

This paper demonstrates the impact of shower gel formulation on water consumption during a shower. It thus demonstrates the importance of formulating shower gels to reduce the total amount of water needed to shower. It also introduces the distinction between 'useful water' which refers strictly to the volume of water objectively needed to rinse off a product and the 'used water' which refers to the total shower volume of water. This distinction helps to better strategize actions in order to reduce water consumption from rinse-off cosmetic products used during showers.

Water scarcity in agriculture: An overview of causes, impacts and approaches for reducing the risks

Freshwater is a vital resource for both ecosystem health and human survival, and it is the natural resource that is the most extracted at the global level. Excessive freshwater consumption can be responsible for a scarcity in the circulation rate, which occurs when the freshwater demand exceeds its availability. Hence, water consumption needs to be optimised in all human activities, given the increasing freshwater scarcity due to climate changes and to the annual net increase in the human population of 81,000,000. Freshwater plays many important roles in daily life for example, agriculture is responsible for nearly 70% of that withdrawal volume, and it is therefore, the most water-intensive sector. This puts emphasis upon the urgent need of transitioning towards more sustainable agricultural and food-production/consumption systems. Water Footprint (WF) is increasingly playing a guiding role in that context. Indeed, it makes it possible to quantify water consumption and related environmental consequences. With the objective of contributing to enhancement of research and of supporting practitioners and decision-makers in environmentally sustainable and resilient food production/consumption, the authors of this article addressed the relevant issues connected with: a) physical and economic water scarcity in agriculture, b) practices and tools to reduce water wastage, c) WF assessment methodologies. A number of environmental, economic, and engineering solutions were proposed to mitigate water scarcity. The improvement of irrigation technologies and practices was identified as an important major way to reduce water scarcity. Additionally, solar powered 'reverse-osmosis' is being used in many parts of the world to produce irrigation water from saline water, thereby reducing the need to extract freshwater from underground aquifers. This article confirmed the importance of research on water scarcity; moreover, it can stimulate development and application of solutions that make agricultural production/consumption more efficient and resilient.

Chelating agents supported solar photo-Fenton and sunlight/H2O2 processes for pharmaceuticals removal and resistant pathogens inactivation in quaternary treatment for urban wastewater reuse

In this work, Fe³⁺-iminodisuccinic acid (Fe:IDS) based solar photo Fenton (SPF), an Italian patented method, was investigated in quaternary treatment of real urban wastewater and compared to Fe³⁺-ethylenediamine-N,N'-disuccinic acid (Fe:EDDS) for the first time. Three pharmaceuticals (PCs) (sulfamethoxazole, carbamazepine and trimethoprim) and four pathogens (Escherichia coli, somatic and F-plus coliphages, Clostridium perfringens, consistently with the new EU regulation for wastewater reuse (2020/741)), were chosen as target pollutants. SPF with Fe:EDDS was more effective in PCs removal (80%, 10 kJ L^-1) than the SPF with Fe:IDS (58%), possibly due to the higher capability of generating hydroxyl radicals. On the contrary, Fe:IDS was more effective (4.3 log inactivation for E. coli) than Fe:EDDS (1.9 log) in pathogens inactivation, possibly due to a lower iron precipitation and turbidity which finally promoted an improved intracellular photo-Fenton mechanism. Fe:L based SPF was subsequently coupled to sunlight/H₂O₂. Interestingly, while its combination with Fe:EDDS based SPF slightly increased disinfectant efficacy (2.3 vs 1.9 log inactivation for E. coli), the combination with Fe:IDS decreased inactivation efficiency (3.4 vs 4.3 log reduction). In conclusion, due to the good compromise between PCs removal and disinfection efficiency, Fe:IDS SPF alone is an attractive option for quaternary treatment for urban wastewater reuse.

Water accounting as a tool for tracing the industries responsible for the point-source loads into water bodies

Returning flows of water from the economy to the environment, particularly wastewaters, are highly important contributors to the quality of freshwater resources and the health of aquatic ecosystems. While the total loads of various harmful substances received by wastewater treatment facilities are often measured and reported, the origins of these loads are generally not allocated to specific industries. Instead, they pass from treatment facilities to the environment and are thus simply attributed to arising from the sewerage industry. In this study, we introduce a method for employing high-quality water accounting of the phosphorous and nitrogen loads and apply it to the Finnish economy. We also introduce a means for assessing the quality of the resulting accountancies and, for our Finnish case study, we show a close correspondence between independent top-down and bottom-up calculations, indicating the figures are highly reliable. We thus conclude, firstly, that the presented methodology can produce versatile and reliable data on different wastewater-related loads in the water; secondly, that such data can assist in developing appropriate mitigation strategies; and, thirdly, that the data may also be applied in further sustainability analyses, such as in environmentally extended input-output modelling.

Chromosome-level genome and high nitrogen stress response of the widespread and ecologically important wetland plant Typha angustifolia

Typha angustifolia L., known as narrowleaf cattail, is widely distributed in Eurasia but has been introduced to North America. Typha angustifolia is a semi-aquatic, wetland obligate plant that is widely distributed in Eurasia and North America. It is ecologically important for nutrient cycling in wetlands where it occurs and is used in phytoremediation and traditional medicine. In order to construct a high-quality genome for Typha angustifolia and investigate genes in response to high nitrogen stress, we carried out complete genome sequencing and high-nitrogen-stress experiments. We generated a chromosomal-level genome of T. angustifolia, which had 15 pseudochromosomes, a size of 207 Mb, and a contig N50 length of 13.57 Mb. Genome duplication analyses detected no recent whole-genome duplication (WGD) event for T. angustifolia. An analysis of gene family expansion and contraction showed that T. angustifolia gained 1,310 genes and lost 1,426 genes. High-nitrogen-stress experiments showed that a high nitrogen level had a significant inhibitory effect on root growth and differential gene expression analyses using 24 samples found 128 differentially expressed genes (DEGs) between the nitrogen-treated and control groups. DEGs in the roots and leaves were enriched in alanines, aspartate, and glutamate metabolism, nitrogen metabolism, photosynthesis, phenylpropanoid biosynthesis, plant-pathogen interaction, and mitogen-activated protein kinase pathways, among others. This study provides genomic data for a medicinal and ecologically important herb and lays a theoretical foundation for plant-assisted water pollution remediation.

One-step synthesis of Enteromorpha graphene aerogel modified by hydrophilic polyethylene glycol achieving high evaporation efficiency and pollutant tolerance

Photothermal evaporation using solar energy is a sustainable way to produce fresh water from seawater. Aiming to explore functional materials as a solar-energized evaporator with enhanced evaporation rate and pollutant tolerance, this study was to synthesize a self-floating composite graphene aerogel (GA) doped with Enteromorpha and modified polyethylene glycol (PEG), named as PEGA using solar energy for desalination. Physio-chemical properties and evaporative mechanism of PEGA were experimentally investigated and analyzed with respect to molecular weight, PEG dosage, and ratio of Enteromorpha and graphene oxide. Experimental data revealed that the modification of PEG improved hydrophilic functional ability of PEGA, resulting in increasing the evaporation rate and photothermal conversion efficiency up to 2.55 kg/(m²·h) and 105.71 %, respectively. The ion removal rate of seawater exceeds 99.99 % via the PEGA conducted solar evaporation. Furthermore, PEGA possessed an excellent property of salinity emulsion pollution tolerance. Particularly, the evaporation rate of the PEG-modified biomass-based aerogel was 2.84 kg/(m²·h) in a 15 wt% NaCl solution (1 sun, 6 h) and 2.50 kg/(m²·h) at 1 h. The formation of hydrogen bonds between -OH of PEG and water molecules assist to conduct water along the graphene matrix to improve water evaporation. The cost of the graphene aerogel modified by Enteromorpha was reduced by 38.88 % less than the original graphene aerogel. The results from this study will greatly promote the application of graphene aerogel for desalination via solar evaporation.

Hybrid TiO2:Au nanostars based polymeric membranes for photocatalytic degradation of ciprofloxacin in water samples

Antibiotics represent one increasingly harmful type of contaminant of emerging concern in treated and non-treated water. They cause the generation of antibiotic-multiresistant organisms, one of the major challenges in current medicine. Plasmonic-photocatalysis using solar energy represents a promising solution for their removal with low energy consumption. Its successful application requires the improvement of photocatalysts' efficiency under sunlight and the development of robust, durable, and efficient substrates for photocatalysts immobilisation. In this work, hybrid TiO₂:Au nanostars were initially synthesised. Then, two porous membranes were prepared to support this nanocatalyst based on poly (vinylidenefluoride-co-hexafluoropropylene) polymer. Doctor blade and salt leaching casting methods, combined with temperature-induced phase separation, were used to generate membranes with high porosity, 80-90%, which was maintained after nanoparticle incorporation (3, 8 and 10 wt%). The photocatalytic activity of the nanocomposite membranes was tested through the degradation of the antibiotic ciprofloxacin under UV and visible radiation. Salt-leaching membranes containing 10 wt% nanoparticles presented the highest degradation efficiencies, 45% under UV and 35% under visible radiation. In contrast, doctor blade membranes showed 36% and 32% degradation efficiencies, respectively. The reusability of the membranes was assessed in repeated cycles, presenting an average efficiency loss of only 2% after three uses. Finally, the reusability of these membranes was also tested in treated effluent water matrixes, presenting similar, or even better, degradation efficiencies, and a minimum reusability efficiency lost 0-1%. The results demonstrate that these membranes are a promising alternative for the degradation of a wide variety of contaminants under sunlight radiation.

Evaluating the Feasibility of Employing Dynamic Membranes for the Direct Filtration of Municipal Wastewater

The aim of this study was to assess the feasibility of using dynamic membranes for direct filtration of municipal wastewater. The influence of different alternative supporting materials (one or two layers of flat open monofilament woven polyamide meshes with 1 or 5 µm of pore size) was studied. A stable short-term self-forming DM was achieved (from some hours to 3 days) regardless of the supporting material used, producing relatively similar permeate qualities (total suspended solids, chemical oxygen demand, total nitrogen, total phosphorous and turbidity of 67-88 mg L^-1, 155-186 mg L^-1, 48.7-50.4 mg L^-1, 4.7-4.9 mg L^-1, and 167-174 NTU, respectively). A DM permeability loss rate of from 5.21 to 10.03 LMH bar^-1 day^-1 was obtained, which depended on the supporting material used. Unfortunately, the preliminary energy, carbon footprint, and economic evaluations performed showed that although DMs obtain higher pollutant captures than conventional treatments (primary settler), the benefits are not enough to justify their use for treating average municipal wastewater. However, this alternative scheme could be suitable for treating higher-loaded MWW with a higher fraction of organic matter in the non-settleable solids.

Assessing sectoral water stress states from the demand-side perspective through water footprint dimensions decomposition

Due to its essentiality and scarcity, water is subject to stress from the supply and demand side. The SDG and many methods for assessing water stress (WS) are based on water supply, even though the total water supply is uncontrollable by humans in the short term. Conversely, from a water demand perspective, WS arises from the deliberate and manageable use of water to produce goods and services, with few methods proposing to evaluate WS. We propose a method to assess the sectoral demand-side water stress states (DWSS) to fill this gap. The method comprises a quantitative step followed by a qualitative analysis. Quantitatively, an environmentally extended input-output model integrated Brazilian water resource and economic data for 2010 and 2015, including the imported virtual water in the water footprint calculation. Three dimensions of water footprint (DWF) were calculated: consumptive use of water (CUWF), water consumption (CWF), and return to the environment (REWF). The variations in DWFs over time were used as criteria to define five DWSS ranging from weak to strong. Brazilian economy as a whole presented a moderately weak DWSS. Among economic sectors, the most frequent DWSS was moderately weak, with sixteen sectors. The Livestock and Forestry, fishing, and aquaculture sectors had a strong DWSS, while the Slaughter, meat, and dairy and Public administration sectors had weak DWSS. Despite its limitations, the demand-side analysis can complement the usual method from a supply perspective.

National water shortage for low to high environmental flow protection

Global freshwater biodiversity has been decreasing rapidly, requiring the restoration and maintenance of environmental flows (EFs) in streams and rivers. EFs provide many ecosystem services that benefit humans. Reserving such EFs for aquatic ecosystems, implies less renewable water availability for direct human water use such as agriculture, industry, cities and energy. Here we show that, depending on the level of EF protection, global annual renewable water availability for humans decreases between 41 and 80% compared to when not reserving EFs. With low EF protection, currently 53 countries experience different levels of water shortage, which increases to 101 countries for high EF protection. Countries will carefully have to balance the amount of water allocated to humans and the environment.

Swine Wastewater Treatment in Constructed Wetland Systems: Hydraulic and Kinetic Modeling

The use of constructed wetland systems (CWS) is presented as an alternative for the treatment of effluents since these have reduced implementation costs and relative ease of operation. The present research was undertaken to evaluate to study the hydrodynamic and the fitting of first-order mathematical kinetic models for the removal of pollutants in CWS. Three CWS were built, using expanded clay as filter support: one cultivated with Polygonum punctatum (CWSw), another cultivated with Chrysopogon zizanioides (CWSV), and a control unit (CWSc). The actual retention time was 3.12 days in the CWSc, whereas, in the CWSw and CWSv, we observed values of 4.14 and 4.11 days, respectively. The dispersion values were high in all CWS. The values of chemical oxygen demand (COD) across the length of the CWS were used to fit the kinetic models that describe the first-order decay of organic matter over the CWS. The models that showed a better fit to the experimental data were the plug-flow with residual concentration, the continuous stirred tank reactor, and Shepherd’s models.

Arjen Y. Hoekstra: A Water Management Researcher to Be Remembered

On 18 November 2019, the life of Arjen Y [...]

Quantifying economic-social-environmental trade-offs and synergies of water-supply constraints: An application to the capital region of China

Sustainable water management is one of the sustainable development goals (SDGs) and is characterized by a high level of interdependencies with other SDGs from regional to global scales. Many water assessment studies are restricted to silo thinking, mostly focusing on water-related consequences, while lacking a quantification of trade-offs and synergies of economic, social, and environmental dimensions. To fill this knowledge gap, we propose a "nexus" approach that integrates a water supply constrained multi-regional input-output (mixed MRIO) model, scenario analysis, and multi-criteria decision analysis (MCDA) to quantify the trade-offs and synergies at the sectoral level for the capital region of China, i.e. the Beijing-Tianjin-Hebei urban agglomeration. A total of 120 industrial transition scenarios including nine major industries with high water-intensities and water consumption under current development pathways were developed to facilitate the trade-off and synergy analysis between economic loss, social goals (here, the number of jobs) and environmental protection (with grey water footprint representing water pollution) triggered by water conservation measures. Our simulation results show that an imposition of a tolerable water constraint (a necessary water consumption reduction for regional water stress level to move from severe to moderate) in the region would result in an average economic loss of 68.4 (± 16.0) billion Yuan (1 yuan ≈ 0.158 USD$ in 2012), or 1.3 % of regional GDP, a loss of 1.94 (± 0.18) million jobs (i.e. 3.5 % of the work force) and a reduction of 1.27 (± 0.40) billion m³ or about 2.2% of the regional grey water footprint. A tolerable water rationing in water-intensive sectors such as Agriculture, Food and tobacco processing, Electricity and heating power production and Chemicals would result in the lowest economic and job losses and the largest environmental benefits. Based on MCDA, we selected the 10 best scenarios with regard to their economic, social and environmental performances as references for guiding future water management and suggested industrial transition policies. This integrated approach could be a powerful policy support tool for 1) assessing trade-offs and synergies among multiple criteria and across multiple region-sectors under resource constraints; 2) quantifying the short-term supply-chain effects of different containment measures, and 3) facilitating more insightful evaluation of SDGs at the regional level so as to determine priorities for local governments and practitioners to achieve SDGs.