Sustainable Water Utilization Research Articles

Economic irrigation water productivity of wheat and potato: An earth observation perspective on policy implications in the Litani Basin, Lebanon

Efficient water management is critical in addressing the challenges posed by water scarcity and resource sustainability in agriculture. However, the utilization of remote sensing technology to monitor and enhance water productivity in data-scarce environments remains an open question. This study underscores the importance of integrating earth observation systems into agricultural water management policies, elucidating their potential to shape crucial policy decisions and investment strategies, particularly in regions facing data limitations. To address this issue, we provide a comprehensive framework that blends remote sensing data with field-based economic information, to develop the concept of economic productivity of irrigation water. Leveraging FAO’s Water Productivity Open-access portal (WaPOR) data, we spatially assess yields, water use, crop water productivity, economic water productivity, and economic irrigation water productivity (EIWP) for wheat and potatoes in the Upper Litani Basin of Lebanon's Bekaa Valley. Early season potatoes outperform irrigated wheat significantly, providing up to ten times higher returns on irrigation water ($6/m3 vs. $0.6/m3). Spatial analysis shows that southern areas have 30 % lower potato EIWP than northern areas of the valley but 55 % higher wheat EIWP, mainly due to higher rainfall. Our findings reveal that merely considering crop water productivity is insufficient when deciding what to plant, as it fails to account for profitability. While transitioning to crops or practices with greater EIWP can enhance economic productivity on the short-term, it may simultaneously lead to increased water consumption. As a result, the shift towards highly water-productive systems may require measures such as controlling irrigated areas or implementing restrictions on water withdrawals to maintain stable water consumption levels. This study offers valuable insights for water resource management, agricultural policy, and sustainable water utilization, especially in semi-arid regions like the Litani Basin, providing a foundation for informed decision-making in these resource-constrained environments.

Advanced bionic inverted coral solar evaporator: Enhancing sustainable water utilization with efficient and salt-resistant evaporation

Interfacial solar-driven steam generation technology shows great potential in addressing desalination and wastewater purification. However, there is a lack of advanced evaporators with high evaporation efficiency and salt tolerance, which is an obstacle to its widespread application. Drawing inspiration from marine coral structures, we develop a bionic inverted coral-type 3D solar evaporator with an array structure using structural engineering design. The microscopically porous vertical channel structure within the overall skeleton enhances the longitudinal reflux of salt ions and water evaporation, while macroscopic gaps in the bionic coral branching facilitate lateral advection–diffusion of salt ions. Numerical simulations confirm that this bionic coral structure design improves the diffusion rate of concentrated brine. Due to the localized surface plasma resonance and the Marangoni effect, the evaporator achieves remarkable water evaporation performance (evaporation rate: 2.72 kg m−2h−1, energy efficiency: 95.8 %) and operates reliably even under 20 % brine concentration (evaporation rate: 2.65 kg m−2h−1) without significant salt crystallization. Furthermore, it exhibits good wettability and robust mechanical properties, capable of withstanding a wide range of temperatures. The efficient and salt-resistant evaporation makes it valuable for applications including desalination, various wastewater treatments, and agricultural irrigation, thereby promoting the sustainable utilization of water resources.

Water Resource Utilization Assessment in China Based on the Dynamic Relationship between Economic Growth and Water Use

Water scarcity has significantly hampered China’s economic, social, and environmental development. Ensuring sustainable water utilization is crucial given the mounting water stress accompanying continuous economic growth. A quantitative water resource forewarning model was constructed using the vector autoregressive (VAR) model. By analyzing the key indicators related to water systems and GDP data from 2001 to 2022, the VAR model revealed the long-term dynamic correlation between water consumption and economic growth using generalized impulse response, co-integration, and predictive variance decomposition analyses. The results revealed the presence of a long-term equilibrium between water consumption and economic growth, with a stable co-integration relationship and an optimal lag period of one year. The positive impact of water consumption on economic development increased during the 2001–2022 period, indicating a rising dependence of GDP on water resources. Water usage rose with economic development, while the water resource carrying capacity remained high and continued to grow. Based on the generalized impulse response, co-integration, and predictive variance decomposition analyses, this study predicted water-use-related indicators, providing vital early warnings for China’s water environment carrying capacity from 2023 to 2050. This enabled informed decision-making and fostered sustainable water management practices for the future.

Assessment of Huixian Karst Wetland for Local Water Augmentation in Guilin, China

Due to the rapid exploitation of water resources in the Huixian karst wetland in the southwest of China in the past decades, the wetland has suffered from shrinkage in size and serious degradation of ecological functioning. To assess how much water within the wetland could still be taken out for local supply purposes while the wetland can still be kept in its normal ecological functioning. Through the use of multi-methods, including field surveys by a multi-disciplinary team, water balance, Remote Sensing, GIS and numerical simulation, this paper characterizes the wetland regime of the study area and finally determines scenarios of water resource utilization for local water supply within acceptable parameters of wetland ecological health. Through the analysis of the methods, it was found that the hydrological characteristics of the study area were conditioned by not only the karst water but also the regional precipitation fluctuations. A zone of mobile watersheds for Lake Mudong was established as opposed to a conventional single watershed. If the wetland ecosystem is kept at the current status of class III, a scenario of withdrawal of up to 20% of lake inflows could be accommodated. The results and their approaches would provide much-needed information for the protection of the wetland and its sustainable water utilization per se. It would offer a basic reference for similar problems in karst areas of southwest China and other areas alike.

Irrigation Scheduling for Small-Scale Crops Based on Crop Water Content Patterns Derived from UAV Multispectral Imagery

A timely irrigation schedule for small-scale farms is imperative for ensuring optimum crop production in the wake of drought and climate change. Owing to the large number of irrigated small-scale farms that grow different crops across all seasons in the Mutale River catchment, this study sought to develop irrigation scheduling for these crops for sustainable water utilization without compromising crop yields. Unmanned aerial vehicle (UAV) images were utilized as the base from which crop water content patterns were derived. A total of four (4) spectral vegetation indices, viz, the Greenness Normalized Difference Vegetation Index (GNDVI), Normalized Difference Vegetation Index (NDVI), Normalized Difference Red-Edge Index (NDRE), and Optimized Soil-Adjusted Vegetation Index (OSAVI), were generated to characterize crop types and water content in this study. Crop water content data, in the form of the relative water content (RWC), were measured in the field for each type of crop. Crop water content was modelled based on the empirical relationships between spectral indices and field-measured RWC. The linear regression analysis revealed a significant association between the GNDVI and the water content of sweet potato, maize, sugar beans, and Florida broadleaf mustard, with r2 values of 0.948, 0.995, 0.978, and 0.953, respectively. The NDVI revealed a strong association with the water content of Solanum retroflexum, pepper, and cabbage, with r2 values of 0.949, 0.956, and 0.995, respectively. The NDRE, on the other hand, revealed a strong relationship with water content in peas and green beans, with r2 values of 0.961 and 0.974, respectively. The crop water content patterns simulation revealed that Solanum retroflexum, sweet potato, maize, sugar beans, and Florida broadleaf mustard reached their respective wilting points on day four after irrigation, implying that irrigation of these crops should be scheduled after every four (4) days. Peas, green beans, pepper, and cabbage reached their respective wilting points on day five after irrigation, implying that irrigation of these crops should be scheduled after every five days. The results of this study highlight the significance of considering crop water content derived from spectral bands of UAV imagery in scheduling irrigation for various types of crops. This study also emphasized the on-going significance of remote sensing technology in addressing agricultural issues that impede hunger alleviation and food security goals.

Tree Rings as Proxies of Historical Runoff in a National Park in Northern Mexico: A Major Ecosystem Service Provider

A dendrochronological network of conifers (Pinus leiophylla, Pinus cembroides, Pinus engelmannii) was developed in the Cumbres de Majalca National Park (CMNP) in Chihuahua, Mexico, to reconstruct historical runoff patterns and examine the impact of ocean–atmosphere phenomena. The CMNP plays a vital role as a runoff source for Conchos River tributaries and groundwater recharge for Chihuahua City and nearby populations. The ring-width chronologies displayed a common signal from 1859 to 2021, with the highest association found between P. engelmannii and P. leiophylla (r = 0.65) and the lowest between P. cembroides and P. engelmannii (r = 0.55). The first principal component explained 75.7% of the variance, and among the species, P. leiophylla exhibited the highest correlation (0.624, p < 0.05) with the accumulated streamflow records from the previous November to July, allowing the construction of a bootstrapped model for runoff reconstruction. The reconstructed streamflow spanned from 1859 to 2014, with an average of 2.732 × 108 m3. Periods of low runoff occurred in 1860–1880, 1940–1960, and 1994–2014, while extreme wet years with high runoff occurred in 1865, 1884, and 1987. The interannual streamflow variability correlated significantly with ENSO indices (SOI, MEI, TRI, and sea surface temperature anomalies), particularly during the winter–spring seasons, indicating that warm phases of the ENSO increased precipitation and runoff. The analysis of return periods revealed probabilities for specific runoff volumes, enabling stakeholders to use the information to develop effective strategies for sustainable water allocation and utilization in the region.

Collaborative optimal allocation of water resources and sewage discharge rights in watershed cities: considering equity among water sectors.

Water supply systems in watershed cities face challenges due to increasing water demand and arbitrary sewage discharge allocations. Previous studies have primarily focused on water resource allocation and sewage discharge rights, neglecting the intricate interactions between the two. This study introduces a novel approach by integrating sewage discharge rights into the watershed's water resource allocation mechanism. A multi-objective optimization model was developed, employing the Gini coefficient to balance the equitable and economic aspects across various water sectors. This model takes into account the distinct water demands and sewage discharge requirements of different sectors. The findings of this study are as follows: (a) the Gini coefficients for water demand allocation and sewage discharge rights allocation exhibit simultaneous optimization and display consistent trends; (b) when the importance of sewage discharge relative to other water users increases, the return on investment for domestic and industrial water use decreases, but the fairness of water distribution improves; (c) proper allocation of sewage discharge rights can effectively enhance the economic value of agricultural water use. Overall, this strategy has the potential to enhance both the equality and economic benefits of the water supply system while ensuring the sustainable utilization of water and sewage rights in the basin cities.

Hydrochemical Characteristics of Groundwater and Their Significance in Arid Inland Hydrology

Phreatic groundwater hydrochemistry is important for sustainable water utilization and ecological stability in arid regions. Based on the test data from collected water samples, this study explored the phreatic groundwater recharge, hydrochemical evolution, and quality of the Sugan Lake Basin using hydrogeochemical, isotopic, and multivariate statistical analyses. The stable isotopic results showed that the phreatic groundwater in the alluvial fan, plain, and wetland areas of the basin generally originated from modern water, and the phreatic groundwater in the piedmont was mainly recharged by paleowater under low-temperature conditions. Carbonate is the dominant mineral in the regional rock weathering process. Phreatic groundwater in the piedmont is controlled by mineral dissolution and cation exchange; however, phreatic groundwater in other areas of the basin is significantly affected by river infiltration. This indicates that the hydrochemical regime of phreatic groundwater is sensitive to natural river flow without disturbing human activity. Class I–V groundwater samples accounted for 2.86%, 25.71%, 34.29%, 14.29%, and 22.86%, respectively. Total dissolved solids, total hardness, sulfate, chloride, nitrite, Na, Fe, Hg, and Cr VI are important factors that determine groundwater quality. This study deepens the understanding of phreatic groundwater hydrochemical characteristics and hydrologic cycles in the Sugan Lake Basin and provides background values of hydrochemistry without human interference for further study in arid inland basins.

Simulation of the evolution track of future Production–Living–Ecological Space under the framework of comprehensive assessment of climate change: A case study of Heilongjiang Province, China

Climate change affects the coupling degree of water and land resources and further affects regional food security and sustainable development. Taking the water–land coupling relationship as the starting point, this study evaluated the potential impacts of climate change on the dynamic changes in land and water resources in Heilongjiang Province from the perspective of “setting land by water” by system dynamics (SD) and PLUS model. The research results show the following: (1) The wetting scenario can reduce the water stress index (WSI) by 0.37, effectively delay the reduction of ecological space of 824.63 km 2, balance the expansion of production space and living space, and realize the sustainable utilization of water and land resources cooperatively. (2) A temperature increase of 1°C will affect the increase of 55.97 billion m3 of water resources, and reduce the ecological space of 226.67 km 2. The increases in temperature and decreases in precipitation will lead to the continuous decrease of the coordination effect of water and land resources. (3) The changes in the land use of the Production–Living–Ecological (PLE) were mainly due to the enhancement of agricultural production activities, which led to the occupation of 176.6 km 2 of grassland and other ecological land. The increased use of irrigation water is the main reason for the enhanced spatial correlation between agricultural production land and water area. Our findings highlight that the overall optimization of land resources can be realized by optimizing the spatial–temporal allocation of water resources and put forward feasible suggestions to response to climate change.

Comprehensive Benefit Analysis of Water Resources in Guangzhou by AHP-TOPSIS Model

Water resources play a pivotal role in ensuring high-quality socio-economic development. Comprehensive benefit analysis of water resources is beneficial for enhancing the efficiency on water utilization, as well as realizing sustainable utilization of limited water. This paper constructs an index system, including four aspects: ecology, economy, society, and water resource development and utilization (WRDU). By employing the hierarchical analysis and improved TOPSIS model, we evaluate the characteristics and interfering factors of the comprehensive benefits on water resources in Guangzhou during 2012 and 2021. The results show: (1) The overall comprehensive benefit values of water resources in Guangzhou are between 0.318 and 0.500 , and exhibits a gradual upward trend, with the economic and social benefits increasing notably, while the ecological and WRDU benefits apparently significantly decline; (2) The growth rate of social benefits exceeds that of economic benefits; (3) Due to factors such as socio-economic development in Guangzhou, adjustments in water use structures, ecological environment management, population growth, and the various water resource management policies, the ecological benefits rise after its first declin, whereas the benefits from water resource development and utilization follow an initial rise then decrease pattern.

Biophysical controls of dew formation in a typical cropland and its relationship to drought in the North China Plain

Dew, as an important contribution of non-rainfall water (NRW), is found to be an important hydrological component for ecosystem water stress alleviation and further ecosystem functions maintenance during rainless seasons. The North China Plain (NCP) is facing severe water shortage mainly due to intensive agricultural irrigation. However, few studies have examined the variations and controlling mechanism of dew in the typical croplands predisposed to drought. Here, seasonal variation in dew was examined during growing period in a wheat and maize rotation cropland in the NCP over 3 years (2008–2010), based on the eddy-covariance measurements of latent heat flux (LE) during nighttime, and the ecosystem drought was defined to occur when the relative extractable water content (REW) in the soil dropped below 0.4. Results showed that annual (from April to September) mean dew amount for this cropland was 7.61 ± 0.02 mm, accounting for 2.5 % of precipitation (PPT), and the annual mean dew amount during drought period was 3.11 mm, accounting for 3.4 % of PPT. Seasonal variation in dew was mainly regulated by relative humidity (RH) and surface stomatal conductance (gs), furthermore, dew was influenced by gs and vapor pressure deficit (VPD) during the wheat growing period, and by gs during maize growing period. 51.1 %–72.0 % of drought events occurred during wheat growing season. Compared to maize growing season with higher nocturnal evapotranspiration (ETN), the higher frequency of dew occurrence during wheat growing season had reduced the ETN amount. Drought timing, duration, and degree together influenced dew amount. Long-term drought (e.g. >1-month drought) would induce an increase of dew amount after drought period. Our findings clarified the temporal dynamics in dew across different crop growing periods (such as wheat and maize); and contribute to the sustainable utilization of non-rainfall water (especially dew) in cropland in the context of extreme climate (such as droughts) in the future.

Exploring the Sustainable Use Strategy of Scarce Water Resources for Rural Revitalization in Yanchi County from Arid Region of Northwest China

Water scarcity limits the coordination between economic development and ecological protection of arid regions. This study presented the consumption pattern and future challenges for water resources and proposed sustainable use strategies for water security in Yanchi county from the arid region of northwest China. Our results showed that water withdrawals were close to the total available water resources. Agriculture consumed about 84.72% of the total water supply. Agricultural water use was influenced by breeding stock, rural per capita net income and effective irrigation area. Estimation of agricultural water demand was about 6582.20 × 104 m3 under the rural revitalization scenario. Limited water supply and increased water demand pose challenges and impediments for rural revitalization and water security in Yanchi county. Water sustainable utilization can be achieved by increasing water supply from unconventional water resources and improving water use efficiency with governmental management. These findings may help policymakers to develop sustainable water use strategies during rural revitalization in arid regions.

Integrated SWAT-MODFLOW Modeling-Based Groundwater Adaptation Policy Guidelines for Lahore, Pakistan under Projected Climate Change, and Human Development Scenarios

Urban aquifers are experiencing increasing pressures from climate change, land-use change, and abstraction, consequently, altering groundwater levels and threatening sustainable water availability, consumption, and utilization. Sustainability in such areas requires the adaptation of groundwater resources to these stressors. Consequently, this research made projections about future climate, land use, and abstraction, examines how these drives will affect groundwater levels, and then proposes adaptation strategies to reduce the impact on Lahore’s groundwater resources. The objectives are achieved using an integrated modeling framework involving applications of Soil Water Assessment Tool (SWAT) and MODFLOW models. The results indicated a projected rise in Tmin by ~2.03 °C and Tmax by ~1.13 °C by 2100 under medium (RCP 4.5) and high-end (RCP 8.5) scenarios, respectively. Future precipitation changes for mid, near and far periods are projected to be −1.0%, 25%, and 24.5% under RCP4.5, and −17.5%, 27.5%, and 29.0% under RCP8.5, respectively. The built-up area in the Lahore division will dominate agricultural land in the future with an expansion from 965 m2 to 3716 km2 by the year 2100 under R1S1 (R2S2) land-use change scenarios (significant at p = 5%). The future population of the Lahore division will increase from 6.4 M to 24.6 M (28.7 M) by the year 2100 under SSP1 (SSP3) scenarios (significant at p = 5%). Groundwater level in bult-up areas will be projected to decline from 185 m to 125 m by 2100 due to increasing groundwater abstraction and expansion in the impermeable surface under all scenarios. In contrast, agricultural areas show a fluctuating trend with a slight increase in groundwater level due to decreasing abstraction and multiple recharge sources under combined scenarios. The results of this study can be a way forward for groundwater experts and related institutions to understand the potential situation of groundwater resources in the Lahore division and implement adaptation strategies to counteract diminishing groundwater resources.

Assessment of Sustainable Water Utilization Based on the Pressure–State–Response Model: A Case Study of the Yellow River Basin in China

Based on the pressure–state–response (PSR) framework, in this paper, we construct an assessment system for sustainable water utilization (SWU) in 60 prefecture-level cities along the Yellow River Basin. Then, a spatial autocorrelation model is employed to analyze the spatial distribution characteristics of SWU. Further, nine related variables are selected to explore the key factors affecting the spatial differentiation of SWU with a geographic detector model. The results are as follows: (1) The overall level of SWU in the Yellow River Basin is not high, and the level of SWU in five cities is much higher than that in other cities. (2) Overall, the SWU shows noticeable spatial autocorrelation characteristics along the Yellow River Basin. Additionally, locally, it shows high–high agglomeration, low–high agglomeration, and low–low agglomeration. (3) The most important factors affecting the spatial differentiation of SWU in the Yellow River Basin are precipitation, population density, and the proportion of tertiary industry in regional GDP.

Two-linker MOFs-based glass fiber paper monolithic adsorbent for atmospheric water harvesting in arid climates

With the increasing demand for freshwater resources, the sustainable and effective utilization of atmospheric water has become a critical issue. Herein, an efficient and stable monolithic water-adsorbent is designed via functionalizing glass fiber paper loaded with two-linker metal-organic frameworks (CGF-mixed-MOFs(Al)). Firstly, a chitosan (CTS) polyelectrolyte layer is constructed on glass fiber paper to improve the MOFs loading capacity (306.71%) through electrostatic interaction and hydrophilic interaction. Subsequently, a series of two-linker metal-organic frameworks (mixed-MOFs(Al)) composed of MIL-160(Al) and Al-fumarate are tailor-made on CGF surface through a situ synthesis self-assembly technology. The resultant mixed-MOFs(Al) monolith exhibits better water harvesting ability and faster adsorption kinetics at low humidity owing to possessing more active adsorption sites. Different from CGF-MIL-160(Al) and CGF-Al-fumarate, the water sorption of CGF-mixed-MOFs(Al)5 at 30% RH, 25% RH and 20% RH reaches 0.37 g/g, 0.31 g/g and 0.25 g/g, respectively. The lab-scale atmospheric water harvesting device based on CGF-mixed-MOFs(Al)5 confirms the feasibility of this work-tailored product as a potential water sorbent in low-humidity environments. The cyclability results (50 times) indicate that CGF-mixed-MOFs(Al)5 maintains good water capture performance, integrity (no MOFs leakage) and crystallinity, which guarantees its working reliability and sustainable benefits. Therefore, our customized water adsorption system provides a simple, long-effective, economical and advanced strategy to capture more fresh water from atmosphere in arid climates.

Alternative cropping systems and optimized management practices for saving groundwater and enhancing economic and environmental sustainability

Rapid decline in groundwater table due to excessive withdrawal of water for irrigation has been posing a serious threat to sustainable agricultural production in hot arid region of India. Alternative cropping systems having low irrigation requirement have been proposed to resolve unsustainable groundwater use but trade-off with other dimensions such as yield, profitability, and environmental impacts is not well-documented. An integrated analysis of amount of groundwater use, productivity, profitability, resource-use efficiency (RUE), and environmental impacts of three cluster bean-based cropping systems [conventional cluster bean (Cyamopsis tetragonoloba)–wheat (Triticum aestivum) (CB–W), and two alternative cropping systems, namely cluster bean-Indian mustard (Brassica juncea) (CB–IM) and cluster bean–blond psyllium (Plantago ovata) (CB–BP)] under different soil management practices [two tillage types, i.e., conventional (CT), and deep tillage (DT); and three farmyard manure (FYM) application rates, i.e., 0, 5, 10 Mg ha-1] was carried out. Based on a three-year field experiment, compared to conventional CB–W, alternative cropping systems produced 28.6–47.4 % lower seed yield, but enhanced economic returns (7.6–31.1 %), while reduced amount of irrigation (− 27.9 to − 37.2 %), energy (− 22.4 to − 37.0 %), and nutrient (− 17.4 to − 46.1 %) used, global warming potential (− 20.2 to − 45.9 %) and greenhouse gas intensity (− 27.3 to − 57.7 %). Alternative cropping systems saved 1.87–2.50 × 103 m3 per year per hectare of groundwater than conventional cropping systems. Soil management practices influenced agro-economic and environmental dimensions of cropping systems. Deep tillage (DT) enhanced yield (14.0 %), economic profit (18.8 %), RUE (13.2 %, 13.8 % and 8.5 % for nutrient, water and energy use efficiency, respectively). Addition of FYM increased yield (up to 23.0 %), economic net return (up to 21.8 %), RUE (up to 22.7 %, 16.5 %, 91.0 % in water, energy and nutrient use efficiency), and reduced global warming potential (up to − 7.9 %). The CB-BP cropping system with DT and FYM addition offered the best balance of yield, profit, saving of irrigation water, energy and nutrient, while minimizing GWP. This study provides empirical evidence of the opportunities for alternative cropping systems which balance the multiple objectives of sustainable groundwater use, farmer profitability and environmental sustainability for arid region of India. The results have direct implications for sustainable utilization of underground water for similar regions of the world facing water shortage.

Spatiotemporal differentiation and driving patterns of water utilization intensity in Yellow River Basin of China: Comprehensive perspective on the water quantity and quality

Water utilization intensity (WUI) has drawn great attention due to the necessity to respond to water scarcity and water contamination in Yellow River Basin in China. Against this background, it is worthwhile to strengthen researches of the quantification of WUI and its driving patterns. Based on provincial panel data of the Yellow River Basin from 2000 to 2020, an indicator system of the WUI is constructed from the comprehensive perspective of water quantity and water quality, the spatiotemporal differentiation and driving patterns of WUI are analyzed by the descriptive statistics method, Logarithmic Mean Division Index and Least Square Error model. Results showed that the overall trends of the WUI in Yellow River Basin are decreasing year by year, with the sharp decreases in water pollution contributing more than water consumption. This intensity varied significantly from upper reaches to lower reaches in the provincial disparity analysis and departmental disparity analysis. Among the 7 selected driving factors, intensity effect, structural effect, exploitation effect and economy effect strongly promoted the decline of WUI. In addition, the driving patterns of WUI in Yellow River Basin include three types: two-effect dominance, three-effect synergy Ⅰ and three-effect synergy Ⅱ. Our analysis of spatiotemporal differentiation of the WUI and its driving patterns is of great significance for integrating water consumption and water pollution in the current situation of WUI, which are beneficial for informing policies towards sustainable water utilization and providing theoretical support for the rational water utilization.

The sustainable utilization of anaerobic digestion effluents treating in suspended filler algae assisted systems

Significant amounts of anaerobic digestion effluents (ADE) containing high concentration of inorganic salts (source of nitrogen and phosphorus) and hardly degradable organic matter are produced during the generation of biogas using livestock manure. Without appropriate treatment, the imbalanced carbon to nitrogen ratio may lead to severe pollution of the environment. Considering different environmentally friendly processes such as recycling, energy regeneration, and sustainable development, suspended fillers were added to traditional algal-bacterial symbiosis (ABS) systems. In the present research, three systems including suspended filler algae assisted bio-reactor (SFA-PBR), no filler algae assisted bio-reactor (NFA-PBR), and single activated sludge system (ABS) were examined. Changes in bacterial communities were analyzed using high throughput sequencing. In addition, the mechanisms of ADE degradation in the presence and absence of suspended algae fillers were studied by comparing their effect on the degradation of COD (chemical oxygen demand), TN (total nitrogen), AN (ammonia nitrogen), and TP (total phosphorus). Systems where the ratio of active microalgae to bacteria was higher promoted the interaction between the two types of microorganisms, accelerating the stability of the ABS. Thus, the daily COD degradation rate in the stage was still high. Flora such as microalgae and bacteria were embedded in the filler spheres, which increased the microorganisms resistance to the poor environment induced by high concentrations of inorganic nutrients and organic matter present in the ADE. This favored the sustainable water utilization of ADE. After the treatment in the SFA-PBR system, the COD degradation rate was 75.32 %. The effluent COD concentration was 334.21 ± 39.18 mg/L. TN and AN degradation rates were 89.34 and 91.32%, respectively. The TN and AN concentrations in the effluent were 35.42 ± 2.65 and 29.97 ± 2.65 mg/L, respectively. The degradation rate of TP was 95.39 %. The effluent TP concentration was 0.86 ± 0.18 mg/L. The Chao diversity and ACE index values in the SFA-PBR system were higher than those of other groups. This result further supports the conclusion formulated with the Shannon diversity index result. Specifically, the effective sequence in the SFA-PBR system group presented a higher degree of homogeneity and abundance.

Hydrochemical Characteristics and the Relationship between Surface and Groundwater in a Typical ‘Mountain–Oasis’ Ecosystem in Central Asia

Water environment monitoring is an important way to optimize the allocation and sustainable utilization of regional water resources and is beneficial for ensuring the security of regional water resources. In order to explore hydrochemical distributions in a mountain–oasis ecosystem in Central Asia, surface water and groundwater samples from the Kaidu River basin were collected over four seasons. pH values, major ions, total dissolved solids (TDS) and stable isotopes were determined during the period from 2016 to 2017. The results showed: (1) that most water bodies in the study areas were mildly alkaline and that hydrochemical distributions showed significant seasonal and spatial variation; (2) that δD and δ18O in surface water and groundwater showed enrichment in summer and autumn and poverty in spring and winter, with higher δ18O values appearing in the oasis area and lower δ18O values appearing in the mountain area; (3) that most of the water bodies in the study areas were of HCO3−Ca2+ type, with the hydrochemical types of groundwater presenting obvious spatial inconsistency relative to surface water; (4) that rock weathering was the main factor controlling hydrochemical composition in the study areas and that human activities had an influence on the groundwater environment in the oasis area; (5) and that surface water–groundwater interactions also displayed spatial inconsistency, especially in summer. The interaction between river water and groundwater was more obvious in the traditional oasis area, especially in spring and summer. The results will be important for regional water resource management and sustainable water utilization.

Reuse of Textile Dyeing Wastewater Treated by Electrooxidation

Wastewater reuse has been addressed to promote the sustainable water utilization in textile industry. However, conventional technologies are unable to deliver treated wastewater with the quality required for reuse, mainly due to the presence of dyes and high salinity. In this work, the feasibility of electrooxidation, using a boron-doped diamond anode, to provide treated textile dyeing wastewater (TDW) with the quality required for reuse, and with complete recovery of salts, was evaluated. The influence of the applied current density on the quality of treated TDW and on the consecutive reuse in new dyeing baths was studied. The ecotoxicological evaluation of the process towards Daphnia magna was performed. After 10 h of electrooxidation at 60 and 100 mA cm−2, discolorized treated TDW, with chemical oxygen demand below 200 (moderate-quality) and 50 mg L−1 (high-quality), respectively, was obtained. Salt content was unchanged in both treatment conditions, enabling the consecutive reuse without any salt addition. For the two reuse cycles performed, both treated samples led to dyed fabrics in compliance with the most restrictive controls, showing that an effective consecutive reuse can be achieved with a moderate-quality water. Besides the water reuse and complete salts saving, electrooxidation accomplished an ecotoxicity reduction up to 18.6-fold, allowing TDW reuse without severe ecotoxicity accumulation.