Special Issue "Emerging Integrated Processes for Sustainable Water-Energy-Materials-Food Nexus"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Water, Agriculture and Aquaculture".

Deadline for manuscript submissions: closed (15 September 2021).

Special Issue Editors

Dr. Svetlozar Velizarov
E-Mail Website
Guest Editor
Laboratory for Green Chemistry (LAQV), Faculty of Science and Technology, New University of Lisbon, 2829-516 Caparica, Portugal
Interests: clean (mainly membrane-assisted) (bio)chemical processes and technologies; electromembrane processes; water treatment; sustainable salinity gradient-based (“blue”) energy generation and/or storage
Special Issues, Collections and Topics in MDPI journals
Dr. Alberto Figoli
E-Mail Website
Guest Editor

Special Issue Information

Dear Colleagues,

Integrated processes have become preferred choices in a number of important water treatment or usage applications. Integration of separation(s) with (bio)reaction(s) offers possibilities for achieving various goals. Exploring possible synergisms, benefiting from distinct process mechanisms often leads to the development of novel, more efficient, and sustainable technologies to be applied in a variety of domains, ranging from integrating the production of clean water for potable uses, agriculture and irrigation with energy generation and valuable resources recovery (e.g., via seawater mining, selective extraction of valuable elements from brines or appropriate industrial effluents, high added-value compounds from agro-food wastewater, etc.) to energy generation through salinity gradients and other water-based production ways.

Therefore, this Special Issue of the journal Water seeks contributions to assess the current state-of-the-art and encourage future developments in the field of such integrated processes. Topics include but are not limited to emerging water treatment technologies, innovative process design, modeling and validation, life cycle analysis, and novel applications, especially such including membrane-assisted unit operations. Both original papers and reviews are welcome.

Dr. Svetlozar Velizarov
Dr. Alberto Figoli
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • circular water economy
  • energy from sea and saline brines
  • energy from wastewaters
  • life cycle assessment (LCA)
  • mechanistic process modelling
  • membrane-assisted processes for clean water and energy
  • multivariate statistical modelling
  • novel integrated (hybrid) processes
  • recovery of high added-value agro-food compounds
  • saline brines valorization
  • salinity gradient power
  • seawater mining
  • sustainable water-based energies

Published Papers (7 papers)

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Research

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Article
Biochar and Zeolite as Alternative Biofilter Media for Denitrification of Aquaculture Effluents
Water 2021, 13(19), 2703; https://doi.org/10.3390/w13192703 - 29 Sep 2021
Viewed by 370
Abstract
Denitrification processes are crucial in aquaculture as they convert the undesirable nitrate to safer forms of nitrogen. Conventionally, plastic media are used for the biofiltration of wastewater. However, alternative media may be as effective/better than plastic and enhance the sustainability of the system. [...] Read more.
Denitrification processes are crucial in aquaculture as they convert the undesirable nitrate to safer forms of nitrogen. Conventionally, plastic media are used for the biofiltration of wastewater. However, alternative media may be as effective/better than plastic and enhance the sustainability of the system. This study evaluated biochar and zeolite as alternatives for the denitrification of aquaculture effluents. Triplicates of laboratory-scale bioreactors were fabricated to compare the denitrification efficiencies of biochar and zeolite to that of plastic. The bioreactors were fed synthetic aquaculture wastewater having nitrate loading rates of 50, 125, and 150 mg/L. Zeolite exhibited highest values of surface roughness in terms of arithmetic mean height (0.89 µm), maximum height (6.52 µm), and root-mean-square height (1.17 µm), as corroborated by surface profilometry and scanning electron microscopy. The results revealed that under pseudo-steady-state conditions, zeolite displayed the highest nitrate removal efficiency (maximum 95.02 ± 0.01%), which was followed by biochar and plastic (maximum 92.91 ± 0.01% and 92.57 ± 0.02%, respectively) due to its extraordinary surface roughness that provided better adhesion to the bacteria. However, by the end of the study, all the media exhibited comparable rates. Thus, both zeolite and biochar are sustainable alternatives of biomedia for nitrate removal. However, time and labor constraints must be accounted for to scale-up such bioreactors. Full article
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Article
Combined Adsorption and Photocatalytic Degradation for Ciprofloxacin Removal Using Sugarcane Bagasse/N,S-TiO2 Powder Composite
Water 2021, 13(16), 2300; https://doi.org/10.3390/w13162300 - 22 Aug 2021
Viewed by 486
Abstract
N,S-TiO2 deposited on three kinds of pre-treated sugarcane bagasse was synthesized via a sol–gel method. The obtained composites were characterized by various techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). UV-visible induced degradation [...] Read more.
N,S-TiO2 deposited on three kinds of pre-treated sugarcane bagasse was synthesized via a sol–gel method. The obtained composites were characterized by various techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). UV-visible induced degradation of ciprofloxacin was investigated. The influence of some experimental parameters such as contact time, pH, dosage, and initial concentration on the efficiency of ciprofloxacin elimination was also evaluated. The highest efficiency was observed for the alkaline pre-treated sugarcane bagasse combined with N,S-TiO2, about 86% under optimal conditions (contact time 150-min irradiation, pH 5.5–6, dosage 0.5 g L−1, and the initial concentration CIP 30 ppm). There may be a rapid ciprofloxacin transition from the adsorption site to the photocatalytic site, and the alkaline pre-treated sugarcane bagasse/N,S-TiO2 prevented the recombining of holes and electrons of the photocatalyst. Furthermore, the alkaline pretreatment sugarcane bagasse/N,S-TiO2 composite material was sustainable, with only a 10% reduction after reusing the material three times. The presence of sugarcane bagasse made the material easy to recover from the liquid phase. Full article
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Article
Membrane Filtration Opportunities for the Treatment of Black Liquor in the Paper and Pulp Industry
Water 2021, 13(16), 2270; https://doi.org/10.3390/w13162270 - 19 Aug 2021
Cited by 1 | Viewed by 571
Abstract
Black liquor is a highly alkaline liquid by-product of the kraft pulping process, rich in organic molecules (hemicelluloses, lignin, and organic acids) and inorganic pulping chemicals such as sodium salts and sulphur-containing compounds. The release of this wastewater without further treatment could have [...] Read more.
Black liquor is a highly alkaline liquid by-product of the kraft pulping process, rich in organic molecules (hemicelluloses, lignin, and organic acids) and inorganic pulping chemicals such as sodium salts and sulphur-containing compounds. The release of this wastewater without further treatment could have serious environmental and financial implications. Therefore, a costly treatment process is used nowadays. Nanofiltration has been studied in the last few years as a promising alternative to recycle the cooking chemicals required for the separation of lignin and cellulose, but the development of pH-stable membranes with the potential to operate at industrial scales is fundamental in order to make this possible. In this study, the filtration performance of two in-house made membranes is evaluated and compared with a commercial NF membrane to determine the viability of their use for the treatment of black liquor. For this purpose, filtration experiments with simulated black liquor were performed. We identified that Membrane A has the higher potential for this application due to its competitive permeate flux (ca. 24 L m−2 h−1 at a trans-membrane pressure of 21.5 bar), and high rejection of organic components and salts from the cooking liquor (on average, 92.50% for the TOC, 84.10% for the CO32−, 88.70% for the sulphates, 73.21% for the Na+, and 99.99% for the Mg2+). Full article
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Article
Fluoride Polluted Groundwaters in Calabria Region (Southern Italy): Natural Source and Remediation
Water 2021, 13(12), 1626; https://doi.org/10.3390/w13121626 - 09 Jun 2021
Cited by 3 | Viewed by 733
Abstract
Excessive ingestion of fluoride through the consumption of F-rich drinking water could cause adverse effects to human health. For this reason, the WHO has fixed 1.5 mg/L as the maximum F- concentration for drinking water. In this work, a detailed geochemical [...] Read more.
Excessive ingestion of fluoride through the consumption of F-rich drinking water could cause adverse effects to human health. For this reason, the WHO has fixed 1.5 mg/L as the maximum F- concentration for drinking water. In this work, a detailed geochemical characterization was performed to define the source of natural pollution of two groundwaters (samples Pc and Bg) coming from deep crystalline aquifers located in the Calabria region (southern Italy) and to define and optimize the most appropriate water treatment strategy. The samples were classified as a F enriched NaHCO3 type of water. In particular, the F concentrations observed were 30 mg/L and 8.9 mg/L for the Pc and Bg samples, respectively. Based on the acquired geochemical characterization knowledge, the groundwaters were treated by two thin-film composite NF membranes, namely SPR 10113 and SPR 10114 which have so far not been used for water defluoridation. It was found that the SPR 10114 membrane was able to guarantee water permeates with F contents lower than the threshold value of 1.5 mg/L for both treated waters, whereas the fluoride content remained above the threshold value when the Pc sample was treated using the SPR 10113 membrane. The obtained permeates were characterized by a low ionic load and were not suitable for long-term consumption as drinking water. However, all of the produced waters did not need any further re-mineralizing processes for agricultural irrigation or other purposes. Full article
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Article
Performance of Reverse Electrodialysis System for Salinity Gradient Energy Generation by Using a Commercial Ion Exchange Membrane Pair with Homogeneous Bulk Structure
Water 2021, 13(6), 814; https://doi.org/10.3390/w13060814 - 16 Mar 2021
Cited by 2 | Viewed by 974
Abstract
Salinity gradient energy is a prominent alternative and maintainable energy source, which has considerable potential. Reverse electrodialysis (RED) is one of the most widely studied methods to extract this energy. Despite the considerable progress in research, optimization of RED process is still ongoing. [...] Read more.
Salinity gradient energy is a prominent alternative and maintainable energy source, which has considerable potential. Reverse electrodialysis (RED) is one of the most widely studied methods to extract this energy. Despite the considerable progress in research, optimization of RED process is still ongoing. In this study, effects of the number of membrane pairs, ratio of salinity gradient and feed velocity on power generation via the reverse electrodialysis (RED) system were investigated by using Fujifilm cation exchange membrane (CEM Type 2) and FujiFilm anion exchange membrane (AEM Type 2) ion exchange membranes. In the literature, there is no previous study based on a RED system equipped with Fujifilm AEM Type II and CEM Type II membranes that have homogeneous bulk structure. Using 400 µm of intermembrane distance, maximum obtainable power density by 5 pairs of Fujifilm membranes at 1:45 salinity ratio and with a linear flow rate of 0.833 cm/s was 0.426 W/m2. Full article
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Article
Bioelectrochemical Greywater Treatment for Non-Potable Reuse and Energy Recovery
Water 2021, 13(3), 295; https://doi.org/10.3390/w13030295 - 26 Jan 2021
Cited by 2 | Viewed by 1005
Abstract
Greywater normally represents the largest fraction of wastewater generated in buildings and may be suitable for non-potable reuse after on-site treatment. Conventional technologies for greywater treatment include sequencing batch reactors, membrane filtration, and membrane biological reactors. Even though these can be very effective, [...] Read more.
Greywater normally represents the largest fraction of wastewater generated in buildings and may be suitable for non-potable reuse after on-site treatment. Conventional technologies for greywater treatment include sequencing batch reactors, membrane filtration, and membrane biological reactors. Even though these can be very effective, they are highly energy consuming and may negatively impact the energy balance of the building where they are installed. Microbial fuel cells (MFCs) have emerged as a sustainable technology for contaminant removal and energy production from a variety of substrates. In this study, the application of MFCs for greywater treatment is reported, with a particular focus on the analysis of energy losses, in view of non-potable reuse. MFCs were fed with different types of greywater, characterized by either high or low conductivity, because greywater’s conductivity may greatly differ based on its origin; in either case, organic matter (chemical oxygen demand; COD) removal was higher than 85% and not influenced by the influent conductivity, coupled with a maximum power production of 0.46 mW L−1 and 0.38 mW L−1. Electrolyte overpotentials were dramatically higher in the case of low conductivity greywater (20% vs. 10%, compared to high conductivity influent); these overpotentials are related to the conductivity of the influent, showing that low conductivity hindered energy generation, but not COD removal. Polarization and power curves showed higher internal resistance in the case of low conductivity, confirming the overpotentials’ analysis. Results showed the feasibility of the use of MFCs in greywater treatment, with potential to reduce the energy demand connected to its reuse compared to conventional technologies; coupling with a disinfection stage would be necessary to fully comply with most non-potable reuse regulations. Full article
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Case Report
Analysis of the Intake Locations of Salinity Gradient Plants Using Hydrodynamic and Membrane Models
Water 2021, 13(9), 1133; https://doi.org/10.3390/w13091133 - 21 Apr 2021
Viewed by 493
Abstract
The gain in net power produced by Salinity Gradient plants in river mouths due to the optimal location of water intakes is analysed in this paper. More precisely, this work focuses on stratified river mouths and the membrane-based technology of Pressure-Retarded Osmosis. A [...] Read more.
The gain in net power produced by Salinity Gradient plants in river mouths due to the optimal location of water intakes is analysed in this paper. More precisely, this work focuses on stratified river mouths and the membrane-based technology of Pressure-Retarded Osmosis. A methodology for this analysis is proposed and then applied to a case study in Colombia. Temperature, salinity and water discharge data were gathered at the Magdalena river mouth to develop a hydrodynamic model that represents the salinity profile along the river channel. The net power production of a pressure-retarded osmosis plant is then estimated based on the power produced at membrane level, considering different locations for the saltwater and freshwater intakes. The most adequate locations for the intakes are then deduced by balancing higher power production (due to higher salinity differences between the water intakes) with lower pumping costs (due to shorter pumping distances from the intakes). For the case study analysed, a gain of 14% can be achieved by carefully selecting the water intakes. Full article
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