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Science and Technology for Water Purification, 2nd Edition
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Science and Technology for Water Purification, 2nd Edition

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Wastewater Treatment and Reuse".

Deadline for manuscript submissions: 25 September 2025 | Viewed by 7468

Special Issue Editors

Dr. Yuanfeng Qi

E-Mail Website
Guest Editor
School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, China
Interests: wastewater recycling and resource; by-product analysis and remedy; novel management methodologies; specific fillers and carriers; processing models; wastewater reactors; the construction of wastewater engineering; wastewater eco-environmental damage and evaluation
Special Issues, Collections and Topics in MDPI journals
Dr. Kai He

E-Mail Website
Guest Editor
School of Civil Engineering; Sun Yat-sen University, No. 2 University Road, Zhuhai 519082, China
Interests: water and wastewater engineering; water quality; water and wastewater treatment; water analysis; drinking water quality; water chemistry; environmental analysis; environmental remediation; environmental biodegradation; biological effluent; treatment processes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Water resource scarcity and water pollution are serious global problems. The supply of adequate freshwater is essential in order to guarantee the welfare of people and the development of the global economy. Continuous research on water and wastewater treatment has promoted the evolution of water purification science and technology, leading to greater accessibility and affordability of clean water. Emerging technologies have also been studied to further support sustainable water supply.

This Special Issue on “Science and Technology for Water Purification, 2nd Edition” invites contributions that explore promising water and wastewater treatment technologies, as well as related scientific topics. Solutions to renew the existing water purification technology, in terms of its pollutant removal efficiency, energy consumption, and resource recovery, are also welcome.

In this Special Issue, research areas may include (but are not limited to) the following topics:

  • The evaluation and performance of wastewater reactors and techniques;
  • The identification, analysis, and remedy of novel pollutants and by-products;
  • Wastewater eco-environmental damage and evaluation;
  • Novel materials for wastewater treatment;
  • Processing models and process management;
  • Eco-friendly wastewater engineering;
  • Wastewater recycling, reuse, and resource.

Authors are invited to submit their latest results; both original research articles and reviews are welcomed.

We look forward to receiving your contributions.

Dr. Yuanfeng Qi
Dr. Kai He
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 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

  • recycling and resources
  • pollutant removal
  • by-product remedy
  • process management
  • specific fillers and carriers
  • processing models
  • reactors
  • wastewater engineering
  • identification and analysis

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Further information on MDPI's Special Issue policies can be found here.

Related Special Issue

Published Papers (6 papers)

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Research

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10 pages, 3552 KiB  
Communication
Co/Al–Layered Double Hydroxide-Modified Silicon Carbide Membrane Filters as Persulphate Activator for Aniline Degradation
by Yunfei Zhang, Hongmei Shen, Wenzheng Zheng, Tong Wu, Xianjuan Pu, Diwen Zhou, Senyuan Shen and Yingchao Lin
Water 2025, 17(3), 355; https://doi.org/10.3390/w17030355 - 27 Jan 2025
Viewed by 761
Abstract
Novel catalytic silicon carbide membrane filters (SCMFs) are synthesized with Co/Al–layered double hydroxide (Co/Al-LDH)-coated silicon carbide powder. After capsuled in a self-designed membrane shell, the SCMFs are utilized in activating persulphate for aniline degradation. Thermal analysis conducted via TG/DTG/DSC examination shows that the [...] Read more.
Novel catalytic silicon carbide membrane filters (SCMFs) are synthesized with Co/Al–layered double hydroxide (Co/Al-LDH)-coated silicon carbide powder. After capsuled in a self-designed membrane shell, the SCMFs are utilized in activating persulphate for aniline degradation. Thermal analysis conducted via TG/DTG/DSC examination shows that the heating treatment is beneficial in elevating the activating ability of SCMFs, and the derived Co3O4 displays superior catalytical efficiency than Co/Al-LDHs precursor. The XRD patterns and SEM images indicate the sheet-like Co/Al-LDHs are uniformly coprecipitated throughout the surface of SCMFs. Within 20 min, around 95% of aniline is eliminated under 0.7 m of flow velocity and 8:1 of persulphate to aniline ratio. Three-dimensional fluorescence and GC chromatography reveal that distinct by-products exist in the early stage of the aniline degradation process between the sintered and non-sintered Co/Al-LDH-coated SCMFs. The integration strategy of Co/Al-LDH coatings and heating treatment endows traditional SCMFs with robust catalytic properties for engineering-oriented applications in wastewater treatment. Full article
(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)
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19 pages, 5619 KiB  
Article
Graphitic Carbon Nitride/CeO2 Nanocomposite for Photocatalytic Degradation of Methyl Red
by Khansaa Al-Essa, Ethar M. Al-Essa, Alaa Qarqaz, Suhad Al-Issa, Solhe F. Alshahateet and O’la Al-Fawares
Water 2025, 17(2), 158; https://doi.org/10.3390/w17020158 - 9 Jan 2025
Cited by 1 | Viewed by 1107
Abstract
Nanosized ceria (CeO2) and a graphitic carbon nitride-loaded ceria (CeO2/GCN) nanocomposite were synthesized using a straightforward and efficient method and characterized by XRD, FTIR, SEM, TEM, TGA, and BET analyses. These techniques confirmed that CeO2 was effectively supported [...] Read more.
Nanosized ceria (CeO2) and a graphitic carbon nitride-loaded ceria (CeO2/GCN) nanocomposite were synthesized using a straightforward and efficient method and characterized by XRD, FTIR, SEM, TEM, TGA, and BET analyses. These techniques confirmed that CeO2 was effectively supported on the surface of GCN, with particle sizes of the CeO2/GCN composite in the range of 10–15 nm and a pore size of 3.33 nm. The photocatalytic activity of the CeO2/GCN nanocomposite and CeO2 NPs in the degradation of methyl red dye under sunlight radiation was studied using UV–visible spectroscopy. A noticeable red shift in the CeO2/GCN nanocomposite compared to pure CeO2 NPs suggests a reduction in its band gap energy, calculated at 3.90 eV for CeO2 NPs and 2.97 eV for the CeO2/GCN nanocomposite. This band gap reduction enhances the photocatalytic degradation process, achieving a removal efficiency of 99.92% within a short irradiation time of 40 min for the CeO2/GCN nanocomposite, compared to 69.47% for CeO2 NPs. These findings indicate that graphitic carbon nitride significantly enhances the photocatalytic properties of CeO2 NPs. Full article
(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)
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17 pages, 5308 KiB  
Article
Optimising Salt Recovery—Four-Year Operational Insights into Na2SO4 Recovery from Saline Waters Using Pipe Freeze-Crystallization
by Kagiso S. More, Johannes P. Maree and Mlungisi Mahlangu
Water 2025, 17(1), 101; https://doi.org/10.3390/w17010101 - 2 Jan 2025
Viewed by 923
Abstract
Managing high-salinity industrial wastewater poses environmental and operational challenges, particularly in recovering valuable salts like Na2SO4. Traditional methods such as evaporation and distillation are energy-intensive (2200 kJ/kg) and environmentally unsustainable. Addressing these limitations, this study investigates the application and [...] Read more.
Managing high-salinity industrial wastewater poses environmental and operational challenges, particularly in recovering valuable salts like Na2SO4. Traditional methods such as evaporation and distillation are energy-intensive (2200 kJ/kg) and environmentally unsustainable. Addressing these limitations, this study investigates the application and optimisation of pipe freeze-crystallization (PFC), an innovative, energy efficient technology operating at 330 kJ/kg, to achieve zero-waste treatment objectives. This research used OLI ESP software to model the crystallization dynamics, accurately predicting Na2SO4 recovery and reductions in sulphate concentrations from 74.3 g/L to 6.9 g/L at temperatures below −2 °C. The recovered Na2SO4 was analysed using X-ray diffraction with its purity increasing over the years from 50% to 84.9%. Over a four-year operational period at a demonstration plant in Olifantsfontein, South Africa, modifications including extending pipe length from 90 m to 120 m and increasing pipe diameter from 20 mm to 25 mm improved salt recovery rates from 3.5 t/month to 9.1 t/month. Enhanced chiller performance sustained sub-zero temperatures, achieving a cooling capacity of 7 kW while enabling consistent salt and ice recovery. Results showed that feedwater composition substantially influenced crystallization dynamics, with high NaCl concentrations delaying Na2SO4 crystallization. The plant’s adaptability to diverse feedwaters and scalability for broader industrial applications highlights its potential as a cost-effective solution. These findings establish PFC as a transformative technology for sustainable saline wastewater treatment, offering industry compliance with environmental regulations, and economic benefits through resource recovery. Full article
(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)
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12 pages, 6071 KiB  
Article
Coupled Electrolysis–Microfiltration System for Efficient Phosphorus Removal and Recovery in the Form of Iron Phosphate Compounds from Wastewater
by Hengfei Yan, Lifeng Wang, Weiping Liu, Xiaofeng Liu and Di Liu
Water 2024, 16(23), 3397; https://doi.org/10.3390/w16233397 - 26 Nov 2024
Viewed by 908
Abstract
Electrochemical technology presents a promising approach for phosphorus recovery from wastewater. Nevertheless, its application in industry is hindered by relatively low phosphorus recovery efficiency, high energy consumption and complex reactor configurations. In this study, a coupled electrolysis and microfiltration system was designed for [...] Read more.
Electrochemical technology presents a promising approach for phosphorus recovery from wastewater. Nevertheless, its application in industry is hindered by relatively low phosphorus recovery efficiency, high energy consumption and complex reactor configurations. In this study, a coupled electrolysis and microfiltration system was designed for phosphorus recovery in the shape of iron phosphate compounds with the use of steel pickling wastewater as the iron source. In the electrolysis unit, the anode diffusion layer was extracted from the porous anode surface with the production of an acid effluent and an alkaline effluent. The alkaline effluent was mixed with the stainless steel acid washing wastewater generated from the steel pickling process and then introduced into the microfiltration unit to intercept the iron phosphate crystals. The filtered effluent was finally introduced into the air aeration unit to further reduce the phosphorus content in the water. And the extracted acid solution could be reused in the pickling step of the iron and steel manufacturing process. The experimental results show that the coupled system achieved phosphorus recovery of 42~80% at a current density of 5~20 mA cm−2, accompanying energy consumption of 5.78~9.15 kWh (kg P)−1 and current efficiency of 79~43%, when the phosphorus concentration was 3 mM and the iron–phosphorus molar ratio was 1.5. After the microfiltration treatment, the residual phosphorus could be further reduced to 0.5 mg L−1 within 30 min at an aeration rate of 80 mL min−1, which met the discharge standard. The presence of interfering ions (HCO3− and SiO42−) posed inhibited effects on phosphorus recovery. Generally, this study provides a green and environmentally friendly way to efficiently recover phosphorus resources from wastewater. Full article
(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)
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17 pages, 3473 KiB  
Article
Pipeline Leak Identification and Prediction of Urban Water Supply Network System with Deep Learning Artificial Neural Network
by Fei Xi, Luyi Liu, Liyu Shan, Bingjun Liu and Yuanfeng Qi
Water 2024, 16(20), 2903; https://doi.org/10.3390/w16202903 - 12 Oct 2024
Cited by 1 | Viewed by 1972
Abstract
Pipeline leakage, which leads to water wastage, financial losses, and contamination, is a significant challenge in urban water supply networks. Leak detection and prediction is urgent to secure the safety of the water supply system. Relaying on deep learning artificial neural networks and [...] Read more.
Pipeline leakage, which leads to water wastage, financial losses, and contamination, is a significant challenge in urban water supply networks. Leak detection and prediction is urgent to secure the safety of the water supply system. Relaying on deep learning artificial neural networks and a specific optimization algorithm, an intelligential detection approach in identifying the pipeline leaks is proposed. A hydraulic model is initially constructed on the simplified Net2 benchmark pipe network. The District Metering Area (DMA) algorithm and the Cuckoo Search (CS) algorithm are integrated as the DMA-CS algorithm, which is employed for the hydraulic model optimization. Attributing to the suspected leak area identification and the exact leak location, the DMA-CS algorithm possess higher accuracy for pipeline leakage (97.43%) than that of the DMA algorithm (92.67%). The identification pattern of leakage nodes is correlated to the maximum number of leakage points set with the participation of the DMA-CS algorithm, which provide a more accurate pathway for identifying and predicting the specific pipeline leaks. Full article
(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)
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Review

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20 pages, 1665 KiB  
Review
The Utilization of Dissolved Organic Matter Spectral and Molecular Properties in Freshwater Eutrophication Studies: A Mini Review
by Wengang Yan, Junfeng Xing, Chunzhao Chen, Yihua Xiao and Changqing Liu
Water 2025, 17(2), 151; https://doi.org/10.3390/w17020151 - 8 Jan 2025
Viewed by 913
Abstract
Eutrophication is a major environmental issue affecting freshwater ecosystems worldwide. While its impact on the composition of dissolved organic matter (DOM) is well recognized, the relationships between DOM’s optical and molecular properties across eutrophication gradients remain underexplored. This review synthesizes recent research on [...] Read more.
Eutrophication is a major environmental issue affecting freshwater ecosystems worldwide. While its impact on the composition of dissolved organic matter (DOM) is well recognized, the relationships between DOM’s optical and molecular properties across eutrophication gradients remain underexplored. This review synthesizes recent research on DOM’s optical properties (derived from UV-Vis absorption and fluorescence spectroscopy) and molecular characteristics (analyzed using Fourier-transform ion cyclotron resonance mass spectrometry, FT-ICR MS) in freshwater systems of varying trophic states. Generalized additive model (GAM) analysis was used to assess correlations between DOM’s properties and the trophic state index (TSI). The dissolved organic carbon (DOC), a254, SUVA254, SR, HIX, BIX, and FI averaged 11.44 ± 11.97 mg/L, 23.23 ± 16.95 m−1. 2.98 ± 0.99 L·mg−1·m−1, 1.42 ± 0.38, 2.38 ± 1.31, 1.08 ± 0.16, and 2.11 ± 0.44, respectively, from mesotrophic to middle-eutrophic sites. The GAM results revealed a significant linear correlation between DOC and DOM’s optical properties, including a254, SUVA254, and FI, with the TSI, suggesting that DOM accumulation intensifies with eutrophication. DOM’s molecular properties, such as O/C and H/C ratios, double bond equivalents (DBEs), and CHOS% content, exhibited nonlinear correlations with the TSI. These trends imply a shift in DOM sources from terrestrial and macrophyte-derived inputs to those dominated by algal- and sediment-derived sources as eutrophication progresses. We concluded that DOM’s molecular indices alone may not serve as a reliable indicator of freshwater trophic states; future studies should focus on integrating both optical and molecular indices to offer a more comprehensive assessment of freshwater trophic states. Given the limited number of molecular variables examined in this study, this work only offers a preliminary investigation into the relationship between DOM molecular changes and freshwater eutrophication. More systematic studies focusing on the molecular-level analyses of DOM across varying trophic states on a broader geographic scale are needed. Full article
(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)
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