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Water Quality Engineering and Wastewater Treatment III

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

Deadline for manuscript submissions: 31 December 2024 | Viewed by 36456

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Special Issue Editors

Prof. Dr. Yung-Tse Hung

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Guest Editor

Department of Civil and Environmental Engineering, Cleveland State University, Cleveland, OH 44115, USA
Interests: water supply and water treatment; municipal wastewater treatment; industrial waste treatment; biological waste treatment; water and wastewater treatment plant design; water pollution control; water quality engineering
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Prof. Dr. Hamidi Abdul Aziz

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Guest Editor

School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal 14300, Penang, Malaysia
Interests: water and wastewater treatment and management; solid waste management; landfill leachate treatment; industrial waste treatment and disposal; biological; chemical and tertiary wastewater treatment; pollution control; water quality engineering
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Issam A. Al-Khatib

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Institute of Environmental and Water Studies, Faculty of Graduate Studies, Birzeit University, Birzeit P.O. Box 14, West Bank, Palestine
Interests: water recourses management and quality; environmental assessment; wastewater management; advocacy; coordination and networking
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Rehab O. Abdel Rahman

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Hot Laboratories and Waste Management Center, Atomic Energy Authority, Inshas, Cairo 13759, Egypt
Interests: water and wastewater treatment; pollution control; radioactive wastes; mathematical modeling; nanomaterials; cement-based materials; hazardous waste immobilization
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Tsuyoshi Imai

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Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1, Tokiwadai, Ube City 755-8611, Yamaguchi, Japan
Interests: biological wastewater treatment (aerobic, anaerobic); biological treatment/recycling of organic solid waste; oxygen supply methods in aerobic wastewater treatment; CO₂ removal and storage
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Clean water is one of the most important natural resources on Earth. Wastewater, which is spent water, is also a valuable natural resource in the world. However, wastewater may contain numerous contaminants and, thus, cannot be released back into the environment until these contaminants are removed. Untreated wastewater and inadequately treated wastewater may have a detrimental effect on the environment and harmful effect on human health. Water quality engineering addresses the sources, transport, and treatment of chemical and microbiological contaminants that affect water. Our objective is the treatment of wastewater such that the treated wastewater meets national effluent standards for the protection of both the environment and public health.

This Special Issue seeks contributions on advanced technologies applied to the treatment of municipal and industrial wastewater and sludge. Of specific interest are contributions that deal with recent advances in municipal wastewater, industrial wastewater, and sludge-treatment technologies; the health effects of municipal wastewater; risk management; energy-efficient wastewater treatment; water sustainability; and water reuse and resource recovery.

Prof. Dr. Yung-Tse Hung
Prof. Dr. Hamidi Abdul Aziz
Prof. Dr. Issam A. Al-Khatib
Prof. Dr. Rehab O. Abdel Rahman
Prof. Dr. Tsuyoshi Imai
Guest Editors

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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

advanced wastewater technology
onsite wastewater treatment
natural wastewater treatment system
biological treatment
physicochemical treatment
tertiary treatment
water quality
sludge treatment and disposal
energy-efficient wastewater treatment
water reuse
resource recovery
municipal wastewater
industrial wastewater
nutrient removal

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Published Papers (13 papers)

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Research

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18 pages, 2579 KiB

Open AccessArticle

Assessing the Synergies of Photo-Fenton at Natural pH and Granular Activated Carbon as a Quaternary Treatment

by Paula Núñez-Tafalla, Irene Salmerón, Silvia Venditti and Joachim Hansen

Water 2024, 16(19), 2824; https://doi.org/10.3390/w16192824 - 4 Oct 2024

Viewed by 887

Abstract

The challenge of microcontaminants (MCs) in wastewater effluent has been addressed by using different technologies, including advanced oxidation processes (AOPs) and adsorption. This work evaluates the benefits and synergies of combining these two processes. The AOPs were photo-Fenton and UV/H₂O₂ operated under natural pH but with different reagents dosages, lamps, and chelating agents. Chelating agents were used at analytical (ethylenediamine-N,N-disuccinic acid and citric acid) and technical grade (citric acid) to simulate scaling-up conditions. The adsorption process was studied via granular activated carbon (GAC) filtration using fresh and regenerated GAC. Four AOP scenarios were selected and coupled with GAC filtration, showing benefits for both processes. AOP treatment time decreased from 10–15 min to 5 min, resulting in a reduction in energy consumption of between 50 and 66%. In the photo-Fenton process, it was possible to work with low reagent dosages (1.5 mg L⁻¹ iron and 20 mg L⁻¹ of H₂O₂). However, the use of UV/H₂O₂ showed close removal, highlighting it as a real alternative. An extension of the GAC lifetime by up to 11 times was obtained in all the scenarios, being higher for regenerated than for fresh GAC. Furthermore, the toxicity and phytotoxicity of the treated wastewater were evaluated, and no acute toxicity or slight variation in the phytotoxicity was observed in the combination of these processes. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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19 pages, 5514 KiB

Open AccessArticle

Methyl Red Adsorption from Aqueous Solution Using Rumex Abyssinicus-Derived Biochar: Studies of Kinetics and Isotherm

by Meseret Dawit Teweldebrihan and Megersa Olumana Dinka

Water 2024, 16(16), 2237; https://doi.org/10.3390/w16162237 - 8 Aug 2024

Cited by 1 | Viewed by 1054

Abstract

This work focused on the decolorization of methyl red (MR) from an aqueous solution utilizing Rumex abyssinicus-derived biochar (RAB). RAB was prepared to involve unit operations such as size reduction, drying, and carbonization. The pyrolysis of the precursor material was carried out at a temperature of 500 °C for two hours. After that, the prepared RAB was characterized by the pH point of zero charge (pHpzc), the Brunauer–Emmett–Teller (BET) method, Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared (FTIR) spectroscopy. On the other hand, a batch adsorption experiment of MR removal onto RAB was conducted, considering four operating parameters: pH, contact time, adsorbent dose, and initial dye concentration. The characterization of the adsorbent material revealed a porous and heterogeneous surface morphology during SEM, a specific surface area of 45.8 m²/g during the BET method, the presence of various functional groups during FTIR, and a pHpzc of 6.2. The batch adsorption experiment analysis results revealed that a maximum removal efficiency of 99.2% was attained at an optimum working condition of pH 6, contact time of 40 min, initial dye concentration of 70 mg/L and adsorbent dosage of 0.2 g/100 mL. Furthermore, Freundlich isotherm (R² = 0.99) and pseudo-second-order kinetics (R² = 0.99) models confirmed the heterogeneous surface interaction and chemisorption nature. Generally, this study highlighted that RAB could be a potential adsorbent for the detoxification of MR-containing industrial effluents. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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23 pages, 4096 KiB

Open AccessArticle

Impact of Design and Mixing Strategies on Biogas Production in Anaerobic Digesters

by Thomas Neuner, Michael Meister, Martin Pillei, Thomas Senfter, Simon Draxl-Weiskopf, Christian Ebner, Jacqueline Winkler and Wolfgang Rauch

Water 2024, 16(15), 2205; https://doi.org/10.3390/w16152205 - 4 Aug 2024

Viewed by 1538

Abstract

Anaerobic digestion (AD) is a biological process that breaks down organic matter in the absence of oxygen, producing biogas and nutrient-rich digestate. Various reactor designs and mixing strategies are well-established in AD processes, each with their own advantages and benefits. The presented study summarizes and investigates the state of the art of AD in domestic wastewater treatment plants (WWTPs) in an Austrian alpine region, with a primary focus on finding similarities among the most efficient plants regarding digester design, mixing approaches, and biogas production. By combining surveys and detailed field studies in cooperation with 34 WWTPs, the study provides a comprehensive overview of common AD practices, reactor shapes, and inherent mixing methods, highlighting their potential regarding energetic efficiency and biogas production. The results of the survey reveal qualitative trends in efficient AD design alongside detailed quantitative data derived from the supervised in-field optimization studies. Notably, one of the studies demonstrated energetic savings of 52% with no decrease in biogas production, achieved by transitioning from gas injection to mechanical agitation. Redundant impeller-based overmixing was also practically investigated and demonstrated in another field study. After optimization, the adaptations also resulted in energy savings of 30%, still proving sufficient substrate mixing with biomethane potential analysis. In conclusion, this research emphasizes the economic and environmental importance of energy-refined practices and optimized processes while highlighting the sustainability of AD, particularly for large domestic WWTPs but also for different comparable applications. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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13 pages, 899 KiB

Open AccessArticle

Mercury Concentrations in Dust from Dry Gas Cleaning of Sinter Plant and Technical Removal Options

by Claudia Hledik, Yilan Zeng, Tobias Plattner and Maria Fuerhacker

Water 2024, 16(14), 1948; https://doi.org/10.3390/w16141948 - 10 Jul 2024

Viewed by 675

Abstract

Mercury (Hg) is a naturally occurring element and has been released through human activities over an extended period. The major source is the steel industry, especially sinter plants. During a sintering process, high amounts of dust and gaseous emission are produced. These gases contain high loads of SO_x and NO_X as well as toxic pollutants, such as heavy metals like Hg. These toxic pollutants are removed by adsorbing to solids, collected as by-products and deposited as hazardous waste. The by-products contain a high amount of salt, resulting in a high water solubility. In this study, to ultimately reduce the waste amount in landfills, leachates of the by-products have been produced. The dissolved Hg concentration and its distribution across different charges were determined. Hg concentrations between 3793 and 12,566 µg L⁻¹ were measured in the leachates. The objective was to lower the Hg concentration in leachates by chemical precipitation with sodium sulfide (Na₂S) or an organic sulfide followed by filtration. Both reagents precipitate Hg with removal rates of up to 99.6% for the organic sulfide and 99.9% for Na₂S, respectively. The dose of the precipitator as well as the initial Hg concentration affected the removal rate. In addition to Hg, other relevant heavy metals have to be included in the calculation of the amount of precipitator as well. Between relevant heavy metals including Hg and sulfide, the ratio should be more than 1.5. The novelty of this study is the measurement and treatment of Hg in wastewater with a high ionic strength. The high salt concentrations did not influence the efficiency of the removal methods. An adjustment of the precipitator dose for each sample is necessary, because an overdose potentially leads to the re-dissolving of Hg. It could be shown that the emission limit of 0.005 mg L⁻¹ could be reached especially by precipitation with Na₂S. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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12 pages, 1193 KiB

Open AccessArticle

Growing an Enhanced Culture of Polyphosphate-Accumulating Organisms to Optimize the Recovery of Phosphate from Wastewater

by Njabulo Thela, David Ikumi, Theo Harding and Moses Basitere

Water 2023, 15(11), 2014; https://doi.org/10.3390/w15112014 - 26 May 2023

Cited by 1 | Viewed by 1940

Abstract

Having certain bacteria called phosphorus-accumulating organisms (PAOs) is important for getting rid of phosphorus (P) in wastewater from homes. This happens in a process called enhanced biological phosphorus removal (EBPR), where PAOs are active in activated sludge. To design and make EBPR processes work better, we need to have an in-depth understanding of how PAOs work. The best way to learn about them is by studying them in a laboratory. This study undertook to culture these microorganisms in the laboratory. A University of Cape Town membrane bioreactor (UCTMBR) activated sludge (AS) system was used to grow the microorganisms and see how well it worked. This paper looked at what type of substrate PAOs like best, either acetate or propionate, and how providing them with more of their preferred substrate affects how they grow. During the process, it was observed that P was not released or taken up significantly when acetate was added to the influent. The levels were consistently low at around 5.74 ± 4.47 mgP/L infl (release) and 19.9 ± 7.17 mgP/L infl (uptake). The signs become much better when propionate was used instead of acetate. When the amount of propionate in the influent was increased from 50% to 76% (as a percentage of influent total chemical oxygen demand), the amount of P released went up to 155 ± 17.7 mgP/L infl, and the amount of P taken up went up to 213.7 ± 11.4 mgP/L infl. The proof given indicated that propionate is preferred by PAOs. This study found that when more propionate was added to the wastewater, the concentration of PAO biomass went up. This was shown by certain signs that PAOs display when they are present. Results presented in this journal article emanate from an MSc Thesis (Thela, 2022) published in open-source UCT. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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15 pages, 4625 KiB

Open AccessArticle

Utilizing Electricity-Producing Bacteria Flora to Mitigate Hydrogen Sulfide Generation in Sewers through an Electron-Pathway Enabled Conductive Concrete

by Huy Thanh Vo, Tsuyoshi Imai, Masato Fukushima, Tasuma Suzuki, Hiraku Sakuma, Takashi Hitomi and Yung-Tse Hung

Water 2023, 15(9), 1749; https://doi.org/10.3390/w15091749 - 1 May 2023

Viewed by 2097

Abstract

This study aims to demonstrate the effectiveness of using biological oxidation for hydrogen sulfide (H₂S) control. A long-term experiment was conducted using a rod-shaped electrode made of highly conductive concrete, which provided an electron pathway for H₂S mitigation. Bacterial flora analysis was conducted using PCR-DGGE and metagenomic analysis by next-generation sequencing to identify electricity-producing bacteria. Results showed that H₂S was effectively mitigated, and electricity-producing bacteria, including Geobacter sp. and Pelobacter sp., were found around the inner surface of the anode. The study found that highly conductive concrete can create an electron pathway for biological oxidation of H₂S. Oxygen from the air layer near the surface of the water can act as an electron acceptor, even under anaerobic conditions, enabling effective H₂S control in sewer systems. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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15 pages, 2172 KiB

Open AccessArticle

Chromium Removal from Aqueous Solution Using Natural Clinoptilolite

by Tonni Agustiono Kurniawan, Mohd Hafiz Dzarfan Othman, Mohd Ridhwan Adam, Xue Liang, Huihwang Goh, Abdelkader Anouzla, Mika Sillanpää, Ayesha Mohyuddin and Kit Wayne Chew

Water 2023, 15(9), 1667; https://doi.org/10.3390/w15091667 - 25 Apr 2023

Cited by 26 | Viewed by 3065

Abstract

This work investigates the applicability of clinoptilolite, a natural zeolite, as a low-cost adsorbent for removing chromium from aqueous solutions using fixed bed studies. To improve its removal performance for the inorganic pollutant, the adsorbent is pretreated with NaCl to prepare it in the homoionic form of Na⁺ before undertaking ion exchange with Cr³⁺ in aqueous solution. This work also evaluates if treated effluents could meet the required effluent discharge standard set by legislation for the target pollutant. To sustain its cost-effectiveness for wastewater treatment, the spent adsorbent is regenerated with NaOH. It was found that the clinoptilolite treated with NaCl has a two-times higher Cr adsorption capacity (4.5 mg/g) than the as-received clinoptilolite (2.2 mg/g). Pretreatment of the clinoptilolite with NaCl enabled it to treat more bed volume (BV) (64 BV) at a breakthrough point of 0.5 mg/L of Cr concentration and achieve a longer breakthrough time (1500 min) for the first run, as compared to as-received clinoptilolite (32 BV; 250 min). This suggests that pretreatment of clinoptilolite with NaCl rendered it in the homoionic form of Na⁺. Although pretreated clinoptilolite could treat the Cr wastewater at an initial concentration of 10 mg/L, its treated effluents were still unable to meet the required Cr limit of less than 0.05 mg/L set by the US Environmental Protection Agency (EPA). Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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25 pages, 2346 KiB

Open AccessArticle

Selection of Wastewater Treatment Technology: AHP Method in Multi-Criteria Decision Making

by Jasmina Ćetković, Miloš Knežević, Radoje Vujadinović, Esad Tombarević and Marija Grujić

Water 2023, 15(9), 1645; https://doi.org/10.3390/w15091645 - 23 Apr 2023

Cited by 8 | Viewed by 5505

Abstract

Wastewater treatment is a process that reduces pollution to those quantities and concentrations at which purified wastewater is no longer a threat to human and animal health and safety and does not cause unwanted changes in the environment. Municipal wastewater is classified as biodegradable water. Special importance should be given to wastewater with a high content of organic matter (COD), phosphorus (P) and nitrogen (N). MBBR technology, developed on the basis of the conventional activated sludge process and the bio filter process, does not take up much space and does not have problems with activated sludge, as in the case of conventional biological reactors, and has shown good results for the removal of organic matter, phosphorus and nitrogen. The aim of this paper is to optimize the wastewater treatment process in the municipality of Dojran, North Macedonia. Three alternative solutions for improving the capacity for wastewater treatment in the municipality of Dojran were analyzed. The shortlist of variants was made on the basis of several criteria, including: analysis of the system in the tourist season and beyond, assessment of the condition and efficiency of the existing wastewater treatment plant (WWTP) in combination with a new treatment plant, treatment efficiency when using different wastewater treatment technologies, the size of the site needed to accommodate the capacity, as well as the financial parameters for the proposed system. The selection of the most favorable solution for the improvement of the wastewater treatment system was made using the AHP (analytic hierarchy process) method. In order to select the optimal solution, a detailed analysis was conducted, considering several decision-making criteria, namely the initial investment, operating costs and management complexity. Based on the obtained results, Variant 3 was recommended, that is, the construction of a completely new station with MBBR technology, with a capacity for 6000 equivalent inhabitants. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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Review

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18 pages, 1949 KiB

Open AccessReview

Unraveling the Potential of Microbial Flocculants: Preparation, Performance, and Applications in Wastewater Treatment

by Yang Yang, Cancan Jiang, Xu Wang, Lijing Fan, Yawen Xie, Danhua Wang, Tiancheng Yang, Jiang Peng, Xinyuan Zhang and Xuliang Zhuang

Water 2024, 16(14), 1995; https://doi.org/10.3390/w16141995 - 14 Jul 2024

Cited by 1 | Viewed by 1761

Abstract

Microbial flocculants (MBFs), a class of eco-friendly and biodegradable biopolymers produced by various microorganisms, have gained increasing attention as promising alternatives to conventional chemical flocculants in wastewater treatment and pollutant removal. This review presents a comprehensive overview of the current state of MBF research, encompassing their diverse sources (bacteria, fungi, and algae), major categories (polysaccharides, proteins, and glycoproteins), production processes, and flocculation performance and mechanisms. The wide-ranging applications of MBFs in removing suspended solids, heavy metals, dyes, and other pollutants from industrial and municipal wastewater are critically examined, highlighting their superior efficiency, selectivity, and environmental compatibility compared to traditional flocculants. Nonetheless, bioflocculants face significant challenges including high substrate costs, low production yields, and intricate purification methodologies, factors that impede their industrial scalability. Moreover, the risk of microbial contamination and the attendant health implications associated with the use of microbial flocculants (MBFs) necessitate thorough evaluation. To address the challenges of high production costs and variable product quality, strategies such as waste valorization, strain improvement, process optimization, and biosafety evaluation are discussed. Moreover, the development of multifunctional MBF-based flocculants and their synergistic use with other treatment technologies are identified as emerging trends for enhanced wastewater treatment and resource recovery. Future research directions are outlined, emphasizing the need for in-depth mechanistic studies, advanced characterization techniques, pilot-scale demonstrations to accelerate the industrial adoption of MBF, and moreover, integration with novel wastewater treatment processes, such as partial nitrification and the anammox process. This review is intended to inspire and guide further research and development efforts aimed at unlocking the full potential of MBFs as sustainable, high-performance, and cost-effective bioflocculants for addressing the escalating challenges in wastewater management and environmental conservation. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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29 pages, 4994 KiB

Open AccessReview

A Systematic Literature Review for Addressing Microplastic Fibre Pollution: Urgency and Opportunities

by Carmen Ka-Man Chan, Chris Kwan-Yu Lo and Chi-Wai Kan

Water 2024, 16(14), 1988; https://doi.org/10.3390/w16141988 - 13 Jul 2024

Cited by 4 | Viewed by 1871

Abstract

Microplastic fibre (MPF) pollution is a pressing concern that demands urgent attention. These tiny synthetic textile fibres can be found in various ecosystems, including water and air, and pose significant environmental risks. Despite their size (less than 5 mm), they can harm aquatic and terrestrial organisms and human health. Studies have demonstrated that these imperceptible pollutants can contaminate marine environments, thereby putting marine life at risk through ingestion and entanglement. Additionally, microplastic fibres can absorb toxins from the surrounding water, heightening their danger when consumed by aquatic organisms. Traces of MPFs have been identified in human food chains and organs. To effectively combat MPF pollution, it is crucial to understand how these fibres enter ecosystems and their sources. Primary sources include domestic laundry, where synthetic textile fibres are released into wastewater during washing. Other significant sources include industrial effluents, breakdown of plastic materials, and atmospheric deposition. Additionally, MPFs can be directly released into the environment by improperly disposing of consumer products containing these fibres, such as non-woven hygienic products. A comprehensive approach is necessary to address this pressing issue, including understanding the sources, pathways, and potential risks of MPFs. Immediate action is required to manage contamination and mitigate MPF pollution. This review paper provides a systematic literature analysis to help stakeholders prioritise efforts towards reducing MPFs. The key knowledge gaps identified include a lack of information regarding non-standardised test methodology and reporting units, and a lack of information on manufacturing processes and products, to increase understanding of life cycle impacts and real hotspots. Stakeholders urgently need collaborative efforts to address the systematic changes required to tackle this issue and address the proposed opportunities, including targeted government interventions and viable strategies for the industry sector to lead action. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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35 pages, 5497 KiB

Open AccessReview

Permeable Concrete Barriers to Control Water Pollution: A Review

by Rehab O. Abdel Rahman, Ahmed M. El-Kamash and Yung-Tse Hung

Water 2023, 15(21), 3867; https://doi.org/10.3390/w15213867 - 6 Nov 2023

Cited by 2 | Viewed by 3038

Abstract

Permeable concrete is a class of materials that has long been tested and implemented to control water pollution. Its application in low-impact development practices has proved its efficiency in mitigating some of the impacts of urbanization on the environment, including urban heat islands, attenuation of flashfloods, and reduction of transportation-related noise. Additionally, several research efforts have been directed at the dissemination of these materials for controlling pollution via their use as permeable reactive barriers, as well as their use in the treatment of waste water and water purification. This work is focused on the potential use of these materials as permeable reactive barriers to remediate ground water and treat acid mine drainage. In this respect, advances in material selection and their proportions in the mix design of conventional and innovative permeable concrete are presented. An overview of the available characterization techniques to evaluate the rheology of the paste, hydraulic, mechanical, durability, and pollutant removal performances of the hardened material are presented and their features are summarized. An overview of permeable reactive barrier technology is provided, recent research on the application of permeable concrete technology is analyzed, and gaps and recommendations for future research directions in this field are identified. The optimization of the mix design of permeable reactive concrete barriers is recommended to be directed in a way that balances the performance measures and the durability of the barrier over its service life. As these materials are proposed to control water pollution, there is a need to ensure that this practice has minimal environmental impacts on the affected environment. This can be achieved by considering the analysis of the alkaline plume attenuation in the downstream environment. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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47 pages, 2214 KiB

Open AccessReview

Emerging Contaminants and Their Removal from Aqueous Media Using Conventional/Non-Conventional Adsorbents: A Glance at the Relationship between Materials, Processes, and Technologies

by Cristina E. Almeida-Naranjo, Víctor H. Guerrero and Cristina Alejandra Villamar-Ayala

Water 2023, 15(8), 1626; https://doi.org/10.3390/w15081626 - 21 Apr 2023

Cited by 20 | Viewed by 6551

Abstract

Emerging contaminants (ECs) are causing negative effects on the environment and even on people, so their removal has become a priority worldwide. Adsorption and the associated technologies where this process occurs (filtration/biofiltration) have gained great interest, due to its low cost, easy operation, and effectiveness mainly in the removal (up to 100%) of lipophilic ECs (log K_ow > 4). Activated carbon continues to be the most efficient material in the removal of ECs (>850 mg/g). However, other conventional materials (activated carbon, clays, zeolites) and non-conventional materials (agro-industrial/forestry/industrial residues, nanomaterials, among others) have shown efficiencies greater than 90%. Adsorption depends on the physicochemical properties of the materials and ECs. Thus, physical/chemical/thermal modifications and nanomaterial synthesis are the most used procedures to improve adsorption capacity. A material with good adsorptive properties could be used efficiently in filtration/biofiltration technologies. Agro-industrial residues are promising alternatives to be used in these technologies, due to their high availability, low toxicity, and adsorption capacities (up to 350 mg/g). In filtration/biofiltration technologies, the material, in addition to acting as adsorbent, plays a fundamental role in operation and hydraulics. Therefore, selecting the appropriate material improves the efficiency/useful life of the filter/biofilter. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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18 pages, 3472 KiB

Open AccessReview

Physicochemical Technique in Municipal Solid Waste (MSW) Landfill Leachate Remediation: A Review

by Hamidi Abdul Aziz, Siti Fatihah Ramli and Yung-Tse Hung

Water 2023, 15(6), 1249; https://doi.org/10.3390/w15061249 - 22 Mar 2023

Cited by 9 | Viewed by 3633

Abstract

Leachate generation is among the main challenging issues that landfill operators must handle. Leachate is created when decomposed materials and rainwater pass through the waste. Leachate carries many harmful pollutants, with high concentrations of BOD, COD, colour, heavy metals, ammoniacal nitrogen (NH₃-N), and other organic and inorganic pollutants. Among them, COD, colour, and NH₃-N are difficult to be completely eliminated, especially with a single treatment. They should be handled by appropriate treatment facilities before being safely released into the environment. Leachate remediation varies based on its properties, the costs of operation and capital expenditures, as well as the rules and regulations. Up until now, much scientific and engineering attention was given to the development of comprehensive solutions to leachate-related issues. The solutions normally demand a multi-stage treatment, commonly in the form of biological, chemical, and physical sequences. This review paper discussed the use of contemporary techniques to remediate landfill leachate with an emphasis on concentrated COD, colour, and NH₃-N levels with low biodegradability that is normally present in old landfill or dumping grounds in developing countries. A semi-aerobic type of landfill design was also discussed, as this concept is potentially sustainable compared to others. Some of the challenges and future prospects were also recommended, especially for the case of Malaysia. This may represent landfills or dumpsites in other developing countries with the same characteristics. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment III)

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