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18 pages, 2396 KB

Open AccessArticle

Microbiological and Physicochemical Parameters Related to Legionella spp. Colonisation in Hot Water Distribution Systems in Madrid: Case Study in Sports Centres

by María Concepción Almonacid Garrido, Alejandra García-Alonso, María José Villanueva-Suárez and María Dolores Tenorio-Sanz

Appl. Sci. 2026, 16(3), 1628; https://doi.org/10.3390/app16031628 - 5 Feb 2026

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Abstract

Domestic hot water systems are one of the most important reservoirs of Legionella. It is thought that physicochemical and microbiological water quality influences bacterial development. Accordingly, the objective of this study was to evaluate this relationship in domestic hot water in public [...] Read more.

Domestic hot water systems are one of the most important reservoirs of Legionella. It is thought that physicochemical and microbiological water quality influences bacterial development. Accordingly, the objective of this study was to evaluate this relationship in domestic hot water in public buildings in Madrid for potential health risks and to assess the parameters that could be associated with Legionella contamination, which would assist in developing control strategies to prevent legionellosis. A total of 1695 DHW samples were evaluated over a 14-year period (2007–2020). Legionella was analysed using culture plates and qPCR. The influencing parameters (pH, electrical conductivity, colour, turbidity, Fe nitrites, and coliforms) were analysed following official methods. Furthermore, sport centre risk assessment was carried out. Legionella was isolated in 64 samples. Non-compliance levels for turbidity, colour, iron, nitrites and coliforms were found primarily in samples containing Legionella. Nitrites > 0.5 mg/L, turbidity > 1 NFU, colour ≥ 1 Pt/Co, and building type were good parameters to test Legionella colonisation. The selected influencing factors may be a useful tool for ensuring water supply quality. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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21 pages, 793 KB

Open AccessArticle

SUVA-Based Modelling of THMFP Under Ozonation Using Regression and ANN Approaches

by Arzu Teksoy

Appl. Sci. 2026, 16(3), 1256; https://doi.org/10.3390/app16031256 - 26 Jan 2026

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Abstract

Drinking-water treatment systems must effectively control natural organic matter (NOM), a major precursor of regulated disinfection by-products (DBPs). Specific ultraviolet absorbance (SUVA) is widely used as an operational surrogate for NOM aromaticity and hydrophobicity; however, ozonation and subsequent filtration can disrupt the linear [...] Read more.

Drinking-water treatment systems must effectively control natural organic matter (NOM), a major precursor of regulated disinfection by-products (DBPs). Specific ultraviolet absorbance (SUVA) is widely used as an operational surrogate for NOM aromaticity and hydrophobicity; however, ozonation and subsequent filtration can disrupt the linear relationship between SUVA and trihalomethane formation potential (THMFP). This study evaluates whether SUVA can reliably predict THMFP under two ozonation configurations frequently applied in drinking-water treatment: pre-ozonation prior to coagulation–filtration and final ozonation following filtration. Experimental data were analyzed using conventional linear regression and artificial neural network (ANN) models, with SUVA employed as the sole predictor variable. Across all treatment configurations, reductions in SUVA were consistently more pronounced than corresponding decreases in THMFP, indicating a decoupling between chromophoric loss and chlorine-reactive precursor dynamics under ozonation-dominated conditions. Linear regression models exhibited only moderate predictive performance (R² = 0.63–0.76), reflecting the limitations of proportional surrogate-based approaches when NOM undergoes oxidative and adsorptive transformation. In contrast, single-parameter ANN models captured the nonlinear SUVA–THMFP relationship with substantially higher accuracy across both pre- and final-ozonation regimes (R² = 0.88–0.99), successfully resolving process-dependent patterns embedded within optically compressed SUVA signals. These findings demonstrate that, although SUVA alone cannot linearly represent the multistep transformation of NOM during ozonation and adsorption, it retains process-relevant structure information on DBP precursor reactivity that can be effectively extracted using nonlinear modelling. The results highlight the potential of integrating ANN-driven tools into advanced monitoring and DBP-control strategies in modern drinking-water treatment systems. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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16 pages, 2143 KB

Open AccessArticle

On-Demand Neutral Electrolyzed Water-Containing Hydrogel with Tunable Available Chlorine Concentration Based on Methylcellulose–Agar Composite

by Yuki Nagamatsu, Hiroshi Ikeda and Hiroshi Nagamatsu

Appl. Sci. 2026, 16(3), 1216; https://doi.org/10.3390/app16031216 - 24 Jan 2026

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Abstract

Neutral electrolyzed water (NW) is widely used in dentistry because of its strong bactericidal activity and high biosafety; however, its clinical application is limited by short retention time in the oral cavity and by the difficulty in maintaining and adjusting the available chlorine [...] Read more.

Neutral electrolyzed water (NW) is widely used in dentistry because of its strong bactericidal activity and high biosafety; however, its clinical application is limited by short retention time in the oral cavity and by the difficulty in maintaining and adjusting the available chlorine concentration (ACC) on-site. This study aimed to develop an on-demand NW-containing hydrogel (NWJ) that allows adjustment of ACC immediately before use while maintaining antimicrobial efficacy and handling properties. A methylcellulose–agar composite gel was prepared as a base gel and mixed with high-concentration NW to obtain prototype NWJs with target ACCs ranging 20–100 mg/L. Physicochemical properties (pH and ACC), time-dependent changes in ACC, bactericidal activity against Streptococcus mutans, and gel spreadability were evaluated. The base gel showed improved resistance to syneresis compared with an agar-only gel. All NWJs maintained a pH of approximately 6–7, exceeding the critical pH for enamel demineralization. Loss of ACC during gel preparation was less than 5%, and gradual ACC reduction was observed. Complete bactericidal activity was achieved at ACCs of 10 mg/L or higher, and gelation did not compromise antibacterial efficacy. These findings demonstrate that the developed NWJ provides a practical platform for clinical application of NW in dentistry. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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16 pages, 4291 KB

Open AccessArticle

New CdS–Bentonite Composites with Photocatalytic Properties

by Anca Dumbrava, Cristian Matei, Florin Moscalu, Diana Jecu and Daniela Berger

Appl. Sci. 2026, 16(2), 649; https://doi.org/10.3390/app16020649 - 8 Jan 2026

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Abstract

Cadmium sulfide is an important II-VI semiconductor known for its valuable photocatalytic properties ascribable to its band gap energy, which allows light absorption in the visible domain. Nonetheless, the application of cadmium sulfide in wastewater organic pollutant degradation is restricted due to its [...] Read more.

Cadmium sulfide is an important II-VI semiconductor known for its valuable photocatalytic properties ascribable to its band gap energy, which allows light absorption in the visible domain. Nonetheless, the application of cadmium sulfide in wastewater organic pollutant degradation is restricted due to its high toxicity to humans, soil, and marine life. To address this issue, we developed new composite materials by depositing CdS on a bentonite support in a 1:9 mass ratio to develop a photocatalyst with lower toxicity. In the first step, bentonite was activated using an aqueous HCl solution; for the deposition of CdS powder, we proposed the trituration method and compared it with chemical precipitation and hydrothermal synthesis, using thioacetamide as a sulfide ion source. The modified bentonite underwent characterization using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, UV-Vis, and FTIR spectroscopy. The photocatalytic activity was tested in the degradation of Congo red (CR), a persistent diazo dye. The efficiency of removing CR with CdS–bentonite composites depended on the deposition method of CdS, and it was higher than that of pristine CdS and of only adsorption onto acid-activated bentonite. The photocatalytic degradation mechanism was estimated by the scavenger test using ethylenediaminetetraacetic acid disodium salt, ascorbic acid, ethanol, and silver nitrate as radical scavengers. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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24 pages, 2297 KB

Open AccessArticle

Utilization of Spent Yerba Mate as an Unconventional Sorbent for the Removal of Acid and Basic Dyes from Aqueous Solutions

by Tomasz Jóźwiak, Urszula Filipkowska and Kacper Gradzik

Appl. Sci. 2025, 15(23), 12794; https://doi.org/10.3390/app152312794 - 3 Dec 2025

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Abstract

This study investigated the potential use of Yerba Mate (YM) residue as an unconventional sorbent for removing acid dyes—Acid Red 18 (AR18) and Acid Yellow 23 (AY23)—and basic dyes—Basic Violet 10 (BV10) and Basic Red 46 (BR46)—from aqueous solutions. The research included characterization [...] Read more.

This study investigated the potential use of Yerba Mate (YM) residue as an unconventional sorbent for removing acid dyes—Acid Red 18 (AR18) and Acid Yellow 23 (AY23)—and basic dyes—Basic Violet 10 (BV10) and Basic Red 46 (BR46)—from aqueous solutions. The research included characterization of YM (FTIR, BET specific surface area, porosity, pH_PZC), examination of the effect of pH on dye sorption efficiency, analysis of sorption kinetics (pseudo-first-order and pseudo-second-order models, intraparticle diffusion model), and determination of maximum sorption capacity (Langmuir I and II models, and the Freundlich model). The sorption efficiency of the dyes onto YM was highest at pH 2 for AR18 and AY23, at pH 3 for BV10, and at pH 6 for BR46. The sorption equilibrium time for all dyes onto YM mainly depended on their initial concentration, ranging from 180 min (at 50 mg/L) to 210 min (at 500 mg/L). The kinetics of dye sorption were best described by the pseudo-second-order model. The maximum sorption capacity (Q_max) of YM for the acid dyes AR18 and AY23 was 24.95 mg/g and 22.86 mg/g, respectively. The sorption capacities of the tested sorbent for the basic dyes were higher, with Q_max = 46.24 mg/g for BV10 and Q_max = 60.54 mg/g for BR46. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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15 pages, 2103 KB

Open AccessArticle

Analysis of Reservoir Water Quality by Smartphone Color Image Analysis: A Case Study of Three Reservoirs in Taiwan

by Anisa Fitri Santosa, Youxiang Huang, Muhammad Bilhaq Ashlah, Se-Min Jeong, Wonjung Choi and Wu-Yang Sean

Appl. Sci. 2025, 15(23), 12370; https://doi.org/10.3390/app152312370 - 21 Nov 2025

Cited by 1 | Viewed by 562

Abstract

This work investigates smartphone-based image processing for monitoring reservoir water quality, driven by the necessity for accessible and economical environmental evaluation techniques. The objective is to examine the correlation between water color and essential water quality parameters, including turbidity, total phosphorus, and chlorophyll-a, [...] Read more.

This work investigates smartphone-based image processing for monitoring reservoir water quality, driven by the necessity for accessible and economical environmental evaluation techniques. The objective is to examine the correlation between water color and essential water quality parameters, including turbidity, total phosphorus, and chlorophyll-a, utilizing basic, readily accessible technology. The concept entails taking water photos from three principal reservoirs in Taiwan—Shimen, Liyutan, and Hushan—utilizing a smartphone camera, succeeded by sophisticated image processing algorithms, encompassing RGB color space analysis and ripple filtering. The findings indicate strong correlations between the G/R ratio obtained from the photos and conventional water quality parameters, particularly turbidity and chlorophyll-a. The correlation analysis yielded R² = 0.72 (p < 0.01) for turbidity and R² = 0.68 (p < 0.05) for chlorophyll-a, confirming the statistical significance of the results. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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21 pages, 2076 KB

Open AccessArticle

Groundwater Quality Near Riverbanks and Its Suitability for Agricultural Use in Semi-Arid Regions

by Layth Saleem Salman Al-Shihmani, Ali Jawad Al-Sarraji, Ahmed Abed Gatea Al-Shammary, Jesús Fernández-Gálvez and Andrés Caballero-Calvo

Appl. Sci. 2025, 15(22), 12338; https://doi.org/10.3390/app152212338 - 20 Nov 2025

Viewed by 588

Abstract

Water scarcity has become one of the most pressing challenges to agricultural sustainability, particularly in arid and semi-arid regions where climate change, dam construction, and rapid population growth have intensified the pressure on water and food resources. Groundwater adjacent to rivers represents a [...] Read more.

Water scarcity has become one of the most pressing challenges to agricultural sustainability, particularly in arid and semi-arid regions where climate change, dam construction, and rapid population growth have intensified the pressure on water and food resources. Groundwater adjacent to rivers represents a potential supplementary resource that can reduce reliance on restricted surface water supplies. This study assessed the hydrochemical characteristics and agricultural suitability of shallow groundwater located near the Tigris River, Iraq. Fieldwork involved monitoring four active wells and collecting samples over six periods from October 2022 to May 2023, combined with twelve soil samples from surrounding agricultural fields. Laboratory analyses determined key water and soil properties, including pH, electrical conductivity, major cations and anions, and a range of salinity and sodicity indices such as total dissolved solids (TDS), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), potential salinity (PS), magnesium ratio, Simpson ratio (SR), Jones ratio (JR), and sodium percentage (Na%). Results indicated that groundwater levels fluctuated seasonally in tandem with the Tigris River, which directly influenced salinity levels. SI values were positive, TDS values were in the high salinity class, RSC values were consistently negative, PS values were in the medium to poor category, Na% values and MR values were within acceptable limits for irrigation, and SR values were moderately to highly contaminated. Groundwater quality, according to the U.S. Salinity Laboratory classification, was categorized between the C4S1 class (very high salinity, low sodium) and the C3S1 (high salinity, low sodium). Soil analyses showed predominantly light-textured soils with moderate Ec and SAR values below sodicity thresholds. The combination of soil permeability and groundwater characteristics suggests that irrigation is feasible under specific management practices. The study concludes that groundwater adjacent to rivers can serve as a valuable supplementary source for agriculture in semi-arid regions. Its use is most effective when applied to salt-tolerant crops, supported by leaching requirements, or blended with fresh water. These findings emphasize the importance of integrated groundwater management for enhancing agricultural resilience and sustainable land use under water-scarce conditions. Excessive extraction of groundwater near rivers can also pose long-term sustainability challenges. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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10 pages, 1764 KB

Open AccessArticle

Effects of Tetracycline on Growth and Nutrient Removal by Lemna aoukikusa and Spirodela polyrhiza Under Short-Term Cultivation

by Uyen Thi To Dinh, Shoki Nakagawa, Toshiyuki Shimizu and Satoshi Soda

Appl. Sci. 2025, 15(21), 11621; https://doi.org/10.3390/app152111621 - 30 Oct 2025

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Abstract

This study assessed the effects of tetracycline (TC) on growth of Lemna aoukikusa and Spirodela polyrhiza under batch conditions. The duckweeds were exposed to a range of 0.0–5.0 mg L⁻¹ of TC for 7 days in a medium containing 10 mg L [...] Read more.

This study assessed the effects of tetracycline (TC) on growth of Lemna aoukikusa and Spirodela polyrhiza under batch conditions. The duckweeds were exposed to a range of 0.0–5.0 mg L⁻¹ of TC for 7 days in a medium containing 10 mg L⁻¹ total nitrogen (TN) and 1 mg L⁻¹ total phosphorus (TP). The relative growth rate (RGR) of each species was determined from the frond area measurement using image analysis. The EC₅₀ values as the TC concentrations causing a 50% reduction in RGR, were 4.4 mg L⁻¹ for L. aoukikusa and 0.65 mg L⁻¹ for S. polyrhiza. At 5.0 mg L⁻¹ TC, TP removal decreased to 60% in the L. aoukikusa culture and 77% in the S. polyrhiza culture, compared to 85–91% and 96%, respectively, under lower TC exposure. Nevertheless, TN and TP removals were not significantly impaired at TC concentrations found in swine wastewater. The TC removals were 76–94% for the L. aoukikusa culture and 68–91% for the S. polyrhiza culture, which were attributed to adsorption and plant uptake. These findings highlight the feasibility of duckweed-based stabilization ponds for simultaneous antibiotic attenuation and nutrient removal. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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18 pages, 2955 KB

Open AccessArticle

Synergistic Role of Low-Strength Ultrasound and Co-Digestion in Anaerobic Digestion of Swine Wastewater

by Changgee Lee, Jaehun Gwon, Min-Sang Kim, Taehwan Lee, Uijeong Han, Yeongmi Park, Hongmok Jo and Si-Kyung Cho

Appl. Sci. 2025, 15(19), 10548; https://doi.org/10.3390/app151910548 - 29 Sep 2025

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Abstract

Swine manure poses significant challenges for anaerobic digestion due to its low carbon-to-nitrogen (C/N) ratio and elevated ammonia concentrations, both of which restrict methane generation. This study investigated the impact of integrating low-intensity ultrasound with co-digestion of piggery wastewater and food waste leachate. [...] Read more.

Swine manure poses significant challenges for anaerobic digestion due to its low carbon-to-nitrogen (C/N) ratio and elevated ammonia concentrations, both of which restrict methane generation. This study investigated the impact of integrating low-intensity ultrasound with co-digestion of piggery wastewater and food waste leachate. Laboratory-scale upflow anaerobic sludge blanket (UASB) reactors were employed under four operational conditions to evaluate anaerobic digestion performance, track shifts in microbial community structure, and assess the abundance of antibiotic resistance genes (ARGs). Co-digestion significantly enhanced methane production, yielding 1.3–3.2 times more than manure alone, while low-intensity ultrasound further increased methane yields by approximately 36–44% at high loading rates. Moreover, coupling low-intensity ultrasound with co-digestion led to the most rapid recovery following an overloading shock. Unexpectedly, ultrasound treatment alone increased the expression of certain ARGs (tetG, sul1, ermB) and the Integrase gene (intI1), while co-digestion led to a reduction in these genetic markers. These findings clearly indicate that the concurrent application of co-digestion and low-intensity ultrasound achieved the highest methane yield, the fastest recovery after organic overloading, and greater suppression of specific ARGs. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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14 pages, 1689 KB

Open AccessArticle

Effect of Sulfoaluminate Clinker Addition on Boron Removal During Water Softening

by Marco Tagliabue, Alessandra de Folly d’Auris, Andrea Pacini, Michela Bellettato, Gianluigi Marra, Sara Perucchini, Cinzia Mazzara, Emanuele Lagrotta and Marco Vocciante

Appl. Sci. 2025, 15(16), 8890; https://doi.org/10.3390/app15168890 - 12 Aug 2025

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Abstract

Boron is frequently present in saline water (e.g., seawater, geothermal water, and hydrocarbon production water) due to the natural release of boric acid from minerals. While essential to life, excess boron is toxic, particularly to citrus plants, necessitating its regulation for safe water [...] Read more.

Boron is frequently present in saline water (e.g., seawater, geothermal water, and hydrocarbon production water) due to the natural release of boric acid from minerals. While essential to life, excess boron is toxic, particularly to citrus plants, necessitating its regulation for safe water use. Current boron removal methods, such as reverse osmosis, chelating resin adsorption, and magnesium-based precipitation softening, increase water treatment complexity and cost. Ettringite, (Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O), is a clay and an effective anion adsorbent. It is also a key hydration product of Portland cement. This study explores boron removal via precipitation softening using sulfoaluminate clinker as an ettringite precursor. Raw water, a first-stage reverse-osmosis permeate from an Italian oil-and-gas site, contained approximately 15.0 mg/L of boron. Optimal removal required sulfoaluminate clinker in excess with respect to the stoichiometric dose and 150 min of contact time. The preliminary results demonstrate the feasibility of this approach, offering a viable alternative to existing methods. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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21 pages, 2498 KB

Open AccessArticle

Effective Adsorption of Phenoxyacetic Herbicides by Tomato Stem-Derived Activated Carbons

by Krzysztof Kuśmierek, Beata Doczekalska, Maciej Sydor and Andrzej Świątkowski

Appl. Sci. 2025, 15(12), 6816; https://doi.org/10.3390/app15126816 - 17 Jun 2025

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Abstract

Six activated carbons from tomato (Solanum lycopersicum L.) stems (TS-AC) were synthesized by carbonization and chemical activation using potassium hydroxide (KOH) and sodium hydroxide (NaOH) at temperatures of 550, 650, and 750 °C. These TS-ACs were then evaluated as adsorbents to remove [...] Read more.

Six activated carbons from tomato (Solanum lycopersicum L.) stems (TS-AC) were synthesized by carbonization and chemical activation using potassium hydroxide (KOH) and sodium hydroxide (NaOH) at temperatures of 550, 650, and 750 °C. These TS-ACs were then evaluated as adsorbents to remove 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) from aqueous solutions. The adsorption kinetics of both herbicides followed the pseudo-second-order model, closely correlating with the mesopore volume of the TS-AC. The Langmuir isotherm accurately described the adsorption process for both 2,4-D and MCPA. The porous structure of TS-AC, characterized by micropore volume and specific surface area, significantly influenced the maximum adsorption capacities. The adsorption of both herbicides was pH dependent, but ionic strength had no significant effect. Regeneration testing, conducted over three cycles, showed less than a 15% reduction in herbicide adsorption capacity. This study demonstrates that agricultural waste, specifically tomato stems, can be effectively valorized by using simple activation techniques in TS-AC that are efficient adsorbents to remove organic pollutants, such as herbicides, from aqueous media. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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15 pages, 2743 KB

Open AccessArticle

Effects of Ozone Oxidation Process on Residual Antibiotics and Antibiotic Resistance Genes in a Swine Wastewater Treatment Plant

by Taeyoung Cha, Min-Sang Kim, Yuhoon Hwang, Eun Sook Jeong, Hongmok Jo and Si-Kyung Cho

Appl. Sci. 2025, 15(9), 5158; https://doi.org/10.3390/app15095158 - 6 May 2025

Cited by 2 | Viewed by 3052

Abstract

Extensive antibiotic use in swine production contaminates manure and wastewater with antibiotics. Discharging this waste into the environment, even after treatment, potentially fuels the spread of antibiotic resistance. This study investigated a full-scale swine wastewater treatment plant that combines coagulation–sedimentation, sand filtration, ozonation, [...] Read more.

Extensive antibiotic use in swine production contaminates manure and wastewater with antibiotics. Discharging this waste into the environment, even after treatment, potentially fuels the spread of antibiotic resistance. This study investigated a full-scale swine wastewater treatment plant that combines coagulation–sedimentation, sand filtration, ozonation, activated carbon filtration, and a deaeration process. At each stage of this process, samples were collected and analyzed to determine their water quality parameters, antibiotic concentrations, and antibiotic resistance genes (ARGs). The experimental results showed coagulation–sedimentation effectively removed suspended solids (92.2%) and total phosphorus (96.9%). Ozonation significantly reduced antibiotic levels, including sulfamethazine by over 99.9%, although ARGs such as tetM, sul1, and sul2 were only removed at levels up to 95.9%. Interestingly, partial rebounds of sulfamethazine (438.9 μg/L) and marbofloxacin (0.40 μg/L) appeared in the final effluent, suggesting that desorption or operational factors (e.g., hydraulic fluctuation, filter media saturation, and pH) may affect the treatment process. In addition, strong correlations emerged between the levels of suspended solids and those of certain antibiotics (lincomycin, tiamulin), indicating particle-mediated sorption as a key mechanism. Even though ozonation and coagulation–sedimentation were found to contribute to the substantial removal of pollutants, the observed rebounds and residual ARGs highlight the need for optimized operational strategies and multi-barrier approaches to fully mitigate antibiotic contamination and inhibit the proliferation of resistant bacteria in swine wastewater. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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20 pages, 697 KB

Open AccessReview

Prospects of Algal Strains for Acidic Wastewater Treatment

by Paulina Slick, Neha Arora, Enlin Lo, Diego Santiago-Alarcon and George P. Philippidis

Appl. Sci. 2026, 16(1), 216; https://doi.org/10.3390/app16010216 - 24 Dec 2025

Viewed by 892

Abstract

Rapid industrialization has generated large volumes of acidic wastewater that, without adequate treatment, pose serious environmental and public health risks. Traditional remediation processes, such as chemical neutralization, ion-exchange, and membrane filtration, are effective but costly, energy-intensive, and generate toxic secondary waste. In contrast, [...] Read more.

Rapid industrialization has generated large volumes of acidic wastewater that, without adequate treatment, pose serious environmental and public health risks. Traditional remediation processes, such as chemical neutralization, ion-exchange, and membrane filtration, are effective but costly, energy-intensive, and generate toxic secondary waste. In contrast, acidophilic microalgae offer a sustainable, cost-effective, and eco-friendly alternative. Algae rely on their cellular structure and metabolism to adsorb, absorb, bioaccumulate, and transform toxic metals while simultaneously neutralizing wastewater with minimal secondary waste production. Although acidophilic algae tolerate highly toxic and low pH conditions, their growth rate and biomass productivity, key drivers of algae-based bioremediation, are often compromised under such conditions. Thus, identifying robust species and evolving strains to thrive in these wastewaters without compromising productivity will facilitate adoption of algae-based bioremediation on a large scale. Integrating algal wastewater remediation with biofuel and biofertilizer production can contribute to the circular economy. In this review, we synthesize mechanisms employed by acidophilic algal strains when exposed to acidic and metal-enriched environments to remediate wastewater. We highlight recent studies applying these strains to acidic wastewater remediation and biogas upgrading and discuss current biotechnological tools aimed at enhancing strain performance for future use in commercial systems. Full article

(This article belongs to the Special Issue New Approaches to Water Treatment: Challenges and Trends, 2nd Edition)

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