Search Results (1,773)

Geogenic contamination of groundwater presents a substantial threat to the enduring production and sustainability of irrigated fruit orchards, especially in arid and semi-arid regions where over 60% of horticultural irrigation depends on groundwater sources. Groundwater quality is increasingly threatened by geogenic contamination, presenting a critical global issue. Geogenic contaminants, such as fluoride and arsenic, combined with agricultural practices and inadequate wastewater treatment, pose a significant threat to groundwater. Concentrations of elements including arsenic, fluoride, boron, iron, and sodium often exceed acceptable thresholds. For instance, arsenic (As) levels up to 0.5 ppm have been reported in parts of South Asia, far exceeding the WHO guidelines limit of 0.01 mg/L. Boron concentrations above 2.0 ppm and fluoride concentrations exceeding 1.5 ppm are prevalent in impacted aquifers. Pollution consequences are far reaching, impacting agricultural ecosystems and human health as polluted water infiltrates the food chain via irrigation. These challenges are compounded by climate change and water scarcity, which further strain water sources, including those used in agriculture. Addressing groundwater contamination requires a multi-faceted approach. Strategies include developing crops that can tolerate toxicants, improving irrigation techniques, and employing advanced wastewater treatment technologies. This study solidifies current knowledge concerning the uptake processes and physiological effects of various pollutants in fruit crops. This review emphasizes the synergistic toxicity of many pollutants, identifies gaps in knowledge in species-specific tolerance, and emphasizes the dearth of comprehensive mitigating frameworks. Potential solutions, such as salt-tolerant rootstocks, gypsum amendments, and alternative irrigation timing, are examined to enhance resilient orchard systems in geogenically challenged areas. Full article

The degradation of Mediterranean forest ecosystems, such as holm oak forests, has intensified in recent decades due to climate change, forest fires, and deforestation, compromising the natural regeneration of the soil. In this context, it is essential to apply sustainable strategies to restore soil and promote plant growth, thus helping the regeneration of the ecosystem. One of these strategies is the use of plant growth-promoting bacteria (PGPB) in combination with recovered organic waste, such as that from wastewater treatment plants (WWTPs). In this paper, the effects of a biofertilizer formulated from WWTP residue (with and without sterilization), supplemented with two PGPB strains (Bacillus pretiosus and Pseudomonas agronomica), on the growth of holm oak seedlings (Quercus ilex) were evaluated under field conditions. A study was carried out on its nutritional composition, the rhizospheric cenoantibiogram, and its functional and taxonomic microbial diversity. Nine combinations of chemical and biological treatments using irrigation with water as a control were compared. The results showed that treatments with WWTP, especially combined with PGPB strains, promoted greater plant development and a lower seedling mortality rate. The cenoantibiogram exhibited a reduction in the resistance profile in soils treated with biofertilizer, without affecting soil microbial diversity, which remained unaltered across treatments, as confirmed by metagenomic and functional diversity analyses. Overall, this research reinforces the viability of the use of biofertilizers recovered from WWTP as an ecological and effective strategy for the recovery of degraded holm oak forests. Full article

The production of alumina produces red mud (RM), a highly alkaline solid waste. The majority of it is disposed of in landfills, which seriously pollutes the environment. It needs to be recycled and handled with care to protect the environment. RM is a promising raw material for wastewater and waste gas treatment owing to its high alkalinity and abundant metal compounds. It can efficiently remove diverse pollutants while facilitating large-scale utilization of RM resources. Reviews of the use of RM resources to create catalysts for environmental governance are, nevertheless, scarce. Therefore, this paper analyzes and summarizes the pertinent research on RM-based catalysts to remove pollutants from the environment based on journal literature related to RM resource utilization from 2015 to 2025. This study reviews the application of RM-based catalysts for degrading pollutants in wastewater and exhaust gases via advanced oxidation processes (AOPs)—including photocatalysis, Fenton-like catalysis, ozonation catalysis, and persulfate catalysis—as well as catalytic oxidation, chemical looping combustion (CLC), and selective catalytic reduction (SCR). The paper emphasizes the analysis of modification strategies and catalytic mechanisms of RM-based catalysts in environmental remediation and examines the environmental risks and corresponding mitigation measures related to their preparation from RM resources. Finally, it outlines that future research should prioritize green, low-energy modification processes; catalytic systems for the synergistic removal of multiple pollutants; and efficient, recyclable separation and recovery technologies. These directions aim to promote the sustainable application of RM in large-scale environmental remediation and to achieve the integrated advancement of resource utilization and ecological protection. Full article

The reuse of treated wastewater (TWW) offers a sustainable solution for water management in agriculture, particularly in arid regions like Saudi Arabia. However, its success depends on farmers’ acceptance, influenced by perceptions of economic benefits, social acceptability, environmental impacts, and health risks. This study surveys 391 farmers across five regions in Saudi Arabia to assess their attitudes toward TWW reuse in irrigation, exploring how advanced wastewater treatment technologies can improve acceptance. Results show that 65% of farmers use TWW, with usage peaking at 72% in Al-Ahsa and Qatif, driven by water scarcity and lack of alternatives. While 78% are satisfied with TWW, concerns persist regarding pests, consumer acceptance, health risks, and soil quality. Advanced technologies can mitigate these issues by enhancing water quality and safety. The highest positive impact of the use of TWW in irrigation from was the impact on productivity, reduction in the cost of fertilizers and savings in the cost of water abstraction. With only 57% of farmers receiving extension services, integrating education on these technologies could further boost confidence. This study highlights key acceptance factors, underscoring the need for technological and educational interventions to promote sustainable TWW reuse in agriculture. Full article

The growing depletion of global phosphorus reserves underscores the urgent need for sustainable and circular nutrient recovery solutions. Rich in phosphorus, piggery wastewater represents not just a waste stream but a valuable resource. In this study, we explore an innovative approach by recovering alginate-like exopolymers (ALE) from activated sludge (AS) and utilizing them to produce biosorbent hydrogel beads capable of removing phosphorus directly from real piggery wastewater. The ALE extraction process yielded approximately 175 $\mathrm{m}\mathrm{g} {\mathrm{V}\mathrm{S}}_{\mathrm{A}\mathrm{L}\mathrm{E}}/\mathrm{g}{\mathrm{V}\mathrm{S}}_{\mathrm{s}\mathrm{l}\mathrm{u}\mathrm{d}\mathrm{g}\mathrm{e}}$, highlighting the potential of wastewater biomass as a source of functional biopolymers. Adsorption experiments revealed phosphorus removal efficiencies approaching 80%, with capacities ranging from 0.68 to 1.18 mgP/gVS_ALE. Structural and chemical characterizations confirmed both the successful adsorption of phosphorus and the stability of the biosorbent post-treatment. This work demonstrates a dual benefit: the recovery of critical nutrients and the transformation of wastewater-derived materials into value-added biosolids. By integrating phosphorus capture and biosorbent production, the approach offers a cost-effective and environmentally responsible pathway toward nutrient recycling and wastewater valorization. Full article

With increasing wastewater treatment demands and decarbonization goals, synergistic reduction in pollutants and green house gas (GHG) emissions is crucial. High process emissions like N₂O pose significant challenges, yet optimized carbon reduction strategies for conventional plants are lacking. This study developed three mathematical models to quantify the impact of dissolved oxygen (DO), influent salinity, and C/N ratio on direct emissions (CH₄, N₂O) and indirect emissions. Response Surface Methodology (RSM) optimized these factors to minimize GHG emissions under three accounting scenarios: (1) plants with CH₄ reuse systems: salinity = 0.5 g L⁻¹, DO = 3.67 mg L⁻¹, C/N = 12.75; (2) plants focusing solely on direct emissions: salinity = 0.5 g L⁻¹, DO = 3.35 mg L⁻¹, C/N = 3; and (3) plants assessing total emissions: salinity = 0.5 g L⁻¹, DO = 2.5 mg L⁻¹, C/N = 7.18. Key findings indicated that increasing salinity exacerbated greenhouse gas emissions. Elevated DO levels in the aerobic stage reduced N₂O emissions but increased indirect emissions in the A²/O process. Higher C/N ratios promoted anaerobic CH₄ production, but sufficient carbon reduced N₂O by enabling complete heterotrophic denitrification. A 60−day continuous GHG emissions monitoring campaign was conducted at a WWTP to validate the actual emission reductions achievable under the identified optimal control conditions. An analysis and comparison of operational and economic costs were also performed. The findings provide practical insights into sustainable GHG emission management and offer potential solutions to advance the synergistic reduction in GHG emissions and pollutants. Full article

Environmental pollution driven by socioeconomic development has intensified the need for advanced and sustainable wastewater treatment technologies. Herein, TiO₂-based photocatalysis emerged as a promising solution due to its oxidative potential, chemical stability, and eco-friendliness but does have unavoidable immobilized recoverability challenges. Therefore, this study explored the challenges and prospects of TiO₂-based photocatalysis for the degradation of emerging contaminants in wastewater. A comprehensive keyword analysis was conducted by using a decade of publications retrieved from Google Scholar, Scopus, and Web of Science (WOS) databases via Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework. From a pool of 518 refined publications, 318 significant keyword occurrences related to TiO₂-based photocatalysis advanced oxidation processes (AOPs) were revealed. The review delved into various types of AOP mechanisms and catalysts and highlighted the synergistic effect of process parameters and magnetization as recoverability potential for TiO₂-based photocatalysts. Furthermore, emerging strategies including surface modifications, doping, and hybrid AOP integrations were discussed to improve photocatalysis performance and industrial scalability. The study underscores the economic opportunity and environmental sustainability of degrading persistent organic pollutants by integrating a TiO₂-based photocatalytic system with a regenerative magnetic field into the water sector. Full article

Municipal sewage sludge is a potential soil amendment rich in organic matter and nutrients, yet its reuse is often constrained by heavy metal contamination. This study evaluated six heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in sludge collected from seven centralized wastewater treatment plants in Bangkok, Thailand, by analyzing physicochemical properties, total metal concentrations, and chemical speciation. Three ecological risk indices, the geo-accumulation index (I_geo), risk assessment code (RAC), and potential ecological risk index (PERI), were applied to assess contamination status, mobility, and ecological threat. The sludge exhibited high levels of organic matter and essential nutrients, indicating potential for agricultural reuse; however, elevated electrical conductivity at some sites may pose salinity risks if unmanaged. Speciation analysis revealed that Cd and Zn were largely present in mobile and redox-sensitive fractions, Cr and Pb were primarily in stable residual forms, and Cu and Ni occurred in moderately mobile forms influenced by environmental conditions. Across all indices, Cd consistently posed the highest ecological risk, followed by Zn, in a site-dependent manner, while Cr and Pb represented low risk. These findings provide a clearer understanding of metal behavior in sewage sludge and underscore the importance of integrating chemical speciation with multi-index risk assessment in sludge management. Incorporating such approaches into national guidelines, particularly in countries lacking established heavy metal limits, can strengthen monitoring frameworks, guide safe and sustainable reuse, and support regulatory development in contexts with limited monitoring data. Full article

Ciprofloxacin (CIP), a persistent fluoroquinolone antibiotic, poses serious environmental concerns due to its low biodegradability and widespread presence in aquatic ecosystems. This study investigates the synergistic application of low-frequency ultrasonic cavitation and biological treatment to enhance CIP removal efficiency. Experiments have shown that under the optimal biological treatment conditions (6 g/L sludge concentration, pH 8), single biological treatment for 48 h can only remove 41.9% CIP and 24.9% total organic carbon (TOC). Ultrasonic pretreatment was conducted under varying frequencies and pH conditions to determine optimal cavitation parameters, while biodegradation performance was evaluated at different sludge concentrations and pH levels. Results indicated that in 10 mg/L CIP wastewater under alkaline conditions (pH 9.0), CIP and TOC removal efficiencies reached 58.9% and 35.2%, respectively, within 30 min using 15 kHz ultrasound irradiation. When ultrasonic pretreatment was followed by biological treatment, overall removal rates increased to 96.3% for CIP and 90.4% for TOC, significantly outperforming either method alone. LC-MS analysis identified several degradation intermediates during ultrasonic pretreatment, revealing key transformation pathways such as piperazine ring cleavage, hydroxylation, and defluorination. Furthermore, toxicity evaluation using the T.E.S.T. model confirmed a substantial reduction in ecological risk after ultrasonic treatment. Overall, the combined ultrasonic–biological process offers a cost-effective and environmentally sustainable strategy for the efficient removal of fluoroquinolone antibiotics from wastewater. Full article

The rational design of functional and sustainable polymers is central to addressing global environmental challenges. In this context, unmodified lignin derived from Sarkanda grass (Tripidium bengalense), an abundant agro-industrial lignocellulosic byproduct, was systematically investigated as a natural polymeric adsorbent for the remediation of aqueous media contaminated with heavy metals. The study evaluates lignin’s behavior toward nine metal(loid) ions: arsenic, cadmium, chromium, cobalt, copper, iron, nickel, lead, and zinc. Adsorption performance was systematically investigated under static batch conditions, optimizing key parameters, with equilibrium and kinetic data modeled using established isotherms and rate equations. Surface characterization and seed germination bioassays provided supporting evidence. Unmodified Sarkanda grass lignin demonstrated effective adsorption, exhibiting a clear preference for Cu(II) followed by other divalent cations, with lower capacities for As(III) and Cr(VI). Adsorption kinetics consistently followed a pseudo-second-order model, indicating chemisorption as the dominant mechanism. Thermodynamic studies revealed spontaneous and endothermic processes. Bioassays confirmed significant reduction in aqueous toxicity and strong metal sequestration. This work positions unmodified Sarkanda grass lignin as a bio-based, low-cost polymer platform for emerging water treatment technologies, contributing to circular bioeconomy goals and highlighting the potential of natural polymers in sustainable materials design. Full article

Industrial processes like farming, food processing, petroleum refinery, and leather manufacturing produce a lot of high-salinity wastewater. This wastewater presents serious environmental risks, such as soil degradation, eutrophication, and water salinization, if it is released without adequate treatment. The sources and features of high-salinity wastewater are outlined in this review, along with the main methods for removing organic pollutants, such as physicochemical, biological, and combined treatment approaches. Membrane separation, coagulation–flocculation, and advanced oxidation processes are the primary physicochemical techniques. Anaerobic and aerobic technologies are the two categories into which biological treatments fall. Physicochemical–biological combinations and the fusion of several physicochemical techniques are examples of integrated technologies. In order to achieve sustainable and effective treatment and resource recovery of high-salinity wastewater, this review compares the effectiveness and drawbacks of each method and recommends that future research concentrate on the development of salt-tolerant catalysts, anti-fouling membrane materials, halophilic microbial consortia, and optimized hybrid treatment systems. Full article

The excessive emission of cadmium (Cd²⁺) poses a serious threat to the aquatic environment due to its high toxicity and bioaccumulation potential. This study constructed three types of vertical-subsurface-flow constructed wetlands configured with iron–carbon–zeolite composite substrates, including an iron–carbon–zeolite constructed wetland (TF-CW), a zeolite–iron–carbon constructed wetland (FT-CW), and an iron–carbon–zeolite mixed constructed wetland (H-CW), to investigate the purification performance and mechanisms of constructed wetlands for cadmium-containing wastewater (0~6 mg/L). The results demonstrated that iron–carbon–zeolite composite substrates significantly enhanced Cd²⁺ removal efficiency (>99%) through synergistic redox-adsorption mechanisms, where the iron–carbon substrate layer dominated Fe-Cd co-precipitation, while the zeolite layer achieved short-term cadmium retention through ion-exchange adsorption. FT-CW exhibited superior NH₄⁺-N removal efficiency (77.66%~92.23%) compared with TF-CW (71.45%~88.05%), while iron–carbon micro-electrolysis effectively inhibited NO₃⁻-N accumulation (<0.1 mg/L). Under cadmium stress, Typha primarily accumulated cadmium through its root systems (>85%) and alleviated oxidative damage by dynamically regulating antioxidative enzyme activity, with the superoxide dismutase (SOD) peak occurring at 3 mg/L Cd²⁺ treatment. Microbial community analysis revealed that iron–carbon substrates promoted the relative abundance of Bacteroidota and Patescibacteria as well as the enrichment of Saccharimonadales, Thauera, and Rhodocyclaceae (genera), enhancing system stability. This study confirms that iron–carbon–zeolite CWs provide an efficient and sustainable technological pathway for heavy metal-contaminated water remediation through multidimensional mechanisms of “chemical immobilization–plant enrichment–microbial metabolism”. Full article

The pharmaceutical contamination of water, especially by widely used drugs, presents important environmental and health concerns due to the inefficiency of conventional treatment methods. The present study proposes a sustainable solution using biochar (Bch) obtained from tomato waste, functionalized with Fe₃O₄ and MnO₂ nanoparticles, for the removal of paracetamol from aqueous solutions. The composite materials were synthesized, characterized, and evaluated under varying conditions, including pH, temperature, contact time, initial drug concentration, and adsorbent dose. The materials exhibited porous structures with wide pore size distributions. Optimal removal efficiency was achieved for 30 mg L⁻¹ paracetamol concentration, pH 2, 25 °C, 0.3 g L⁻¹ adsorbent dose, and 20 min contact time. The Freundlich isotherm provided the best fit for the adsorption data. Kinetic studies revealed that the pseudo-second-order model best described the adsorption process. Thermodynamic parameters indicated that the process was spontaneous, feasible, and exothermic. Compared with similar materials derived from agricultural waste, the tomato waste-based composites demonstrated competitive adsorption capacities. These findings suggest that Bch-HCl/MnO₂ and Bch-HCl/Fe₃O₄/MnO₂ are promising, cost-effective adsorbents for mitigating pharmaceutical pollutants in wastewater. Full article

The wastewater treatment (WWT) industry is currently facing challenges imposed by the revised urban WWT directive, particularly in terms of nitrogen (N) and phosphorus (P) removal. This implies the need for mandatory tertiary treatment, for which microalgae cultivation shows great sustainability promise. This study investigated the impact of hydraulic retention time (HRT) on nutrient removal in open-air microalgae cultivation for tertiary WWT under winter conditions. Two pilot-scale semi-continuous raceway systems were operated with indigenous microalgae, natural sunlight, and no pH control. HRT values of 4, 5.5, and 7 days were tested, and N, P, and carbon (C) removal and recovery were measured. All conditions allowed nitrogen removal, complying with the revised urban WWT directive. Regarding P, only the 7-day HRT condition consistently complied with the directive’s lowest limit (<0.5 mg P·L⁻¹) in the treated water, while 5.5 and 4 days left up to 0.7 and 1.0 mg P·L⁻¹, respectively, in up to 25% of the samples. A stable microalgae consortium was established under variable light, pH, and dissolved oxygen conditions, albeit with variable biomass productivity. Elemental mass balances revealed that nutrients were mostly recovered in the produced biomass, particularly at high HRT, including effective CO₂ capture from the atmosphere. Full article

Wastewater treatment plants (WWTPs) are critical infrastructure that lessen the environmental impacts of human activity by stabilizing wastewaters laden with organics, chemicals, and nutrients. WWTPs face an increasing global population, greater wastewater volumes, stricter environmental regulations, and additional societal pressures to implement more sustainable and energy-efficient waste management strategies. WWTPs are energy-intensive facilities that generate significant GHG emissions and involve high operational costs. Therefore, improving the process efficiency can lead to widespread environmental and economic benefits. One promising approach is to integrate anaerobic digestion (AD) with hydrothermal carbonization (HTC) to enhance sludge treatment, optimize energy recovery, create valuable bio-based materials, and minimize sludge disposal. This study employs an LCA to evaluate the environmental impact of coupling HTC with AD compared to conventional AD treatment. HTC degrades wastewater sludge in an aqueous medium, producing carbon-dense hydrochar while reducing sludge volumes. HTC also generates an aqueous byproduct containing >30% of the original carbon as simple organics. In this system model, the aqueous byproduct is returned to AD to generate additional biogas, which then provides heat and power for the WWTP and HTC process. The results indicate that the integrated AD + HTC system significantly reduces environmental emissions and sludge volumes, increases net energy recovery, and improves wastewater sludge valorization compared to conventional AD. This research highlights the potential of AD + HTC as a key circular bioeconomy strategy, offering an innovative and efficient solution for advancing the sustainability of WWTPs. Full article