Search Results (134)

The agro-industrial valorization of unripe plantain peels through flour production represents a sustainable strategy for waste reduction and nutrient recovery. This study investigated the process intensification of plantain peel drying by evaluating the combined effects of UV-C-assisted hot-air drying with ultrasound and oxalic acid pretreatments. A 2³ full factorial design was employed to evaluate the effects of UV-C lamp distance, ultrasound time and oxalic acid concentration on drying kinetics, effective moisture diffusivity, and the retention of bioactive compounds. The combination of the most intense levels of the pretreatments with a 9 cm distance between the radiation source and the sample achieved a 40.68% reduction in drying time compared to the control (without pretreatments). Among the mathematical models tested, the Logarithmic model provided the most accurate fit (R² > 0.99), effectively describing the falling-rate period and mass transfer phenomena. Scanning electron microscopy revealed structural modifications, including microchannels and surface pores, consistent with enhanced moisture transport and increased effective moisture diffusivity. The accelerated drying kinetics also led to higher contents of bioactive compounds, including total phenolics, ascorbic acid, and carotenoids, while maintaining adequate water activity and color stability. These findings demonstrate the combined potential of UV-C radiation, ultrasound, and oxalic acid to intensify drying efficiency while improving the functional quality of unripe plantain peel flour. Full article

A. filiculoides is a fast-growing aquatic fern with potential for laboratory-scale biomass production, nutrient recovery and biorefinery-oriented bioprocessing. However, its cultivation in controlled bioreactors remains limited by insufficient integration of treatment formulation, physicochemical monitoring and predictive optimization. This study evaluated A. filiculoides biomass production for 30 days in semi-closed 5 L glass bioreactors under three cultivation conditions: Hoagland-type mineral solution (T1), Murashige and Skoog (MS) medium (T2), and an aqueous growth-regulator treatment containing 6-benzylaminopurine and indole-3-acetic acid (BAP–IAA; 1 mg L⁻¹ each) (T3). The initial biomass was standardized at 0.10 g FW L⁻¹. By day 30, T3 showed the highest final fresh biomass concentration 1.208 ± 0.043 g FW L⁻¹, followed by T1 0.948 ± 0.025 g FW L⁻¹ and T2 0.538 ± 0.033 g FW L⁻¹. Principal component analysis and k-means clustering showed that dissolved oxygen, oxidation–reduction potential, electrical conductivity, resistivity, pH and water temperature structured the cultivation environment. The physicochemical-modulated Gompertz model showed high internal predictive performance, with training R² = 0.997, RMSE = 0.016 and MAE = 0.013, and cross-validation R² = 0.986, RMSE = 0.033 and MAE = 0.024. Model-based optimization identified T3 at day 30 as the optimal condition, with predicted biomass of approximately 1.224 g FW L⁻¹. The associated operating window corresponded to pH 7.34–7.52, dissolved oxygen 5.70–6.30 mg L⁻¹, ORP 75.40–102.00 mV, EC 983.90–1077.80 µS cm⁻¹ and resistivity 0.928–1.016 kΩ cm. These results support the use of coupled temporal monitoring, multivariate analysis and kinetic modeling for laboratory-scale optimization of Azolla biomass production. Full article

Light limitation can constrain primary production and ecosystem recovery in shallow eutrophic lakes even when nutrients remain abundant. We evaluated the effects of reduced physical disturbance on underwater light availability in Utah Lake, Utah, USA, using large limnocorrals that reduced exposure to wave-driven disturbance and restricted access by benthivorous fishes. Water transparency was assessed using Secchi depth during 2022–2023 and vertical profiles of photosynthetically active radiation (PAR) during 2024; the two datasets were analyzed independently. The mean Secchi depth was approximately 81% greater inside than outside the limnocorrals (39.8 vs. 22.0 cm; p < 0.001). Similarly, PAR declined to a theoretical photosynthetic threshold of 0.01 µmol photons m⁻² s⁻¹ at an estimated depth of 101 cm inside the corrals compared with 81 cm outside the corrals, representing a 25% increase in potential photosynthetic depth. Phytoplankton biovolume was not a detectable predictor of Secchi depth after accounting for treatment and month (p = 0.996), although chlorophyll a and phycocyanin were associated with PAR at shallow depths and phytoplankton became more important during late-season bloom conditions. Total suspended solids (TSSs) were associated with PAR throughout the measured depth profile but differed only slightly between treatments (72.89 vs. 75.16 mg L⁻¹; p = 0.08). Thus, the large optical response cannot be explained by changes in bulk TSS concentration alone and may instead reflect changes in the optically active suspended-particle fraction, including preferential settling of fine, strongly scattering particles; particle-size distributions and optical properties were not directly measured. These results demonstrate that reducing physical disturbance can substantially improve underwater light conditions in a large, shallow, nutrient-rich lake. Management approaches that reduce sediment resuspension and restore benthic light availability may therefore provide a direct pathway toward ecosystem reorganization, particularly where large internal nutrient stores and atmospheric inputs limit the effectiveness of external nutrient reductions alone. Full article

The intensification of poultry production in Poland generates enormous quantities of excreta and associated biomass. While these constitute valuable sources of macro- and micronutrients, inadequate waste management leads to environmental pollution, nutrient leaching, and ammonia emissions. This paper analyses the fertilising potential of avian excreta, the legal provisions governing their application, and modern management technologies within the context of the circular economy. The study addresses two global threats—antimicrobial resistance (AMR) and the eutrophication of aquatic ecosystems—evaluating mitigation strategies and advanced biotechnological processing methods. Industrial farming turns excreta into a reservoir of active antibiotics, leading to the contamination of soils, waters, and crops. As a preventative strategy to reduce reliance on veterinary antibiotics—thereby indirectly mitigating the environmental dissemination of AMR—the dietary application of phytobiotics is highlighted. To counteract eutrophication, supplementing feed with exogenous microbial phytase plays a pivotal role, improving phytate phosphorus absorption and reducing its excretion by up to 50%. Furthermore, anaerobic co-digestion with carbon-rich substrates enhances methane yield, while advanced recovery systems (struvite precipitation, electrodialysis, bioelectrochemical concentration, and membrane techniques) show significant potential for safer nutrient concentration. An integrated technological approach to waste processing constitutes the foundation of sustainable agricultural production. Full article

Increased contamination and complexity of wastewater due to rapid industrialization, urbanization, and new contaminants have highlighted the limitations of conventional treatment technologies. The treatment of complex wastewater matrices containing heavy metals, refractory organic contaminants, pharmaceuticals, per- and polyfluoroalkyl substances (PFAS), nutrients, and pathogens requires an integrated treatment approach with complementary removal mechanisms. This review critically analyzes the principles, recent developments, and engineering applications of biosorption, membrane separation, and advanced oxidation processes (AOPs), and highlights their possible combination in hybrid wastewater treatment systems. Recent advances in engineered biosorbents, multifunctional membranes, and catalytic materials, including their mechanisms, material innovations, operational benefits, and limitations, are critically evaluated. Special focus is placed on the mechanistic synergy among the different technologies, showing how contaminant load reduction, membrane fouling mitigation, selective concentration, and oxidative degradation collectively improve treatment efficiency with reduction in energy and chemical consumption. This article also introduces a framework for process-engineered integrated hybrid treatment systems. Comparative analyses of hybrid configurations, engineering challenges, research gaps, and a decision support framework are provided to aid the selection of the technologies based on the wastewater characteristics and treatment objectives. New opportunities for artificial intelligence, digital process control, multifunctional materials, and circular resource recovery are also addressed. Overall, this review emphasizes that intelligently engineered hybrid systems integrating biosorption, membrane separation, and AOPs can be a promising pathway toward efficient contaminant removal, water reuse, resource recovery, and sustainable wastewater management. Full article

Silica gel is extensively used as a desiccant for dehumidifying methane gas during natural gas treatment operations. Over time, the adsorbent becomes saturated with total petroleum hydrocarbons (TPHs), including saturated, unsaturated, and aromatic compounds, rendering it ineffective. This study presents a laboratory-scale bioremediation technology employing a consortium of non-pathogenic bacterial strains (Bacillus amyloliquefaciens, Bacillus pumilus, Bacillus subtilis, and Bacillus macerans) combined with a nutrient supplement to degrade TPH compounds adsorbed on silica gel granules. Three replicate experiments were conducted over 42 days with periodic aeration and partial water replacement every three days. The initial TPH concentration of 1309.06 mg/kg was reduced to 1.006 mg/kg after 42 days, corresponding to a removal efficiency of 99.92%. TPH degradation followed first-order kinetics (k = 0.192 day⁻¹, R² = 0.987, t₁/₂ = 3.6 days). Water adsorption capacity of the treated silica gel was 28% w/w compared to 35% w/w for virgin material, representing an 80% recovery of desiccant performance. These results demonstrate that biological remediation constitutes a cost-effective and environmentally sound alternative to landfill disposal of spent silica gel in the natural gas industry, with strong potential for industrial scale-up. Full article

Brackish-water aquaculture provides important livelihoods for many coastal regions worldwide, but it also generates nutrient-rich wastewater that may cause eutrophication if untreated. The use of plants to absorb dissolved nutrients and convert them into harvestable biomass has become an important research direction in aquaculture wastewater management. This study evaluated the performance of Sesuvium portulacastrum L. grown on floating rafts placed directly on the water surface of 0.5 m³ plastic tanks used for Litopenaeus vannamei culture under controlled salinity conditions ranging from 5 to 25‰. During the 28-day experiment, plant growth, shrimp growth performance, plant nutrient accumulation, and nitrogen/phosphorus mass-balance partitioning were assessed. The results showed that S. portulacastrum grew well under brackish conditions, with stronger biomass production at salinities below 15‰, while shrimp growth performance was most favorable at 10–15‰. Nutrient analysis of harvested S. portulacastrum biomass showed that the plant accumulated 19,735–29,433 mg N kg⁻¹ DW and 1099–1912 mg P kg⁻¹ DW, indicating its capacity to recover inorganic N and P through harvestable biomass. At 10‰ salinity, the integrated system reached the highest apparent total nitrogen removal/recovery efficiency of 46.98%, calculated from system-level mass-balance partitioning rather than water-concentration reduction alone. The areal nitrogen recovery rate in harvested S. portulacastrum biomass reached 383 mg N m⁻² day⁻¹. Although S. portulacastrum is a salt-tolerant plant, higher salinity levels (≥20‰) reduced plant biomass production and nutrient recovery efficiency. These findings indicate that integrating floating-raft S. portulacastrum into brackish shrimp-culture systems at moderate salinity, particularly 5–15‰, is a feasible strategy for converting dissolved nutrients into harvestable plant biomass. Full article

Floating wetlands have emerged as a sustainable alternative for improving water quality, and although some studies have investigated their performance, there is still much to be understood regarding their integration with energy-generating technologies. This study evaluated a combined system of floating wetlands and microbial fuel cells (MFCs) for treating real wastewater and generating bioelectricity. Experiments were conducted in batch mode to simulate application in natural water bodies, using real wastewater collected on different dates. As a result of the natural variability of the influent, initial chemical oxygen demand (COD) concentrations of 405 and 289 mg/L were observed. Performance was assessed in terms of organic matter and nitrogen removal, as well as voltage generation. COD removal efficiencies reached 50% and 69% for the higher and lower organic loads, respectively, indicating improved treatment at reduced concentrations. Maximum removals of 56% for ammoniacal nitrogen (NH₃-N) and 40% for total nitrogen (TN) were achieved, reflecting moderate nutrient removal capacity. Voltage generation was sustained for approximately 21 days, confirming stable bioelectrochemical activity, and power output was found to depend on the organic load serving as substrate for electrogenic microorganisms. Overall, the system represents a viable approach for wastewater treatment with the added benefit of energy recovery, although its performance is influenced by influent characteristics and operation conditions. Full article

Sewage sludge management is increasingly shifting from a liability-focused “treat-and-dispose” approach toward resource recovery, where digestion residues and their liquid fractions are treated as secondary feedstocks for nutrient, water, and energy recovery. In Europe, the recast Urban Wastewater Treatment Directive strengthens performance and monitoring requirements and reinforces the need for efficient sludge treatment and downstream valorization routes. This review synthesizes evidence on how pretreatment-induced changes in digestate properties translate into membrane performance outcomes and maps practical design implications for selecting pretreatment-membrane trains for nutrient recovery and reclaimed water production. Pressure-driven membrane methods (MF/UF/NF/RO), together with membrane distillation and electrodialysis, are central candidates for producing clarified water streams and concentrating nutrients; however, their performance is governed by digestate rheology, colloidal stability, and the composition of soluble microbial products and inorganic ions, which collectively shape fouling and scaling risks. Pretreatments such as thermal hydrolysis and microwave conditioning can modify floc structure and solubilize organics, with potential benefits for dewaterability and mass transfer, but can also shift particle size distributions toward fines and increase fouling propensity if not coupled with appropriate solid–liquid separation and conservative flux control. Emphasis is placed on mechanisms and operational trade-offs rather than single-point performance claims, highlighting where evidence is robust and where further comparability and full-scale validation remain necessary. Full article

To determine the factors influencing juvenile recruitment of the kelp Eisenia bicyclis, a seven-year monitoring survey was conducted in an area affected by seismic subsidence caused by the 2011 earthquake and subsequent breakwater restoration. Juvenile recruitment was high in September 2011 and in May to June of 2013–2015, but low in 2012, 2016 and 2017. Analysis of the relationship between environmental factors and juvenile recruitment revealed that recruitment was associated with light intensity, with lower water temperature two months prior, and an increase in nutrients four months prior. The seasonal increase in nutrient concentrations during winter may have been influenced by the seasonal northwestward coastal current. In contrast, despite elevated nutrient concentrations, recruitment was relatively poor in 2016–2017. This might be attributed to the unstable seabed environment associated with the breakwater construction. Our monthly monitoring of both the number of E. bicyclis juvenile recruitments and environmental factors at the same site demonstrated that a time-lagged increase in nutrient concentrations and a decrease in water temperature are associated with Eisenia bicyclis juvenile recruitment. This study provides fundamental information on kelp recruitment that will contribute to predicting the recovery of kelp communities following disturbances and recruitment dynamics under environmental change. Full article

The increasing generation of agro-industrial residues like nejayote (maize lime-cooking wastewater from the maize nixtamalization process) poses significant environmental challenges in Mexico due to its elevated chemical oxygen demand (COD) and organic load. This study evaluates the physical separation of nejayote via membranes and its use as a low-cost substrate for producing lipids and carotenoids using Rhodotorula glutinis. A batch culture followed by pulse-feeding achieved a COD removal efficiency of 53.6% (0.22 g COD/(L h)) and a biomass concentration of 3.72 ± 0.45 g COD/L within 48 h. The yeast demonstrated a high specific metabolic efficiency, yielding 0.457 g of lipids and 0.0049 g of carotenoids per gram of biomass, with an oleaginous fraction of 46.21% in dry weight. Experimental data calibrated a process model in SuperPro Designer, simulating full-scale processes treating 100, 1000, and 10,000 m³ of nejayote per batch, producing up to 2137.11 MT of lipids and 22.90 MT of carotenoids annually. A techno-economic analysis estimated the investment, operating costs, and financial indicators for all scenarios. Strategies like evaporation and reverse osmosis to concentrate nejayote significantly improved profitability by reducing equipment size. Additionally, a circular economy approach was modeled, recovering process water and nutrient-rich side streams. These findings confirm that integrated physical and biological treatment, coupled with resource recovery, transforms this particularly agro-industrial residue into a technically robust and economically viable biorefinery feedstock, aligning industrial production with sustainable waste management. Full article

Forward osmosis (FO) offers a promising route for urine concentration and nutrient recovery, yet inorganic scaling under high water recovery remains a significant challenge. This study systematically investigated scaling during FO treatment of synthetic fresh urine (SFU) and synthetic hydrolysed urine (SHU) over three consecutive cycles to 80% water recovery. SFU exhibited moderate flux decline (~14.4 → 4–5 LMH), with minimal hydraulic resistance from sparse calcium-deficient Ca–P deposits (Ca:P ≈ 1.2; ACP/OCP-like). In contrast, SHU caused severe cumulative scaling, progressively reducing flux from 19 → 14.46 → 1.3 LMH, dominated by struvite (Mg:P ≈ 1.02) and mixed Mg–carbonate phases. Visual MINTEQ thermodynamic modelling correctly identified the dominant mineral families in both feeds, while kinetic effects governed the formation of metastable phases, demonstrating that equilibrium modelling and experimental characterisation are complementary tools for scaling prediction under transient FO conditions. Physical cleaning restored ~98–99% of water flux for both feeds, confirming that even severe SHU-induced scaling is largely hydraulically reversible. High rejection of multivalent ions (PO₄³⁻, Mg²⁺, and Ca²⁺) was maintained throughout, confirming membrane integrity was preserved despite severe scaling. These findings demonstrate that urine hydrolysis fundamentally governs scaling pathways, severity, and reversibility in FO systems, and that simple hydraulic flushing is an effective fouling-control strategy, providing practical guidance for operating condition selection and cleaning strategy design in FO-based urine treatment applications. Full article

Water security in rapidly urbanising river basins is increasingly threatened by untreated city effluents, industrial discharges, and legacy agricultural contamination. The Tula River basin in central Mexico illustrates this issue, absorbing the majority of Mexico City’s effluent while sustaining a heavily exploited aquifer beneath one of the nation’s largest irrigation districts. This study provides an integrated assessment of surface water and groundwater quality throughout the basin, including the Endhó Dam and its associated aquifer. Water quality analysis revealed severe surface water contamination (WQI > 300), driven by untreated sewage and inadequate sanitation infrastructure. Elevated COD, BOD, and nutrient concentrations indicate significant organic loading and eutrophication risk. Near Tula City, arsenic, copper, and zinc were detected at levels posing direct risks to human health. Groundwater quality was comparatively favourable, with 71% of wells recording WQI < 100; however, arsenic exceeded permissible limits more than twentyfold in select wells, attributed to geological sources. The detection of SVOCs in both hydrological compartments confirms cross-compartment contamination. Point-source reduction alone is insufficient for aquifer recovery; comprehensive sanitation strategies and long-term monitoring are urgently required. These findings carry direct relevance for water governance in megacity-dependent basins globally, where urban, agricultural, and geological stressors demand integrated management approaches. Full article

Rivers are dynamic systems that flow from higher elevations to lowlands, eventually discharging into lakes, seas, or oceans, and play a key role in sustaining ecosystems and supporting human activities. River basin characterisation extends beyond the watercourse itself, encompassing land uses, tributaries and hydromorphological features that influence ecological processes. This review analyses three river basins in northern Portugal, Ave, Douro, and Vouga, using a holistic characterisation approach. These basins represent contrasting river systems in terms of size, hydrological regulation and dominant land uses, while simultaneously being subject to pressures frequently reported in many other river basins in Europe, and around the world. The analysis includes a general basin description, a hydromorphological assessment with emphasis on land use, and an evaluation of water ecological status, with particular focus on estuarine ecosystems. Water quality in the three basins has been strongly influenced by anthropogenic pressures, including industrial and agricultural activities, and wastewater discharges. Although the implementation of the European Water Framework Directive has led to improvements in recent decades, the degree of recovery varies among basins. Persistent challenges, such as nutrient concentrations, microbial contamination, and heavy metal pollution, highlight the need for integrated river basin management and improved monitoring strategies. This review provides transferable insights for the management of river basins facing similar environmental pressures. Full article

Treatment of wastewater effluent is essential to reduce environmental impact and keep surface water clean, meeting sustainable criteria. While plant-based coagulants are known for their eco-friendly profiles, their dual application for high-efficiency nutrient removal and subsequent sludge valorization in fish farm systems remain under-explored. Therefore, this study was conducted to determine the optimum conditions for using natural coagulants to recover nutrients from fish farm effluent. Two types of natural coagulants, Alhagi graecorum leaves and apricot seeds, were evaluated for the treatment and recovery of nutrients from fish farm effluent due to their high removal efficiency, non-toxicity, and cost-effectiveness. In this study, optimization was performed using Response Surface Methodology (RSM) with a Central Composite Design (CCD) to investigate the effects of three factors: coagulant concentration (1000–7000 mg/L), wastewater pH (5–9), and settling time (15–35 min). The primary responses measured were the removal efficiencies of phosphate (PO₄) and nitrate (NO₃). According to the CCD results, maximum removal efficiencies reached 92.63% and 73.49% for PO₄ and NO₃, respectively. The optimal conditions were identified as pH 5, 1000 mg/L coagulant concentration, and a 35 min settling time for A. graecorum, and pH 9, 1000 mg/L concentration, and a 15 min settling time for apricot seed. These findings establish the optimal conditions for using these natural substances as effective agents for sustainable wastewater treatment and nutrient recovery. Full article