Search Results (994)

Sewage sludge, as a by-product of wastewater treatment, represents a significant cost factor in the operation of wastewater treatment plants and accounts for up to 50% of total costs. As sewage sludge still contains a high proportion of water after the basic treatment processes (thickening, stabilization and dewatering), sludge drying helps to reduce further treatment and disposal costs. Conventional drying methods are associated with high energy consumption, making solar drying a more cost-effective alternative. This paper analyzes the economic aspects of constructing a sewage sludge solar drying facility with the help of an expert system based on neural networks. The system considers a range of parameters (plant capacity, transport distance, transport and treatment costs, etc.) to assess the values of the investment as well as the operation and maintenance costs. The analysis was carried out using NeuralTools (Lumivero). Two main options for sludge disposal were investigated: treatment at a regional center (with the sub-options of own or outsourced transport) and handing over of sludge to another legal entity. In total, five neural network models were developed based on the input load (from 75 to 10,000 t/year and from 10,000 to 20,000 t/year) and transport method (own or outsourced transport), resulting in an analysis of over 670,000 scenarios. The key output variable was the net present value of costs over a 30-year period. The results demonstrated high model accuracy (error < 5%) and allowed a comparison of the profitability of constructing a sewage sludge solar drying facility with alternative methods of sludge disposal, in particular with the transport and disposal of the dewatered sludge. Full article

Small-scale thermal treatment systems can provide environmentally improved sewage sludge treatment due to processing sludge locally, which lowers transport costs and emissions. However, the combined effect of confined volume and complex sludge properties makes achieving strict regulations on flue gas emissions and end-ash composition challenging. System development thus requires the use of advanced, 3D CFD simulation supported studies. An important step forward regarding these is the application of combustion models which introduce tailored surrogate fuels and apply detailed chemical kinetics to achieve a high-fidelity combustion description in confined volumes. In relation to this, the paper presents an innovative computationally efficient sewage sludge surrogate-based combustion model capable of defining surrogates, tailored to sewage sludge, and capable of providing detailed insight into reaction zone evolution in small-scale sludge incineration systems. The validity of the proposed model and surrogates is confirmed via simulated temperatures differing from measurements in the small-scale system for less than 30 K. The validated model of a small-scale system is used in the parametric analysis of variable air–fuel ratios, higher fuel moisture presence, varying bed temperature, and varying thermal power to enable unprecedentedly accurate and efficient definition of design features of small-scale systems and to provide key guidelines for operation optimization. Full article

Second-, third-, and fourth-generation biofuels represent an important response to the challenges of clean energy supply and climate change. In this context, the Horizon 2020 “TO-SYN-FUEL” project aimed to produce advanced biofuels together with phosphorus from municipal wastewater sludge through a combination of technologies including a Thermo-Catalytic Reforming system, Pressure Swing Adsorption for hydrogen separation, Hydrodeoxygenation, and biochar gasification for phosphorous recovery. This article presents the environmental performance results of the demonstrator installed in Hohenberg (Germany), with a capacity of 500 kg per hour of dried sewage sludge. In addition, four alternative scenarios are assessed, differing in the source of additional thermal energy used for sludge drying: natural gas, biogas, heat pump, and a hybrid solar greenhouse. The environmental performance of these scenarios is then compared with that of conventional fuel. The comparative study of these scenarios demonstrates that the biofuel obtained through wood gasification complies with the Renewable Energy Directive, while natural gas remains the least sustainable option. Heat pumps, biogas, and greenhouse drying emerge as promising alternatives to align biofuel production with EU sustainability targets. Phosphorus recovery from sewage sludge ash proves essential for compliance, offering clear environmental benefits. Although sewage sludge is challenging due to its high water content, it represents a valuable feedstock whose sustainable management can enhance both energy recovery and nutrient recycling. Full article

This study aimed to evaluate the effect of seasonal dynamics of phytoplankton biomass in the Bay of Gdansk (Southern Baltic Sea, Poland) on its usability for anaerobic digestion. Biomass samples were collected between May and October (2023–2024) for quantitative, taxonomic, and chemical analyses as well as for anaerobic digestion in mesophilic periodical bioreactors. Study results demonstrated substantial seasonal variations in the taxonomic composition of phytoplankton, with green algae and dinoflagellates prevailing in the spring, cyanobacteria in the summer, and diatoms in the autumn. These fluctuations were also reflected in the chemical composition of the biomass and its anaerobic digestion efficiency. The highest methane yield of 270 ± 13 mL CH₄/g VS and its highest production rate reaching 32.5 ± 1.6 mL CH₄/g VS·d were recorded in August, i.e., in the period of cyanobacteria predominance with the maximal contents of TOC (51.4 ± 2.1% TS), sugars (599 ± 42 mg/g TS), and lipids (126 ± 13 mg/g TS) in the biomass. In contrast, the lowest biomethanation efficiency was determined in October under diatom prevalence. A strong correlation was found between taxonomic, structural, and chemical properties of the substrate, and anaerobic digestion efficiency. This study’s findings underscore the enormous potential of phytoplankton biomass from summer blooms for energy production as a crucial element of sustainable management of coastal ecosystems and the circular economy. Full article

This study reports on green-synthesized zinc oxide nanoparticles (ZnONPs), focusing on their physicochemical characterization, photocatalytic properties, and agricultural applications. Dynamic light scattering (DLS) analysis revealed a mean hydrodynamic diameter of 337.3 nm and a polydispersity index (PDI) of 0.400, indicating moderate polydispersity and nanoparticle aggregation, typical of biologically synthesized systems. High-resolution transmission electron microscopy (HR-TEM) showed predominantly spherical particles with an average diameter of ~28 nm, exhibiting slight agglomeration. Energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental composition of zinc and oxygen, while X-ray diffraction (XRD) analysis identified a hexagonal wurtzite crystal structure with a dominant (002) plane and an average crystallite size of ~29 nm. Photoluminescence (PL) spectroscopy displayed a distinct near-band-edge emission at ~462 nm and a broad blue–green emission band (430–600 nm) with relatively low intensity. The ultraviolet–visible spectroscopy (UV–Vis) absorption spectrum of the synthesized ZnONPs exhibited a strong absorption peak at 372 nm, and the optical band gap was calculated as 2.67 eV using the Tauc method. Fourier-transform infrared spectroscopy (FTIR) analysis revealed both similarities and distinct differences to the pigeon extract, confirming the successful formation of nanoparticles. A prominent absorption band observed at 455 cm⁻¹ was assigned to Zn–O stretching vibrations. X-ray photoelectron spectroscopy (XPS) analysis showed that raw pigeon droppings contained no Zn signals, while their extract provided organic biomolecules for reduction and stabilization, and it confirmed Zn²⁺ species and Zn–O bonding in the synthesized ZnONPs. Photocatalytic degradation assays demonstrated the efficient removal of pollutants from sewage water, leading to significant reductions in total dissolved solids (TDS), chemical oxygen demand (COD), and total suspended solids (TSS). These results are consistent with reported values for ZnO-based photocatalytic systems, which achieve biochemical oxygen demand (BOD) levels below 2 mg/L and COD values around 11.8 mg/L. Subsequent reuse of treated water for irrigation yielded promising agronomic outcomes. Wheat and barley seeds exhibited 100% germination rates with ZnO NP-treated water, which were markedly higher than those obtained using chlorine-treated effluent (65–68%) and even the control (89–91%). After 21 days, root and shoot lengths under ZnO NP irrigation exceeded those of the control group by 30–50%, indicating enhanced seedling vigor. These findings demonstrate that biosynthesized ZnONPs represent a sustainable and multifunctional solution for wastewater remediation and agricultural enhancement, positioning them as a promising candidate for integration into green technologies that support sustainable urban development. Full article

The aim of the study was to evaluate the feasibility of using exhaust gases as a CO₂ source in the cultivation of Tetraselmis subcordiformis microalgae for biomass and hydrogen production. It was shown that the growth rate of T. subcordiformis biomass and its biochemical composition depended on the CO₂ source. The highest growth rate of 286 ± 15 mgVS/L-d and a final biomass concentration of 2710 ± 180 mgVS/L were achieved in the variant where exhaust gases from a coal and biomass supplementary combustion plant were the CO₂ source (V2). The highest CO₂ reduction efficiency of 90.3 ± 3.2% was achieved in the case where waste gases from biogas combustion were the CO₂ source (V1). In V2, the highest CO₂ utilization efficiency was achieved (CO₂UE = 46.7 ± 2.4%). Analyzing the biomass composition confirmed differences in total carbon content (TC) and polysaccharide fraction. The highest H₂ production efficiency and rate, which were 70.9 ± 2.7 mL/gVS and 2.27 ± 0.08 mL/gVS·h, respectively, were obtained in V2. The results obtained indicate the possibility of integrating fuel combustion processes with the cultivation of T. subcordiformis and photobiological H₂ production, which is a promising solution in the context of climate neutrality and the implementation of circular economy postulates. This approach demonstrates a sustainable strategy for linking industrial CO₂ emissions with the production of renewable biohydrogen and thus contributes to climate protection and the promotion of circular economy concepts. Full article

In the context of global carbon neutrality, municipal wastewater treatment plants (WWTPs), as key sources of greenhouse gas emissions, urgently require quantification of carbon emissions and implementation of mitigation strategies. This study establishes a life-cycle carbon footprint model encompassing the stages of pretreatment, biological treatment (AAO process), and sludge treatment, with integrated consideration of municipal sewer networks. Key findings reveal the following: The biological treatment stage contributes 68.14% of total carbon emissions. N₂O (nitrous oxide), due to its high global warming potential (GWP), is the primary source of direct emissions (0.333 kg CO₂eq/m³). In the pretreatment stage, 80.4% of carbon emissions originate from the electricity consumption of sewage lifting pump stations (0.030 kg CO₂eq/m³). During the sludge treatment stage, carbon emissions are concentrated in residual sludge lifting (0.0086 kg CO₂eq/m³) and sludge dewatering/pressing (0.0088 kg CO₂eq/m³). Accordingly, this study proposes the following mitigation strategies: novel nitrogen removal processes should be implemented to optimize aeration control and enhance methane (CH₄) recovery during the biological period, and variable frequency drive (VFD) pumps and IoT (Internet of Things) technologies should be employed to reduce energy consumption during the pretreatment period, and during the sludge treatment period, low-carbon dewatering technologies should be adopted. This work provides a theoretical foundation for process-specific carbon management in WWTPs and facilitates the synergistic advancement of environmental stewardship and dual-carbon objectives through technology–system integration. Full article

The consumption of illicit psychoactive substances, such as cocaine, poses significant public health and socioeconomic challenges due to its widespread use and impact on the central nervous system. This study aimed to develop and validate an analytical method for quantifying cocaine in surface water using an adapted QuEChERS extraction procedure and gas chromatography–mass spectrometry (GC-MS). The research included a bibliographic review of about 40 articles and laboratory analyses conducted at the Federal University of Northern Tocantins (UFNT). The results showed a matrix effect of −54.24%. This negative matrix effect impacted accuracy, as interference from other sample components can suppress the analyte signal, resulting in a smaller measured quantity. This indicates signal suppression, which can be corrected through matrix-matched calibration. Recovery values ranged from 61.3% to 107.7%, demonstrating satisfactory accuracy. The validated method proved suitable for monitoring cocaine in surface water and can serve as a biomarker for untreated sewage discharges. Full article

Access to microbiologically safe water in preschool educational settings constitutes a pressing public health challenge, particularly in rural areas with deficient infrastructure. Repeated exposure to enteropathogens present in contaminated water has been associated with acute gastrointestinal infections, environmental enteropathy, and disruptions in the intestinal microbiota of young children. Motivated by this concern, the present study evaluates the microbiological quality of water in 32 public preschool facilities in the municipality of Matehuala, San Luis Potosí—18 urban and 14 rural—by analyzing the presence of aerobic mesophilic bacteria (AMB), total coliforms (TC), fecal coliforms (FC), and helminth eggs. The assessment was conducted in accordance with Mexican standards NOM-092-SSA1-1994 and NOM-230-SSA1-2002 and supplemented with the World Health Organization’s guidelines for drinking-water quality. The findings revealed a marked territorial disparity: 100% of rural schools that relied on rooftop water tanks exceeded permissible limits for TC, and 35.7% tested positive for FC. In contrast, all urban schools—supplied through piped water systems—complied with current regulations. Statistical analysis (Mann–Whitney U test, p < 0.05) confirmed significant differences in microbiological contamination based on geographic location and type of water supply. In all FC-positive cases, a lack of sewage infrastructure and inadequate sanitation practices in storage containers were documented. These results demonstrate that formal access to water does not ensure its microbiological safety, particularly in settings with poor structural conditions. The study underscores the urgent need to implement point-of-use water treatment technologies, establish regular microbiological monitoring protocols, and provide training for educational staff in water hygiene practices. Full article

Urban rivers, as crucial components of ecosystems, serve multiple functions, including flood control, drainage, and landscape services. However, with the acceleration of urbanization, factors such as industrial wastewater discharge, domestic sewage leakage, and surface runoff pollution have led to increasingly severe degradation of water quality in urban rivers. Unmanned aerial vehicle (UAV) remote sensing technology, with its sub-meter spatial resolution and operational flexibility, demonstrates significant advantages in the detailed monitoring of complex urban water systems. This study proposes an Ensemble Self-Attention Enhanced Mixture Density Network (ESA-MDN), which integrate an ensemble learning framework with a mixture density network and incorporates a self-attention mechanism for feature enhancement. This approach better captures the nonlinear relationships between water quality parameters and remote sensing features, achieving high-precision modeling of water quality parameter distributions. The resulting spatiotemporal distribution maps provide valuable support for pollution source identification and management decision making. The model successfully retrieved five water quality parameters, Chl-a, TSS, COD, TP, and DO, and validation metrics such as R², RMSE, MAE, MSE, MAPE, bias, and slope were utilized. Key metrics for the ESA-MDN test set were as follows: Chl-a (R² = 0.98, RMSE = 0.31), TSS (R² = 0.93, RMSE = 0.27), COD (R² = 0.93, RMSE = 0.39), TP (R² = 0.99, RMSE = 0.02), and DO (R² = 0.88, RMSE = 0.1). The results indicated that ESA-MDN can effectively extract water quality parameters from multispectral remote sensing data, with the generated spatiotemporal water quality distribution maps providing crucial support for pollution source identification and emergency response decision making. Full article

The urgent need to reduce the environmental footprint of agricultural inputs, alongside the rising cost and limited availability of mineral fertilizers, has encouraged the exploration of organic waste materials as alternative nutrient sources. This review examines how organic and nutrient-rich waste streams—from livestock excreta and food industry residues to sewage sludge and combustion by-products—can be converted into effective fertilizers through biological, thermal, and chemical processes, reducing dependence on mineral fertilizers and supporting more circular and resilient cropping systems. It also analyzes the agronomic performance of these waste-derived materials in terms of nutrient release dynamics, impact on soil functions, and crop response under different management conditions. Examples of commercial waste-derived fertilizers are included, together with their effects on soil quality and crop productivity, and regulatory frameworks and commercialization challenges are considered, with emphasis on current European policies and real-world product examples. The broader contribution of these practices to climate mitigation, resource recovery, and rural development is also discussed. While promising, the implementation of waste-based fertilization strategies requires further efforts in standardization, safety assurance, and farmer engagement. This article provides an integrated overview of the topic and identifies key areas for future research, innovation, and policy development in support of sustainable nutrient management. Full article

The unsuitable performance of or deficit in basic sanitation infrastructure, especially in sparsely populated rural communities, remains critical, particularly in many developing regions, and demands sustainable, cost-effective, and easily operated solutions. Thus, the objective of this Review is to analyze design parameters for evapotranspiration tanks (EvapTs), adopted as nature-based solutions for zero-discharge domestic sewage treatment. The literature search was conducted using the Scopus and Web of Science databases, complemented by backward citation tracking. From 4434 records, 29 studies were selected based on specific criteria, such as the availability of design data and their application in urban or rural contexts. The main findings indicated required areas per inhabitant ranging from 0.5 to 7.7 m², primarily influenced by climate conditions and the type of plant used. Statistical analysis showed a negative correlation between the area of the evaporation tanks and the mean annual temperature, with a Pearson correlation coefficient (r of −0.74). For mean annual temperatures between 19 and 27 degrees Celsius, linear regression showed a variation between 4.7 and 0.6 m²/inhabitant with a reduction coefficient of −0.51 per degree Celsius, suggesting that warmer climates require smaller system areas per capita. Most studies were conducted at full scale, with Brazil accounting for the highest number of publications. EvapT is identified as a promising ecological technology that is particularly suitable for rural settings. However, it still requires technical standardization, cost–benefit analysis, and research on social acceptance. The adoption of clear design criteria may enhance system replicability, support public policy development, and contribute to SDG 6—Clean Water and Sanitation for All. Full article

Excessive nitrogen export from lowland polders is a key contributor to cultural eutrophication in downstream aquatic ecosystems. This study investigated the spatiotemporal characteristics, migration pathways, and sources of nitrogen pollution in a typical polder system. Eight surface water sampling campaigns were conducted at 13 sites in Quyuan Polder, Dongting Lake, from 2022 to 2023, combining ArcGIS spatial analysis, multivariate statistics, and dual-isotope (δ¹⁵N-NO⁻), δ¹⁸O-NO₃⁻) techniques. Nitrate and ammonium nitrogen dominated the nitrogen pool, accounting for ~76% of total nitrogen. Concentrations were higher in the dry season (2.48 mg/L) than in the wet season (1.89 mg/L) and differed significantly among hydrological periods (p < 0.05). Within the polder, total nitrogen and ammonium nitrogen were elevated, whereas nitrate nitrogen was higher at the outlet, reflecting distinct nitrogen profiles along the hydrological gradient. Nitrogen transport patterns were largely consistent with flow direction, driven by both upstream inputs and in situ generation. Isotopic signatures indicated that nitrate originated mainly from ammonium fertilizer and soil nitrogen, with contributions from manure and sewage. These findings enhance understanding of nitrogen dynamics in lowland catchments and provide a scientific basis for targeted pollution control in polder waters. Full article

Municipal wastewater treatment relies primarily on biological methods, yet effective disposal of residual sludge remains a major challenge. Converting sludge into biochar via oxygen-limited pyrolysis presents a novel approach for waste resource recovery. This study prepared sludge-based biochar (SBC) through one-step pyrolysis of sewage sludge and applied it to activate peroxymonosulfate (PMS) for degrading diverse contaminants. Characterization (SEM, XPS, FTIR) revealed abundant pore structures and diverse surface functional groups on SBC. Using Acid Orange 7 (AO7) as the target pollutant, SBC effectively degraded AO7 across pH 3.0–9.0 and catalyst dosages (0.2–2.0 g·L⁻¹), achieving a maximum observed rate constant (k_obs) of 0.3108 min^–1. Salinity and common anions showed negligible inhibition on AO7 degradation. SBC maintained 95% degradation efficiency after four reuse cycles and effectively degraded sulfamethoxazole, sulfamethazine, and rhodamine B besides AO7. Mechanistic studies (chemical quenching and ESR) identified singlet oxygen (¹O₂) and superoxide radicals (O₂^•− ) as the dominant reactive oxygen species for AO7 degradation. XPS indicated a 39% reduction in surface carbonyl group content after cycling, contributing to activity decline. LC-MS identified five intermediates, suggesting a potential degradation pathway driven by SBC/PMS system. ECOSAR model predictions indicated significantly reduced biotoxicity of the degradation products compared to AO7. This work provides a strategy for preparing sludge-derived catalysts for PMS activation and pollutant degradation, enabling effective solid waste resource utilization. Full article

Municipal sewage sludge represents a significant environmental challenge due to its large-scale production and limited disposal options. Pyrolysis, a thermal decomposition process, offers a promising approach for converting sewage sludge into biochar, a carbon-rich material with diverse environmental applications. Sewage sludge-derived biochars were prepared at pyrolysis temperatures of 300 °C, 500 °C, 700 °C, and 900 °C (denoted as B300 to B900) and evaluated for their structural, adsorption, and catalytic performance. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and energy dispersive X-ray spectrometry (EDS) analyses revealed a distinct temperature-dependent morphological evolution and mineral exposure. The B900 biochar exhibited a BET surface area of 83.8 m²/g and the highest pore volume of 0.101 cm³/g, indicating a well-developed mesoporous structure. In catalytic degradation tests using 20 mg/L persulfate and 500 mg/L B900, rapid oxidation was observed, achieving 91% methylene blue (MB) degradation in 30 min, highlighting its role in activating persulfate via surface-bound Fe and Al species. Optimization studies confirmed that MB removal efficiency was highest at 500 mg/L biochar and 40 mg/L persulfate, and the system was not significantly affected by the tap and synthetic wastewater matrices. This work demonstrates that biochar obtained from sewage sludge can serve as an eco-friendly and multifunctional material for resource recovery and environmental cleanup. Full article