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20 pages, 2869 KiB  
Article
Influence of Polyester and Denim Microfibers on the Treatment and Formation of Aerobic Granules in Sequencing Batch Reactors
by Victoria Okhade Onyedibe, Hassan Waseem, Hussain Aqeel, Steven N. Liss, Kimberley A. Gilbride, Roxana Sühring and Rania Hamza
Processes 2025, 13(7), 2272; https://doi.org/10.3390/pr13072272 - 16 Jul 2025
Viewed by 476
Abstract
This study examines the effects of polyester and denim microfibers (MFs) on aerobic granular sludge (AGS) over a 42-day period. Treatment performance, granulation, and microbial community changes were assessed at 0, 10, 70, 210, and 1500 MFs/L. Reactors with 70 MFs/L achieved rapid [...] Read more.
This study examines the effects of polyester and denim microfibers (MFs) on aerobic granular sludge (AGS) over a 42-day period. Treatment performance, granulation, and microbial community changes were assessed at 0, 10, 70, 210, and 1500 MFs/L. Reactors with 70 MFs/L achieved rapid granulation and showed improved settling by day 9, while 0 and 10 MFs/L reactors showed delayed granule formation, which was likely due to limited nucleation and weaker shear conditions. Severe clogging and frequent maintenance occurred at 1500 MFs/L. Despite > 98% MF removal in all reactors, treatment performance declined at higher MF loads. Nitrogen removal dropped from 93% to 68%. Phosphate removal slightly increased in reactors with no or low microfiber loads (96–99%), declined in reactors with 70 or 210 MFs/L (92–91%, 89–88%), and dropped significantly in the reactor with1500 MFs/L (86–70%, p < 0.05). COD removal declined with increasing MF load. Paracoccus (denitrifiers) dominated low-MF reactors; Acinetobacter (associated with complex organic degradation) and Nitrospira (nitrite-oxidizing genus) were enriched at 1500 MFs/L. Performance decline likely stemmed from nutrient transport blockage and toxic leachates, highlighting the potential threat of MFs to wastewater treatment and the need for upstream MF control. Full article
(This article belongs to the Special Issue State-of-the-Art Wastewater Treatment Techniques)
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20 pages, 6006 KiB  
Article
Development of Grouting Materials from Shield Sludge via Alkaline Hydrothermal Activation: A Resource Utilization Approach
by Lianjun Chen, Meiyue Liu, Penghui Li, Junxiang Wang and Xiaoqiang Cao
Materials 2025, 18(12), 2673; https://doi.org/10.3390/ma18122673 - 6 Jun 2025
Viewed by 419
Abstract
Frequently, the viscous mixture from shield operations is disposed of because its significant water ratio and the presence of polymers like foaming agents result in subpar structural qualities, contributing to the unnecessary consumption of land and the squandering of soil assets. Therefore, these [...] Read more.
Frequently, the viscous mixture from shield operations is disposed of because its significant water ratio and the presence of polymers like foaming agents result in subpar structural qualities, contributing to the unnecessary consumption of land and the squandering of soil assets. Therefore, these problems urgently need to be solved economically and effectively. This study relies on the shield sludge produced by Qingdao Metro Line 6 project, and sand and shield sludge were used as the raw materials for synchronous grouting. By applying the basic principles of geopolymerization, ingredients like shield sludge and ground granulated blast furnace slag (GGBS) were mixed with sodium hydroxide, serving as the activating agent, in the preparation of the simultaneous grout formulas. A broad range of laboratory tests was conducted to evaluate the performance of these grout formulations. The effects of varying material ratios on key performance indicators—namely, fluidity, water secretion rate, setting time, and 3-day unconfined compressive strength (UCS)—were systematically analyzed. Based on these findings, the optimal material ratios for shield sludge-based synchronous grouting materials were proposed. Subsequently, component geopolymer was prepared from the activated shield sludge and shield sludge without adding any additional alkaline activators by simply adding water. A geopolymer with a 28-day compressive strength of 51.08 MPa was obtained when the shield sludge dosing was 60 wt%. This study aims to provide a reference for the preparation of synchronous grouting materials for the resource utilization of shield sludge. Full article
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16 pages, 5355 KiB  
Article
Multiscale Characterization of Anammox Granules and Microbial Migration Under Variable Nitrogen Loading Rates
by Xiaoliang Fan, Yunzhi Qian, Xueying Yang, Yilin Wang, Hong Yang and Shilong He
Water 2025, 17(11), 1653; https://doi.org/10.3390/w17111653 - 29 May 2025
Viewed by 356
Abstract
The sustainable restoration of river and lake ecosystems requires advanced wastewater treatment technologies to control nitrogen pollution, a key driver of aquatic degradation. This study explores the physiological responses of anammox granular sludge (AnGS) to varying nitrogen loading rates (NLRs), offering insights into [...] Read more.
The sustainable restoration of river and lake ecosystems requires advanced wastewater treatment technologies to control nitrogen pollution, a key driver of aquatic degradation. This study explores the physiological responses of anammox granular sludge (AnGS) to varying nitrogen loading rates (NLRs), offering insights into microbial stability under environmental stress. AnGS samples with different particle sizes (<1.0 mm, 1–2 mm, >2 mm) were subjected to NLRs ranging from 0.9 to 3.6 gN/L/d. As the NLR increased, the NO2-N/NH4⁺-N consumption ratio rose from 1.0 to 1.2, and the most active particle size shifted to 1–2 mm. Hydroxyapatite (HAP) crystals formed at higher NLRs, enhancing the settling and activity of 1–2 mm AnGS but inhibiting larger granules (>2 mm). Microbial analysis revealed that Candidatus Brocadia dominated at high NLRs (10.5%), outperforming Candidatus Kuenenia (2.47%). The enrichment of these key genera across granules indicates adaptive microbial migration under loading stress. These findings provide critical operational strategies for sustaining AnGS performance through particle size regulation, contributing to nitrogen control solutions vital for river and lake restoration efforts. Full article
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15 pages, 1986 KiB  
Article
Impact of the Anaerobic Feeding Strategy on the Formation and Stability of Aerobic Granular Sludge Treating Dairy Wastewater
by Thomas Dobbeleers, Marc Feyaerts and Jan Dries
Water 2025, 17(11), 1648; https://doi.org/10.3390/w17111648 - 29 May 2025
Viewed by 467
Abstract
Industrial activated sludge plants in many sectors, including the dairy industry, face sludge separation problems caused by sludge bulking. Aerobic granular sludge (AGS) could be a solution by forming well-settling granules. The key to successful granulation is the microbial selection of slow-growing glycogen-accumulating [...] Read more.
Industrial activated sludge plants in many sectors, including the dairy industry, face sludge separation problems caused by sludge bulking. Aerobic granular sludge (AGS) could be a solution by forming well-settling granules. The key to successful granulation is the microbial selection of slow-growing glycogen-accumulating organisms (GAOs) by introducing an anaerobic feeding/reaction step. The objective of the current study was to investigate the impact of two slow feeding strategies to achieve granulation in existing sequencing batch reactors treating real dairy wastewater, by microbial selection only. The first strategy consisted of slow 90 min mixed feeding. The second strategy combined 45 min static and 45 min mixed feeding to build up a substrate gradient. The feeding strategies did not affect the effluent quality, but significantly impacted the sludge morphology, settling properties, and microbial community composition. Mixed feeding led to filamentous overgrowth by Thiothrix species, up to 45% abundance, and deteriorating settling, with sludge volume index (SVI) values up to 125 mL/g. In contrast, static feeding yielded densified sludge with SVI values below 45 mL/g and up to 35% GAO abundance. In conclusion, the results show successful granulation when using a simple static slow feeding mode, which could benefit the industrial application of AGS technology. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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26 pages, 10141 KiB  
Article
Study of Novel Geopolymer Concrete Prepared with Slate Stone Cutting Sludge, Chamotte, Steel Slag and Activated with Olive Stone Bottom Ash
by Raul Carrillo Beltran, Elena Picazo Camilo, Griselda Perea Toledo and Francisco Antonio Corpas Iglesias
Materials 2025, 18(9), 1974; https://doi.org/10.3390/ma18091974 - 26 Apr 2025
Cited by 2 | Viewed by 648
Abstract
The expansion of the construction sector has contributed to the depletion of raw materials and an increased demand for resources; therefore, sustainable approaches are required to satisfy the construction demand. The present study explores the development of geopolymers by utilizing industrial by-products from [...] Read more.
The expansion of the construction sector has contributed to the depletion of raw materials and an increased demand for resources; therefore, sustainable approaches are required to satisfy the construction demand. The present study explores the development of geopolymers by utilizing industrial by-products from mining, ceramics, olive oil production, and steel manufacturing. Specifically, slate stone cutting sludge (SSCS) and chamotte (CH) are used as aluminosilicate precursors, with olive biomass bottom ash (OSBA) acting as an alkaline activator, along with sodium silicate, and steel granulated slag (SGS) incorporated as an aggregate. Novel geopolymers were prepared with consistent proportions of SSCS and OSBA while varying the CH content from 10 to 2 wt.%. The SGS proportion was adjusted from 35 to 50 wt.%, and different Na2SiO3/OSBA ratios (0.35, 0.31, 0.19, and 0.08) were examined. To identify the optimal mix, a series of physical and mechanical tests was conducted, complemented by FTIR and SEM analysis to evaluate the chemical and microstructural changes. The best-performing formulation achieved a compressive strength of 42.8 MPa after 28 days of curing. FTIR analysis identified quartz and carbonate phases, suggesting that quartz did not fully dissolve and that carbonates formed during the heating process. SEM examination of the optimal mixture indicated that the incorporation of SGS (up to 45 wt.%) facilitated the creation of a compact, low-porosity structure. EDX results revealed the presence of Ca-, Na-, Si-, Al-, and K-enriched phases, supporting the formation of (N, C)-A-S-H gel networks. These results demonstrate the potential of utilizing SSCS, CH, OSBA, and SGS to create geopolymer concretes, showcasing the viability of using industrial by-products as eco-friendly substitutes for traditional construction materials. Full article
(This article belongs to the Special Issue Advances in Function Geopolymer Materials)
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19 pages, 23865 KiB  
Article
Optimization of Technical Parameters for the Vacuum Preloading-Flocculation-Solidification Combined Method for Sustainable Sludge Utilization
by Chao Han, Hongwu Li, Kun Duan, Rongjun Zhang, Qian Peng, Liang Liu, Yimu Guo, Ke Sun and Peng Tu
Sustainability 2025, 17(6), 2710; https://doi.org/10.3390/su17062710 - 19 Mar 2025
Viewed by 353
Abstract
High-water content dredged sludge from waterways, with potential for sustainable use as high-performance fillers, was effectively treated using the vacuum preloading-flocculation-solidification combined method (denoted as the VP-FSCM). This study investigated the effect of flocculant and curing agent dosages on the solidification of sludge [...] Read more.
High-water content dredged sludge from waterways, with potential for sustainable use as high-performance fillers, was effectively treated using the vacuum preloading-flocculation-solidification combined method (denoted as the VP-FSCM). This study investigated the effect of flocculant and curing agent dosages on the solidification of sludge with initially poor mechanical properties. Ground granulated blast-furnace slag (GGBS) and ordinary Portland cement (OPC) were selected as composite curing agents, while anionic polyacrylamide (APAM) and slaked lime were used as a mixed flocculant. Laboratory experiments were conducted to examine the effects of different dosages of curing agents and flocculants on deposition dehydration, strength characteristics, water content after curing, as well as the spatial distribution of them under the combined method. Additionally, the conventional sludge solidified method treated by GGBS and OPC (denoted as the GCSM) was also investigated and compared. The results indicate that increasing the dosage of curing agent from 4.5% to 10.5% enhances the shear strength of samples treated with VP-FSCM by up to 3–5 times compared to those treated with GCSM. The optimal ratio for the composite curing agent is GGBS/OPC = 1, with optimum dosages for the composite flocculant composed of APAM at 0.125% and slaked lime at 1.5%. When admixture dosage is optimal, it allows for better utilization of the advantages from coupling effects such as flocculation dehydration, vacuum preloading, and chemical curing, thereby significantly improving mechanical properties of the sludge. Full article
(This article belongs to the Special Issue Soil Stabilization and Geotechnical Engineering Sustainability)
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15 pages, 5354 KiB  
Article
Study on the Influence of Clay Content on the Freeze–Thaw Characteristics and Mechanisms of Solidified Low-Liquid-Limit Clay
by Ruifan Lu, Junjie Yang and Yalei Wu
Appl. Sci. 2025, 15(6), 3005; https://doi.org/10.3390/app15063005 - 10 Mar 2025
Viewed by 715
Abstract
This study investigates the effects of clay content on the strength and microstructural mechanisms of artificially prepared low-liquid-limit clay solidified with SSGM binder, composed of salt sludge (SAS), steel slag (SS), ground granulated blast-furnace slag (GGBS), and light magnesium oxide (MgO), and the [...] Read more.
This study investigates the effects of clay content on the strength and microstructural mechanisms of artificially prepared low-liquid-limit clay solidified with SSGM binder, composed of salt sludge (SAS), steel slag (SS), ground granulated blast-furnace slag (GGBS), and light magnesium oxide (MgO), and the law of influence of viscous particles content on the strength of the solidified low-liquid-limit clay and its microscopic mechanism were investigated through a freeze–thaw cycle test and microscopic test. The results indicate that, under freeze–thaw cycles, both the mass and unconfined compressive strength of the solidified soil decrease with increasing cycle number. At the same number of cycles, samples with lower clay content exhibit smaller mass loss rates and unconfined compressive strength loss rates. Microstructural tests reveal that the hydration products of the binder, including C-S-H, C-A-S-H, C-A-H, and AFt, not only cement soil particles and fill internal pores but also interconnect to form a mesh-like structure, enhancing internal stability. However, as freeze–thaw cycles progress, the structure of the solidified soil deteriorates, with an increase in large pores and the formation of penetrating cracks and voids, leading to reduced strength. The SSGM binder demonstrates excellent freeze–thaw resistance for solidifying low-liquid-limit clay and improves the utilization rate of industrial waste, showing promising application potential in permafrost regions. Full article
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23 pages, 2691 KiB  
Article
Production and Quality Assessment of Fertilizer Pellets from Compost with Sewage Sludge Ash (SSA) Addition
by Paweł Cwalina, Sławomir Obidziński, Aneta Sienkiewicz, Małgorzata Kowczyk-Sadowy, Jolanta Piekut, Ewelina Bagińska and Jacek Mazur
Materials 2025, 18(5), 1145; https://doi.org/10.3390/ma18051145 - 4 Mar 2025
Cited by 1 | Viewed by 1257
Abstract
This article examines the process of pressure agglomeration of garden waste compost mixed with sewage sludge ash (SSA) to produce granulated fertilizer material, using a flat die rotating compaction roller system. The study evaluated the effects of adding SSA at mass fractions of [...] Read more.
This article examines the process of pressure agglomeration of garden waste compost mixed with sewage sludge ash (SSA) to produce granulated fertilizer material, using a flat die rotating compaction roller system. The study evaluated the effects of adding SSA at mass fractions of 0%, 10%, 20%, 30%, 40%, and 50% on the process of pelleting and the quality of pellets. Increasing the SSA content from 0% to 50% reduced the power demand of the pellet mill by 13.5% (from 4.92 kW to 4.25 kW), decreased the kinetic strength of the pellets by 0.7% (from 98.21% to 97.56%), and slightly increased the pellet density, by 2.6% (from 1641.17 kg·m−3 to 1684.09 kg·m−3). The high density of the pellets, i.e., over 1600 kg·m−3, indicates that they are of market quality. A chemical analysis revealed that SSA addition positively influenced fertilizer properties. A higher SSA content (up to 50%) decreased the nitrogen content (1.4% to 0.73%) but significantly increased the phosphorus content (0.32% to 2.67%). The potassium content remained stable, at approximately 1.3%. The process of co-pelleting also diluted the heavy metals present in SSA, reducing the final product’s lead and cadmium levels to meet the standards set for fertilizers. Although the SSA contained high levels of heavy metals (lead: 93.89 mg·kgd.m.−1, cadmium: 11.28 mg·kgd.m.−1), these elements were not detected in the compost. Co-pelleting of compost and SSA produces high-density, high-quality fertilizer pellets with favorable nutrient profiles and heavy metal contents, complying with regulatory standards. Moreover, by converting garden waste and SSA into valuable agricultural products, the process supports sustainable waste management. This study evaluated the impact of SSA additives on the composition and water absorption of the granulate, providing insights into its suitability as an eco-friendly fertilizer alternative and its potential implications for sustainable agricultural practices. Full article
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14 pages, 1607 KiB  
Article
Impact of Polyethylene Terephthalate Microplastics on Aerobic Granular Sludge Structure and EPS Composition in Wastewater Treatment
by Piotr Jachimowicz and Agnieszka Cydzik-Kwiatkowska
Water 2025, 17(2), 270; https://doi.org/10.3390/w17020270 - 18 Jan 2025
Cited by 1 | Viewed by 1312
Abstract
Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. Granules have a compact microbial structure and a high potential for pollutant removal. Despite its advantages, the impact of microplastics (MPs) on AGS remains poorly understood, posing a potential risk to the [...] Read more.
Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. Granules have a compact microbial structure and a high potential for pollutant removal. Despite its advantages, the impact of microplastics (MPs) on AGS remains poorly understood, posing a potential risk to the stability and efficiency of biological wastewater treatment processes. This study investigates the effects of polyethylene terephthalate (PET) MPs on AGS structure and extracellular polymeric substance (EPS) composition, providing new insights into the interaction between MPs and AGS. Four granular sequencing batch reactors (GSBRs) were operated with varying concentrations of PET MPs in the influent wastewater (0, 1, 10, 50 mg/L). Key findings include MP-induced changes in granule size distribution, with an increase in smaller granules (<90 µm) observed in reactors exposed to PET MPs. EPS concentrations (51–77 mg/L) exhibited significant differences among reactors, with notable shifts in protein (PN) and polysaccharide (PS) fractions. A higher PET MP dose resulted in an increased PN/PS ratio (from 1.96 to 5.40) and elevated hydrophobicity of AGS. These changes suggest that MPs can alter AGS structure and EPS composition, potentially affecting granule stability and treatment performance. This study provides novel evidence on the disruptive effects of MPs in wastewater treatment systems, emphasizing the need to address MP pollution in the context of biological treatment processes. The results contribute to a deeper understanding of the interactions between MP and AGS and form the basis for strategies to mitigate their adverse effects. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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20 pages, 6013 KiB  
Article
Sustainable Utilization of Dewatering Sludge for the Development of Reinforcement Grouting Materials in Downhole Applications
by Xianxiang Zhu, Yanhui Du and Song Li
Water 2025, 17(2), 192; https://doi.org/10.3390/w17020192 - 12 Jan 2025
Viewed by 974
Abstract
The mining and processing of coal resources generate substantial coal-based solid wastes, such as coal gangue and slag, which pose environmental challenges, occupy land, and are difficult to manage. However, utilizing these wastes for the stabilization and solidification (S/S) of municipal sludge containing [...] Read more.
The mining and processing of coal resources generate substantial coal-based solid wastes, such as coal gangue and slag, which pose environmental challenges, occupy land, and are difficult to manage. However, utilizing these wastes for the stabilization and solidification (S/S) of municipal sludge containing chromium (Cr) and nickel (Ni) offers an effective solution for mitigating environmental and groundwater pollution while enabling sustainable waste treatment and resource utilization. This study applied an alkali-activated coal gangue–S95 granulated blast furnace slag-based binder (CGS) to the S/S treatment of municipal sludge. The effects of the liquid-to-solid ratio, alkali activator dosage, sludge content, and incineration on compressive strength and the leaching of Cr and Ni were analyzed. The results showed that compressive strength decreased with increases in the sludge content and liquid-to-solid ratio, while incinerated sludge (ESA) samples exhibited better strength than raw sludge (ES). Incineration decomposed the calcite (CaCO3) into CaO, which facilitated the oxidation of Cr(III) to Cr(VI) and increased Cr leaching in the ESA. However, the ESA samples demonstrated superior heavy metal stabilization, as CGS reduced Cr(VI) to Cr(III) and immobilized it through the formation of chromite phases. Using ESA as a binder in CGS provides a safe, efficient approach for resource recovery and heavy metal stabilization, offering a novel solution for the environmental management and utilization of coal-based solid wastes. Full article
(This article belongs to the Special Issue Engineering Hydrogeology Research Related to Mining Activities)
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21 pages, 3710 KiB  
Article
Optimization of Wastewater Treatment Through Machine Learning-Enhanced Supervisory Control and Data Acquisition: A Case Study of Granular Sludge Process Stability and Predictive Control
by Igor Gulshin and Olga Kuzina
Automation 2025, 6(1), 2; https://doi.org/10.3390/automation6010002 - 27 Dec 2024
Cited by 2 | Viewed by 2024
Abstract
This study presents an automated control system for wastewater treatment, developed using machine learning (ML) models integrated into a Supervisory Control and Data Acquisition (SCADA) framework. The experimental setup focused on a laboratory-scale Aerobic Granular Sludge (AGS) reactor, which utilized synthetic wastewater to [...] Read more.
This study presents an automated control system for wastewater treatment, developed using machine learning (ML) models integrated into a Supervisory Control and Data Acquisition (SCADA) framework. The experimental setup focused on a laboratory-scale Aerobic Granular Sludge (AGS) reactor, which utilized synthetic wastewater to model real-world conditions. The machine learning models, specifically N-BEATS and Temporal Fusion Transformers (TFTs), were trained to predict Biological Oxygen Demand (BOD5) values using historical data and real-time influent contaminant concentrations obtained from online sensors. This predictive approach proved essential due to the absence of direct online BOD5 measurements and an inconsistent relationship between BOD5 and Chemical Oxygen Demand (COD), with a correlation of approximately 0.4. Evaluation results showed that the N-BEATS model demonstrated the highest accuracy, achieving a Mean Absolute Error (MAE) of 0.988 and an R2 of 0.901. The integration of the N-BEATS model into the SCADA system enabled precise, real-time adjustments to reactor parameters, including sludge dose and aeration intensity, leading to significant improvements in granulation stability. The system effectively reduced the standard deviation of organic load fluctuations by 2.6 times, from 0.024 to 0.006, thereby stabilizing the granulation process within the AGS reactor. Residual analysis suggested a minor bias, likely due to the limited number of features in the model, indicating potential improvements through additional data inputs. This research demonstrates the value of machine learning-driven predictive control for wastewater treatment, offering a resilient solution for dynamic environments. By facilitating proactive management, this approach supports the scalability of wastewater treatment technologies while enhancing treatment efficiency and operational sustainability. Full article
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17 pages, 3268 KiB  
Article
Influence of Filler Types on the Treatment of Rural Domestic Wastewater in a Biological Trickling Filter: Simultaneous Nitrogen and Phosphorus Removal Performance, Microbial Community, and Metabolic Functions
by Yuxin Geng, Zhengwei Pan, Liangang Hou, Jiarui Li, Mingchao Wang, Tianhao Shi, Dongyue Li and Jun Li
Water 2024, 16(23), 3343; https://doi.org/10.3390/w16233343 - 21 Nov 2024
Viewed by 1053
Abstract
Biological trickling filtration (BTF) has the advantages of simple operation, low energy consumption, and low sludge production, and its application in the treatment of domestic wastewater in rural areas has been widely discussed. In this study, ceramic granule (R1), zeolite (R2), and sponge [...] Read more.
Biological trickling filtration (BTF) has the advantages of simple operation, low energy consumption, and low sludge production, and its application in the treatment of domestic wastewater in rural areas has been widely discussed. In this study, ceramic granule (R1), zeolite (R2), and sponge (R3), three typical nitrogen and phosphorus removal fillers, were selected to investigate the differences in the removal performance of COD, nitrogen, and phosphorus in BTF, analyze the characteristics of the fillers and biofilm, and determine the performance of simultaneous nitrogen and phosphorus removal. The results show that among the three fillers, zeolite has the larger specific surface area and roughness and has the best treatment effect on the adhesion performance of sewage and biofilm. The richness and diversity of the microbial community are higher, and the system is more stable, with a COD removal rate of 77.10 ± 8.67% and an NH4+-N removal rate of 75.20 ± 6.64%. The TP removal rate was 22.04 ± 10.27%. The surface of ceramic particles showed a regular cluster structure with a loose distribution. The removal rate of COD was 78.49 ± 6.92%, the concentration of NH4+-N in the effluent was 27.95 ± 8.23 mg/L, and the removal rate of TP was 38.83 ± 12.14%. As a polymer composite material, the sponge has large internal pores and a smooth surface, which is not conducive to biofilm adhesion. Therefore, the removal rate of nitrogen and phosphorus in sewage is poor; the removal rate of COD is 75.94 ± 6.98%, NH4+-N is 27.89 ± 21.06%, and the removal rate of TP is 14.07 ± 11.76%. Compared with the metabolic function of genes, zeolites have a more stable enzyme digestion ability than the other two fillers, and the genes related to the nitrification process (amo, hao, nxr, etc.) and functional genes encoding key enzymes related to the TCA cycle are relatively abundant. Full article
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17 pages, 3842 KiB  
Article
Metallurgical Waste for Sustainable Agriculture: Converter Slag and Blast-Furnace Sludge Increase Oat Yield in Acidic Soils
by Olga V. Zakharova, Peter A. Baranchikov, Svetlana P. Chebotaryova, Gregory V. Grigoriev, Nataliya S. Strekalova, Tatiana A. Grodetskaya, Igor N. Burmistrov, Sergey V. Volokhov, Denis V. Kuznetsov and Alexander A. Gusev
Agronomy 2024, 14(11), 2642; https://doi.org/10.3390/agronomy14112642 - 9 Nov 2024
Cited by 1 | Viewed by 1412
Abstract
The study is the first to examine the combined use of blast-furnace sludge as a source of microelements and converter slag as a soil-deoxidizing agent in oat (Avena sativa L.) cultivation in sod-podzolic soils. It has been established that blast-furnace sludge is [...] Read more.
The study is the first to examine the combined use of blast-furnace sludge as a source of microelements and converter slag as a soil-deoxidizing agent in oat (Avena sativa L.) cultivation in sod-podzolic soils. It has been established that blast-furnace sludge is a highly dispersed waste, which contains about 50% iron, 7% zinc, and a small amount of calcium, silicon, magnesium, aluminum, and sulfur. Hazardous components such as lead, arsenic, etc., are not detected. Converter slag comprises porous granules up to 3 mm in size, consisting mainly of calcium compounds (CaO, Ca(CO)3, CaSiO3, CaFe2O4) and a small amount of Mn, Al, and Mg trace elements. In a laboratory experiment, blast-furnace sludge increased the germination of oats by 5–10%, regardless of the addition of a deoxidizer (slag), but at the same time suppressed the growth of stem length by a maximum of 18% at 1 g∙kg−1. The addition of slag raised substrate pH and increased the index by 8% at a sludge concentration of 0.1 g∙kg−1. Root length in deoxidizer-free variants increased by 50–60% and with the addition of slag by 27–47%. Root dry mass also increased under the addition of sludge by 85–98%; however, the addition of slag reduced the indicator to the control level. In a field experiment with the combined application of waste, an increase in yield by more than 30% was shown. When soil was treated with slag and sludge, the height of plants increased by an average of 18%. It should be noted that the introduction of waste did not affect the quality of the grain. The use of slag increased the lead content in the soil, which is probably due to the sorption properties of calcium compounds in the slag, since lead was not found in the analyzed waste. Presumably, lead is sorbed by slag from the lower soil horizons, concentrating and immobilizing it in the upper layer. This version is supported by the absence of lead accumulation in straw and oat grain. The zinc-containing sludge increased the content of this element by 33% in the soil, as well as by 6% in straw and by 14% in grain. Thus, we found that the studied metallurgical wastes can be used as nutrients for agriculture, both individually and jointly. Overall, the proposed approach will contribute both to reducing the amount of accumulated waste and to improving the efficiency and sustainability of agricultural production and CO2 sequestration. However, the features of the accumulation of heavy metals in soil and plants under the influence of the analyzed types of waste require more in-depth study, including within the framework of long-term field experiments. Full article
(This article belongs to the Section Plant-Crop Biology and Biochemistry)
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17 pages, 4107 KiB  
Article
A Novel Landfill Liner Material for Solidified Lake Sediment Based on Industrial By-Product and Construction Waste: Engineering Behavior and Cr(VI) Breakdown Characteristics
by Wencheng Meng, Lin Guo, Jiayue Yuan, Shiyu Chen, Guanghua Cai and Haijun Lu
Buildings 2024, 14(11), 3447; https://doi.org/10.3390/buildings14113447 - 29 Oct 2024
Cited by 1 | Viewed by 1051
Abstract
Engineering sludge, industrial waste, and construction waste are marked by high production volumes, substantial accumulation, and significant pollution. The resource utilization of these solid wastes is low, and the co-disposal of multiple solid wastes remains unfeasible. This study aimed to develop an effective [...] Read more.
Engineering sludge, industrial waste, and construction waste are marked by high production volumes, substantial accumulation, and significant pollution. The resource utilization of these solid wastes is low, and the co-disposal of multiple solid wastes remains unfeasible. This study aimed to develop an effective impermeable liner material for landfills, utilizing industrial slag (e.g., granulated blast furnace slag, desulfurized gypsum, fly ash) and construction waste to consolidate lake sediment. To assess the engineering performance of the liner material based on solidified lake sediment presented in landfill leachate, macro-engineering characteristic parameters (unconfined compressive strength, hydraulic conductivity) were measured using unconfined compression and flexible wall penetration tests. Simultaneously, the mineral composition, functional groups, and microscopic morphology of the solidified lake sediment were analyzed using microscopic techniques (X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy + energy dispersive spectroscopy). The corrosion mechanism of landfill leachate on the solidified sediment liner material was investigated. Additionally, the breakdown behavior of heavy metal Cr(VI) within the solidified sediment liner barrier was investigated via soil column model experiments. The dispersion coefficient was computed based on the migration data of Cr(VI). Simultaneously, the detection of Cr(VI) concentration in pore water indicated that the solidified sediment liner could effectively impede the breakdown process of Cr(VI). The dispersion coefficient of Cr(VI) in solidified sediments is 5.5 × 10−6 cm2/s–9.5 × 10−6 cm2/s, which is comparable to the dispersion coefficient of heavy metal ions in compacted clay. The unconfined compressive strength and hydraulic conductivity of the solidified sediment ranged from 4.90 to 5.93 MPa and 9.41 × 10−8 to 4.13 × 10−7 cm/s, respectively. This study proposes a novel approach for the co-disposal and resource utilization of various solid wastes, potentially providing an alternative to clay liner materials for landfills. Full article
(This article belongs to the Special Issue Green Building Materials and Intelligent Construction Technology)
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30 pages, 4907 KiB  
Review
Advancements in Lightweight Artificial Aggregates: Typologies, Compositions, Applications, and Prospects for the Future
by Narinder Singh, Jehangeer Raza, Francesco Colangelo and Ilenia Farina
Sustainability 2024, 16(21), 9329; https://doi.org/10.3390/su16219329 - 27 Oct 2024
Cited by 12 | Viewed by 2875
Abstract
Currently, the environment and its natural resources face many issues related to the depletion of natural resources, in addition to the increase in environmental pollution resulting from uncontrolled waste disposal. Therefore, it is crucial to identify practical and effective ways to utilize these [...] Read more.
Currently, the environment and its natural resources face many issues related to the depletion of natural resources, in addition to the increase in environmental pollution resulting from uncontrolled waste disposal. Therefore, it is crucial to identify practical and effective ways to utilize these wastes, such as transforming them into environmentally friendly concrete. Artificial lightweight aggregates (ALWAs) are gaining interest because of their shift in focus from natural aggregates. Researchers have developed numerous ALWAs to eliminate the need for natural aggregates. This article explores the diverse applications of ALWAs across different industries. ALWAs are currently in the research phase due to various limitations compared to the availability of the various natural aggregates that form more durable solutions. However, researchers have discovered that certain artificial aggregates prioritize weight over strength, allowing for the effective use of ALWAs in applications like pavements. We thoroughly studied the various ALWAs discussed in this article and found that fly ash and construction waste are the most diverse sources of primary material for ALWAs. However, the production of these aggregates also presents challenges in terms of processing and optimization. This article’s case study reveals that ALWAs, consisting of 80% fly ash, 5% blast-furnace slag, and only 15% cement, can yield a sustainable solution. In the single- and double-step palletization, the aggregate proved to be less environmentally harmful. Additionally, the production of ALWAs has a reduced carbon footprint due to the recycling of various waste materials, including aggregates derived from fly ash, marble sludge, and ground granulated blast-furnace slag. Despite their limited mechanical strength, the aggregates exhibit superior performance, making them suitable for use in high-rise buildings and landscapes. Researchers have found that composition plays a key role in determining the application-based properties of aggregates. This article also discusses environmental and sustainability considerations, as well as future trends in the LWA field. Simultaneously, recycling ALWAs can reduce waste and promote sustainable construction. However, this article discusses and researches the challenges associated with the production and processing of ALWAs. Full article
(This article belongs to the Section Sustainable Materials)
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