Search Results (105)

Although biofloc technology (BFT) currently offers advantages such as improving aquaculture water quality, providing natural bait for cultured animals, and reducing pests and diseases, single BFT systems face technical bottlenecks, including the complex regulation of the carbon–nitrogen ratio, accumulation of suspended substances, and acidification of the bottom sludge. Therefore, constructing a composite system with complementary functions through technology integration, such as with aquaponics, biofilm technology, integrated multi-trophic aquaculture systems (IMTAs), and recirculating aquaculture systems (RASs), has become the key path to breaking through industrialization barriers. This paper systematically reviews the action mechanisms, synergistic effects, and challenges of the four mainstream integration models incorporating BFT, providing theoretical support for the environmental–economic balance of intensive aquaculture. Full article

This study explores innovative strategies for decarbonizing sludge thermal treatments used in electrical power generation, with a focus on integrating sensor technologies and artificial intelligence. Sludge, a carbon-intensive byproduct of wastewater treatment, presents both environmental challenges and opportunities for energy recovery. The paper provides a comprehensive analysis of thermal processes such as pyrolysis, gasification, co-combustion, and emerging methods, including hydrothermal carbonization and supercritical water gasification. It evaluates their carbon mitigation potential, energy efficiency, and economic feasibility, emphasizing the importance of catalyst selection, carbon dioxide capture techniques, and reactor optimization. The role of real-time monitoring via sensors and predictive modeling through artificial intelligence (AI) is highlighted as critical for enhancing process control and sustainability. Case studies and recent advances are discussed to outline future pathways for integrating thermal treatment with circular economy principles. This work contributes to sustainable waste-to-energy practices, supporting global decarbonization efforts and advancing the energy transition. Full article

The carbon emissions from the cement industry account for approximately 8% of global carbon emissions, which exerts significant pressure on the environment. In this paper, the microbial-induced calcium carbonate precipitation (MICP) technology was introduced into the carbonization modification research of recycled hardened cement powder (RHCP), and the carbon sequestration performance of RHCP under different pressures was studied. The physicochemical properties of the carbonated products were characterized by microscopic testing methods, and the carbon sequestration mechanism under different pressures was obtained. Subsequently, carbonated RHCP (C-RHCP) was tested as a partial cement substitute for solidified sludge to evaluate its mechanical and durability properties. The results show that when the pressures were 0.3 and 0.5 MPa, the carbon sequestration capacity of RHCP was relatively good, reaching 59.14 and 59.82 g/kg, respectively. Since the carbon sequestration amounts under the two pressures were similar, and considering the energy consumption, in this study, a reaction pressure of 0.3 MPa was selected to prepare C-RHCP. Compared with pure cement, the 28-day unconfined compressive strength (UCS) of the sludge cured with 30% C-RHCP increased by 12.08%. The water stability coefficient of the solidified sludge in the C-RHCP group was greater than 1 after soaking for 7, 14, and 21 days, while the water stability coefficient of the cement group decreased to 0.92 at 14 days. After 20 freeze–thaw cycles, the mass losses of the cement group, the RHCP group, and the C-RHCP group were 31.43%, 38.99%, and 33.09%, respectively. This research not only provides an environmentally friendly strategy for the resource utilization of RHCP but also pioneers a new synergistic model that combines microbial mineralization with the modification of industrial solid waste. It demonstrated significant scientific value and engineering application prospects in reducing carbon emissions in the cement industry and promoted sustainable geotechnical engineering practices based on the “waste–waste” principle. Full article

Wastewater treatment plants traditionally dispose of sludge using the method of landfilling and incineration, with both being carbon-intensive and environmentally harmful. Converting sludge into energy or reusable materials avoids landfills or incineration, helping reduce the volume of waste and associated pollution. Sludge treatment with energy recovery can offset fossil fuel use, further reducing the carbon footprint of sewage treatment processes. This research explores ways to recover energy from sewage sludge, a byproduct of wastewater treatment that is often considered waste. Transforming sludge into valuable resources aligns with the principles of the circular economy, where waste streams are repurposed, minimizing environmental impact and enhancing resource efficiency. In this paper, a method is presented to reduce the volume of wastewater sludge by drying it in a hot flue gas stream at 700 °C. The energy of the exhaust gas is recovered in an organic Rankine cycle system, which powers the wastewater treatment facilities themselves, making them more self-sustaining. Full article

This paper presents a study on the ring formation phenomenon in lime kilns using simulation. The research focuses on the chemical recovery cycle integrated into the pulp production process at a pulp mill, with particular emphasis on the calcium cycle within the lime kilns. Lime kilns are critical components, as their unavailability can significantly impact the overall cost-effectiveness of the facility. The calcination of lime sludge occurs in a rotary kiln, where calcium carbonate in the lime sludge is converted into calcium oxide (lime). Under certain conditions, material can progressively accumulate, leading to ring formation and eventual kiln clogging, resulting in operational downtime. To investigate this issue, the authors developed a physics-based model using a finite-dimensional, one-dimensional approach that considers only longitudinal variation. Several approximations were made to maintain a reasonable simulation time without compromising accuracy. Simulations based on real operational data identified fluctuations in fuel flow rate and sulfur content from non-condensable gases as key contributors to ring formation. The results showed that these fluctuations caused instability in the temperature profiles of the solids and gas beds, leading to periods of cooling before the lime sludge reaches the outlet to the coolers. This cooling promotes the recarbonation of lime and, consequently, the formation of rings. The findings highlight that stabilizing fuel flow and managing sulfur content could mitigate ring formation and improve kiln efficiency. The developed model provides a valuable tool for predictive analysis and process optimization, potentially supporting the development of a digital twin to enhance real-time monitoring and operational control. Full article

The paper reviews the patent descriptions of methods for obtaining humic substances and the procedures used in their industrial production. Selected humus substances, obtained using three different methods, were also examined. In the first one, humic substances were obtained due to the hydrolytic-oxidative decomposition of lignosulfonate. The second one consists of alkaline extraction from brown coal. According to the third, humus substances were extracted from digested sewage sludge. In the obtained humus substances, molecular composition, inorganic impurities, IR spectrum, gravimetric analysis, and the % shares of fulvic and humic acids were determined. The physico-chemical properties of the tested substances were also assessed. Based on the study’s results, the advantages and disadvantages of the obtained humus substances were determined, and methods for their modification to improve utility values were provided. Research on humic substances is a very important issue, especially concerning improving soil management and developing sustainable agricultural practices. They are key in improving soil structure and increasing its capacity to retain water and essential nutrients such as N, P, K, S, Ca, and Mg. In addition, humic substances are an important store of carbon in soils, which is important in the context of climate change. Full article

Currently, the key challenge of the oil-refining industry worldwide is to produce environmentally friendly fuel in large volumes to meet market demand, which is due to strict environmental standards governing the permissible sulfur content in fuel. Natural gas, refinery gas, and coal gas contain acid gases such as hydrogen sulfide and carbon dioxide. These compounds must be removed from the gas stream because of the toxicity of H₂S and to prevent the acid gas-induced corrosion of pipelines and facilities. Hydrogen sulfide is released as a result of various industrial processes, and its removal is critical because this compound can cause corrosion and environmental damage even at low concentrations. Sulfur compounds are also present in natural gas, biofuels and other fuel gases used in power plants. This article proposes new adsorbents of natural and waste origin and presents the results of their testing for the removal of acid gases. This paper also considers methods for the preparation of adsorbents from waste and procedures for the removal of sulfur-containing compounds. Using agricultural, industrial waste to produce activated sorbents not only solves the problem of waste disposal but also reduces the cost of desulfurization, contributing to the creation of sustainable and environmentally friendly technologies. The Review Section comprehensively summarizes current research on hydrogen sulfide removal in gas cleaning processes using agricultural and industrial waste as highly efficient adsorbents. In the Experimental Section, 10 composite materials based on natural raw materials and wastes, as well as 6 commercial adsorbents, were synthesized and tested under laboratory conditions. The choice of materials for the adsorbent production was based on the principles of environmental friendliness, availability, and cost-effectiveness. The developed materials based on modified sludge from water treatment plants of thermal power plants are effective sorbents for the purification of gas emissions from petrochemical enterprises. For industrial use, it is necessary to solve the problems of increasing the economic attractiveness of sorbents from waste, the ability of regeneration, the competitive adsorption of pollutants, the use of indicator sorbents, the optimization of operating conditions, and safe waste disposal. Full article

This paper explores the advantages of the co-pyrolysis of municipal sewage sludge with agricultural and forestry biomass, emphasizing its potential for environmental and economic benefits. Co-pyrolysis with lignocellulosic biomass significantly enhances biochar quality, reduces the heavy metal content, increases porosity, and improves nutrient retention, which are essential for soil applications. The biochar produced through co-pyrolysis demonstrates enhanced stability and a lower oxygen-to-carbon (O/C) ratio, making it more suitable for long-term carbon (C) sequestration and pollutant adsorption. Additionally, co-pyrolysis generates bio-oil and syngas with improved calorific value, contributing to renewable energy recovery from sewage sludge. This synergistic process also addresses waste management challenges by reducing harmful emissions and immobilizing heavy metals, thus mitigating the environmental risks associated with sewage sludge disposal. This paper covers key sections on the properties of waste materials, improvements in biochar quality and energy products, and the environmental benefits of co-pyrolysis, such as emissions reduction and heavy metal immobilization. The paper highlights trends and challenges in co-pyrolysis technology, aiming to optimize parameters for maximizing biochar yield and energy recovery while aligning with sustainability and circular economy goals. The paper concludes with recommendations for optimizing co-pyrolysis processes and scaling applications to support sustainable waste management. Overall, co-pyrolysis represents a sustainable approach to valorizing sewage sludge, transforming it into valuable resources while supporting environmental conservation. Full article

Very large quantities of stone waste sludge are disposed in exhausted quarries and have a very low reuse rate to date. The paper considers the possibility of using these types of industrial waste in partial substitution of natural aggregates for the production of lime-based plasters. Traditional materials based on lime, the only material with a carbon neutrality life cycle, have considerable potential for use as components of green materials for plastering and finishing building surfaces in both new construction and historic heritage conservation. The paper presents the preliminary results of a research activity aimed at developing pre-packaged products based on Traditional Lime Putty (TLP) by partially replacing natural aggregates with Stone Waste Sludge (SWS), with a low rate of recovery from the Apricena limestone production district in Apulia. The mineralogical and chemical analysis carried out using XRD (X-Ray Diffraction), TG-DTA (Thermo Gravimetry-Differential Thermal Analysis), and hydrochloric acid attack test showed that the SWS consisted of 98.4 % CaCO₃ by mass. The particle sizes measured by laser diffraction technique are below 22.5 μm for the 92% mass of the sample. The high fineness of the stone waste was confirmed by the Blaine-specific surface method, which equals to 9273.79 cm²/gr. The behavior of three fresh mixtures for prepacked coarse plaster, fine plaster, and finishing plaster with 12.90%, 17.94%, and 18.90 by mass of SWS, respectively, was evaluated by spreading test and applicability tests on a perforated ceramic slab. The finishing plaster has the highest consistency value of 235 mm, while the fine plaster and the coarse plaster have values of 205 mm and 155 mm, respectively. The coarse plaster is suitable for use as base plaster (arriccio) or second layer rendering (tonachino) up to a thickness of approximately 1 cm. Both the fine plaster and finishing plasters can be used for the surfaces finishing with the application of layers of a few millimeters thick. Full article

In this paper, a lab-scale reactor designed to simulate the operations of the North Water Saline Wastewater Treatment Plant (SWWTP) located in Delfzijl, The Netherlands, was constructed and assessed. Unlike conventional municipal wastewater treatment facilities, this industrial plant deals with wastewater containing stubborn chemicals that are difficult to break down, along with a high ratio of chemical oxygen demand (COD) to nitrogen and elevated sodium chloride levels. Furthermore, its treatment process diverges from standard industrial setups by employing an aerobic process preceding the anaerobic phase. The proposed lab-scale reactors were proven stable and effective in mimicking the conditions of the studied industrial SWWTP, particularly in the presence of abundant glycerol, a factor not explored in similar lab-scale models. Throughout the experiment, the removal of COD (specifically glycerol) and nitrogen were monitored, alongside changes in the microbial community within both reactors. The data enabled us to examine the proliferation of microbial populations within the sludge. The results indicated the complete removal of glycerol and ammonia from the system, with some residual nitrate detected in the effluent. The soluble COD decreased in the first reactor (R1) to approximately 50% of the influent and reduced further to less than 100 mg/L in the second reactor (R2), while nitrogen was majorly removed in the R1. By the experiment’s conclusion, Actinomycetales was identified as the dominant order in the anaerobic reactor (sometimes even exceeding 70% of the population), which is known for its utilization of glycerol as a carbon source and its tolerance to high salt concentrations in the influent. Conversely, the aerobic reactor was predominantly inhabited by the order Flavobacteriales, which correlates with ammonia concentration. Full article

Wastewater treatment plants generate significant amounts of sludge, a residual product that is rich in nutrients, usually considered waste, and traditionally eliminated by storage or incineration, methods that are expensive, environmentally damaging, and often unsustainable. Composting is increasingly recognized as an ecological and durable solution for managing biodegradable waste, including sludge resulting from wastewater treatment. The composting of residual sludge usually requires mixing with bulking agents, such as green waste or agricultural residues, to ensure a well-balanced carbon–nitrogen ratio. This mixture undergoes a controlled aerobic decomposition, sometimes followed by post-treatment, resulting in a stabilized final product that is nutrient-rich and pathogen-free and can be used as soil amendment or fertilizer in different agricultural or landscaping applications. By using composting, communities can reduce elimination costs, reduce greenhouse gas emissions, and minimize the environmental impact of sludge management. This paper reviews recent reported experiences in the laboratory regarding full-scale sludge composting, highlighting the particularities of the processes, the influence factors, the quality of the final product, and the environmental and regulatory constraints. Composting is a sustainable and ecological solution for managing wastewater sludge, contributing to nutrient circularity, and minimizing the environmental impact. Full article

The increasing discharge of antibiotic wastewater leads to increasing water pollution. Most of these antibiotic wastewaters are persistent, strongly carcinogenic, easy to bioaccumulate, and have other similar characteristics, seriously jeopardizing human health and the ecological environment. As a commonly used wastewater treatment technology, non-homogeneous electro-Fenton technology avoids the hazards of H₂O₂ storage and transportation as well as the loss of desorption and reabsorption. It also facilitates electron transfer on the electrodes and the reduction of Fe³⁺ on the catalysts, thereby reducing sludge production. However, the low selectivity and poor activity of electro-synthesized H₂O₂, along with the low concentration of its products, combined with the insufficient activity of electrically activated H₂O₂, results in a low ∙OH yield. To address the above problems, composites of layered bimetallic hydroxides and carbon materials were designed and prepared in this paper to enhance the performance of electro-synthesized H₂O₂ and non-homogeneous electro-Fenton by changing the composite mode of the materials. Three composites, NiFe layered double hydroxides (LDHs)/reduced graphene oxide (rGO), NiMn LDHs/rGO, and NiMnFe LDHs/rGO, were constructed by the electrostatic self-assembly of exfoliated LDHs with few-layer graphene. The LDHs/rGO was loaded on carbon mats to construct the electro-Fenton cathode materials, and the non-homogeneous electro-Fenton oxidative degradation of organic pollutants was realized by the in situ electrocatalytic reduction of O₂ to ∙OH. Meanwhile, the effects of solution pH, applied voltage, and initial concentration on the performance of non-homogeneous electro-Fenton were investigated with ceftazidime as the target pollutant, which proved that the cathode materials have an excellent electro-Fenton degradation effect. Full article

Copper-containing sludge is a common by-product of industrial activities, particularly electroplating and metal processing. This type of sludge contains high concentrations of heavy metals such as copper, which can pose a potential threat to the environment. Therefore, its treatment and disposal require special attention. Due to its efficient mass and heat transfer characteristics, the suspended state technology has shown significant potential for application in a number of key processes, including the drying, decomposition, and reduction of copper-containing sludge. This paper presents an in-depth analysis of the current status of the application of the suspended state technology in the treatment of copper-containing sludge. Based on this analysis, a device for the treatment of copper-containing sludge in the suspended state was designed, through which the characteristics of copper-containing sludge in the oxidative decomposition and reduction phases are investigated. The research objects were gas concentration, temperature, contact state, and particle size time. Orthogonal experiments were initially employed to investigate the relationship between the influencing factors and the conversion rate of copper oxides. This was followed by a single-factor influence study, which led to the determination of the optimal process parameters for the decomposition experiments of the Cu-containing sludge in an oxidizing atmosphere. The 100 μm Cu-containing sludge was reacted with 10% O₂ gas at a flow rate of 1 m/s for 3 min under the condition of 900 °C. The process parameters were then determined as follows: The research objects were gas concentration, temperature, contact state, and particle size time. Orthogonal experiments were employed to investigate the relationship between the influencing factors and the copper conversion rate. This was followed by a single-factor influence study, which determined the optimal process parameters for the copper-containing sludge reduction experiments. The 200 μm copper-containing sludge was reacted for 5 min at a flow rate of 7% carbon monoxide at a flow rate of 1.5 m/s under the condition of 800 °C. Full article

Municipal sewage sludge (MSS) is an inevitable byproduct of wastewater treatment, with increasing amounts year by year worldwide. The development of environmentally and economically acceptable methods for the sustainable management of MSS is a major environmental challenge. Nowadays, sludge management practices, besides the commonly used stabilization methods, focus attention on alternative sludge-disposal pathways, which encompass enhanced energy and valuable-resource recovery. This review presents the recent advances in the recovery of selected value-added products from sludge. Because of the high nitrogen and phosphorus concentrations, waste MSS can be a nutrient source (e.g., struvite). This paper discusses the conditions of and advances in the technology of struvite recovery. As in the extracellular polymeric substances (EPSs) of biological sludge, alginate-like exopolymers (ALEs) are present in MSS systems that treat municipal wastewater. The yields, dynamics in content, and characterization of ALEs and their possible applications were analyzed. MSS is an important source of humic substances. Their occurrence, characterization, and yields in various types of MSS (e.g., untreated, composted, and digested sludge) and main methods of application are presented. The important aspects and trends of MSS pyrolysis, including the thermochemical conversion to biochar, are discussed in this review. The characterization of biochar derived from MSS and the assessment of the environmental risks are also covered. This paper explores the potential use of biochar derived from MSS in various applications, including soil amendment, carbon sequestration, and environmental remediation. Full article

Sewage sludge and red mud, as common industrial waste, have become a research hotspot in the field of achieving carbon peaking and carbon neutrality, reducing carbon emissions, and solving environmental problems. However, their treatment and disposal have always been a difficult problem in the environmental field. Utilizing these two materials for thermal energy storage can not only improve energy utilization efficiency but also further reduce carbon emissions during their treatment process, providing a new approach for sustainable development in the industrial sector. This article summarizes the research progress for the resource recovery of sewage sludge and red mud for direct thermal energy recovery and composite phase change energy storage. After proper treatment, sludge and red mud can be directly used as energy storage materials. In addition, sludge and red mud can be combined with phase change materials to prepare composite materials with an excellent energy storage performance. This composite has broad application prospects in fields such as solar energy utilization and building energy efficiency. However, there are still some challenges and issues in this resource recovery and utilization, such as potential environmental pollution during the treatment process, the long-term stability of energy storage materials, and cost-effectiveness, which require further research and resolution. The purpose of this paper is to evaluate the potential of sewage sludge and red mud as energy storage materials, to explore their feasibility and advantages in practical applications, and to reveal the research progress, technical challenges, and future development directions of these two materials in the field of thermal energy storage. Full article