Search Results (68)

This study aimed to conduct an ecotoxicological assessment of soils reclaimed with waste, assessing the treatments’ impacts on both plants and the soils themselves. The reclamation experiment was conducted on the former sulfur mine “Jeziórko”. A microplot experiment was established on a slightly clayey sand to assess the possibilities of different technologies for applying mineral wool to degraded soil. The highest toxicity level was observed in the unreclaimed degraded soil. The M index value was 200%, indicating the death of half of the test organisms. At the same time, root growth inhibition reached 75%, indicating significantly limited root system development. The addition of lime and mineral fertilizers contributed to a slight reduction in toxicity—M = 250%, GI = 50%. Application of sewage sludge at a dose of 100 Mg·ha⁻¹ significantly reduced environmental toxicity—M decreased to 333.3% and 500%, and GI to 35% and 10%, respectively. The addition of mineral wool resulted in further improvement. The best results were achieved in the variant where the soil was enriched with lime, sewage sludge and a large volume of mineral wool (400 m³·ha⁻¹). The GI and M levels indicate that, in this variant, soil toxicity was practically eliminated. Full article

Water scarcity is a global crisis and of particular concern in arid regions like Morocco. One creative solution is mining unusual water sources, such as landfill leachate. The presence of nitrogen in the sediment was studied as part of the use of sugar lime sludge in treating landfill leachate for irrigation purposes. A volume of 40 L of landfill leachate was treated with three different concentrations of sugar lime sludge (25%, 35%, and 50%). After homogenization and agitation of the mixture for 24 to 36 h, it was permitted to settle through the concrete decantate and supernatant. Nitrogen was efficiently decanted into the sediment during the composting process with green waste, enhancing the quality of the finished compost. The supernatants underwent physicochemical and microbiological analyses to ascertain their suitability for irrigation. The findings showed that the number of fecal streptococci was decreased by 99.13% at a 25% concentration of sugar lime sludge. The percentage of organic matter in the sediment rose from 10% to 40%, suggesting that the leachate had partially depolluted. The pH and electrical conductivity of the supernatants were within irrigation guidelines. The safety of diluted supernatants for plant germination was verified by phytotoxicity experiments conducted on maize seeds. The compost made from the decantate and green waste showed acceptable physical and chemical properties. Statistical analysis was conducted using JAMOVI software version 2.6.26. One-way ANOVA was used to assess the significance of treatment effects on microbiological and physicochemical parameters. The results confirmed statistically significant differences (p < 0.05) between the sludge concentrations, supporting the effectiveness of the treatment process. This study demonstrates how sugar lime sludge can be used to turn landfill leachate into a sustainable and safe irrigation water source, resolving environmental issues and promoting creative water management techniques. 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

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

Soil stabilization is vital in construction to enhance soil strength and durability. While conventional stabilizers like cement and lime improve soil properties, they contribute to significant carbon emissions. Given their widespread use, exploring eco-friendly alternatives is crucial. This review examines rice husk ash (RHA) and lime sludge (LS) as sustainable substitutes. Previous studies have evaluated their effectiveness in stabilizing clay soil, but a more application-focused approach, along with a detailed cost and sustainability evaluation, is needed. Standard Proctor compaction, California Bearing Ratio, and unconfined compression strength tests were analyzed from the existing literature to determine the optimal ratio of these additives for maximum soil strength. The results were compared to determine the most effective quantities of RHA and LS, either separately or combined, and inferences about their influences on clay soil attributes were drawn. Additionally, comprehensive life cycle assessment (LCA) and cost evaluation were reviewed. Finally, it was concluded that increasing the amounts of RHA and LS and combining them enhanced the strength of clay soil. Moreover, using RHA and LS for soil stabilization proved to be a cost-effective alternative to traditional methods, providing economic and environmental advantages. Full article

The dominant treatment process for removing heavy metals from industrial wastewater is chemical neutralisation precipitation using lime milk as a precipitation agent, resulting in a highly voluminous hydroxide sludge with a low heavy metal concentration. These sludges are predominantly landfilled, and the metals are lost to the circular economy. At the same time, metals are urgently needed as raw materials. A new approach is represented by the low-pressure, low-energy Specific Product-Oriented Precipitation process (SPOP). This approach, however, requires the adjustment of various reaction parameters for optimal operation. This study presents the impacts of the stirring rate during the reaction and the Fe concentration in the solution on the recovery of Cu from Cu-enriched electroplating wastewater. Three different recovery options are described: Option (1), the formation of CuO; Option (2), the generation of brochantite, a Cu-hydroxysulphate; and Option (3), the incorporation of Cu into ferrite. Tenorite (CuO) is precipitated at 40 °C reaction temperature at a low stirring rate of 100–200 rpm. At an accelerated stirring rate of 400–500 rpm, brochantite (Cu₄(OH)₆SO₄) is formed. With high Fe concentrations and a molar ratio of Cu:Fe of 1:2, Cu-ferrite (CuFe₂O₄) is the precipitation product. In any case, the achieved recovery rates in the treated wastewater are better than 99.9%. 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

The treatment and resource utilization of sludge from municipal sewage treatment plants is an important environmental issue. Cement kiln co-processing offers a promising solution, but challenges remain, particularly regarding sludge properties and feasibility in kiln systems. This study analyzes the characteristics of three pretreated sludges: mechanically dewatered sludge, deeply dewatered sludge, and lime-dried sludge. Using techniques such as thermogravimetric analysis (TGA) and X-ray diffraction (XRD), this study investigates their calorific values and raw material utilizability in co-processing. As the sludge moisture content decreases from interstitial to bound water, energy consumption per ton of evaporated water rises, particularly below 30%. At 10 °C/min heating, energy consumption for mechanically dewatered sludge at 80%, 30%, and 10% moisture was 3573, 8220, and 34,751 kJ/kg, respectively; for deeply dewatered sludge at 60%, 30%, and 10%, the values were 4398, 7550, and 11,504 kJ/kg. Keeping moisture content above 30% before kiln entry reduces energy use and enhances calorific value. Sludge utilizability as a raw material depends on its pretreatment. The ash composition of deeply and mechanically dewatered sludge resembles iron-rich raw materials, while lime-dried sludge aligns more with limestone. The utilizable ash content was 23.3%, 8.1%, and 46.3%, respectively, with lime-dried sludge showing the highest potential. This study provides insights into sludge properties and their co-processing potential in cement kilns, offering scientific and technical support for practical applications. Full article

This work concerns the assessment of soil reclamation and its impact on biological life in areas destroyed by the sulfur industry in Jeziórko. Sulfur extraction using the borehole method causes enormous destruction to the soil environment. Among the many forms of degradation, the most pronounced are the chemical transformations of the environment and the disturbances in water relations in large areas, which could theoretically impact areas not within the direct range of the mining plant. This work aimed to assess the condition of biological life in soil reclaimed with waste in areas devastated by the sulfur industry in Jeziórko. The reclamation of these soils was difficult but necessary due to the complete disappearance of biological life. Appropriate actions were taken to restore and improve the properties of the soil, which resulted in an improvement in their production capacity. Reclamation was carried out, among other techniques, by deacidifying the soil using post-flotation lime and fertilizing the soil with municipal sewage sludge and post-use mineral wool. Studies have shown an improvement in many soil properties, such as its physical, water, chemical, and biological properties. The implemented reclamation methods significantly influenced, among other things, the density and water properties of the degraded soil. The soil reclaimed with mineral wool and sewage sludge recorded the highest density and water capacity. Applying mineral wool to the degraded soil influenced the changes in the analyzed physical and water properties. The obtained research results also show the beneficial effect of mineral wool and sewage sludge on the increase in organic carbon content. In the soil treated with these substances, the organic carbon content ranged from 13.60 g·kg⁻¹ to 14.30 g·kg⁻¹. It is shown that reclamation has had a considerable impact on and is essential for biological life in Jeziórko. Full article

Catalysts for the selective catalytic reduction (NO_X SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NO_X SCR shows various SCR efficiencies. In the current work, an SCR catalyst developed from the sludge produced with Fe/C micro-electrolysis Fenton technology (MEF) in wastewater treatment was investigated, taking into account various sludge compositions, Fe/C ratios, and contaminant contents. It was found that, at about 300 °C, the NO_X removal rate could reach 100% and there was a wide decomposition temperature zone. The effect of individual components of electroplating sludge, i.e., P, Fe and Ni, on NO_X degradation performance of the obtained solids was investigated. It was found that the best effect was achieved when the Fe/P was 8/3 wt%, and variations in the Ni content had a limited effect on the NO_X degradation performance. When the Fe/C was 1:2 and the Fe/C/P was 1:2:0.4, the electroplating sludge formed after treatment with Fe/C MEF provided the best NO_X removal rate at 100%. Moreover, the characterization results show that the activated carbon was also involved in the catalytic reduction degradation of NO_X. An excessive Fe content may cause agglomeration on the catalyst surface and thus affect the catalytic efficiency. The addition of P effectively reduces the catalytic reaction temperature, and the formation of phosphate promotes the generation of adsorbed oxygen, which in turn contributes to improvements in catalytic efficiency. Therefore, our work suggests that controlling the composition in the sludge is an efficient way to modulate SCR catalysis, providing a bridge from contaminant-bearing waste to efficient catalyst. Full article

Water treatment sludge (WTS) is the residue produced during water treatment processes for public use. Exploring the reintroduction of these wastes into the production chain to generate new, value-added materials presents a current challenge. This could promote their reuse and reduce the negative environmental impacts associated with their disposal. This study assessed the technical feasibility of using aluminum-based WTS to partially replace silty sand soil in mixtures that include two stabilizers (hydrated lime and Portland cement), potentially for use in road pavements. After conducting a thorough physical, chemical, and geotechnical characterization of both the soil and the sludge, bench-scale experiments were carried out to test the mixtures’ resistance, with WTS proportions of 5%, 8%, 10%, 15%, and 20%, stabilized with either lime or cement. The findings confirm that WTS does not contain potentially toxic elements, according to Brazilian standards, and all tested composites appear suitable for paving. However, the mechanical resistance of the soil–sludge–cement mixtures decreases as the WTS content increases, with an optimum California bearing ratio (CBR) of 41.50% achieved at a 5% WTS addition. Meanwhile, incorporating 15% WTS into soil–sludge–lime mixtures resulted in the highest CBR value of 21.25% for this type of mixture. It is concluded that incorporating stabilizers into soil–WTPS mixtures for road construction allows for an increased percentage of WTPS in silty-sandy soils. Further studies are recommended with different soil types and the addition of fibers to the mixes, to assess the long-term performance of the structure, along with economic and environmental analyses. Full article

Domestic wastewater treatment plants produce large amounts of waste sludge. Sludge can be used to produce activated carbon using potassium hydroxide (KOH) as an activating agent. However, KOH is expensive (relative to the cost of waste carbide lime), making the conversion of waste into valuable products unsustainable. This study explored the utilization of a solid waste by-product, carbide lime waste, as a replacement for KOH to produce sludge-based activated carbon (SBAC). The effects of activation conditions on the characteristics of SBAC were investigated and its performance for methylene blue (MB) removal from a solution was assessed. Post-production analyses using scanning electron microscopy and Fourier-transform infrared spectroscopy indicated that the SBAC produced had a porous surface rich in hydroxyl, aromatic, and alkyl functional groups. Among the tested cases of SBAC prepared using carbide lime, the highest removal of MB (240 mg/g) was achieved for the SBAC prepared at 700 °C with a 1:1 impregnation ratio when activated for 60 min and post-treated with 5M hydrochloric acid. The equilibrium adsorption of MB on SBAC was nonlinear. A strong correlation was found between the pore volume and adsorption capacity of the SBAC produced. The findings of this study suggest that the use of carbide lime waste for SBAC production is a viable alternative to an analytical-grade KOH activator. Full article

To simultaneously solve problems in an eco-friendly manner, introducing a waste residual as a sustainable conditioner to aid alum sludge dewatering is suggested as a cradle-to-cradle form of waste management. In this regard, the superiority of deep dewatering alum sludge with a powdered wood chip composite residual as a novel conditioner was explored, whereby traditional conventional conditioners, i.e., polyelectrolytes and lime, were substituted with powdered wood chips. Initially, Fe₃O₄ was prepared at the nanoscale using a simple co-precipitation route. Next, wooden waste was chemically and thermally treated to attain cellulosic fine powder. Subsequently, the resultant wood powder and Fe₃O₄ nanoparticles were mixed at 50 wt % to attain a wood powder augmented with iron, and this conditioner was labeled nano-iron-cellulose (nIC-Conditioner). This material (nIC-Conditioner) was mixed with hydrogen peroxide to represent a dual oxidation and skeleton builder conditioning substance. Characterization of the resultant conditioner was carried out using transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) transmittance spectrum analysis. The feasibility of the experimental results revealed that the moisture content in the sludge cake was lower after conditioning, and the capillary suction time (CST) was reduced to 78% compared to that of raw alum sludge after 5 min of dewatering time. Moreover, the optimal system parameters, including nIC-Conditioner and H₂O₂ concentrations, as well as the working pH, were optimized, and optimal values were recorded at 1 g/L and 200 mg/L for nIC-Conditioner and H₂O₂, respectively, with a pH of 6.5. Additionally, scanning electron microscope (SEM) analyses of the sludge prior to and after conditioning were conducted to verify the change in sludge molecules due to this conditioning technique. The results of this study confirm the sustainability of an alum sludge and waste management facility. Full article

In a circular economy, the efficient utilization of all materials as valuable resources, with a focus on minimizing waste, is paramount. This study shows the possibilities of upgrading the lowest-valued residuals from the forest industry into a new product with both liming and fertilizing properties on forest soil. Hydrothermal carbonized sludge mixed with bark and ash in the proportions of 45:10:45 was densified into fertilizer pellets that meet the nutrient requirements of 120 kg N per hectare when 7 tons of pellets is spread in forests. The pellets met a high-quality result according to durability and density, which were above 95% and 900 kg/m³. However, pellets exposed to wet and cold conditions lost their hardness, making the pellets dissolve over time. Small amounts, <5‰, of nutrients, alkali ions, and heavy metals leached out from the pellets under all conditions, indicating good properties for forest soil amendment. The conclusion is that it is possible to close the circle of nutrients by using innovative thinking around forest industrial residual products. Full article

The wastewater treatment industry could benefit from new technologies for the removal and recovery of phosphorus (P). The CalPrex precipitation reactor has the potential to recover P in a readily land-applicable form by treating organic acid digestate with calcium hydroxide to produce brushite. Using data from a pilot-scale reactor at the local Nine Springs Wastewater Treatment Plant in Madison, WI, we modified the plant’s BioWin configuration using BioWin 6.2 to model the CalPrex technology and estimate performance under a variety of conditions. We produced dose/response curves for a range of possible lime dosages to estimate the impact of reagent dosage on the quantity and composition of precipitate produced by the CalPrex reactor and characterize the effects on downstream anaerobic digester performance. CalPrex was found to capture 46% of the plant’s influent P, reducing nuisance struvite precipitates by 57% and biosolid sludge production by 14%. The CalPrex module was also tested in two predesigned plant configurations in the BioWin cabinet with the intention of testing applicability to other configurations and searching for the impacts of CalPrex on treatment train performance. This is the first work simulating a full-scale implementation of CalPrex and the first to model interactions of CalPrex with other treatment processes. Full article