Amount Of Sludge Research Articles

Characterization of Stone Waste Sludge and Preliminary Investigation on Green Materials Based on Traditional Lime Putty for Sustainable Construction

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.

Earthworm activity reduces bacterial pathogen loads in sewage sludge.

Wastewater processing plants (WWTPs) produce large amounts of sewage sludge that are mainly disposed of on the land. This represents a health hazard due to the high loads of human bacterial pathogens (HBPs) the sludge generally contains. Vermicomposting, a mesophilic process, can reduce HBPs in organic wastes. This raises the question as to how earthworms eliminate HBPs. We aimed to determine whether earthworms reduce the levels or eliminate HBPs from sewage sludge and to establish whether the reduction/elimination occur during active (earthworm casts) or maturation (vermicompost) stages of vermicomposting. To this end, we analyzed HBPs (Escherichia coli O157, Listeria monocytogenes, Salmonella spp., and total E. coli) in sewage sludge samples from three WWTPs and the fresh earthworm casts and vermicomposts by using qPCR, to assess the impact of earthworms on reducing and/or eliminating HBPs. We did not detect either Salmonella spp. nor E. coli O157 in any of the samples. Earthworms removed or significantly reduced the amounts of E. coli and L. monocytogenes (mean relative abundances of 2.4 × 10-7 and 1.5 × 10-8 respectively) in the sewage sludge. Thus, the abundance of these HBPs was lower (or not present) in casts than in sewage sludge. This was also observed in vermicomposts (95% and 43% reduction in E. coli abundance in casts and vermicompost, respectively). Finally, our findings indicate that vermicompost derived from sewage sludge meets the requirements of organic fertilizers at least regarding the microbial pathogen content. Thus, vermicomposting seems to be a promising technique for managing municipal waste.

Optimizing the final rest period of sludge treatment wetlands: Assessment of biosolids quality

Wastewater Treatment Plants (WWTPs) generate a substantial amount of sludge as a residue of the wastewater treatment process. The management of this sludge requires the adoption of cost-effective and environmentally friendly techniques. Sludge Treatment Wetlands (STW) have emerged as an effective means to manage and treat sludge, resulting in the production of biosolids suitable for agricultural purposes. This study aimed to ascertain the optimal operation in terms of final rest period for STWs in the Mediterranean region to boost the production of biosolids for agricultural applications. Two WWTPs in Spain were monitored for a period of 9 months, during which several physic-chemical parameters were monitored to determine the optimal final rest period. The findings revealed that, when sludge feeding period was stopped in summer, a final rest period of 6 months was sufficient to reach biosolids suitable for agricultural re-use. These biosolids displayed a content of 53% total solids (TS), a mineralization rate of 40% volatile solids (VS/TS), a stabilization degree (SD) of 40%, and a high nutrient content. Moreover, the presence of heavy metals, pathogens, antimicrobial resistance genes (ARGs), antibiotics, and pesticides was generally low. Overall, this study demonstrates that, in the Mediterranean Region, 6 months of rest period starting in summer are appropriate for sludge treatment wetlands to effectively generate biosolids with suitable characteristics to be safely re-used as a bio-based fertilizer.

Energy recovery from poultry manure in the process of semi-continuous anaerobic co-digestion with sewage sludge

In the face of significant legislative changes in renewable energy sources and conservation of natural resources, bio-waste must be managed efficiently. Developing wastewater treatment technologies generate a large amount of sewage sludge requiring appropriate use. A well-known and practiced process is the anaerobic digestion of sewage sludge, but due to its characteristics, the production of biogas is not sufficient enough to ensure the energy self-sufficiency of a wastewater treatment plant. Another waste whose management is a challenge is poultry manure, whose production in Poland is high due to intensive poultry farming. This study investigated the possibility of co-digestion of poultry manure and sewage sludge and its effect on increasing biogas production compared to processing sludge alone. The process was performed in two continuously stirred-tank glass reactors at mesophilic conditions, with 20 days of hydraulic retention time. In the first stage, the batch assay with sewage sludge was applied to promote the development of an anaerobic community. The second stage involved feeding the reactors on a semi-continuous regime with sewage sludge for the control sample and a mixture with the gradual addition of poultry manure from 2.5 % to 60 %. During the experiment, the most important parameters affecting the process and the quantity and quality of the obtained products in the form of biogas and digestate were monitored. The study’s results indicated an advantage of the co-digestion process of poultry manure and sewage sludge over the digestion of sludge alone in terms of process efficiency. The highest biogas production was obtained with a co-substrate ratio of 42 % manure to 58 % sewage sludge (ratio based on volatile solids). Co-digestion had no significant effect on gas quality; in both cases, the methane content was more than 60 %. Moreover, a digestate with fertilizer potential was obtained for each sample.

Preparation and performance study of sludge biomass bamboo charcoal

Abstract The purpose of this study is to explore a new low-cost and high-efficiency biochar adsorption material. The residual sludge as solid waste and fresh bamboo with fast growth and high yield were used as raw materials, modified by the KOH chemical activation method, and pyrolyzed in a tubular furnace with nitrogen atmosphere to obtain sludge biomass bamboo charcoal. In the performance test, the H2S gas adsorption experiment in a fixed bed reactor and the heavy metal adsorption experiment in soil were designed. Using different proportions of biochar, the preparation process of biochar was optimized by adjusting the raw material ratio and activation conditions. The results showed that when dealing with H2S gas, the appropriate amount of sludge can improve the adsorption effect, while the increase of bamboo component will reduce the adsorption rate. In the soil Cr(VI) restoration experiment, it was found that the best restoration effect was achieved after adding 10% biochar and applying it for 28 days, and the restoration rate reached 63.5%.

Synthesis of various types of green biosorbents materials for removals of sulphates from contaminated water for better aquatic environments

Human and industrial activities pollute water resources with sulphur metal, endangering human health and ecosystems. Chemical precipitation and membrane filtration are expensive when treating large amounts of water, inefficient at low metal concentrations, and produce large amounts of toxic sludge and other products that must be disposed of waste water bio-sorption is eco-friendly and alternative. These methods are cheaper, more accessible, and reusable than conventional ones. This study investigates the bio-sorption of sulphur from contaminated water using neem leaf, custard apple leaf, mango tree leaf, orange peels, and banana peels biological waste materials. This work achieves 100 % removal efficiency. Biosorbents remove sulphates from contaminated water: custard leaves 100 % at 4gm, orange peels 40 % at 5gm, tea waste 50 % at 4gm, neem leaves 70 % at 5gm, and mango leaves 75 % at 5gm. The performances of biosorbents for removals of sulphates from water as follows: Custard leaves waste > Mango leaves > Neem leaves > Tea trash > Orange peels the sulphate reduction by biosorbents. The best biosorption occurred at basic pH 6.5, 3.7gm dosage, 90 min contact duration, 30 °C temperature, and 120 rpm agitation speed. The effects of contact time, agitation speed, adsorbent dosage, pH, and temperature are also examined. Before usage, biosorbents materials can be physically and chemically measured the changes. Regenerating and reusing bio-sorbent after sulphates removals makes the method cost-effective for removals of pollutants from water.

Technical and environmental assessment of sludge-derived slag generated from high temperature slagging co-gasification process as a sustainable construction material

Tremendous amount of sludge is generated annually from freshwater treatment or sewage. The high temperature slagging co-gasification converts the sludge to slag showing the potential application for construction material. In this study, the physico-chemical properties of 4 types of slags generated from the co-gasification of municipal solid waste (MSW) with sludge from freshwater treatment or sewage, and ashes from sludge incineration are comprehensively analyzed. Leaching performance of the sludge-derived slag and mortar (with slag as the fine aggregate), as determined based on Toxicity Characteristic Leaching Procedure (TCLP), batch leaching and column leaching tests, indicates the slag can be considered safe for reutilization. Compressive strength test demonstrates that the mortars perform excellently and have the potential to replace sand in concrete production. The consolidation coefficient of slag (1.6 – 39.1 m2/year) is lower than the sandy silt but higher than clay. Additionally, the coefficient of permeability (∼1.96 × 10-3 m/s), angle of shearing resistance (∼39°), and undrained shear strength (375.5 ± 54.8 kPa) of the slag are comparable to sand. The life cycle assessment (LCA) is also conducted to evaluate the environmental impacts and benefits of reutilizing sludge-derived slag as an alternative material for concrete production and land reclamation.

Reverse Solute Diffusion Enhances Sludge Dewatering in Dead-End Forward Osmosis.

Wastewater treatment plants produce high quantities of excess sludge. However, traditional sludge dewatering technology has high energy consumption and occupies a large area. Dead-end forward osmosis (DEFO) is an efficient and energy-saving deep dewatering technology for sludge. In this study, the reverse osmosis of salt ions in the draw solution was used to change the sludge cake structure and further reduce its moisture content in cake by releasing the bound water in cell. Three salts, NaCl, KCl, and CaCl2, were added to the excess sludge feed solution to explore the roles of the reverse osmosis of draw solutes in DEFO. When the added quantities of NaCl and CaCl2 were 15 and 10 mM, respectively, the moisture content of the sludge after dewatering decreased from 98.1% to 79.7% and 67.3%, respectively. However, KCl did not improve the sludge dewatering performance because of the "high K and low Na" phenomenon in biological cells. The water flux increased significantly for the binary draw solute involving NaCl and CaCl2 compared to the single draw solute. The extracellular polymer substances in the sludge changed the structure of the filter cake to improve the formation of water channels and decrease osmosis resistance, resulting in an increase in sludge dewatering efficiency. These findings provide support for improving the sludge dewatering performance of DEFO.

Optimizing paper sludge content and particle size to enhance particleboard properties

The pulp and paper industry generates vast quantities of paper sludge, posing significant environmental challenges due to its disposal in landfills or incineration. This study explores the potential of valorizing paper sludge by incorporating it into particleboard production. It aims to optimize sludge content and particle size to enhance board properties—a novel approach to waste management in the wood composites industry. Through systematic variation of sludge content (0–25%) and particle size (< 0.5 to > 2 mm), we assessed the mechanical and physical properties such as internal bond strength (IB), modulus of rupture (MOR), modulus of elasticity (MOE), water absorption (WA), and thickness swelling (TS). The findings indicate that incorporating paper sludge at moderate levels (5–15%) with optimized particle sizes (< 1 mm) significantly improves the mechanical properties of the particleboard, including increased IB, MOR, and MOE while reducing WA and TS. Principal Component Analysis (PCA) further supported these results, revealing that higher-density boards with enhanced mechanical properties absorb less water, highlighting the interrelationship between structural integrity and moisture resistance. The PCA also identified thickness swelling as an independent factor, suggesting that while mechanical properties can be optimized, additional strategies are needed to control swelling. In conclusion, this study demonstrates that up to 15% paper sludge can be effectively used in particleboard production without compromising quality, provided particle size is carefully controlled. This approach not only offers a sustainable solution for managing paper sludge but also contributes to the development of eco-friendly composite materials, aligning with circular economy principles.

Evaluation of textile effluent treatment plant sludge as supplementary cementitious material in concrete using experimental and machine learning approaches

The growing demand for readymade garments is leading to the production of a large amount of textile effluent sludge (TES) from wastewater treatment plants, which is currently disposed of as backfill, causing land and groundwater contamination. This scenario has prompted researchers to explore the use of industrial waste, such as TES, as a supplementary cementitious material (SCM) to mitigate the carbon footprint of cement production. Therefore, this study aims to investigate the fresh, mechanical, non-destructive characteristics, and predictive modeling of mechanical strengths of TES-based concrete. Machine learning models, including random forest (RF) and artificial neural networks (ANN), were utilized to predict compressive and tensile strengths from various input variables. This study also evaluated the alkalinity, specific gravity, oxide content, and surface area of TES. The findings showed a pH of 9.4 and a CaO content of 33.3 %, indicating TES's potential as an SCM. The research further investigated the properties of concrete with 5–20 % cement-replaced TES, using a total binder content of 488.1 kg/m3 and a water-binder ratio of 0.32. The fresh state properties of the 5–15 % TES incorporated concrete produced normal density concrete, with a slump of 100 ± 20 mm, Kelly ball penetration of 45 ± 7 mm, a compaction factor of 0.92 ± 0.05, and a fresh density of 2464 ± 152 kg/m3. At 28 days, concrete with 15 % TES replacement showed a compressive strength of 25.6 MPa and a tensile strength of 2.88 MPa, achieving 76 % of the strength activity index and 72 % of the relative tensile strength. However, the 15 % TES concrete displayed a water permeability coefficient of 4.4 × 10−12 m/s and an electrical resistivity of 31.5 kΩ cm, compared to the control mix's 2.0 × 10−12 m/s and 37.7 kΩ cm. However, the hardened properties declined significantly after replacing 15 % of cement with TES. The mechanical properties were also estimated using ultra pulse velocity and rebound hammer tests, showing a coefficient of determination (R2) higher than 0.87. The RF model demonstrated superior performance with an R2 value of 0.8802 for compressive strength and 0.8518 for tensile strength, outperforming the ANN model's R2 values of 0.8126 and 0.695, respectively. Scanning electron microscopy confirmed the consistent development of hydration products in the TES-enhanced concrete samples.

Mechanical, freeze-thaw resistance and heavy metals leaching properties of alkali-activated recycled concrete powder solidified sludge

Solidified sludge was an efficient method to consume the large amount of sludge, which can be used as the subgrade filler in road engineering. However, the traditional solidified materials, such as cement and lime, consumed a large amount of natural resources and increased carbon emissions. This study used the alkali-activated recycled concrete powder (ARCP) to solidify sludge, which could be used as a potential subgrade stabilization filler. The optimal factors of ARCP were firstly determined by orthogonal test according to the compressive strength. Then the influences of different ARCP dosage, sludge moisture content and curing method on the mechanical properties, freeze-thaw resistance and heavy metals immobilization of the ARCP solidified sludge (ARCPS) were investigated. At last, microstructures of ARCPS were analyzed by SEM, XRD and TG-DTG tests. The experimental results demonstrated that the optimal mixture for ARCP: the silicate modulus of 1, liquid-solid ratio of 0.48 and calcium hydroxide content of 3 %. The solidified process by ARCP improved the mechanical properties and freeze-thaw resistance of ARCPS greatly. The 7 d unconfined compressive strength of ARCPS could reach 1305–2033 kPa when the sludge moisture content was 15 %, which meet the requirement of 500 kPa from the Chinese standard. The frost heaving rates of ARCPS were between non-frost heaving and mild frost heaving. The sludge moisture content was the most important factor affecting the freeze-thaw resistance of ARCPS. The properties of ARCPS were further improved after carbonation curing. The leaching mass concentration of heavy metals decreased significantly after the solidification of sludge. After 5 freeze-thaw cycles, the heavy metal leaching concentration increased but was still met the requirement of standards. SEM results showed that the surface of carbonated ARCPS was covered by dense scale-like carbonation products, which further enhanced the strength and freeze-thaw resistance of ARCPS. The results can be used to guide the application of sludge and ARCP in construction.

Reuse and Recovery of Water from Industrial Textile Dyeing Effluent Using High-Performance Electrodes Continuous Flow Electrocoagulation Reactor

The dye effluents released from the textile and printing industries contain strong colorants, inorganic salts, and other toxic compounds. The conventional coagulation technique of dye effluent treatment is plagued with issues of low removal rate of color, generation of large quantities of sludge, and toxic end-products. Recently electrocoagulation technique gained immense attention due to its high efficiency. This technique involves the dissolution of the sacrificial anodes to provide an active metal hydroxide as a strong coagulant that destabilizes the pollutants and removes them by precipitation or flocculation. This study is about the efficiency of the electrocoagulation process using titanium coated - aluminum and mild steel electrodes to treat industrial dye wastewater. Effects of parameters such as current density &amp; initial dye concentration were investigated. It was observed that, for the same current density, electrode consumption was higher with TiO2/Al electrode than with mild steel electrode, resulting in more color removal efficiency (CRE) using TiO2/Al electrode. The settling rate of the flocs was higher in the rector having TiO2/Al electrode at the 100 mL with current density (2.5 mL.min-1 to 5.3 mL.min-1), while in the reactor with mild steel electrode, the settling rate was very less. The results showed that dye removal was 95.11% and 92.1% for mild steel and titanium-coated electrodes, respectively. It was observed that 50 % of Aluminum was removed from the treated effluent after the final stage of filtration. Based on the multicriteria analysis to identify the optimum operational parameters to be applied at the field level, it was observed that maximum CRE may be obtained with TiO2/Al electrode and the applied current of 1 Amps with a flow rate of 100 mL.min-1. It can be concluded that electrocoagulation is a highly efficient and the fastest method to treat dye effluents from industries.

The Impacts of Cellulose on Volatile Fatty Acid Production and the Microbial Community in Anaerobic Fermentation of Sludge at High and Medium Temperatures.

During large-scale sewage treatment, a large amount of excessive sludge is produced, which will cause serious pollution in the environment. In recent years, anaerobic digestion technology has been widely promoted because it can achieve better sludge reduction, and the products and byproducts after anaerobic digestion can be fully utilized as resources. In this study, cellulose was added as the co-fermentation substrate during the fermentation process at 30 ℃ and 50 ℃ to enhance the production of VFAs. The result indicated that cellulose could significantly increase the yield of VFAs in both 30 ℃ and 50 ℃. Meanwhile, COD and reducing sugar generation in the fermentation process were also measure. Analysis of the microbial community structure at the class and genus levels revealed that the proportion of several genus closely related with cellulose degradation such as Cellvibrio, Fibrobacter, and Sporocytophaga were significantly increased with the addition of cellulose. Co-fermentation was recognized as an economic and environmental friendly strategy for sludge and other solid waste treatment. The analysis of the effect of cellulose as a substrate on the production of VFAs at high and medium temperatures is highly important for exploring ways to increase the production of VFAs in anaerobic fermentation.

Activated hydrogen-promoted self-generation of H2O2 and reduction of Fe(III) mediated by Pd-based catalysts: A green Fenton-like process

The traditional Fenton process has two issues that hinder its further application and promotion. One is the generation of large amounts of iron sludge. The other is the safe storage and transport of explosive H2O2. The problems could be solved by accelerating to regenerate Fe(II) and realizing to self-generate H2O2. The key to the solution lies in the use of reducing active hydrogen [H] to supply electrons. The effect of different loading methods of Pd0 nanoparticles (NPs), active centres for [H] generation, on the catalytic performance is unknown. Herein, the Pd/UiO-66(Zr) (Pd0 NPs loaded on the surface of UiO-66(Zr)) and Pd@UiO-66(Zr) (Pd0 NPs confined into the pores of UiO-66(Zr)) were synthesized. It confirmed that the [H] could be used to promote to regenerate Fe(II) and self-generate H2O2. Using only a trace amount of ferrous (25 μM) and without H2O2, the trimethoprim (20 mg·L−1) could be thoroughly removed within 90 min. Moreover, the stability of Pd@UiO-66(Zr) was slightly superior to that of Pd/UiO-66(Zr) because of the confinement effect of pore wall on Pd0 NPs, as well as the interception effect on the intermediate products that can be complexed with Pd0 NPs.

Selective adsorption of methylene blue dye by a flocculation sludge-derived adsorbent prepared by carboxymethyl chitosan-based flocculants

The flocculation of dyeing wastewater generated a large amount of sludge that was often disposed as refractory hazardous waste. The resource utilization of flocculation sludge was of great significance in terms of low treatment cost of sludge, low environmental risk and high usage efficiency of reactive dyes. Herein, a flocculation sludge-derived (FSD) adsorbent was prepared via cross-linking of flocculation sludge yielding by carboxymethyl chitosan-based flocculants and dyes. FSD adsorbent had excellent selective adsorption performance for methylene blue (MB) treatment. The highest removal rate of MB and adsorption capacity of FSD adsorbent were 96.48 % and 354.7066 mg/g, attributing to its rich functional groups, negative charges and special micropore structure. FSD adsorbent owned the favorable regeneration efficiency and stability. Its removal rate of MB was still above 71.8 % after 6 regeneration-adsorption cycles. Its leaching rate of dyes was only 0.0016 mg/mg that was rather lower than common dried flocculation sludge. The adsorption processes of FSD adsorbent were complex in accordance with its characteristics, adsorption isotherms, adsorption kinetics and theoretical calculation. Multiple adsorption mechanisms were present in the treatment of dyeing wastewater by FSD adsorbent. The resource utilization of flocculation sludge, as adsorbents, was a potential candidate in field application.

Simulation of Magnetic Separation of Metal Ions in Aqueous Electrolytes

The magnetic separation of metal ions provides an alternative solution to traditional separation techniques such as pyrometallurgy, hydrometallurgy, biometallurgy or electrodialysis. Compared to traditional techniques that either use large amounts of chemicals (usually inorganic acids combined with reducing agent), produce large amounts of sludge as solid waste, consume a large amount of energy, or are difficult to separate ions of different charges [1], the magnetic separation of the metal ions can separate ions based on their magnetic susceptibility. This method is environmentally friendly [2] and consumes a small amount of energy (particularly when the system is designed using permanent magnets instead of electromagnets). The goal of this presentation is twofold. First, we derive the set of transport equations that need to be used to simulate the magnetic separation of metal ions in aqueous solutions. Then, we use these transport equations to simulate the magnetic separation process in various magnetic systems and predict the efficiency of magnetic separation of different systems.The mathematical model developed here is based on coupling the three-dimensional Navier-Stokes equations for flow transport with the drift (migration)-diffusion equations of ion transport [3] in the presence of magnetic field gradients. Both the drift-diffusion model and the Navier-Stokes equations include the magnetic force term as an additional driving force. By solving the entire system of equations self-consistently we analyze the effect of the diffusivity, concentration gradients, magnetic field gradients and fluid velocity over the capturing properties of the system. A detailed presentation of the mathematical model, underlying assumptions of the model, limiting cases, numerical implementation in three-dimensional structures, and simulations results will be presented at the meeting. In addition, we will present predictions for the magnetic separation of Li, Fe, Ni, Mn, and Co from the solution phase. Fortunately, these ions have significantly different magnetic susceptibility, which vary over more than 3 orders of magnitude, and which allows for the efficient extraction and separation of the elements from the solution and from each other.

Co-combustion of sewage sludge with corn stalk based on TG-MS and TG-DSC: Gas products, interaction mechanisms, and kinetic behavior

Rapid urbanization has led to the generation and accumulation of large quantities of sewage sludge, threatening the ecological environment on which mankind depends. Incineration can achieve sewage sludge minimization and energy recovery. In this study, the co-combustion behavior and gas product emission characteristics of sewage sludge and corn stalk were analyzed. The results showed that corn stalk increased the combustion rate of sewage sludge, and its co-combustion performance, flammability and combustion performance were significantly improved. The main influencing factors at each stage were derived by factor analysis. The gaseous products of the co-combustion process were examined by mass spectrometry analyzer, and it was found that co-combustion of sewage sludge with 30 % corn stalk could reduce NOx and SO2 emissions by 82.94 % and 55.73 %, respectively. In addition, the Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods were used to calculate the apparent reaction activation energy. The fuel blended with 30 % corn stalk had the lowest average activation energy (131.17 kJ/mol) and the strongest synergistic effect. The results of this study may provide new ideas for the synergistic combustion of sewage sludge with corn stalk.

Reviewing Improved Anaerobic Digestion by Combined Pre-Treatment of Waste-Activated Sludge (WAS)

The anaerobic digestion of wastewater treatment sludge (WAS) produces a “green” biogas while reducing the amount of residual sludge. To increase the yield of biogas, several individual or combined pre-treatment methods of WAS can be used. These pre-treatment methods substantially reduce the amount of volatile suspended solids (VSSs) and their associated total chemical oxygen demand (TCOD). Pre-treating the sludge will increase the methane yield by 15 to 30%. Although the individual methods have been dealt with in research and large-scale operations, the combined (hybrid) methods have not previously been reviewed. Here, different hybrid treatment methods are reviewed, including (1) thermochemical hydrolysis pre-treatment, using an alkaline or acid addition to enhance solubilization of the sludge cells and increase biogas production; (2) alkaline and high-pressure homogenizer pre-treatment, combining a chemical and mechanical treatment; (3) alkaline and ultrasound pre-treatment, capable of solubilizing organic sludge compounds by different mechanisms, such as the fast and effective ultrasound disruption of cells and the increasing effect of the alkaline (NaOH) treatment; (4) combined alkaline and microwave pre-treatment, which enhances sludge solubilization by at least 20% in comparison with the performance of each separate process; (5) microwave (MW) and peroxidation pre-treatment of WAS suspended solids (SSs), which are quickly (&lt;5 min) disintegrated by MW irradiation at 80 °C; (6) ultrasound and peroxidation pre-treatment, with ozone and peroxides as powerful oxidizing agents; and (7) pulsed electric field (PEF) pretreatment. All literature findings are assessed, discussing relevant operation conditions and the results achieved.

Sustainable valorization of mining waste: Phosphate sludge repurposing for advanced ceramic production

Managing the vast quantities of waste constantly generated by mining activities is one of the major environmental and economic problems facing mankind today. Fluorapatite is separated from the associated gangue minerals by a series of crushing and screening, washing, and flotation processes. These processes produce a significant amount of phosphate sludge, which is stored on the mine site in drift rock and large surface ponds. One possible environmental option is to reuse it as an alternative raw material in ceramics and building materials. Consequently, two phosphate sludges from two different Moroccan towns, Youssoufia and Khouribga, were studied. Due to the complexity of these raw materials resulting from long geological processes, in-depth physical, chemical, mineralogical, and thermal characterization is required. Dry compressed powder pellets were sintered at 900 °C, 1000 °C, and 1100 °C for 2 h. The study focuses on the effect of sintering temperature on mineralogical transformations and ceramic properties such as apparent porosity, water absorption, and mechanical strength. At 1100 °C, a slight increase in density was observed for both phosphate sludges. Water absorption was reduced by 2.51 % in both sludges for pellets sintered at 1100 °C compared to those sintered at 900 °C. Mechanical strength improved significantly, with an increase of about 60 % for samples sintered at 1100 °C, recording 227 N for Youssoufia sludge and 247 N for Khouribga sludge. This work has provided new data on the physical, chemical, mineralogical, and thermal changes in ceramics as the sintering temperature increases. These data will be useful for the manufacture of high-value ceramics.

A Comparison of the Carbon Footprints of Different Digested Sludge Post-Treatment Routes: A Case Study in China

As the “carbon peaking and carbon neutrality” strategy advances, carbon emissions have gradually become a significant indicator in selecting and evaluating sewage and sludge treatment solutions. This study compared the carbon footprints of different digested sludge post-treatment routes, taking the Lu’an project in China as an example. Considering anaerobic digestion and digested sludge post-treatment options, the carbon footprints are as follows: 347.7 kg CO2 (land application) &lt; 459.7 kg CO2 (composting-involved land application) &lt; 858.4 kg CO2 (brickmaking). In general, land application was superior to brickmaking from the perspective of carbon footprints. The power consumption incurred by aerating and turning and the direct N2O and CH4 emissions during composting increase the composting-involved land application carbon footprint. However, digested sludge that is not subject to high-temperature sterilization and compost is phytotoxic and can be fetid, which is a limitation of its applicability. And the composted sludge has a lower N ratio and water content, so the same N input means more sludge usage, which is conducive to solving the disposal problem of large amounts of sludge. Thus, if possible, composting-involved land application should be a preference, and improvements to the technique are required to minimize energy consumption and direct N2O and CH4 emissions.