Recovery Of Sludge Research Articles

Fifty years of sewage sludge management research: Mapping researchers' motivations and concerns

Sewage sludge management is torn between a desire for pollution prevention and reuse of a valuable resource. Reconciling these interests in sustainable management is a challenge for researchers. This study focuses on how research on sewage sludge management practices has evolved and scrutinizes how this research is interlinked with concerns and societal issues such as contaminants, economic efficiency, and legislation. Based on published academic papers on sewage sludge management between 1971 and 2019, this study found four trends in research focused on sewage sludge management: a decreasing interest in disposal (landfilling and sea dumping), a dominant interest in land application, a growing interest in sewage sludge as product, and a stable interest in energy recovery. Research on disposal focuses on increasing sludge volumes, legislative changes, and economic challenges with an interest in waste co-treatment. Research on land application concerns nutrient use and contaminants, mainly heavy metals. Research on sewage sludge as a product focuses on the extraction of certain resources and less on use of sewage sludge specifically. Research on energy recovery of sewage sludge focuses on volume reduction rather than contaminants. Two-thirds of the papers are detailed studies aiming to improve single technologies and assessing single risks or benefits. As management of sewage sludge is multifaceted, the narrow focus resulting from detailed studies promotes some concerns while excluding others. Therefore, this study highlights potential gaps such as the combination of nutrient use and disposal and energy recovery and nutrient use.

Sewage Sludge Quality and Management for Circular Economy Opportunities in Lombardy

From the perspective of a circular economy that prioritizes resource reuse and recovery, sewage sludge could be a source of nutrients for agricultural soils or a source of energy, depending on its characteristics. Lombardy is the region with the highest quantity of sludge production and management in Italy. A methodology was developed to: extract and analyze quantitative data on sewage sludge (EWC 190805) production and management (2017–2018); collect and analyze qualitative data from publicly available documents in tender processes for sewage sludge management (2014–2020). Sludge from Lombardy’s wastewater treatment facilities displayed average qualities that were useful for recovery in agriculture after additional stabilization treatments. Sludge showed generally low heating values and elevated water content and should require additional treatments to be used in mono-combustion. The study discovered that there is still work to be done in sludge recovery in agriculture in Lombardy, taking biosolid quality into account. Sludge, on the other hand, can be converted into energy. The methodology for collecting and analyzing site-specific data presented here can be applied to other areas. The findings can assist and guide decision-makers in developing future regional sewage sludge management strategies.

Preparation of ionic liquids microemulsion and its application for the treatment of oily sludge

The surface-active ILs [C16mim]Cl synthesized by combining imidazole group (C4H6N2) and 1-chlorohexadecane (C16H33Cl) was used as surfactant to prepare ILs microemulsions for sludge treatment. Meanwhile, the treatment conditions were optimized and the optimal conditions were obtained. Due to the strong interaction between ILs and asphaltenes as well as the solubilization of microemulsions, the residual oil rate of oily sludge decreased to 1.33%. The characterization of oily sludge was performed by scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR) and contact angle measurement. Results showed that [C16mim]Cl ILs microemulsions treatment could effectively promoted the desorption of asphaltenes from the surface of sludge solids, which provided a clear understanding of the mechanism for ILs microemulsions-enhanced oily sludge recovery.

Comparative insights into flue gas-to-ash characteristics on co-combustion of walnut shell and bio-oil distillation sludge under atmospheric and oxy-fuel condition

The clean recovery of bio-oil distillation sludge (DS) is a pivotal sector to perfect the biomass refinery system in responses to effective waste management and environmentally friendly consensus. This work aimed to comparatively characterize atmospheric and oxy-fuel co-combustion of walnut shell (WS) and DS in terms of (co-)combustion performance, distributed kinetics, flue gas evolution and ash characteristics. The results indicated co-combustion of WS and DS significantly increased the allocated proportion of char combustion stage and improved co-combustion performance, which was reflected in the enhanced four quantitative combustion indices. The fourth pseudo component, corresponded to the char combustion stage, continuously dominated the whole combustion process by adding more fraction of DS to co-combust with WS, whose activation energy was diminished, thereby optimizing the initial reaction energy barrier. In addition, oxy-fuel combustion promoted the recovery and sequestration of CO2, facilitated the formation of CO, and further endowed the conversion of polycyclic aromatic hydrocarbons into phenols rather than aromatics. Although the composition for mixed molten ash presented the decreased contents for easy-slagging minerals, the co-combustion process was still with potential ash fouling risk owing to basically unchanged ash configuration consistent with WS ash. However, the addition of DS to some extent strengthened anti-slagging performance, consequently optimizing the empirical indices of slagging and fouling for mixed ashes. Also, a higher ash content was yielded in oxy-fuel combustion than that in atmospheric combustion owing to the reducibility of CO2, in which the presence of CO2 contributed to the formations of carbonates and low melting-temperature potassium-containing silicates.

Energy recovery of livestock manure and industrial sludge by co-hydrocarbonisation coupled to pyrolysis and gasification

Hydrothermal carbonization (HTC) of carbonaceous waste is an important way of energy recovery to obtain renewable fuels. Here, cow manure (CM) and industrial sludge (IS), two kinds of wastes with different properties, were pretreated by HTC at different temperatures. The elements migration and the physicochemical structural characteristics of hydrochar during HTC were evaluated. The pyrolysis and gasification performance of hydrochar was also studied. The results show that HTC treatment can significantly increase the carbon content and reduce the oxygen content of feedstocks, so as to obtain clean solid fuels with high energy densification and realize energy recovery from low value wastes. The distribution of pyrolysis products of co-hydrochar is close to that of IS due to the interaction between the components of CM and IS. The co-hydrochar has good gasification reactivity, showing obvious synergistic effect. There is multi-component interaction in the process of co-HTC due to the difference of feedstocks composition and properties between CM and IS. The abundant aliphatic and oxidized aliphatic hydrocarbons in IS may inhibit the polycondensation and aromatization of cellulose and hemicellulose hydrolysates in CM due to hydrogen supply or steric hindrance. Therefore, co-hydrochar has carbon structure and fuel properties close to that of IS hydrochar.

Sludge recovery from industrial wastewater treatment

Industry is a fundamental sector that allows mass production to support a large population. As population grows, many industries produce large amounts of industrial effluents with different pollutants, that must be removed at the industrial wastewater treatment plants, with the consequent production of large amounts of sludge. The present study was conducted to identify and evaluate different sludge treatment/valorisation methodologies, being given priority to the valorisation in detriment of the elimination operations, like incineration or landfill. Therefore, sludges from the wastewater treatment plant of a resin industry, after dehydration operation by a press, were submitted to several valorisation methodologies, such as: application in anaerobic digestion aiming the production of biogas and allowing energy recovery, use in the preparation of adsorbents for the treatment of industrial wastewater, use as cement replacement in mortar production, and application of heterogeneous catalysts to produce biodiesel. The results revealed that all methodologies can be applied as sludge recovery. However, it is possible to conclude that the most promising industrial sludge treatment/recovery hypothesis is anaerobic co-digestion followed by the production of heterogeneous catalysts for biodiesel production.

Optimum utilization and resource recovery of tannery sludge: a review

Optimum utilization and resource recovery of tannery sludge: a review

Simultaneously Enhanced Dewaterability and Biopolymer Release of Sludge by Natural Deep Eutectic Solvents: Performance, Mechanisms, and Insights of Theoretical Calculations

The dewatering and resource recovery of waste-activated sludge (WAS) seemed to be two contradictory processes due to the high moisture content induced by the extracellular polymer substances, which mainly consist of proteins and polysaccharides. Natural deep eutectic solvents (NADESs) were proposed to synergistically enhance dewaterability and biopolymer release of WAS. It showed that NADES with low-temperature pretreatment can significantly improve the dewaterability and release of valuable resources. With the addition of 1.0 mL of NADES combined with 60 °C thermal treatment for 120 min, the capillary suction time (CST) of sludge significantly decreased from 75.9 ± 7.5 to 30.5 ± 1.6 s, and 11.83 mg/L of the total amino acids (AAs) was obtained. The protein and polysaccharide contents were increased to 876.48 and 213.42 mg/L, respectively. This study indicated that NADES combined with low-temperature pretreatment is a green, cost-effective, and environmentally friendly method to improve sludge dewaterability and resource recovery simultaneously. The theoretical calculation results suggested that the generation of NADES···AAs aggregates is an exothermic reaction and proceeds nonspontaneously. A good correlation is also found between the theoretically calculated free-energy change and the concentrations of AAs. On the basis of this study, the biopolymers from WAS can be recovered as value-added resources, enabling a recycling concept within the circular economy vision. The theoretical calculation can be used to guide future experiments for screening highly selective and effective NADES toward resource recovery from WAS.

Self-reduction with escaped sulfur and immobilization of toxic chromium in Co-vitrification for synergistic recovery of chromium sludge and blast furnace slag

Vitrification technology has been widely used to treat hazardous solid waste to form molten glasses. But the heavy metals with active valence in the glass matrix are unstable and easy to dissolve, easily leading to potential environmental risks. Based on the laboratory simulated preheating feed mode, this study first explored the feasibility of using high-temperature melting metallurgical blast furnace slag to synergistic melt chromium sludge to form the stabilized glass matrix. The results found that the stabilization of chromium in the molten glass was highly enhanced by the self-reduction effect of escaping sulfur when chromium sludge and blast furnace slag were co-melted by preheating feed. The leaching concentration of chromium decreased to 0.03 mg/L, which met the limit requirements of resource utilization for molten glasses. TG-MS and XPS supported that SO2 generated from chromium sludge uninterruptedly made more chromium kept in low valence during the co-melting process. As a result, 22.13% of Cr(III) species existed in molten glass produced from preheating feed larger than 6.3% of the heating feed. The polarizing microscope also showed that the increase of the Cr(III) species promoted the formation of micro-crystals, thereby improving the stability of chromium in molten glass. Therefore, this study highlights the new perspective on realizing high value-added utilization of chromium sludge with low energy consumption and higher stability.

Physicochemical and fertility characteristics of microalgal soil ameliorants using harvested cyanobacterial microalgal sludge from a freshwater ecosystem, Republic of Korea

The recovery and reuse strategy of cyanobacterial microalgal sludge (CyanoMS) is a novel sustainable platform that can mitigate cyanobacterial harmful algal blooms (CyanoHABs) in the freshwater system. This study aimed to assess the nutritional feasibility of harvested CyanoMS for microalgal soil ameliorants (MSAs) as efficient biofertilizers by the composting process. Most MSAs exhibited stable nutrient levels during the sequential metabolic phases for the entire period. The qualitative value of all MSAs using CyanoMS as a biofertilizer was verified by the excellent Fertility Index (FI), Clean Index (CI), and plant growth values. Also, successfully matured MSAs provided long-term support for retarded release of nutrients along the microbial transitional pathway. However, suitable CyanoMS contents of 11.7–37.6% (w/w) in MSAs were critical for efficient microbial activation and substrate inhibition. Since these results were fundamentally based on microbial transition on the CyanoMS content, optimum weight content and composting period were required. Nevertheless, MSAs were commercially applicable to high value-added crops due to their high fertilization potential and recyclable value.

Sustainable Sewage Sludge Management Technologies Selection Based on Techno-Economic-Environmental Criteria: Case Study of Croatia

The management and disposal of sewage sludge is becoming a growing concern at the global level. In the past, the main goal was to completely eliminate sewage sludge since it was deemed a threat to humans and the environment, but recently different possibilities for energy generation and material recovery are emerging. Existing technologies such as incineration or direct application in agriculture contribute to quantity reduction and nutrient recovery but are unable to fully exploit the potential of sewage sludge within the frameworks of circular economy and bioeconomy. This paper developed a model within the PROMETHEE method, which analyses technologies for the sustainable management of sewage sludge, which could make the most from it. For the empirical part of the study, the Republic of Croatia was used as a country in which sewage sludge is increasing in quantity as a result of recent upgrades and expansions in the wastewater system. Incineration, gasification, anaerobic digestion, and nutrient recovery were analyzed as treatment concepts for the increased amounts of sewage sludge. The model reveals that the best solution is the material recovery of sewage sludge, using the struvite production pathway through analysis of selected criteria.

Integration of hydrothermal carbonization and aqueous phase reforming for energy recovery from sewage sludge

This study investigates the energy recovery from sewage sludge by combining hydrothermal carbonization and aqueous phase reforming of the generated process water. The hydrothermal treatment was carried out at 170 °C and 230 °C for 1 h, and produced a hydrochar with adequate physicochemical properties, such as a higher heating value (20–24 MJ kg−1) than sludge, improved fuel ratio (0.2–0.5) and a broad comprehensive combustion index (5.8 × 10−7 to 10.0 × 10−7 min−2 °C−3). Aqueous phase reforming of the process water was carried out at 220 °C and 25–29 bar for 4 h. A maximum H2 yield of 98.7 mmol H2 gTOC−1 was achieved using a bimetallic Pt/Rh catalyst supported on carbon black and for the process water obtained at the lowest carbonization temperature. The integration of hydrothermal carbonization and aqueous phase reforming processes is an interesting alternative for the management and energy recovery of sewage sludge, which allows reaching a potential energy recovery of 17.3 MJ per kg of dry sewage sludge, equivalent to 93.5 % gross energy recovery, under optimized conditions.

Recovery of Sewage Sludge in the Cement Industry

This paper presents an analysis of the literature that studies the possibility of sewage sludge being used in the cement industry to reduce carbon dioxide emissions from cement production and thus solve the problem of disposing of sewage sludge so that it is no longer stored, avoiding soil pollution with heavy metals, and reducing pressure on the environment. The ash of sewage sludge is a good pozzolanic material, because when it is finely ground, it can be used as a partial substitute for Portland cement. This reduces waste storage costs. Sewage sludge ash was mixed with cement, and it was analyzed to determine whether the paste obtained could be used as a raw material in the cement industry. The presented results are on the hydration characteristics of the sewage sludge ash, the compressive strength of the cement determined after different days, the workability of the cement, and the porosity of the cement paste and the ash.

Petroleum sludge treatment and disposal techniques: a review.

Petroleum sludge is a solid emulsified waste and contaminant commonly produced in the petroleum industry. In the recent past, there has been increased business growth in the oil sector, resulting in increased volumes of oily sludge characterized by high viscosity and toxicity. Therefore, sludge treatment before discarding is extremely necessary. This review seeks to highlight various conventional and evolving approaches in the treatment, recovery, and disposal of petroleum sludge and assess their suitability under various conditions.

Metal recovery and heavy metal migration characteristics of ferritic stainless steel pickling sludge reduced by municipal sludge

A new method for recovering metals from ferritic stainless steel pickling sludge using municipal sludge as a reducing agent is proposed. The effects of temperature, municipal sludge blending ratio, and reaction atmosphere on the recovery characteristics were studied. The migration characteristics of heavy metals (HMs) at different temperatures were also investigated. The results showed that municipal sludge can be used as a reducing agent for metal recovery from pickling sludge. Under optimized conditions (temperature of 650 °C and blending ratio of 5%), the recovery fractions of Fe, Cr, and Ni were 70.1, 53.7, and 60.3%, respectively. The CO2 atmosphere was beneficial for increasing the recovery fraction of the pickling sludge. The migration fractions of Cr, Mn, and Ni were approximately 10%. The migration fractions of Zn, Cu, and Pb, which are semi-volatile HMs, varied significantly with temperature. The migration fractions of Cd and As, which are volatile HMs, could exceed 70%.

Influence of persulfate on transformation of phosphorus and heavy metals for improving sewage sludge dewaterability by hydrothermal treatment

Activated persulfate oxidation has been proven to be an efficient advanced sludge treatment technique to improve sludge dewaterability. This study investigates the influence of persulfate on the transformation of phosphorus (P) and heavy metals (HMs) during the hydrothermal treatment of sewage sludge. The hydrothermal temperature, time, and persulfate concentration are optimized by a Box-Behnken design to obtain the best sludge dewaterability, which is expressed by capillary suction time (CST). The highest CST reduction efficiency is 90.5% at the optimal hydrothermal temperature, time, and concentration of persulfate, which are 145°C, 2h, and 150mg/g dry sludge (DS), respectively. The distribution and transformation of P and HMs with different persulfate concentrations (100-200mg/g DS) during the hydrothermal process are investigated. Results show that more than 90% of the P and HMs in the sludge are retained in sludge cakes after the hydrothermal treatment. The addition of SPS can make the P in the sludge cakes transform into more stable P species according to the extraction capacity of sequential extracts. It can be found from the ecological risk indexes of the HMs that the addition of SPS during the hydrothermal treatment of sludge can reduce the environmental risk of HMs. This study provides insights into the P and HM distribution and transformation during hydrothermal treatment with persulfate, providing a reference for sludge recovery strategies.

Tolerance and Recovery of Aerobic Granular Sludge: Impact of Perfluorooctanoic Acid

Tolerance and Recovery of Aerobic Granular Sludge: Impact of Perfluorooctanoic Acid

Accelerated Performance Recovery of Anaerobic Granular Sludge after Temperature Shock: Rapid Construction of Protective Barriers (Eps) to Optimize Microbial Community Composition Base on Quorum Sensing

Accelerated Performance Recovery of Anaerobic Granular Sludge after Temperature Shock: Rapid Construction of Protective Barriers (Eps) to Optimize Microbial Community Composition Base on Quorum Sensing

Modern approaches to treatment and recovery of secondary sludge of domestic sewage

For today, pollution of the environment, in particular of surface waters, has led to an environmental crisis in many countries of the world. One of the reasons for this is the use of outdated approaches to the treatment and recovery of sewage sludge. The article presents the results of the study of literary sources in order to analyze the proposals for the treatment of secondary sludge of domestic sewage in different countries. To neutralize sewage sludge, scientists consider the possibility of obtaining fertilizes under conditions of biosulfidogenesis during the dissimilation recovery of poorly soluble sulfates or the use of enhanced oxidation technology.
 A new concept of domestic sewage treatment has also been proposed, which can solve the issue of sewage sludge control at the place of its forming. The main areas of sustainable sludge control are its use in agriculture as fertilizer and for the reclamation of devastated or degraded lands, as well as energy recovery by burning and alternative thermal methods such as pyrolysis, quasi-pyrolysis and gasification. It was established that the applicability of this or that technology of sewage sludge recovery depends on many local factors, in particular: productivity of sewage station; composition and methods of sewage treatment and its sediments; efficiency of sewage treatment plants; climatic zone of the sewage system location; availability of energy and material resources, etc.
 Today, it is relevant to monitor the qualitative composition of sewage sludge, as well as soils and natural waters regarding pollutants that can be detected in the sewage of the corresponding settlement, in order to make operational decisions to control environmental risks, as well as conduct scientific research to improve recycling and recovery technologies for sewage sludge of various composition in agricultural systems, which will help to protect the environment against pollution and rational use of land.

Study on quantitative structure of oil from oily sludge by improved Brown-Ladner (B-L) method

Oily sludge is a mixture of crude oil, mud, and water contaminated by other organic matter. Oil from oily sludge was Soxhlet extracted using toluene solvent. Modern analytical techniques such as FT-IR, GPC, 1H-NMR were applied to characterize the structure of the extracted oil. The quantitative structure of the extracted oil was evaluated by improved B-L method. The average molecular weight and formula of the extracted oil were established. The extracted oil was found paraffin-based crude oil with aliphatic chain structure as main component, aromatic structure as a supplement, and aromatic rings were all the aliphatic side chain substituted unit rings with a high degree of substitution. This paper tried to apply the latest methods during the analysis of the sludge and extracted crude oil and provides theoretical basis of molecular structure for the recovery and utilization of oily sludge.