Characterization Of Sewage Sludge Research Articles

Characterization of sewage sludge in Muscat and estimation of their energy recovery

There is a pressing need to address Oman's sludge management issues. It is crucial to establish a reliable database of solid waste compositions, properties, and energy content in order to implement an effective waste management. This study examines the wastewater treatment sludge (WWTS) from Muscat Governorate's wastewater treatment plants. This study examines two wastewater treatment plants, namely, AL Ansab, and Al Seeb. Sludge samples were collected in February, March, and June 2020. Physiochemical characteristics of WWTS collected from 1 kg samples have been examined after being mixed several times thoroughly. In both treatment plants, the MC of dewatered sludge ranged from 51 to 94%. In WWTS, the volatility ratio ranged from 73.6 to 93.1%, but the loss of ignition ratio was 76.2 to 90.4%, which meant that 9.6 to 26.4% was considered ash. According to WWTS, silica was the most prevalent oxide, followed by ferric oxide. A low carbon to nitrogen (C/N) ratio was found in WWTS. Dulong's equations were used to estimate their high heating values, which varied between 10,800 and 42300 kJ per kg. Therefore, WWTS has a high energy content and a low C/N ratio which can be burned up as a fuel.

Characterization of sewage sludge and biomass ash mixture as future geotechnical material

To reduce the environmental load due to waste generation, there is an urgent need of utilizing the industrial/municipal waste in the bulk. There is a large scope of utilizing the bulk amount of waste as geotechnical material. Several studies have been made to utilize the industrial waste such as fly ash, slag, red mud, mine overburden etc. as geotechnical material, however, the sewage sludge did not get much attention. So, this research has been presented as a preliminary study which includes the physical, chemical, and microstructural property of sewage sludge for futuristic geo-material. Further, the biomass ash has been added with the sewage sludge to know its effect. The test result shows that the sewage sludge contains high concentrations of chromium, mercury and nickel. Dewatered municipal sewage sludge (80%) stabilized with biomass ash (20%) was used as a soil amendment, to predict the behavior of soil under a controlled environment. The application of stabilized sewage sludge over soil sample resulted in a significant increase in pH and electrical conductivity of the soil sample. The effect of stabilized sewage sludge over macronutrients and micronutrients present in soil was also determined and the results of statistical analysis revealed that the usage of sewage sludge stabilized with biomass ash enhances the fertility of the soil.

Physio-chemical characterization of sewage sludge generated from sewage treatment plant at Varanasi, in relation to nutrients and heavy metals for agriculture use

Large amount of sewage sludge is generated during waste water treatment at sewage treatment plant (STP), as a result of the sedimentation and suspension of particles. The safe disposal and management of this concentrated sewage sludge posesa major challenge for town and city municipal corporations. However, this could also be used in agriculture as an input to partially replace recommended doses of fertiliser. Thus, the current study was conducted to investigate the physio-chemical and biological characteristics of sewage sludge (SS) and its potential application in agricultural fields as an organic manure. Sewage sludge samples were collected from sewage treatment plant (STP) at Bhagwanpur, Varanasi, India and sieved in 2 mm mesh before being analysed for various physical and chemical characteristics. The processed sewage sludge possessed both major [total nitrogen (1.76 %), total phosphorous (1.29%), total potassium (1.15%)] and micro nutrients (Fe, Mn, Zn and Cu) and significant amount of organic carbon (8.67 %). However, this sewage sludge was also containing considerable amount of heavy metals like Cadmium (7.3 mg kg-1), chromium (49.2 mg kg-1), nickel (total 27.43 mg kg-1), and lead (39.53 mg kg-1), which were reported to be harmful to human beings, but these were lower than threshold limit recommended by Council of the European Communities, 1988 for agricultural use. Further, Bulk density and water holding capacity was 1.18 g cm-3 and 54.5 % respectively. With respect to microfauna, fungi were found more dominating than actinomycetes and bacteria in this sewage sludge. Therefore,considering use of this sewage sludge for agriculture may decrease the use of chemical fertilisers and make it more sustainable. However, in order to increase soil health without posing an environmental risk, sewage sludge must be carefully evaluated before being applied to soil especially for heavy metals and other hazardous pollutants.

Characterization of Sewage Sludge in Muscat and Estimation of Their Energy Recovery

Characterization of Sewage Sludge in Muscat and Estimation of Their Energy Recovery

Co-digestion of wastewater treatment sewage sludge with various biowastes: A comparative study for the enhancement of biogas production

The objective of the present study is to improve the anaerobic digestion of sewage sludge viaco-digestionwith biowastes. In the study, anaerobic co-digestion of sewage sludge and six organic waste materials as possible co-substrates for enhancement of bio-methane potential were carried out. Furthermore, the possible impact of the co-digestion on digested sludge content in terms of volatile solids (VS), Chemical oxygen demand (COD), and total solids (TS) were examined. Firstly, physicochemical characterization of sewage sludge as the anaerobic digestion feedstock was carried out before anaerobic digestion to obtain their composition. Characterizations such as proximate and ultimate analysis were carried out using a Hach spectrophotometer, a laboratory oven, and a furnace. The characterization feedstock results showed that the sludge contains a reasonable amount of COD, organic matter, TS, and VS along with the inhibitory compounds which shows potential for a high yield of methane in biogas production, as long as the stability of anaerobic digestion is maintained throughout the process. The results show that the sewage sludge has great methane potential during biogas production quantified as 28.6 g CH4/kg feed. When compared to sewage sludge mono digestion, biomethane yield was increased by 3–6 times when thick co-substrates were used. Although high solid content co-substrates generated significantly more methane gas, they also increased the risk of organic overloading. Co-substrates such as molasses, food waste, animal manure, and fresh produce waste performed well at 25% co-digestion ratios. Furthermore, all other solid co-substrates co-digestion resulted in increased VS and COD residuals in digested sludge, withexception of manure. Most of the liquid co-substrates studied here, on the other hand, had a significant synergistic effect, enhancing the removal of TS, VS, and COD during anaerobic digestion.

Sewage Sludge as N-Fertilizers for Crop Production Enabling the Circular Bioeconomy in Agriculture: A Challenge for the New EU Regulation 1009/2019

The fertilizer framework in the European Union has recently been reviewed by EU Regulation 1009/2019 that excluded sewage sludge from the list of the possible constituents of organic fertilizers relying on their origin, not on their quality. This paper aimed to carry out a complete characterization of sewage sludge obtained from a pharmaceutical manufacturing process (PDSS) to demonstrate that sewage sludge obtained from a standardized and controlled manufacturing process can be safely recycled as organic fertilizer. The agronomic and environmental characteristics of the PDSS product were analyzed and compared to other organic fertilizers. Its fertilizing potential was also evaluated through plant growth trials. PDSS was characterized by a high concentration of total N (6.6% w/w), which was all present in organic form. PDSS also showed a low concentration of heavy metals, an absence of pathogens and low concentrations of organic contaminants. Plant growth trials showed that the PDSS was able to improve lettuce and carrot growth (+25 and +46% of dry weight compared to the unfertilized control), as well as their physiological status. Considering all the results, the exclusion of sewage sludge relying only on its origin and not on its quality appears to conflict with the principles of the circular bioeconomy.

Effect of sewage sludge application on growth and photosynthetic pigments in vetiver grass (<em>Vetiveria zizanioides</em> L. Nash)

The study was conducted to evaluate the effect of sewage sludge application on growth and photosynthetic pigments in vetiver grass. Vetiver plants were grown in poly-ethylene U-V stabilized grow bags (24 X 24 X 40) for a period of three months (90 days), where the soil treated with different sewage sludge concentrations (0, 25, 50 and 75%). Physico-chemical characterization of sewage sludge showed that it was slightly acidic with significant concentrations of heavy metals (Cd, Cr, Cu, Pb and Zn), nutrients and mineral ions. Results showed that there were no apparent symptoms of toxicity on the morphology (leaf color, plant height and number of leaves) of the sludge amended vetiver plants. It has been observed that 25% sludge concentration has a favorable effect on the growth and photosynthetic pigments of plants. But at 50 and 75% sludge concentration, photosynthetic pigments such as chlorophylls and Pheophytin content showed a gradual decline with increase in sludge concentration while the carotenoid content was increased gradually. Even though compared to control plants sludge amendment increased the total wet biomass production in all the experimental plants with a gradual increase with increase in sludge concentration. This study proves that use of sewage sludge as an amendment will improve the growth and biomass production in vetiver plants up to 25% of the total soil. But even at this concentration carotenoid content was high and it may be due to defense mechanisms induced in response to heavy metal stress. The study, therefore, suggests that even though the sewage sludge is highly enriched with various nutrients, considering the heavy metal content, the fertilizer application of sewage sludge is dangerous, because the risk of environmental contamination is very high. The study pointed out that the vetiver plants growing in sludge amended area have potentially developed the defense strategy to combat against heavy metal toxicity. Therefore, the highly tolerant vetiver plants (Vetiveria zizanioides, L. Nash) may be used for phytoremediation purposes.

Physico-chemical Characterization of sewage sludge for thermochemical conversion processes

ABSTRACT Thermochemical conversion of sewage sludge has the advantage of being a ‘waste to energy option’ enabling sustainable waste disposal. Among the different methods of waste to energy conversion, the thermochemical route has many advantages over the other methods, such as high reduction in volume of feedstock and lower process time. However, sewage sludge is a non-conventional type of biomass whose characteristics and behavior under various operating conditions are quite different from the conventional type of biomasses because of its distinct composition. The various complex reactions occurring during the thermochemical conversion process depend on the physical and chemical properties of the feedstock. It is essential to have a proper understanding of the physical as well as chemical characteristics of feedstock for better processing and utilization. Accurate and reliable information about the feedstock is required for the design, operation, and optimization of the thermochemical conversion processes. Detailed studies on lignocellulosic biomasses are available in the literature, but only limited works are reported on non-lignocellulosic biomasses such as sewage sludge. This paper provides a comprehensive analysis of physical and chemical characteristics of sewage sludge influencing the thermochemical conversion processes. The results for furnace-dried sludge showed that the volatile matter (49.82% by weight), fixed carbon (7.46% by weight) and higher heating value of sewage sludge (12.26 MJ/kg) samples are comparable to that of conventional biomasses. However, higher moisture and ash contents, presence of heavy metals, sulfur, and acidic oxides revealed its distinct nature and indicated the need for additional primary processing and additives for its suitability in thermochemical conversion.

Characterization of Sewage Sludge and Food Waste-Based Biochar for Co-Firing in a Coal-Fired Power Plant: A Case Study in Korea

Biomass co-firing in coal-fired power plants has been widely accepted to reduce the environmental burden. In this study, food waste (FW) and sewage sludge (SS), which are the main types of municipal organic waste, were selected as solid refuse fuel (SRF). To compensate for the limitations of FW and SS, a mixture of FW and SS with varying ratios was processed using pyrolysis and desalination. The fuel properties such as the calorific value, chlorine content, alkali and alkaline earth metallic species (AAEMs) content, and heavy metal content were determined. The calorific values of all biochars were greater than 12.6 MJ/kg, which satisfies the national threshold of Bio-SRF in Korea. Chlorine and AAEMs contents exhibited clear trends for the FW ratio and pyrolysis temperature. Increasing concentrations of heavy metals were observed with increasing SS ratio and pyrolysis temperature. These results provide important insights into the practical application of municipal waste-based biochar in coal-fired plants, as well as the influence of mixing ratio and pyrolysis temperature.

Physical and chemical characterization of sewage sludge with different proportions of diatomaceous earth

ABSTRACT The use of residues for agricultural production is an alternative for the achievement of sustainability. When mixed with diatomaceous earth (DE) from biofuel filtration, sewage sludge (SS) plays an important role as soil conditioning agent. As a result, the objective of this work was to make a DE vermicompost at different proportions: 0; 7.53; 15.06; 22.59 and 30.12% v/v in relation to a SS pre-compost (PC) and gardening pruning residues. The experiment was carried out in 100-L containers in a randomized block design, with 5 treatments and 5 replications, in which Eisenia foetida earthworms were used in the pre-composting and vermicomposting processes. After four months, the physical characteristics of the vermicompost were analyzed. It was verified that the diatomaceous earth can be vermicomposted, even when soaked in biofuel oil, at amounts of up to 30.12% v/v, with no visible physical damage to earthworms and plants, and this proportion of DE reduced the concentration of nutrients, but improved the physical properties of the vermicompost, making it an excellent physical conditioner for use as a substrate of plants and fertilization of soils.

Thermophilic Dark Fermentation of Sewage Sludge for Biohydrogen Production - Influence of pH

<p>This study investigates the usability of sewage sludge, waste from a waste water treatment facility, at the stable thermophilic temperature and different pH conditions in the biohydrogen production by dark fermentation. Without the addition of a pure hydrogen producer and nutrient source, the effect of a different constant pH in the range of pH 4-9 on biohydrogen production using sewage sludge was compared with that of a different initial pH. It was understood from the results that biohydrogen production varies according to the characterization of sewage sludge. In the experiments, the lag time was insignificant (~2h). The maximum hydrogen production was achieved at pH 5 within the first 24-30 hours of fermentation (92894 mL m-3 H2). Therefore, it was determined that the higher digestion efficiencies of the sewage sludge were obtained at pH 5. In general, with the increase in methanogens in the medium, the hydrogen producing ability and hydrogen content of the sewage sludge gradually decreased. Hydrogen production at almost all the pH values after the third day was less than 1000 mL m-3.</p>

Agroecological Characterization of Sewage Sludge of Kharkov

The high rate of urbanization in the second half of the last century led to not only to the growth of urban population, but also as a result to increasing of amount of production wastes. During solving problems with municipal wastewater treatment inevitably the problem of disposal of sewage sludges is arised. Purpose is to provide agroecological substantiation of possibility of application of sewage sludge of Kharkov in the agricultural sector. Methods. Analytical, laboratory modeling and statistics. Results. Agrochemical and ecological assessment of sewage sludge of WWTP "Bezlutskiy" at Kharkov are given, compliance with the requirements of normative documents and substantiation of possibility of application of sewage sludge in the agricultural sector are established. Conclusions. It is found that sewage sludge contain sufficiently high amount of organic matter (more than 52 %) and major nutrients (total nitrogen and phosphorus) as well as acceptable concentrations of micronutrients and heavy metals according to the requirements of normative documents. Prospects of sewage sludge application as fertilizer is established.

Characterization of sewage sludge generated in Rio de Janeiro, Brazil, and perspectives for agricultural recycling

Sanitary sewage collection and treatment is a serious environmental problem in Brazilian cities, as well as the destination of solid waste resulting from this process, i.e. the sewage sludge, a substance rich in organic matter and nutrients, which is normally discarded in landfills. The aim of this study was to characterize the sewage sludge generated in four treatment stations in Rio de Janeiro State, Brazil and check if they meet the legal criteria of the National Environment Council (CONAMA), Resolution No. 375/2006. It also focused on analyzing the perspectives for its agricultural recycling based on the potential demand for main agricultural crops grown in Rio de Janeiro State. Samples from eight sewage sludge lots from four treatment stations located in the metropolitan area of Rio de Janeiro were analyzed. These stations receive and treat only domestic sewage by activated sludge system. For chemical and biological characterization of these lots, representative samples were collected and analyzed according to parameters of CONAMA Resolution No. 375/2006. In order to analyze the perspectives of agricultural recycling of sewage sludge in Rio de Janeiro State, 10 crops with the largest cultivated area in the state were surveyed and analyzed which of them are apt to receive sewage sludge as fertilizer and/or soil amendment. To determine the potential demand for sewage sludge in agriculture, the area occupied by these crops were multiplied by each fertilizer recommendation considering the sewage sludge as fertilizer. The analyzed sludge presented a high content of nutrients and organic matter and was included in the parameters of heavy metals, pathogenic agents, and bacteriological indicators stipulated by CONAMA Resolution No. 375/2006. The agricultural panorama of Rio de Janeiro State is favorable for agricultural recycling of sewage sludge since there is a great potential demand for this residue and, among the 10 agricultural crops with the largest cultivated area in the state, sludge can be used as fertilizer or soil amendment in eight of them. The implementation of a State Sewage Sludge Recycling Program could dispose of this material in a more sustainable way, as well as improve the quality of agricultural soils and reduce costs with chemical fertilizers, bringing positive results for sanitation companies and producers.

Characterization of sewage sludge generated in Rio de Janeiro, Brazil, and perspectives for agricultural recycling

Sanitary sewage collection and treatment is a serious environmental problem in Brazilian cities, as well as the destination of solid waste resulting from this process, i.e. the sewage sludge, a substance rich in organic matter and nutrients, which is normally discarded in landfills. The aim of this study was to characterize the sewage sludge generated in four treatment stations in Rio de Janeiro State, Brazil and check if they meet the legal criteria of the National Environment Council (CONAMA), Resolution No. 375/2006. It also focused on analyzing the perspectives for its agricultural recycling based on the potential demand for main agricultural crops grown in Rio de Janeiro State. Samples from eight sewage sludge lots from four treatment stations located in the metropolitan area of Rio de Janeiro were analyzed. These stations receive and treat only domestic sewage by activated sludge system. For chemical and biological characterization of these lots, representative samples were collected and analyzed according to parameters of CONAMA Resolution No. 375/2006. In order to analyze the perspectives of agricultural recycling of sewage sludge in Rio de Janeiro State, 10 crops with the largest cultivated area in the state were surveyed and analyzed which of them are apt to receive sewage sludge as fertilizer and/or soil amendment. To determine the potential demand for sewage sludge in agriculture, the area occupied by these crops were multiplied by each fertilizer recommendation considering the sewage sludge as fertilizer. The analyzed sludge presented a high content of nutrients and organic matter and was included in the parameters of heavy metals, pathogenic agents, and bacteriological indicators stipulated by CONAMA Resolution No. 375/2006. The agricultural panorama of Rio de Janeiro State is favorable for agricultural recycling of sewage sludge since there is a great potential demand for this residue and, among the 10 agricultural crops with the largest cultivated area in the state, sludge can be used as fertilizer or soil amendment in eight of them. The implementation of a State Sewage Sludge Recycling Program could dispose of this material in a more sustainable way, as well as improve the quality of agricultural soils and reduce costs with chemical fertilizers, bringing positive results for sanitation companies and producers.

Mixture of biomass to energy reuse

Focusing on the reuse of the energy and aiming at the thermal and kinetic characterization of sewage sludge and its mixture, with pruning residues (50 mass%), the thermogravimetry was used. The kinetic study was elaborated from the local isoconversional integral method in heating rates 10.0, 20.0 and 30.0 °C min−1 at a temperature ranging from 219 to 386 °C at nitrogen atmosphere, in a flow of 100 mL min−1. The average activation energy of sewage sludge sample revealed the value of 219 kJ mol−1 and that of the mixture 161 kJ mol−1, supporting the incorporation of pruning residues in the sewage sludge. During the degradation process, a remarkable increase in activation energy was noticed that ranged from 20 to 70% conversion in the sewage sludge sample, and regarding the mixture, an almost linear behavior was observed during the decomposition reaction. There was no evidence of kinetic compensation effect in the performed studies. The evaluation of the thermal characteristics, as well as the kinetic study of the degradation of sewage sludge and its mixture with pruning residues, can lead to important insights and contribute to a better use of energy regarding the environmental issues.

Gaseous emissions from sewage sludge combustion in a moving bed combustor

Substantial increase in sewage sludge generation in recent years requires suitable destination for this residue. This study evaluated the gaseous emissions generated during combustion of an aerobic sewage sludge in a pilot scale moving bed reactor. To utilize the heat generated during combustion, the exhaust gas was applied to the raw sludge drying process. The gaseous emissions were analyzed both after the combustion and drying steps. The results of the sewage sludge characterization showed the energy potential of this residue (LHV equal to 14.5MJkg−1, db) and low concentration of metals, polycyclic aromatic hydrocarbons (PAH), polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF). The concentration of CO, NOx, BTEX (benzene, toluene, ethylbenzene and xylenes) emitted from the sludge combustion process were lower than the legal limits. The overall sludge combustion and drying process showed low emissions of PCDD/PCDF (0.42ng I-TEQNm−3). BTEX and PAH emissions were not detected. Even with the high nitrogen concentration in the raw feed (5.88% db), the sludge combustion process presented NOx emissions below the legal limit, which results from the combination of appropriate feed rate (A/F ratio), excess air, and mainly the low temperature kept inside the combustion chamber. It was found that the level of CO emissions from the overall sludge process depends on the dryer operating conditions, such as the oxygen content and the drying temperature, which have to be controlled throughout the process in order to achieve low CO levels. The aerobic sewage sludge combustion process generated high SO2 concentration due to the high sulfur content (0.67wt%, db) and low calcium concentration (22.99gkg−1) found in the sludge. The high concentration of SO2 in the flue gas (4776.77mgNm−3) is the main factor inhibiting PCDD/PCDF formation. Further changes are needed in the pilot plant scheme to reduce SO2 and particulate matter emissions, such as the installation of exhaust gas-cleaning systems. According to previous studies, the efficient operation of such cleaning systems is also effective for metals emission control, which makes the combustion of sewage sludge a feasible treatment method from both energetic and environmental perspectives.

Physicochemical characterization of sewage sludge and green waste for agricultural utilization

In order to valorize the organic wastes, a mixture composed of 60 kg of thick sewage sludge from a wastewater treatment plant, 30 kg of green wastes (made of 10 kg straw of wheat, 10 kg manure farm wastes, and 10 kg of dead leaves), and 10 kg of wood chips was prepared. The organic wastes were mixed and put into a wooden cubic composter having a volume of 1.5 m3. Physicochemical analyses were made every 30 days for five months. The results of the analyses showed that the obtained compost had good physicochemical quality and can be used as an organic fertilizer. The main characteristics of this compost were distinguished by its pH from 7.4 to 7.8, with a ratio of organic matter of 40–42%. During composting, the humification process led to an increase in humic acids from 29.5 to 39.1 mg g−1, a decrease in fulvic acids from 32.1 to 10.9 mg g−1, and a global decomposition of hemicellulose, cellulose, and lignin. The obtained results show that a period of 150 days of composting gave a C/N ratio of 15.4. The total metal content in the final compost was much lower than the standard toxic levels for composts to be used as good soil fertilizers. The germination index for the two plants Cicer arietinum and Hordeum vulgare was 93% after the same period of composting, showing that the final compost was not phytotoxic. The study showed the possibility of valorization of the compost and its possible use in the domain of agriculture.

CHARACTERIZATION OF SOIL ADDITIVE DERIVED FROM SEWAGE SLUDGE

Abstract The aim of the present work is to characterize the soil additive derived from sewage sludge as potentially economically acceptable material for agricultural production as well as for soil and environment protection. The soil additive consisting of sewage sludge obtained from the wastewater treatment plant Pannon-Víz Zrt. (Győr, Hungary) and agricultural byproducts represented by wastes from grain mill industry and crushed corn cobs was prepared using the low-capacity granulator equipment constructed by Energy Agency Public Nonprofit Ltd. (Hungary). The characterization of sewage sludge as primary composite and prepared soil additive includes the determination of physico-chemical parameters such as pH determined in suspension with distilled water, 0.01 mol/dm3 CaCl2 or 1 mol/dm3 KCl solutions, pHzpc predicted by potentiometric titration and ProtoFit software, water holding capacity (WHC), cationexchange capacity (CEC) and total organic carbon (TOC). The elemental analysis by X-ray fluorescence spectrometry revealed that sewage sludge as well as prepared soil additive contain significant amount of Zn and Cu as important microelements in plant nutrition. Also, it was found that prepared soil additive represents the considerable source of a significant proportion, strong bound and in this way gradually released microelements. Obtained results suggest on the application potential of prepared soil additive in agricultural production as well as in remediation and reclamation of contaminated or degraded soil.

Seeking Potential Anomalous Levels of Exposure to PCDD/Fs and PCBs through Sewage Sludge Characterization

An approach to detect anomalies in the exposure to Persistent Organic Pollutants (POPs) throughout the food chain is presented. The proposed method is useful also for preventing soil contamination by POPs that would require a remediation intervention. A steel making plant and its surrounding area were selected as a case-study. To investigate the possible effects of the plant on the settled population, sewage sludge samples from four wastewater treatment plants (WWTPs) were taken: one of these was chosen as reference for the population exposed to the emissions of the mill; the remaining three plants were chosen to provide background information about the POP content in sludge. No clear anomalies in dioxins (PCDD/Fs) were detected for the potentially exposed population. In terms of Polychlorinated Biphenyls (PCBs), the steel plant-influenced WWTP showed a total concentration between 2.7 and 4.8-time higher than the other plants; in terms of equivalent toxicity, only slightly higher concentrations were found for the steel plant-influenced WWTP. Therefore, if considering acceptable the daily intake from the diet of the unexposed population, the absence of a dioxin and dioxin-like emergency in the area of the mill is demonstrated. This method represents an innovative and technically simple tool to assess situations of permanent exposure to POP levels that are higher than the background.

Pyrolysis and gasification characterization of sewage sludge for high quality gas and char production

A study on pyrolysis, steam gasification, and carbonization-activation was conducted to produce energy and resource from waste sewage sludge. Carbonization-activation is a sequential process of pyrolysis and steam gasification. The experiment was conducted with a batch-type fixed bed reactor. A comparative analysis on the formation characteristics of products, such as gas, tar, and char, was conducted to evaluate the three cases. For sludge char, carbonization-activation showed the largest amount of porosity in the char, and its specific surface area was 80.28 m2/g with an average pore diameter of 6.229 nm. The best adsorption ability of benzene, a light tar, was 175 mg/g. For the producer gas, steam gasification obtained the largest amount of 20.1 L. Similarly, carbonization-activation showed a large value of 16.6 L. Hydrogen and carbon monoxide concentrations were higher in the producer gas due to steam reforming compared with carbonization-activation. Energy yields were 209 kJ and 226 kJ for steam gasification and carbonization-activation, respectively. The amount of tar formation did not show a significant difference, but the largest one was found in steam gasification. The gravimetric tar amount for steam gasification was 23.5 g/Nm3. However, the selected light tar displayed the lowest concentration for the carbonization-activation. Such concentrations were 2.79 g/Nm3, 0.75 g/Nm3, 0.14 g/Nm3, and 0.14 g/Nm3 for benzene, naphthalene, anthracene, and pyrene, respectively. Therefore, carbonization-activation was found to be the most effective process for producing high quality sludge char and producer gas for utilizing waste sludge into renewable energy and resources.