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Nicky Eshtiaghi - One of the best experts on this subject based on the ideXlab platform.

  • Impact of primary and secondary Sludge mixing ratio on the apparent viscosity of blends of primary, secondary and Digested Sludge
    2014
    Co-Authors: Flora Markis, J.c. Baudez, Paul Slatter, Rajarathinam Parthasarathy, Nicky Eshtiaghi
    Abstract:

    Predicting the flow behaviour (i.e. apparent viscosity) of Sludge is important in the design optimization and operation of various components of the waste water treatment process such as pumps, heat exchangers and anaerobic digesters. This study investigates the impact of primary to secondary Sludge mixing ratio on the apparent viscosity of blends of primary, secondary and Digested Sludge. Any changes prior to and after mixing can be applied to anaerobic digester performance, most notably mixing efficiency, whereby changes in the apparent viscosity have a direct impact on the formation of dead zones (i.e. inactive volume) which leads to changes in the energy requirements necessary for efficient digester mixing. Samples of inlet Sludge feeds - primary and secondary and anaerobic Digested Sludge - were obtained from the Mount Martha treatment plant in Victoria. An equal volume of primary Sludge (4.2% TS) was added to secondary Sludge (4.2% TS); Digested Sludge (4.2% TS) was then added to this Sludge mixture at different volume ratios of primary and secondary Sludge to Digested Sludge (0-1). Successive creep tests were performed using a stress controlled rheometer after 150s preshear and rest for each Sludge sample allowing for the flow curves of each blend to be extracted from the creep data. A master curve was developed based on the flow curves of blends of primary and secondary mixture to Digested Sludge. The dimensionless form of the Herschel-Bulkley model was fitted to experimental data.

  • An investigation on rheological behaviour of thermally treated Digested Sludge: Dependency on solid concentration
    2014
    Co-Authors: Ehsan Farno, J.c. Baudez, Rajarathinam Parthasarathy, Nicky Eshtiaghi
    Abstract:

    This study investigated the effect of temperature and duration of heat treatment on rheological properties of different concentration of Digested Sludge. The flow curve and the yield stress of 2%, 3% and 3.5% Digested Sludge have been measured before and during heat treatment at different temperatures between 20 and 80 C for different heating duration of 1, 15 and 30min. The effect of thermal history on rheology of Sludge was then studied after cooling back Sludge to 20degreesC (thermal history at 50, 60, 70 and 80degreesC). In addition, the effect of temperature and thermal history on solubilized chemical oxygen demand (COD) for Sludge with different solid concentration was also investigated to prove the composition change of Sludge during the heat treatment. The result showed that the irreversible effect of temperature was more evident at higher temperatures and concentrations. At higher concentrations (3% and 3.5%), by increasing the temperature, the yield stress decreased after an initial increase while for 2% Sludge yield stress consistently decreased with increasing temperature and showed a linear relationship with decreasing particulate COD. The yield stress followed a great agreement with an exponential decreasing function of temperature and the temperature of thermal history.

  • Rheological characterisation of thermally-treated anaerobic Digested Sludge: Impact of temperature and thermal history
    Water Research, 2014
    Co-Authors: Ehsan Farno, Rajarathinam Parthasarathy, J.c. Baudez, Nicky Eshtiaghi
    Abstract:

    This study investigated the partially irreversible effect of thermal treatment on the rheology of Digested Sludge when it was subjected to temperature change between 20°C and 80°C and then cooled down to 20°C. The yield stress, infinite viscosity and liquor viscosity of Sludge were measured at 20°C for different thermal histories and were compared to the evolution of the solubilised chemical oxygen demand (COD) of Sludge liquor. The results showed that thermal history irreversibly affects Sludge rheology as the yield stress of Sludge which was heated to 80°C then cooled down to 20°C was 68% lower than the initial yield stress at 20°C. This decrease was due to the irreversible solubilisation of solid matter during heating as underlined by soluble COD data which did not reach its original level after thermal treatment. Measured soluble COD of Sludge which was heated and cooled down was much higher than the soluble COD of initial Sludge. We found a proportionality of the increase of soluble COD with the decrease of the yield stress as well as increase of infinite viscosity.

  • Effect of thermal history on municipal Digested Sludge rheology: Experimental and modeling
    2013
    Co-Authors: Ehsan Farno, J.c. Baudez, Rajarathinam Parthasarathy, Nicky Eshtiaghi
    Abstract:

    The rheological characteristics of Digested Sludge are severely temperature dependent. An effect of temperature on rheological properties of Digested Sludge is partially irreversible. In this paper, the effects of temperature change and thermal history on viscosity of Digested Sludge were studied using a stress-controlled rheometer which was connected to a temperature controlled water bath. Digested municipal Sludge were collected from one of Melbourne wastewater treatment plants and subjected to change of temperature from 20-80 C. In addition, the effect of temperature on the Sludge composition was studied by measuring solubilized chemical oxygen demand (COD) in Sludge liquor. The Herschel-Bulkley equation was used to model the data. The yield stress and the apparent viscosity were measured and compared at different temperatures. The results showed that by changing the temperature, the Sludge becomes more fluid; however, the rheological characteristics of Sludge including yield stress and apparent viscosity do not come back to their original values after cooling the heated Sludge. The solubilized COD showed a composition change after cooling the heated Sludge which confirmed the irreversible change in the rheological characteristics of Digested Sludge.

  • Rheological behaviour of anaerobic Digested Sludge: impact of concentration and temperature
    2013
    Co-Authors: Nicky Eshtiaghi, J.c. Baudez, Paul Slatter
    Abstract:

    Renewable energy is one of the cornerstones of sustainable energy. Biogas from the anaerobic digestion of organic waste materials can provide a clean, easily controlled source of renewable energy, replacing firewood and/or fossil fuels. In order to maintain the requisite constant homogeneous conditions within digesters, operating conditions must be regulated according to the rheological characteristics of the Sludge. An accurate estimate of Sludge rheological properties is required for the design and efficient operation of Sludge pumping and digester mixing. In this paper, we have determined the rheological behaviour of Digested Sludge at different concentrations and different temperatures, and highlighted common features. At low shear stress, Digested Sludge behaves as a viscoelastic solid, but shear banding can occur which modifies the apparent behaviour. At very high shear stress, the behaviour fits well with the Bingham model. Finally, we show that the rheological behaviour of Digested Sludge is qualitatively the same at different solids concentrations and temperatures, and depends only on the yield stress and Bingham viscosity: by normalising the shear stress with the yield stress and the shear rate with the yield stress divided by the Bingham viscosity, a master curve was obtained independent of both temperature and concentration. These two parameters (Yield stress and Bingham Viscosity) increase when the solid concentration increases but decrease when the temperature increases. Furthermore, we show that the rheological behaviour is irreversibly altered by the thermal history. Dissolution of some of the solids may cause a decrease of the yield stress and an increase of the Bingham viscosity. This result suggests that the solid characteristics decreases with temperature and the usual laws used to describe the thermal evolution of the rheological behaviour of fluids are no longer valid with anaerobic Digested Sludge.

Paul Slatter - One of the best experts on this subject based on the ideXlab platform.

  • Impact of primary and secondary Sludge mixing ratio on the apparent viscosity of blends of primary, secondary and Digested Sludge
    2014
    Co-Authors: Flora Markis, J.c. Baudez, Paul Slatter, Rajarathinam Parthasarathy, Nicky Eshtiaghi
    Abstract:

    Predicting the flow behaviour (i.e. apparent viscosity) of Sludge is important in the design optimization and operation of various components of the waste water treatment process such as pumps, heat exchangers and anaerobic digesters. This study investigates the impact of primary to secondary Sludge mixing ratio on the apparent viscosity of blends of primary, secondary and Digested Sludge. Any changes prior to and after mixing can be applied to anaerobic digester performance, most notably mixing efficiency, whereby changes in the apparent viscosity have a direct impact on the formation of dead zones (i.e. inactive volume) which leads to changes in the energy requirements necessary for efficient digester mixing. Samples of inlet Sludge feeds - primary and secondary and anaerobic Digested Sludge - were obtained from the Mount Martha treatment plant in Victoria. An equal volume of primary Sludge (4.2% TS) was added to secondary Sludge (4.2% TS); Digested Sludge (4.2% TS) was then added to this Sludge mixture at different volume ratios of primary and secondary Sludge to Digested Sludge (0-1). Successive creep tests were performed using a stress controlled rheometer after 150s preshear and rest for each Sludge sample allowing for the flow curves of each blend to be extracted from the creep data. A master curve was developed based on the flow curves of blends of primary and secondary mixture to Digested Sludge. The dimensionless form of the Herschel-Bulkley model was fitted to experimental data.

  • Rheological behaviour of anaerobic Digested Sludge: impact of concentration and temperature
    2013
    Co-Authors: Nicky Eshtiaghi, J.c. Baudez, Paul Slatter
    Abstract:

    Renewable energy is one of the cornerstones of sustainable energy. Biogas from the anaerobic digestion of organic waste materials can provide a clean, easily controlled source of renewable energy, replacing firewood and/or fossil fuels. In order to maintain the requisite constant homogeneous conditions within digesters, operating conditions must be regulated according to the rheological characteristics of the Sludge. An accurate estimate of Sludge rheological properties is required for the design and efficient operation of Sludge pumping and digester mixing. In this paper, we have determined the rheological behaviour of Digested Sludge at different concentrations and different temperatures, and highlighted common features. At low shear stress, Digested Sludge behaves as a viscoelastic solid, but shear banding can occur which modifies the apparent behaviour. At very high shear stress, the behaviour fits well with the Bingham model. Finally, we show that the rheological behaviour of Digested Sludge is qualitatively the same at different solids concentrations and temperatures, and depends only on the yield stress and Bingham viscosity: by normalising the shear stress with the yield stress and the shear rate with the yield stress divided by the Bingham viscosity, a master curve was obtained independent of both temperature and concentration. These two parameters (Yield stress and Bingham Viscosity) increase when the solid concentration increases but decrease when the temperature increases. Furthermore, we show that the rheological behaviour is irreversibly altered by the thermal history. Dissolution of some of the solids may cause a decrease of the yield stress and an increase of the Bingham viscosity. This result suggests that the solid characteristics decreases with temperature and the usual laws used to describe the thermal evolution of the rheological behaviour of fluids are no longer valid with anaerobic Digested Sludge.

  • The impact of temperature on the rheological behaviour of anaerobic Digested Sludge
    Chemical Engineering Journal, 2012
    Co-Authors: J.c. Baudez, Paul Slatter, Nicky Eshtiaghi
    Abstract:

    The rheological properties of municipal anaerobic Digested Sludge rheology are temperature dependent. In this paper, we show that both solid and liquid characteristics decrease with temperature. We also show that the yield stress and the high shear (Bingham) viscosity are the two key parameters determining the rheological behaviour. By normalising the shear stress with the yield stress and the shear rate with the yield stress divided by the Bingham viscosity, a master curve was obtained, independent of both temperature and concentration. We also show that the rheological behaviour is irreversibly altered by the thermal history. Dissolution of some of the solids may cause a decrease of the yield stress and an increase of the Bingham viscosity. This result suggests that the usual laws used to describe the thermal evolution of the rheological behaviour of fluids are no longer valid with anaerobic Digested Sludge. Finally, the impact of temperature and thermal history have to be taken into account for the design of engineering hydrodynamic processes such as mixing and pumping.

  • The viscoelastic behaviour of raw and anaerobic Digested Sludge: strong similarities with soft-glassy materials.
    Water research, 2012
    Co-Authors: J.c. Baudez, Nicky Eshtiaghi, Rahul K. Gupta, Paul Slatter
    Abstract:

    Over the last few decades, municipal and industrial wastewater treatment activities have been confronted with a dramatically increasing flow of sewage Sludge. To improve treatment efficiency, process and material parameters are needed but engineers are dealing with vast quantities of fundamentally poorly understood and unpredictable material Thus, accurate prediction of critically important, but analytically elusive process parameters is unattainable and is a matter of grave concern. Because engineers need reliable flow properties to simulate the process, this work is an attempt to approach Sludge rheological behaviour with well-known materials which have similar characteristics. Sludge liquid-like behaviour is already well documented so, we have focused mainly on the solid-like behaviour of both raw and Digested Sludge by performing oscillatory measurements in the linear and non-linear regimes. We have shown that the viscoelastic behaviour of Sludge presents strong similarities with soft-glassy materials but differences can be observed between raw and Digested Sludge. Finally, we confirm that colloidal glasses and emulsions may be used to model the rheological behaviour of raw and anaerobic Digested Sludge.

  • The rheological behaviour of anaerobic Digested Sludge
    Water research, 2011
    Co-Authors: J.c. Baudez, Flora Markis, Nicky Eshtiaghi, Paul Slatter
    Abstract:

    Producing biogas energy from the anaerobic digestion of wastewater Sludge is one of the most challenging tasks facing engineers, because they are dealing with vast quantities of fundamentally scientifically poorly understood and unpredictable materials; while digesters need constant flow properties to operate efficiently. An accurate estimate of Sludge rheological properties is required for the design and efficient operation of digestion, including mixing and pumping. In this paper, we have determined the rheological behaviour of Digested Sludge at different concentrations, and highlighted common features. At low shear stress, Digested Sludge behaves as a linear viscoelastic solid, but shear banding can occur and modify the apparent behaviour. At very high shear stress, the behaviour fits well to the Bingham model. Finally, we show that the rheological behaviour of Digested Sludge is qualitatively the same at different solids concentrations, and depends only on the yield stress and Bingham viscosity, both parameters being closely linked to the solids concentration.

J.c. Baudez - One of the best experts on this subject based on the ideXlab platform.

  • An investigation on rheological behaviour of thermally treated Digested Sludge: Dependency on solid concentration
    2014
    Co-Authors: Ehsan Farno, J.c. Baudez, Rajarathinam Parthasarathy, Nicky Eshtiaghi
    Abstract:

    This study investigated the effect of temperature and duration of heat treatment on rheological properties of different concentration of Digested Sludge. The flow curve and the yield stress of 2%, 3% and 3.5% Digested Sludge have been measured before and during heat treatment at different temperatures between 20 and 80 C for different heating duration of 1, 15 and 30min. The effect of thermal history on rheology of Sludge was then studied after cooling back Sludge to 20degreesC (thermal history at 50, 60, 70 and 80degreesC). In addition, the effect of temperature and thermal history on solubilized chemical oxygen demand (COD) for Sludge with different solid concentration was also investigated to prove the composition change of Sludge during the heat treatment. The result showed that the irreversible effect of temperature was more evident at higher temperatures and concentrations. At higher concentrations (3% and 3.5%), by increasing the temperature, the yield stress decreased after an initial increase while for 2% Sludge yield stress consistently decreased with increasing temperature and showed a linear relationship with decreasing particulate COD. The yield stress followed a great agreement with an exponential decreasing function of temperature and the temperature of thermal history.

  • Impact of primary and secondary Sludge mixing ratio on the apparent viscosity of blends of primary, secondary and Digested Sludge
    2014
    Co-Authors: Flora Markis, J.c. Baudez, Paul Slatter, Rajarathinam Parthasarathy, Nicky Eshtiaghi
    Abstract:

    Predicting the flow behaviour (i.e. apparent viscosity) of Sludge is important in the design optimization and operation of various components of the waste water treatment process such as pumps, heat exchangers and anaerobic digesters. This study investigates the impact of primary to secondary Sludge mixing ratio on the apparent viscosity of blends of primary, secondary and Digested Sludge. Any changes prior to and after mixing can be applied to anaerobic digester performance, most notably mixing efficiency, whereby changes in the apparent viscosity have a direct impact on the formation of dead zones (i.e. inactive volume) which leads to changes in the energy requirements necessary for efficient digester mixing. Samples of inlet Sludge feeds - primary and secondary and anaerobic Digested Sludge - were obtained from the Mount Martha treatment plant in Victoria. An equal volume of primary Sludge (4.2% TS) was added to secondary Sludge (4.2% TS); Digested Sludge (4.2% TS) was then added to this Sludge mixture at different volume ratios of primary and secondary Sludge to Digested Sludge (0-1). Successive creep tests were performed using a stress controlled rheometer after 150s preshear and rest for each Sludge sample allowing for the flow curves of each blend to be extracted from the creep data. A master curve was developed based on the flow curves of blends of primary and secondary mixture to Digested Sludge. The dimensionless form of the Herschel-Bulkley model was fitted to experimental data.

  • Effect of thermal history on municipal Digested Sludge rheology: Experimental and modeling
    2013
    Co-Authors: Ehsan Farno, J.c. Baudez, Rajarathinam Parthasarathy, Nicky Eshtiaghi
    Abstract:

    The rheological characteristics of Digested Sludge are severely temperature dependent. An effect of temperature on rheological properties of Digested Sludge is partially irreversible. In this paper, the effects of temperature change and thermal history on viscosity of Digested Sludge were studied using a stress-controlled rheometer which was connected to a temperature controlled water bath. Digested municipal Sludge were collected from one of Melbourne wastewater treatment plants and subjected to change of temperature from 20-80 C. In addition, the effect of temperature on the Sludge composition was studied by measuring solubilized chemical oxygen demand (COD) in Sludge liquor. The Herschel-Bulkley equation was used to model the data. The yield stress and the apparent viscosity were measured and compared at different temperatures. The results showed that by changing the temperature, the Sludge becomes more fluid; however, the rheological characteristics of Sludge including yield stress and apparent viscosity do not come back to their original values after cooling the heated Sludge. The solubilized COD showed a composition change after cooling the heated Sludge which confirmed the irreversible change in the rheological characteristics of Digested Sludge.

  • Rheological behaviour of anaerobic Digested Sludge: impact of concentration and temperature
    2013
    Co-Authors: Nicky Eshtiaghi, J.c. Baudez, Paul Slatter
    Abstract:

    Renewable energy is one of the cornerstones of sustainable energy. Biogas from the anaerobic digestion of organic waste materials can provide a clean, easily controlled source of renewable energy, replacing firewood and/or fossil fuels. In order to maintain the requisite constant homogeneous conditions within digesters, operating conditions must be regulated according to the rheological characteristics of the Sludge. An accurate estimate of Sludge rheological properties is required for the design and efficient operation of Sludge pumping and digester mixing. In this paper, we have determined the rheological behaviour of Digested Sludge at different concentrations and different temperatures, and highlighted common features. At low shear stress, Digested Sludge behaves as a viscoelastic solid, but shear banding can occur which modifies the apparent behaviour. At very high shear stress, the behaviour fits well with the Bingham model. Finally, we show that the rheological behaviour of Digested Sludge is qualitatively the same at different solids concentrations and temperatures, and depends only on the yield stress and Bingham viscosity: by normalising the shear stress with the yield stress and the shear rate with the yield stress divided by the Bingham viscosity, a master curve was obtained independent of both temperature and concentration. These two parameters (Yield stress and Bingham Viscosity) increase when the solid concentration increases but decrease when the temperature increases. Furthermore, we show that the rheological behaviour is irreversibly altered by the thermal history. Dissolution of some of the solids may cause a decrease of the yield stress and an increase of the Bingham viscosity. This result suggests that the solid characteristics decreases with temperature and the usual laws used to describe the thermal evolution of the rheological behaviour of fluids are no longer valid with anaerobic Digested Sludge.

  • The impact of temperature on the rheological behaviour of anaerobic Digested Sludge
    Chemical Engineering Journal, 2012
    Co-Authors: J.c. Baudez, Paul Slatter, Nicky Eshtiaghi
    Abstract:

    The rheological properties of municipal anaerobic Digested Sludge rheology are temperature dependent. In this paper, we show that both solid and liquid characteristics decrease with temperature. We also show that the yield stress and the high shear (Bingham) viscosity are the two key parameters determining the rheological behaviour. By normalising the shear stress with the yield stress and the shear rate with the yield stress divided by the Bingham viscosity, a master curve was obtained, independent of both temperature and concentration. We also show that the rheological behaviour is irreversibly altered by the thermal history. Dissolution of some of the solids may cause a decrease of the yield stress and an increase of the Bingham viscosity. This result suggests that the usual laws used to describe the thermal evolution of the rheological behaviour of fluids are no longer valid with anaerobic Digested Sludge. Finally, the impact of temperature and thermal history have to be taken into account for the design of engineering hydrodynamic processes such as mixing and pumping.

Qilin Wang - One of the best experts on this subject based on the ideXlab platform.

  • Persulfate and zero valent iron combined conditioning as a sustainable technique for enhancing dewaterability of aerobically Digested Sludge
    Chemosphere, 2019
    Co-Authors: Yan Xiaofang, Xiaohu Dai, Jing Sun, Xueming Chen, Lai Peng, Wei Wei, Dongbo Wang, Shun Mao, Qilin Wang
    Abstract:

    Aerobic digestion followed by dewatering is a widely applied method for Sludge stabilization and reduction in decentralized wastewater treatment plants. It is important to enhance the Sludge dewaterability of the aerobically Digested Sludge due to its considerable impact on cost of Sludge disposal and management. In this study, an innovative technique is developed for improving the dewaterability of aerobically Digested Sludge by combined conditioning with persulfate (PS) and zero valent iron (ZVI). The results demonstrated that the dewaterability of aerobically Digested Sludge could be significantly enhanced with the PS and ZVI dosage in the range of 0–0.5 g/gTS and 0–0.4 g/gTS, respectively. The highest improvement was achieved at 0.05 g ZVI/g TS with 0.1 g PS/g TS, and the capillary suction time was reduced by ∼80%. The extracellular polymeric substances (EPS) characterization revealed that the combined PS-ZVI treatment could largely reduce proteins, polysaccharides and humic acids-like compounds in the tightly bounded EPS of the aerobically Digested Sludge, leading to bound water releasing from Sludge flocs. The recovery of the ZVI particles could reach around 45%–80% after the treatment, further proved the sustainability of the approach. The proposed PS-ZVI conditioning would not have significant impact on the final choice of Sludge disposal and the mainstream wastewater treatment. However, plant-scale test are still required for better assessing the proposed technique.

  • improving dewaterability of anaerobically Digested Sludge by combination of persulfate and zero valent iron
    Chemical Engineering Journal, 2016
    Co-Authors: Kang Song, Dongbo Wang, Peng Liu, Xu Zhou, Yiqi Liu, Guojun Xie, Tingting Zhang, Chunshuang Liu, Beibei Zhou, Qilin Wang
    Abstract:

    Abstract Biological wastewater treatment process generates large amounts of Sludge, the treatment and disposal of which incur substantial costs. Enhancement of Sludge dewaterability is of great importance for decreasing the Sludge disposal cost in a wastewater treatment plant (WWTP). This study proposes an innovative conditioning approach to improve the dewaterability of the anaerobically Digested Sludge (ADS) collected from a full-scale WWTP for the first time. The ADS dewaterability was significantly improved in the presence of persulfate (0–1.0 g/g TS; TS: total solids) and zero valent iron (ZVI) (0–4.0 g/g TS) at neutral pH. The largest improvement of ADS dewaterability was obtained at 2.0 g ZVI/g TS and 0.5 g persulfate/g TS, under which the capillary suction time (an indicator of Sludge dewaterability) was decreased by approximately 90%. Compared with the traditional Fenton process (Fe2+ + H2O2 at pH 2.0), economic analysis indicated that the ZVI–persulfate conditioning process is more economically attractive for enhancing ADS dewaterability.

Souhila Poncin - One of the best experts on this subject based on the ideXlab platform.

  • Rheological characterization of Digested Sludge by solid sphere impact.
    Bioresource technology, 2016
    Co-Authors: Jiankai Jiang, Souhila Poncin
    Abstract:

    Abstract An impact method was applied to investigate the rheological characteristics of Digested Sludge and reveal its transient dynamics. A high-speed camera allowed visualizing the dynamic impact process and observing interaction between impacting sphere and targeted Sludge. A damping oscillation was observed after the impact. The crater diameter followed an exponential function, while the crater depth varied as a logarithmic function of both sphere diameter and free fall height. Furthermore, the viscosity and elasticity of Digested Sludge were evaluated by establishing a simplified impact drag force model. The impact elastic modulus was consistent with the Young’s modulus measured by a penetrometer. The impact viscosity was reasonable as the estimated impact shear stress was greater than the yield stress of Digested Sludge resulting in the formation of crater. The impact method offers an alternative way to reveal the viscoelasticity of Digested Sludge through a dynamic process.

  • Rheological characteristics of highly concentrated anaerobic Digested Sludge
    Biochemical Engineering Journal, 2014
    Co-Authors: Jiankai Jiang, Souhila Poncin
    Abstract:

    Highly concentrated anaerobic Sludge digestion is a favorable way to treat a considerable quantity of sewage Sludge and recover biogas from both environmental and energetic point of view. For enhancing mass transfer and ensuring efficient anaerobic digestion, pumping and mixing are crucial operations which are directly conditioned by the rheology of Sludge. The present work aims at studying the rheological characteristics of highly concentrated anaerobic Digested Sludge with TS (total solid) content more than 8%. The dependence on both TS content and temperature is investigated, respectively, in dynamic and flow measurements. The results show a shear-thinning behavior with a yield stress under flow measurements and a viscoelastic property in dynamic measurements, comparable to a pasty material. The Herschel-Bulkley model can describe these experimental results and a master curve is then proposed. In addition, the yield stress as well as cohesion energy increase with TS content following a power-law. The effect of temperature is relatively smaller, as a consequence of pronounced internal interactions strengthening the interior structure after the digestion, in the form of networks and steric linking.