Structural model to study the influence of thermal treatment on the thixotropic behaviour of waste activated sludge

Ruiz-Hernando, Maria; Labanda, Jordi; Llorens, Joan

doi:10.1016/j.cej.2014.09.097

Cited by 31 publications

(4 citation statements)

References 39 publications

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“…For instance, fouling in membrane bioreactors is greatly affected by the protein and carbohydrates contents as well as their molecular sizes (Judd, 2011). In a similar way, the composition of soluble biopolymers in the medium also has effect on its viscosity, the settleability and wettability of the remaining solids or the biodegradability and chemical properties of the supernatant (Liu et al, 2013;Martins et al, 2011;Ruiz-Hernando et al, 2015;Wang et al, 2014;Zhang et al, 2015). Moreover, taking into account that sewage sludge consists of 61% proteins and 11% carbohydrates (Chen et al, 2007), this gives rise to the following question: is it possible to obtain valuable products from the sludge by means of thermal treatments?…”

Section: Introductionmentioning

confidence: 99%

Sludge hydrothermal treatments. Oxidising atmosphere effects on biopolymers and physical properties

Urrea

García

Collado

et al. 2018

Journal of Environmental Management

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In this work, the role of an oxidising atmosphere during the hydrothermal treatment of an activated sludge at 160 °C and 40 bar, was determined. The composition and molecular weight sizes of the soluble biopolymers generated during the sludge treatment in presence (wet oxidation "WO") or absence (thermal hydrolysis "TH") of oxygen were compared. Likewise, the characteristics of organic material, settleability, colour and pH of the treated sludge during both treatments were analysed. The thermal treatment in presence of oxygen provided better results in terms of solubilisation, settleability and mineralisation. WO initially favoured a more intense cellular lysis, causing a higher degree of solubilisation than that achieved by TH. Either in presence or absence of oxygen, thermal treatments caused a marked worsening of the settleability of the sludge. However, the degradation of biopolymers during WO led subsequently to an improvement of the settleability properties for longer reaction times. Both treatments caused a fast solubilisation of biopolymers at the beginning by effect of the release of extracellular and intracellular material from sludge. Subsequently, the presence of oxygen produced a significant decrease in the concentration of those biopolymers. In contrast, the proteins were the only one biopolymer that was degraded during TH.

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Section: Introductionmentioning

confidence: 99%

Sludge hydrothermal treatments. Oxidising atmosphere effects on biopolymers and physical properties

Urrea

García

Collado

et al. 2018

Journal of Environmental Management

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“…where t is the shear stress (Pa); _ g is the shear rate (s À1 ); t y is the yield stress (Pa); k is the consistency index (Pa$s n ), which can reveal the average firmness of sample (Ruiz-Hernando et al, 2014); and n is the flow behavior index (dimensionless), which is equal to 1 for Newtonian fluids, higher than 1 for dilatant fluids and lower than 1 for pseudo-plastic fluids (Ruiz-Hernando et al, 2015). A decrease or increase of n from 1 indicates that the non-Newtonian flow characteristics are strengthened (Feng et al, 2014a).…”

Section: Rheological Measurementsmentioning

confidence: 99%

Rheological properties of sewage sludge during enhanced anaerobic digestion with microwave-H2O2 pretreatment

et al. 2016

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a b s t r a c tThe rheological behavior of sludge is of serious concern in anaerobic digestion. This study investigated the rheological properties of sewage sludge during enhanced anaerobic digestion with microwave-H 2 O 2 pretreatment (MW-H 2 O 2 ). The results showed that MW-H 2 O 2 pretreatment resulted in the improvement of sludge flowability and weakening of its viscoelastic properties. Further positive effects on the rheological properties of digested sludge during anaerobic digestion were observed. The flowability was improved with a low level of apparent viscosity. The decrease of the consistency index and increase of the flow behavior index indicated that the strength of the inner structures and non-Newtonian flow characteristics of digested sludge weakened. Both the storage modulus (G 0 ) and loss modulus (G 00 ) decreased, indicating that the viscoelastic behavior became weak. These effects were possibly attributed to the changes of the digested sludge micro-structures, such as extracellular polymeric substances (EPS). This study concluded that anaerobic digestion for treating sewage sludge combined with pretreatment is a more favorable option than single anaerobic digestion from the perspective of rheology.

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“…To quantify the thixotropy of sludge under different conditioning agent dosage sequences, the structural model proposed by [47] was used to assess the thixotropy of sludge. The thixotropic kinetic coefficient (K) and normalized viscosity changes are shown in Table 3 and Figure 8c.…”

Section: Sludge Rheology Curvesmentioning

confidence: 99%

Impact of Conditioning Agent Addition Sequence on Dewatering Performance of Advanced Anaerobic Digested Sludge

Cao,

Yu,

Wang

2024

Water

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The advanced anaerobic digestion process enhances sludge resource utilization. However, thermal hydrolysis pretreatment of anaerobically digested sludge reduces dewatering efficiency due to excessive organic matter decomposition. This necessitates significant time and effort for sludge conditioning in wastewater treatment plants. Using conditioning agents can achieve high dewatering efficiency. This study investigates how the order of adding coagulants and flocculants impacts the dewatering performance of digested sludge. The results indicate that, compared to the flocculation–coagulation process with the same dosage, the coagulation–flocculation process leads to a 15–20% increase in the average particle size of digested sludge. The content of polysaccharides and proteins in S-EPS decreases by 28.8–30.8% and 10.1–11.3%, respectively. The filter cake solids content increases by 8.5%, and there is an increase in surface water channels within the flocs. This is because initially adding coagulants efficiently adsorbs small particles, forming larger aggregates that settle effectively. This promotes the breakdown of extracellular polymeric substances, releasing more bound water. Adding flocculants later bridges the aggregates, further enhancing settling and filtration performance, thereby improving sludge dewatering efficiency. These research findings contribute to a better understanding of the mechanisms of coagulant and flocculant co-conditioning for digested sludge and provide recommendations for optimizing sludge conditioning steps.

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Structural model to study the influence of thermal treatment on the thixotropic behaviour of waste activated sludge

Cited by 31 publications

References 39 publications

Sludge hydrothermal treatments. Oxidising atmosphere effects on biopolymers and physical properties

Sludge hydrothermal treatments. Oxidising atmosphere effects on biopolymers and physical properties

Rheological properties of sewage sludge during enhanced anaerobic digestion with microwave-H2O2 pretreatment

Impact of Conditioning Agent Addition Sequence on Dewatering Performance of Advanced Anaerobic Digested Sludge

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