Applying rheological analysis to better understand the mechanism of acid conditioning on activated sludge dewatering

Wang, Hou‐Feng; Ma, Yunjie; Wang, Huajie; Hu, Hao; Yang, Haiyang; Zeng, Raymond J.

doi:10.1016/j.watres.2017.05.002

Cited by 107 publications

(28 citation statements)

References 58 publications

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“…Likewise, reduction in tan() value suggests that iron-conditioned sludge exhibits the weaker solidlike (or elastic) properties (Liu et al, 2016c) and in consequence, the proportion of energy dissipation to energy storage on applying external shear (Mezger, 2006) would be reduced, subsequently resulting improved sludge flowability (Wang et al, 2017). Such improvement in flowability of ironconditioned sludge is also likely due to existence of weak colloidal forces and sludge network strength (Feng et al, 2014a), as supported by reduced Hla values observed herein.…”

Section: Changes In Rheological Propertiessupporting

confidence: 61%

“…However, solely analyzing different physicochemical properties cannot fully elucidate the underlying fundamental mechanism behind resultant variability in sludge dewaterability, as suggested in previous study (Wang et al, 2017). Achieving better solid-liquid separation in sludge dewatering process equally demands the understanding of sludge hydrodynamics or rheology.…”

Section: Introductionmentioning

confidence: 94%

“…Higgins et al (2004) showed that lower M + /D ++ cations ratio reflects the higher dewatered cake solids content (%). Similarly, improved dewatering rate can usually be related to ease in sludge moisture reduction (Wang et al, 2017) and this can be assessed by measuring the bound water content of the sludge. In addition, sludge morphology (size/structure/compactness), also plays an important role in sludge dewaterability (Pham et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Mechanistic Understanding of Beneficial Aspects of Iron Salts and Waterworks Sludge Uses in Urban Wastewater System

Shrestha¹

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Iron (Fe)-salts are widely used as the inorganic chemical coagulants for water and wastewater treatment processes. In retrospect, Fe-salts application in different domains of the urban wastewater system (UWWS) (e.g. sewers, bioreactor, digester) has been in isolation. The choice and application of Fe-salts are at present primarily driven by considerations merely at the subsystem level, with their I acknowledge that the copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis and have sought permission from co-authors for any jointly authored works included in the thesis. vi Publications during candidature Peer-reviewed scientific journal articles • Sohan Shrestha, Keshab Sharma, Zhongwei Chen, Zhiguo Yuan (2019). Unravelling the influences of sewer-dosed iron salts on activated sludge properties with implications on settleability, dewaterability and sludge rheology.

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Section: Changes In Rheological Propertiessupporting

confidence: 61%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Mechanistic Understanding of Beneficial Aspects of Iron Salts and Waterworks Sludge Uses in Urban Wastewater System

Shrestha¹

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“…8−11 Chemical conditioning aims to change sludge physicochemical or electrochemistry properties by adding acids, coagulants/flocculants, and it is a relatively mature, cost-effective, and user-friendly sludge dewatering technology. 12−21 Physical conditioning mainly refers to thermal hydrolysis, ultrasonic conditioning, freeze–thaw treatment, and biological conditioning adopts enzymes and bioflocculants. 22−27 In many pretreatments, coagulants/flocculants are the most common agents for sludge conditioning in practice because of lower cost and higher efficiency.…”

Section: Introductionmentioning

confidence: 99%

Establishment of the Permeability Model for Soft Solid Sludge Conditioned with Flocculants

Guo

Bai

et al. 2019

ACS Omega

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Permeability plays a decisive role in the dewatering process and reflects the difficulty of filtration, especially for soft solid material such as sludge. In this paper, the physicochemical properties and dewatering performance of sludge conditioned with different kinds of flocculants were investigated. Results showed that the flocculant could change the sludge microstructure such as floc morphology, specific surface area, and fractal dimension. Compared with filtration pressure, flocculants had a greater influence on sludge permeability which was a significant negative correlation with filtration pressure and was a positive correlation with flocculant dosage. In order to describe the fact that fluid flows through the porous voids for soft solid sludge, the improved Kozeny constant was corrected. Research showed that permeability was more significant in the dewatering process for the sludge conditioned with inorganic flocculants than that with organic flocculants. The Kozeny constant was not only relevant with suspension nature but also with filtration pressure. The range of the improved Kozeny constant was reasonably determined based on flocculant type, concentration, and filtration pressure, which was of great help to project applications. For raw sludge, the improved Kozeny constant was 958 times than that of the original value, and it decreased significantly for conditioned sludge.

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“…It is well known that sewage sludge is a non-Newtonian fluid, that exhibits rheological behavior, such as shear-thinning, thixotropy, yield stress and viscoelasticity. 43–46 Many reports showed that some pretreatment methods such as acid, 47 alkali, 48 ultrasonic, 24 hydrothermal, 24 composite salt 49 can change the previous rheological characteristics that can be used to reveal the change of physicochemical properties and dewaterability. However, little is known about the effects of KMnO 4 conditioning on sludge rheology and how this would affect sludge dewaterability.…”

Section: Introductionmentioning

confidence: 99%

Effects of potassium permanganate conditioning on dewatering and rheological behavior of pulping activated sludge: mechanism and feasibility

et al. 2018

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The difficulties in sludge dewatering are associated with the high organic content, colloidal materials in sludge solids and the high hydrophilicity of extracellular polymeric substances (EPS). Based on the principle of advanced oxidation processes, waste pulping activated sludge was subjected to potassium permanganate (KMnO 4 ) oxidation pretreatment and then the influence and mechanism on sludge dewatering were comprehensively investigated in the present study. At lower KMnO 4 dosage, changes of the physicochemical and rheological characteristics were that: (1) as the sludge disintegration degree increased, the total extractable EPS increased and then the bound water were released; (2) the rheological behavior showed that the yield stress and viscosity decreased while flowability increased and the positive thixotropic behavior weakened; (3) the particle size and microscopic structure were changed insignificantly. These changes resulted in damaging the gel-like environment and making the surface of sludge floc stripped but did not completely induce the floc breakage as a result of KMnO 4 with lower redox potential. Thus, sludge dewaterability was improved with the optimum dosage of 16 g kg À1 dry solid. On the perspective of environmental safety, KMnO 4 conditioning on sludge dewatering is feasible.

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Applying rheological analysis to better understand the mechanism of acid conditioning on activated sludge dewatering

Cited by 107 publications

References 58 publications

Mechanistic Understanding of Beneficial Aspects of Iron Salts and Waterworks Sludge Uses in Urban Wastewater System

Mechanistic Understanding of Beneficial Aspects of Iron Salts and Waterworks Sludge Uses in Urban Wastewater System

Establishment of the Permeability Model for Soft Solid Sludge Conditioned with Flocculants

Effects of potassium permanganate conditioning on dewatering and rheological behavior of pulping activated sludge: mechanism and feasibility

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