1
|
Lin F, Qin W, Wei J, Lv J, Yang P. Effect of chemical regulation combined with mechanical filtration on deep dewatering and consolidation characteristics of sludge. Environ Sci Pollut Res Int 2023; 30:89088-89100. [PMID: 37450183 DOI: 10.1007/s11356-023-28766-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 07/08/2023] [Indexed: 07/18/2023]
Abstract
To reveal the mechanism underlying deep dewatering of municipal sludge, this paper investigated the sludge characteristics from the perspective of soil mechanics, and analyzed the sludge physical and mechanical properties, stress as well as dewatering behavior during the dewatering process. Before and after cationic polyacrylamide (CPAM) and chitosan (HACC) conditioning, the pressure filtration dewatering time of treated sludge was shorter than that of raw sludge, and the water removal rate was greater than 70% at the 6 MPa pressure. However, with the increase in filter pressing time, the filtration resistance coefficient of sludge increased, and the water pressure in sludge pores rose up, and a longer time was needed for dissipation at the larger pressure, resulting in the slowdown of sludge consolidation. In addition, based on the three-stage Terzaghi Voigt model, when the pressure rose from 2 to 6 MPa, the time from filtration stage to compression stage of raw sludge was shortened, and the second stage played the most important role in the dewatering process. Compared with the raw sludge, the sludge filtration stage was shortened after CPAM or HACC conditioning, and the main dewatering mechanism changed from the second compression stage to the first compression stage, which means the bound water in sludge flocs was transformed into free water. This was also the reason why the dewatering, compression and consolidation rate of the conditioned sludge was faster than that of the raw sludge.
Collapse
Affiliation(s)
- Feng Lin
- School of Chemical Technology, Guangdong Industry Polytechnic, Guangzhou, China.
| | - Weihua Qin
- State Key Laboratory of Pulp and Paper Engineering, School of Light Industry and Engineering, South China University of Technology, Guangzhou, China
| | - Jiongxian Wei
- School of Chemical Technology, Guangdong Industry Polytechnic, Guangzhou, China
| | - Jiangtao Lv
- School of Chemical Technology, Guangdong Industry Polytechnic, Guangzhou, China
| | - Peng Yang
- School of Chemical Technology, Guangdong Industry Polytechnic, Guangzhou, China
| |
Collapse
|
2
|
Lu Y, Zheng G, Wu W, Cui C, Zhou L. Significances of deflocculated sludge flocs as well as extracellular polymeric substances in influencing the compression dewatering of chemically acidified sludge. Sep Purif Technol 2017; 176:243-51. [DOI: 10.1016/j.seppur.2016.12.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
3
|
Raynaud M, Vaxelaire J, Olivier J, Dieudé-Fauvel E, Baudez JC. Compression dewatering of municipal activated sludge: effects of salt and pH. Water Res 2012; 46:4448-4456. [PMID: 22735341 DOI: 10.1016/j.watres.2012.05.047] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 05/10/2012] [Accepted: 05/24/2012] [Indexed: 06/01/2023]
Abstract
Even after mechanical dewatering, activated sludge contains a large amount of water. Due to its composition and biological nature this material is usually highly compressible and known to be difficult to dewater. In the present work, two treatments (salt addition and pH modification) are proposed to highlight some aspects which could explain the poor dewaterability of activated sludge. Dewatering tests are carried out in a pressure-driven device in order to well examine both, filtration and compression stages. Physico-chemical parameters, such as surface charge, hydrophobicity, extracellular polymeric substances (EPS) content and filtrate turbidity are measured on the tested sludge, for a better analysis of dewatering results. The dewatering ability of the sludge is widely linked to the cohesion of the flocculated matrix and the presence of fine particles. Both treatments alter the flocculated matrix and release fine particles. The release of fine particles tends to clog both, the filter cake and the filter medium. Consequently, the filtration rate decreases due to higher resistances to the flow. On another hand, the polymeric matrix breakdown enables to release some water trapped within the floc to the bulk liquid phase and thus facilitates its removal, which tends to decrease the moisture content of the filter-cake. It also impacts the compression dewatering step. The more destroyed structures lead to less elastic cakes and thus a slower primary consolidation stage. At the opposite, the mobility of the broken aggregates within the filter-cake does not seem to be improved by size reduction (the kinetics of the secondary consolidation stage are not significantly modified).
Collapse
Affiliation(s)
- Mickael Raynaud
- Laboratoire de Thermique Energétique et Procédés, Université de Pau et des Pays de l'Adour, ENSGTI, Rue Jules Ferry, BP 7511, 64075 Pau Cedex, France
| | | | | | | | | |
Collapse
|
4
|
|
5
|
|
6
|
|
7
|
|
8
|
Iritani E, Sato T, Katagiri N, Hwang KJ. Multi-Stage Creep Effect in Consolidation of Tofu and Okara as Soft Colloids. J Chem Eng Japan / JCEJ 2010. [DOI: 10.1252/jcej.09we177] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Eiji Iritani
- Department of Chemical Engineering, Nagoya University
| | - Takashi Sato
- Department of Chemical Engineering, Nagoya University
| | | | - Kuo-Jen Hwang
- Department of Chemical and Materials Engineering, Tamkang University
| |
Collapse
|
9
|
Das K, Raha S, Somasundaran P. Effect of polyacrylic acid molecular weight on the floc stability during prolonged settling. Colloids Surf A Physicochem Eng Asp 2009. [DOI: 10.1016/j.colsurfa.2009.08.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
10
|
|
11
|
Yang Z, Peng XF, Lee DJ, Ay S. Advective flow in spherical floc. J Colloid Interface Sci 2007; 308:451-9. [PMID: 17275013 DOI: 10.1016/j.jcis.2007.01.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 11/08/2006] [Accepted: 01/11/2007] [Indexed: 11/15/2022]
Abstract
Numerous structural models of flocs, such as homogeneous model or radially-varying model, were proposed in literature for predicting the extent of advective flow on the intrafloc transport processes. This work probed the three-dimensional structure of original and chemically flocculated wastewater flocs using the fluorescence in situ hybridization (FISH) and the confocal laser scanning microscope (CLSM) techniques, from which the spherical mesh model on real floc structure was constructed. Simulation results revealed that if an average characteristic of sludge floc, such as porosity or drag force correction factor of sludge floc is of concern, both homogeneous or radially-varying models may be able to apply, particularly for those flocs that were closely compacted. However, the detailed flow patterns inside real floc are much more tortuous than those of the homogeneous or radially-varying models. If local hydrodynamic environment within the floc is of interest, then only the complicated structural model with real floc could be applicable.
Collapse
Affiliation(s)
- Z Yang
- Department of Thermal Engineering, Tsinghua University, Beijing 100084, People's Republic of China
| | | | | | | |
Collapse
|
12
|
|
13
|
Laspidou CS, Rittmann BE. Modeling the development of biofilm density including active bacteria, inert biomass, and extracellular polymeric substances. Water Res 2004; 38:3349-3361. [PMID: 15276752 DOI: 10.1016/j.watres.2004.04.037] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2003] [Revised: 01/13/2004] [Accepted: 04/29/2004] [Indexed: 05/24/2023]
Abstract
We present the unified multi-component cellular automaton (UMCCA) model, which predicts quantitatively the development of the biofilm's composite density for three biofilm components: active bacteria, inert or dead biomass, and extracellular polymeric substances. The model also describes the concentrations of three soluble organic components (soluble substrate and two types of soluble microbial products) and oxygen. The UMCCA model is a hybrid discrete-differential mathematical model and introduces the novel feature of biofilm consolidation. Our hypothesis is that the fluid over the biofilm creates pressures and vibrations that cause the biofilm to consolidate, or pack itself to a higher density over time. Each biofilm compartment in the model output consolidates to a different degree that depends on the age of its biomass. The UMCCA model also adds a cellular automaton algorithm that identifies the path of least resistance and directly moves excess biomass along that path, thereby ensuring that the excess biomass is distributed efficiently. A companion paper illustrates the trends that the UMCCA model is able to represent and shows a comparison with experimental results.
Collapse
Affiliation(s)
- Chrysi S Laspidou
- Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3109, USA.
| | | |
Collapse
|
14
|
|
15
|
Abstract
The sedimentation characteristics of flocculated wastewater sludge have not been satisfactorily explored using the non-destructive techniques, partially owing to the rather low solid content (ca. 1-2%) commonly noted in the biological sediments. This paper investigated, for the first time, the spatial-temporal gravitational settling characteristics of original and polyelectrolyte flocculated waste activated sludge using Computerized Axial Tomography Scanner. The waste activated sludge possessed a distinct settling characteristic from the kaolin slurries. The waste activated sludges settled more slowly and reached a lower solid fraction in the final sediment than the latter. Flocculation markedly enhanced the settleability of both sludges. Although the maximum achievable solid contents for the kaolin slurries were reduced, flocculation had little effects on the activated sludge. The purely plastic rheological model by Buscall and White (J Chem Soc Faraday Trans 1(83) (1987) 873) interpreted the consolidating sediment data, while the purely elastic model by Tiller and Leu (J. Chin. Inst. Chem. Eng. 11 (1980) 61) described the final equilibrated sediment. Flocculation produced lower yield stress during transient settling, thereby resulting in the more easily consolidated sludge than the original sample. Meanwhile, the flocculated activated sludge was stiffer in the final sediment than in the original sample. The data reported herein are valuable to the theories development for clarifier design and operation.
Collapse
Affiliation(s)
- C P Chu
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | | | | |
Collapse
|
16
|
Affiliation(s)
- C. P. Chu
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4792
| | - S. P. Ju
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4792
| | - D. J. Lee
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4792
| | - F. M. Tiller
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4792
| | - K. K. Mohanty
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4792
| | - Y. C. Chang
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4792
| |
Collapse
|
17
|
|
18
|
Abstract
The study experimentally investigated the centrifugal separation of moisture from activated sludge subject to cationic polyelectrolyte flocculation. An arm-suspended centrifuge was employed which allowed in-situ detection on all positions of interfaces of centrifuged sludge as functions of time. Experimental results revealed that, sludge flocculation would yield a significant sedimentation effect at the first phase of centrifugation. Therefore, not as suggested in conventional centrifugal-filtration models, the most significant moisture-removal stages included filtrate to flow through a wet cake. Moreover, an optimal rotational speed exists at which the moisture-removal rate reaches a maximum value. New theories/correlations are required to describe centrifugation dewatering of polyelectrolyte flocculated sludge.
Collapse
Affiliation(s)
- C P Chu
- Department of Chemical Engineering, National Taiwan University, Taipei
| | | |
Collapse
|
19
|
Abstract
Breaking down the time limit constraints for conventional compression-permeation (C-P) cell test, this work has, for the first time, experimentally evaluated the cake characteristics of viable waste-activated sludge subject to polyelectrolyte flocculation and to freeze/thaw treatment under a pressure range of 25-200 kPa. There exists a threshold pressure exceeding which the cake structure would significantly deteriorate. Also, the present biological sludge is a "super-compactible" sludge, whose compactibility is greater than most data ever reported in open literature. The information presented herein has implications to filter design/operation and can be used as a reference data set for examining the existing filtration theories.
Collapse
Affiliation(s)
- R M Wu
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan ROC
| | | | | | | | | |
Collapse
|
20
|
Wu RM, Lee DJ, Wang CH, Zhao J, Tan RBH. Discrepancy in Cake Characteristic Measurement: Compression-Permeability Cell. J Chem Eng Japan / JCEJ 2000. [DOI: 10.1252/jcej.33.869] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Rome Ming Wu
- Department of Chemical Engineering, National Taiwan University
| | - Duu Jong Lee
- Department of Chemical Engineering, National Taiwan University
- Department of Chemical and Environmental Engineering, National University of Singapore
| | - Chi Hwa Wang
- Department of Chemical Engineering, National Taiwan University
- Department of Chemical and Environmental Engineering, National University of Singapore
| | - Jing Zhao
- Department of Chemical and Environmental Engineering, National University of Singapore
| | - Reginald Beng Hee Tan
- Department of Chemical and Environmental Engineering, National University of Singapore
| |
Collapse
|
21
|
Abstract
This work evaluates filtration followed by consolidation characteristics of sodium chloride containing activated sludge. Experimental results indicate that contact time and salinity level affect the dewatering efficiency. Considering the consolidation stage, a critical salinity level (around 1-2% (w/w)) is observed at which the contribution of secondary consolidation stage reaches its minimum. Meanwhile the creeping among constituent aggregates becomes much easier than in the original sludge. In addition, double-layer compression/hydrophobic interactions and ion exchange partially account for the experimental results. Copyright 1999 Academic Press.
Collapse
Affiliation(s)
- DS Jean
- Department of Chemical Engineering, National Taiwan University, Taipei, 10617, Taiwan
| | | |
Collapse
|
22
|
Abstract
This work has experimentally investigated the characteristics of filtration followed by consolidation dewatering of an alum sludge, with especial attention to the effects of adding ionic surfactants (SDS or CTAB). The filtration and consolidation stages at a pressure of 3000 psi were discussed separately. The efficiency of filtration is enhanced in the presence of surfactant molecules; however, the cationic surfactant (CTAB) raises the consolidation rate while the anionic surfactant (SDS) retards it. A newly proposed rheological model has been employed for interpreting the consolidation data. CTAB would not alter markedly the moisture distribution in the sludge, but SDS does increase markedly the amount of the tightly bound moisture by diminishing the portion occupied by pore water. The possible role of surfactants in the sludge flocs is considered. Both surfactants can be used as conditioning aids during the filtration stage. However, the applications of SDS to the consolidation stage are not encouraged. Copyright 1998 Academic Press.
Collapse
Affiliation(s)
- CP Chu
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan, 10617
| | | | | |
Collapse
|
23
|
Abstract
The ability of treated alum sludge to remove fluoride from aqueous solution has been investigated. The studies were carried out as functions of contact time, concentration of adsorbent and adsorbate, temperature, pH, and effect of concentrations of other anions. The data indicate that treated alum sludge surface sites are heterogeneous in nature and that fits into a heterogeneous site binding model. The optimum pH for complete removal of fluoride from aqueous solution was found to be 6. The rate of adsorption was rapid during the initial 5 minutes, and equilibrium was attained within 240 minutes. The adsorption followed first-order rate kinetics. The present system followed the Langmuir adsorption isotherm model. The loading factor (i.e., the milligram of fluoride adsorbed per gram of alum sludge) increased with initial fluoride concentration, whereas a negative trend was observed with increasing temperature. The influence of addition of anions on fluoride removal depends on the relative affinity of the anions for the surface and the relative concentrations of the anions. Copyright 1998 Academic Press.
Collapse
Affiliation(s)
- MG Sujana
- Regional Research Laboratory (CSIR), Bhubaneswar-, 751 013, India
| | | | | |
Collapse
|