Effect of centrifugation on the removal of extracellular polymers and physical properties of activated sludge

1994 ◽  
Vol 30 (8) ◽  
pp. 117-127 ◽  
Author(s):  
F. Dilek Sanin ◽  
P. Aarne Vesilind
Keyword(s):  
Activated Sludge ◽  
Physical Properties ◽  
Inorganic Materials ◽  
Extracellular Polymers ◽  
Capillary Suction ◽  
The Past ◽  
Main Components ◽  
The Relationship ◽  
Flocculated Suspension ◽  
Extracellular Polymer

Activated sludge is a flocculated suspension of living and dead microorganisms enmeshed together in a polymer matrix along with some organic and inorganic materials. Extracellular polymers, main components of which are the polysaccharides, proteins, and nucleic acids, act as a protective barrier to the living microbial community, and give the floc its integrity and rigidity. These polymers have been found to affect the dewatering and settling characteristics of activated sludge. Even though they were studied considerably in the past there is not a complete understanding of the relationship between the amount of polymer and changes in the physical properties of sludge. The purpose of this research is to observe the effects of centrifugal force on the extraction of the extracellular polymers from an activated sludge and to correlate the amount of polymer extracted to the subsequent physical properties of the sludge. Centrifugal forces of 2000, 5000, 8000, 11,000, 14,000, and 16,500 G were tested for their effects on the amount of extracellular polymer collected, as well as the final properties of sludge like viscosity, filterability, compactability and supernatant turbidity. Results were evaluated in comparison to those of an uncentrifuged control waste activated sludge. Removal of extracellular polymers seems to affect the viscosity of activated sludge. Filterability, as measured by the capillary suction time instrument, was affected by the extraction of polymers to a great degree. Results of the independent tests correlated well with each other and with the amount of polymers extracted. Results of this study have important implications on sludge pumping and dewatering.

Extracellular polymeric substances and dewaterability of waste activated sludge during anaerobic digestion

2014 ◽  
Vol 70 (9) ◽  
pp. 1555-1560 ◽  
Author(s):  
Fenxia Ye ◽  
Xinwen Liu ◽  
Ying Li
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Extracellular Polymeric Substance ◽  
Extracellular Polymeric Substances ◽  
Waste Activated Sludge ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Relationship Analysis ◽  
The Relationship ◽  
Insight Into

Anaerobic digestion of waste activated sludge was conducted to gain insight into the mechanisms underlying change in sludge dewaterability during its anaerobic digestion. Unexpectedly, the results indicated that sludge dewatering properties measured by capillary suction time only deteriorated after 10 days of anaerobic digestion, after which dewaterability recovered and remained stable. The loosely bound extracellular polymeric substance (LB-EPS) content increased three-fold after 20 days of anaerobic digestion, and did not change significantly during the remaining 30 days. The tightly bound EPS (TB-EPS) content reduced slightly after 20 days of anaerobic digestion, and stabilized during the last 30 days. Polysaccharides (PS) and proteins (PN) content in LB-EPS increased after 10 days of anaerobic digestion. However, PS and PN contents in TB-EPS decreased slightly. The relationship analysis showed that only LB-EPS correlated with dewaterability of the sludge during anaerobic digestion.

Extracellular polymers of ozonized waste activated sludge

2001 ◽  
Vol 44 (10) ◽  
pp. 137-142 ◽  
Author(s):  
J.C. Liu ◽  
C.H. Lee ◽  
J.Y. Lai ◽  
K.C. Wang ◽  
Y.C. Hsu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Activated Sludge ◽  
Weight Distribution ◽  
Specific Resistance ◽  
Optimal Dose ◽  
Cationic Polyelectrolyte ◽  
Waste Activated Sludge ◽  
Extracellular Polymers ◽  
Capillary Suction ◽  
Ozone Dose

Effect of ozonation on characteristics of waste activated sludge was investigated in the current study. Concentrations of cell-bound extracellular polymers (washed ECPs) did not change much upon ozonation, whereas the sum of cell-bound and soluble extracellular polymers (unwashed ECPs) increased with increasing ozone dose. Washed ECPs in original sludge as divided by molecular weight distribution was 39% < 1,000 Da (low MW), 30% from 1,000 to 10,000 Da (medium MW), and 31% > 10,000 Da (high MW). It was observed that the low-MW fraction decreased, and the high-MW fraction increased in ozonized sludge. The unwashed ECPs were characterized as 44% in low MW, 30% in medium MW, and 26% in high MW. Both low-MW and medium-MW fractions of unwashed ECPs decreased while high-MW fraction increased in ozonized sludge. The dewaterability of ozonized sludge, assessed by capillary suction time (CST) and specific resistance to filtration (SRF), deteriorated with ozone dose. The optimal dose of cationic polyelectrolyte increased with increasing ozone dose. The production rate and the accumulated amount of methane gas of ozonized sludge were also higher.

Biomass dewaterability, filterability and settleability in a membrane bioreactor operated with different sludge ages

2007 ◽  
Vol 2 (1) ◽  
Author(s):  
A. Pollice ◽  
G. Laera ◽  
C. Giordano ◽  
D. Saturno ◽  
G. Mininni ◽  
...  
Keyword(s):  
Steady State ◽  
Physical Properties ◽  
Membrane Bioreactors ◽  
Volume Index ◽  
Excess Sludge ◽  
Capillary Suction ◽  
Bench Scale ◽  
Conventional Activated Sludge ◽  
The Relationship

Membrane bioreactors (MBR) are designed to maintain high solid concentrations, thus limiting sludge production and the related operational costs of the process. Sludge physical properties strongly affect the operation of these systems, due to their influence on the filtration process and also on excess sludge handling. This study reports the physical characterization of a bench scale MBR biomass with different sludge ages and with complete sludge retention. The results span over a period of three years when a bench scale MBR was operated under the same conditions except for the sludge retention time (SRT). The main dewatering properties were measured over time and their steady state average values were related to the SRT. The capillary suction time (CST) and the specific resistance to filtration (SRF) showed similar decreasing trends during the transient phase and reached equilibrium values under steady state conditions, except in the case of complete sludge retention. Under all the tested conditions, the average equilibrium values of the CST, the SRF and the compressibility (s) of the MBR sludge were similar to those reported for conventional activated sludge, suggesting the adoption of the same dewatering technologies. In terms of settleability, the relationship between the diluted sludge volume index (DSVI) and the sludge age appeared weak for SRT higher than 20 days. Under the tested conditions, the best performances in terms of physical properties of the MBR excess sludge were obtained for sludge retention times between 40 and 80 days.

B-N as a C-C substitute in aromatic systems

2009 ◽  
Vol 87 (1) ◽  
pp. 8-29 ◽  
Author(s):  
Michael J.D Bosdet ◽  
Warren E Piers
Keyword(s):  
Transition Metal Complexes ◽  
Aromatic Hydrocarbons ◽  
Inorganic Materials ◽  
Biological Chemistry ◽  
New Materials ◽  
Main Group Chemistry ◽  
The Past ◽  
New Applications ◽  
The Relationship ◽  
Structural Aspects

The substitution of isoelectronic B–N units for C–C units in aromatic hydrocarbons produces novel heterocycles with structural similarities to the all-carbon frameworks, but with fundamentally altered electronic properties and chemistry. Since the pioneering work of Dewar some 50 years ago, the relationship between B–N and C–C and the wealth of parent all-carbon aromatics has captured the imagination of organic, inorganic, materials, and computational chemists alike, particularly in recent years. New applications in biological chemistry, new materials, and novel ligands for transition-metal complexes have emerged from these studies. This review is aimed at surveying activity in the area in the past couple of decades. Its organization is based on ring size and type of the all-carbon or heterocyclic subunit that the B–N analog is derived from. Structural aspects pertaining to the retention of aromaticity are emphasized, along with delineation of significant differences in physical properties of the B–N compound as compared to the C–C parent.Key words: boron-nitrogen heterocycles, aromaticity, organic materials, main-group chemistry.

Municipal wastewater sludge dewaterability and the presence of microbial extracellular polymer

2001 ◽  
Vol 44 (2-3) ◽  
pp. 373-379 ◽  
Author(s):  
J. J. Houghton ◽  
J. Quarmby ◽  
T. Stephenson
Keyword(s):  
Municipal Wastewater ◽  
Extraction Process ◽  
Wastewater Sludge ◽  
Optimum Level ◽  
Wastewater Treatment Process ◽  
Capillary Suction ◽  
Sludge Dewaterability ◽  
The Uk ◽  
The Relationship ◽  
Extracellular Polymer

Dewatering of sewage sludge is an essential and costly part of the wastewater treatment process. The presence of microbial extracellular polymer (ECP) is important for sludge flocculation, but ECP has also been shown to have a detrimental effect on the dewaterability of certain sludge types. This paper investigates the relationship between sludge dewaterability and the level of ECP present in a range of sludges obtained from 8 full-scale municipal treatment works in the UK. Sludge dewaterability was determined using the capillary suction time (CST) test, and a thermal extraction process followed by solvent precipitation was used for ECP extraction. The results indicate that for each type of sludge examined there appears to be an optimum level of ECP (raw sludge 20 mg ECP/g SS; activated sludge 35 mg ECP/g SS; digested sludge 10 mg ECP/g SS) at which the sludge should exhibit maximum dewaterability. The establishment of a trend between sludge dewaterability and the quantity of ECP present opens up the possibility of manipulating the level of microbial polymer present to aid sludge dewatering, and hence reduce plant operating costs.

Effect of carbon to nitrogen ratio on the composition of microbial extracellular polymers in activated sludge

2001 ◽  
Vol 44 (10) ◽  
pp. 221-229 ◽  
Author(s):  
B. Durmaz ◽  
F.D. Sanin
Keyword(s):  
Activated Sludge ◽  
Protein Concentration ◽  
Polymer Composition ◽  
Relative Distribution ◽  
Extracellular Polymers ◽  
Carbon To Nitrogen Ratio ◽  
Carbohydrate Concentration ◽  
Low Carbohydrate ◽  
Nitrogen Ratio ◽  
Extracellular Polymer

Effect of carbon to nitrogen ratio (C/N) on the sludge extracellular polymer composition is studied in synthetically fed semi-continuous reactors with 8 days of sludge age. Results show that C/N ratio influences the relative distribution of polymer carbohydrate and protein. At low C/N ratio of 5, polymer extracts have high protein and low carbohydrate content. As the C/N ratio is increased to 17.5 and then to 40, carbohydrate concentration increases sharply and protein concentration decreases.

Scanning tunneling microscopy (STM) of DNA and RNA

1989 ◽  
Vol 47 ◽  
pp. 34-35
Author(s):  
Patricia G. Arscott ◽  
Gil Lee ◽  
Victor A. Bloomfield ◽  
D. Fennell Evans
Keyword(s):  
Molecular Structures ◽  
Inorganic Materials ◽  
Resolving Power ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Form And Function ◽  
Dna And Rna ◽  
Calf Thymus ◽  
And Function ◽  
The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

Poor Acceptance of the Past is Related to Depressive Symptoms in Older Adults

GeroPsych ◽  
2020 ◽  
Vol 33 (4) ◽  
pp. 246-251
Author(s):  
Gozde Cetinkol ◽  
Gulbahar Bastug ◽  
E. Tugba Ozel Kizil
Keyword(s):  
Older Adults ◽  
Regression Analysis ◽  
Depressive Symptoms ◽  
Death Anxiety ◽  
Geriatric Depression ◽  
Ego Integrity ◽  
The Past ◽  
Depressed Group ◽  
Total Death ◽  
The Relationship

Abstract. Depression in older adults can be explained by Erikson’s theory on the conflict of ego integrity versus hopelessness. The study investigated the relationship between past acceptance, hopelessness, death anxiety, and depressive symptoms in 100 older (≥50 years) adults. The total Beck Hopelessness (BHS), Geriatric Depression (GDS), and Accepting the Past (ACPAST) subscale scores of the depressed group were higher, while the total Death Anxiety (DAS) and Reminiscing the Past (REM) subscale scores of both groups were similar. A regression analysis revealed that the BHS, DAS, and ACPAST predicted the GDS. Past acceptance seems to be important for ego integrity in older adults.

A literature review on firms' internationalisation through e-commerce

2019 ◽  
pp. 121-143
Author(s):  
Riccardo Resciniti ◽  
Federica De Vanna
Keyword(s):  
Systematic Review ◽  
Literature Review ◽  
International Business ◽  
Decision Process ◽  
Foreign Markets ◽  
New Markets ◽  
Integrative Framework ◽  
The Past ◽  
The Relationship

The rise of e-commerce has brought considerable changes to the relationship between firms and consumers, especially within international business. Hence, understanding the use of such means for entering foreign markets has become critical for companies. However, the research on this issue is new and so it is important to evaluate what has been studied in the past. In this study, we conduct a systematic review of e-commerce and internationalisation studies to explicate how firms use e-commerce to enter new markets and to export. The studies are classified by theories and methods used in the literature. Moreover, we draw upon the internationalisation decision process (antecedents-modalities-consequences) to propose an integrative framework for understanding the role of e-commerce in internationalisation

Policy Making Introduction

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Nina TERREY ◽  
Sabine JUNGINGER
Keyword(s):  
Policy Implementation ◽  
Policy Making ◽  
Creative Industries ◽  
Design Management ◽  
Support Design ◽  
The Past ◽  
Academic Researchers ◽  
Design Activities ◽  
The Relationship ◽  
Professional Impact

The relationship that exists between design, policies and governance is quite complex and presents academic researchers continuously with new opportunities to engage and explore aspects relevant to design management. Over the past years, we have witnessed how the earlier focus on developing policies for design has shifted to an interest in understanding the ways in which design contributes to policy-making and policy implementation. Research into policies for design has produced insights into how policy-making decisions can advance professional impact and opportunities for designers and the creative industries. This research looked into how design researchers and design practitioners themselves can benefit from specific policies that support design activities and create the space for emerging design processes.

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