Shape descriptors - settling characteristics of irregular shaped particles

Abstract Nine sets of batch experiments, each of ten to twelve days duration, were conducted in the laboratory on return-sludge samples collected from activated sludge treatment plant at Windsor. The thickened sludge samples were blended daily in a waring blender and were continuously aerated in twelve-litres capacity jars. Parallel runs were made on control sludge samples which were not blended. Amongst the parameters varied were the speed and frequency of blending and the aeration rate. The effects of these variables on progressive bio-degradation of volatile suspended solids and the settling characteristics of the sludge were determined. Blended sludge showed significant improvement in the rate of bio-degradation and its settling characteristics as compared to the control unblended sludge

Methods for determining the settling velocity profiles of solids in storm sewage

10.2166/wst.1996.0190 ◽

1996 ◽

Vol 33 (9) ◽

pp. 117-125 ◽

Cited By ~ 5

Author(s):

Emmanuelle Aiguier ◽

Ghassan Chebbo ◽

Jean-Luc Bertrand-Krajewski ◽

Peter Hedges ◽

Naomi Tyack

Keyword(s):

Suspended Solids ◽

Settling Velocity ◽

Test Procedure ◽

Velocity Profiles ◽

Test Methods ◽

Efficient Treatment ◽

Experimental Procedure ◽

Comparative Tests ◽

Settling Process ◽

Recently, research has shown that a settling process is an efficient treatment for the removal of suspended solids from storm sewage. In order to design settling tanks, there is a need to determine the settling velocity characteristics of these solids. Devices and test methods for measuring settling velocities of solids in storm sewage have been developed by researchers. A literature review has revealed that the settling velocity profiles obtained with some methods (Chebbo, 1992), (Michelbach and Wohrle, 1993) and (Tyack et al., 1993) are very different. In order to explain why the results are different and to quantify the influence of the experimental procedure on the settling velocity grading curves, we have compared the selected methods when tested with the same sample and we have studied the effects of the conservation of the sample before the test, of the concentration of solids in the device and of the nature of the water on the settling velocity profiles. The results of the comparative tests indicate that the settling velocities are significantly lower with both the Cergrene and Aston methods than with the UFT test procedure. Moreover, the study has shown that the settling characteristics of solids change with time, that the use of sewage liquor rather than demineralised water or drinking water can change the results of the measurement and that the higher the concentration of solids, the greater the velocity of settled particles.

Experiences with sludge settleability in different process alternatives for nutrient removal

10.2166/wst.1996.0321 ◽

1996 ◽

Vol 33 (12) ◽

pp. 137-146 ◽

Cited By ~ 5

Author(s):

Kjær Andreasen ◽

Lars Sigvardsen

Keyword(s):

Nutrient Removal ◽

Plant Layout ◽

Filamentous Microorganisms ◽

Positive Effect ◽

Sludge Settleability ◽

Settling Characteristics ◽

P Removal

SVI and DSVI were measured three times at almost 100 Danish nutrient removal plants and the filamentous microorganisms were subsequently characterized in the laboratory. Information about the plant layout and the operation was collected by means of a questionnaire. In general, the sludge settleability index becomes worse by the introduction of nutrient removal. Among nutrient removal plants the best settling characteristics are found among plants with biological P removal and the poorest among the plants that perform simultaneous denitrification. When compared to iron products, aluminium products in some cases seem to reduce the filament number and improve the settling characteristics in plants that apply simultaneous precipitation for P removal. Selectors may have a positive effect on the filament number but the effect may not be enough to prevent bulking.

On-line measurements of settling characteristics in activated sludge

10.2166/wst.1997.0144 ◽

1997 ◽

Vol 36 (4) ◽

pp. 307-312

Author(s):

Michael R. Rasmussen ◽

Torben Larsen

Keyword(s):

Activated Sludge ◽

Settling Velocity ◽

Continuous Measurement ◽

Batch Reactor ◽

Volume Index ◽

Sludge Volume Index ◽

Dynamic Variations ◽

On Line ◽

Settling Column ◽

An on-line settling column for measuring the dynamic variations of settling velocity of activated sludge has been developed. The settling column is automatic and self-cleansing insuring continuous and reliable measurements. The settling column was tested on sludge from a batch reactor where sucrose was added as an impulse to activated sludge. The continuous measurement of settling velocity revealed a highly dynamic response after the sucrose was added. The results were verified with simultaneous measurement of the initial settling rate. A 200 hour experiment showed variations in settling velocity, which was not apparent in the DSVI (Diluted Sludge Volume Index).

Vertical clinging and leaping induced evolutionary rate shifts in postcranial evolution of tamarins and marmosets (Primates, Callitrichidae)

BMC Ecology and Evolution ◽

10.1186/s12862-021-01848-z ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Léo Botton-Divet ◽

John A. Nyakatura

Keyword(s):

Elbow Joint ◽

Evolutionary Rate ◽

Large Diameter ◽

Morphological Diversity ◽

Locomotor Behavior ◽

Shape Descriptors ◽

High Affinity ◽

Associated Species ◽

Future Work ◽

Shape And Size

Abstract Background Callitrichids comprise a diverse group of platyrrhine monkeys that are present across South and Central America. Their secondarily evolved small size and pointed claws allow them to cling to vertical trunks of a large diameter. Within callitrichids, lineages with a high affinity for vertical supports often engage in trunk-to-trunk leaping. This vertical clinging and leaping (VCL) differs from horizontal leaping (HL) in terms of the functional demands imposed on the musculoskeletal system, all the more so as HL often occurs on small compliant terminal branches. We used quantified shape descriptors (3D geometric morphometrics) and phylogenetically-informed analyses to investigate the evolution of the shape and size of the humerus and femur, and how this variation reflects locomotor behavior within Callitrichidae. Results The humerus of VCL-associated species has a narrower trochlea compared with HL species. It is hypothesized that this contributes to greater elbow mobility. The wider trochlea in HL species appears to correspondingly provide greater stability to the elbow joint. The femur in VCL species has a smaller head and laterally-oriented distal condyles, possibly to reduce stresses during clinging. Similarly, the expanded lesser trochanters visible in VCL species provide a greater lever for the leg retractors and are thus also interpreted as an adaptation to clinging. Evolutionary rate shifts to faster shape and size changes of humerus and femur occurred in the Leontocebus clade when a shift to slower rates occurred in the Saguinus clade. Conclusions Based on the study of evolutionary rate shifts, the transition to VCL behavior within callitrichids (specifically the Leontocebus clade) appears to have been an opportunity for radiation, rather than a specialization that imposed constraints on morphological diversity. The study of the evolution of callitrichids suffers from a lack of comparative analyses of limb mechanics during trunk-to-trunk leaping, and future work in this direction would be of great interest.

Effects of sludge settling characteristics in the BNR system

10.2166/wst.2000.0392 ◽

2000 ◽

Vol 42 (3-4) ◽

pp. 283-288 ◽

Cited By ~ 3

Author(s):

Z. Yun ◽

W. Yo ◽

Y. Yi ◽

S. Choi ◽

E. Choi ◽

...

Keyword(s):

Settling Tank ◽

Volume Index ◽

Anoxic Zone ◽

Sludge Volume Index ◽

Analytical Accuracy ◽

Fast Settling ◽

Sludge Settling ◽

Extracellular Polymer ◽

Sludge Settleability ◽

Although the BNR system design assumes no sludge settling problems in the final settling tank, the fluctuation of daily loading and up to 40% of anaerobiosis in the BNR system would be considerable factors in determining the sludge settleability. The sludge volume index (SVI) is a classical parameter to examine the sludge settleability but it has a limited value to evaluate the overall settling characteristics. The extracellular polymer (ECP) content in sludge has long been considered as an indicator of biological flocculation in activated sludge process, but the skepticism on analytical accuracy limits the usage in settling study. This study focused on evaluating the BNR system performance related to the sludge settling characteristics under the controlled laboratory environment. A 5-stage BNR system (anaerobic-anoxic-3 stage oxic) was operated with the HRTs from 3.9 to 7.6 hours. In order to determine the sludge settling properties, both SVI and ECP content were monitored. The ECP contents in the sludge sample were measured by the slime-washing step followed by high-G centrifugation and sonication. The gel-electrophoresis was used to detect the DNA in the sonicated samples to determine the intracellular polymer contamination. It has been found that the anaerobiosis in the anaerobic and anoxic zone that consisted of 37% of reactor volume could not deteriorate the sludge settling properties even at the HRT of 3.9 hours. The SVI values of sludge taken from the reactor with the HRT of 7.2 hours averaged to less than 50 mL/gr. It was postulated that a fast settling sludge in the BNR system could not always ensure production of clear effluent. The sludge with very low SVI might not achieve a complete biological flocculation potential. In addition, the degree of denitrification in the BNR system could be related to the sludge settleability.