The role of compactibility in liquid–solid separation of wastewater sludges

2006 ◽  
Vol 53 (7) ◽  
pp. 121-126 ◽  
Author(s):  
E. Emir ◽  
A. Erdincler
Keyword(s):  
Particle Size ◽  
Specific Resistance ◽  
Particle Packing ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Solids Concentration ◽  
Lower Particle Size ◽  
Wastewater Sludges

The dewaterability of sludges is generally evaluated by the measurement of specific resistance to filtration (SRF) and capillary suction time (CST). It is generally, but not truly, agreed that the lower figures of these parameters indicate the easiness of sludge dewatering. The biological sludges which have the lower particle size and EPS contents may be characterised as hard-to-filter sludges based on SRF and CST measures. However, cake solids concentration of such a kind of sludge can be unexpectedly higher when the centrifugation is used as the dewatering mechanism. This study introduces compactibility, which is cake solids concentration of sludges after centrifugation as a new measure of dewaterability of hard-to-filter sludges. The results of this study claim that although the filterability indexes (CST and SRF) are moderately high for hard-to-filter sludges, their compactibility might be high indicating particle packing characteristics.

Comparison of lime and alum as oily sludge conditioners

1997 ◽  
Vol 36 (12) ◽  
pp. 117-124 ◽  
Author(s):  
Tay Joo Hwa ◽  
S. Jeyaseelan
Keyword(s):  
Specific Resistance ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Oily Sludge ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Sludge Cake ◽  
Solids Content ◽  
Optimum Chemical

Chemical conditioning improves sludge dewatering. Choice of chemical conditioners is very much dependent on the characteristics of the sludges and the type of dewatering devices. Lime, alum, ferric chloride and polyelectrolytes are commonly used chemical conditioners. Anaerobic digested sludge samples collected from a sewage treatment plant with different oil contents varying from 1.8% to 8.0% by weight have been examined in the laboratory to find out their specific resistance, capillary suction time and filter yield. Lime and alum were used separately as conditioners. Different dosages of conditioner varying from 2% to 12% by weight were used to determine the optimum chemical dosage for varying oil contents. Lime dosages of about 6% were found to yield favourable characteristics. Addition of alum decreases the specific resistances and capillary suction times of oily sludges rapidly up to 4% dosages. Alum dosages beyond 4% only increase the solids content in the sludge cake and increase the sludge volume to be handled. A correlation between CST and specific resistance to filtration was established. CST can be measured easily and quickly in the laboratories. Using the CST and the correlation a quick prediction on dewaterability can be established.

On the role of aluminium hydroxide in the conditioning of an alum sludge

1998 ◽  
Vol 38 (2) ◽  
pp. 33-40 ◽  
Author(s):  
E. N. Papavasilopoulos ◽  
D. H. Bache
Keyword(s):  
Specific Resistance ◽  
Polymer Adsorption ◽  
Optimum Dose ◽  
Capillary Suction ◽  
Viscosity Measurements ◽  
Nonionic Polymer ◽  
Saturation Coverage ◽  
Prime Determinant ◽  
Alum Sludge

This study dwells on the optimum dosage of a nonionic polymer during the conditioning of an alum sludge arising from the treatment of a coloured, upland water. Dewaterability was investigated through Capillary Suction Time (CST) and Specific Resistance to Filtration (SRF) tests, together with viscosity measurements on the liquid phase of sludge. The optimum dose associated with CST and SRF was 1.5 kg/T while for the case of viscosity behaviour it was 2.0 kg/T. From polymer adsorption studies on the sludge, it was shown that the optimum doses associated with the viscosity measurements were linked to a dose at which the adsorption capacity reached a saturation value (1.8 kg/T). The SRF and CST optima were found to correspond to a state of 70-85% of the saturation coverage. Parallel adsorption tests on alum sludge and pure precipitate showed that polymer adsorption on the precipitate was the prime determinant of the adsorption characteristics of the sludge and suggested that the optimum dose was linked to the mass of precipitate present in the sludge.

Sludge dewatering using centrifuge with thermal/polymer conditioning

2001 ◽  
Vol 44 (10) ◽  
pp. 321-325 ◽  
Author(s):  
C.F. Lin ◽  
Y. Shien
Keyword(s):  
Water Treatment ◽  
Thermal Treatment ◽  
Specific Resistance ◽  
Treatment Plant ◽  
Water Treatment Plant ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Temperature Changes ◽  
Biological Sludge ◽  
Sludge Particle

Sludge dewatering is preceded by a conditioning operation to enhance water removal efficiency. In the conditioning operation, chemical coagulants or polymers are added to promote sludge particle aggregation for easier dewatering. In this study, an alternative conditioning method for sludge thermal treatment at temperatures up to 80°C was extensively investigated. Dewatering characteristics such as sludge capillary suction time and specific resistance to filtration, sludge viscosity and concentration of solid cakes were examined thoroughly. A good correlation between capillary suction time and specific resistance to filtration was established for sludges from water treatment, but not for biological sludge. Cationic polymer exhibits the best enhancement on sludge moisture removal. The sludge rheogram varies from 60 to 5 cP as temperature changes from 20 to 80°C for sludges from water treatment plant. The dewatering ability of sludge can be greatly enhanced by thermal treatment in conjunction with the use of polymers.

Dewatering Base Metal Mine Drainage Sludge

1975 ◽  
Vol 10 (1) ◽  
pp. 42-64
Author(s):  
H. Campbell ◽  
B.P. Le Clair
Keyword(s):  
Base Metal ◽  
Pilot Plant ◽  
Suspended Solids ◽  
Filter Press ◽  
Vacuum Filter ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Bench Scale ◽  
Metal Mine ◽  
Solids Concentration

Abstract Sludge dewatering studies were carried out at the Brunswick Mining and Smelting Corporation’s No. 12 mill as part of a pilot plant program on the removal of heavy metals from base metal mining effluents. A mobile sludge dewatering trailer located on site was used to assess the feasibility of basket centrifugation, solid bowl centrifugation, vacuum filtration and pressure filtration as possible methods of dewatering. The effect of control variables on performance, and the applicability of existing bench-scale methods to design were studied for each process. Cake solids of 25% and suspended solids recoveries of 95% were attainable on all four pilot-scale dewatering units. The use of a basket centrifuge may not be practical due to very short cycle times which result from the high sludge feed solids concentration (7%). The addition of cationic polyelectrolyte was necessary to achieve recoveries in excess of 75% with the centrifuges, but was not required with either the vacuum filter or the filter press. The filter press, which produced a filter cake of 38 to 45% and a filtrate quality of 0 to 10 mg/1 of suspended solids, produced the best cake solids and effluent quality. However, the vacuum filter would require the lowest operating cost of units tested. Bench-scale work included penetration tests, Buchner funnel tests, capillary suction time, leaf filter tests and bench filter tests. Scale-up from bench to pilot plant was not possible for centrifugation with existing methodology. Filter yields and pressing time were predicted from bench tests for the vacuum filter and pressure filter respectively, and compared with the results obtained. Specific sludge characteristics such as zeta potential, particle size distribution and rheology were also determined and related to solids concentration and level of polymer addition.

The role of carbohydrate and protein parts of extracellular polymeric substances on the dewaterability of biological sludges

2004 ◽  
Vol 50 (9) ◽  
pp. 49-56 ◽  
Author(s):  
S. Cetin ◽  
A. Erdincler
Keyword(s):  
Extracellular Polymeric Substances ◽  
Cation Exchange Resin ◽  
Capillary Suction ◽  
Factors Affecting ◽  
Biological Sludge ◽  
Floc Structure ◽  
Solids Concentration ◽  
Ft Ir ◽  
Synthetic Media

There are many factors affecting the biological sludge dewaterability such as particle size distribution, floc structure, extracellular polymeric substances (EPS), etc. In this research, the role of the protein and carbohydrate parts of EPS (EPScarbohydrate, and EPSprotein) on the dewaterability of biological ludges was investigated. The sludge EPS composition was altered by feeding the sludges of same origin, in different reactors, with synthetic media having carbon to nitrogen (C/N) ratios of 8, 19 and 30 (in terms of OD/NH3-N), respectively. EPS in sludge samples were extracted by a cation exchange resin (CER). The characteristics of EPS were investigated by analytical methods and by using FT-IR spectroscopy. The dewaterability of the sludges was determined in terms of filterability and compactibility. Filterability, as filterability constant (X), and compactibility, as cake solids concentration, of sludges were determined by using the capillary suction time (CST) test and the centrifugation, respectively. The floc structure of sludge samples was also observed microscopically. Filterability and compactibility of the sludge samples were improved considerably with the increasing carbohydrate part and the decreasing protein part of the sludge EPS. EPSprotein was inversely related to the cake solids concentration, which might be explained by the water holding capacity of EPSprotein. Filterability and compactibility of sludges improved by the increase of the size and strength of the flocs.

Effect of using different proportions of inoculum during bioleaching on sludge dewaterability

2018 ◽  
Vol 2017 (3) ◽  
pp. 802-811 ◽  
Author(s):  
Qingfang Zhang ◽  
Wenfeng Yang ◽  
Qiyong Yang ◽  
Tianfeng Wang ◽  
Shenliang Chen ◽  
...  
Keyword(s):  
Crucial Role ◽  
Extracellular Polymeric Substances ◽  
Reduction Potential ◽  
Specific Resistance ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Geological Materials ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Sludge Dewaterability

Abstract Bioleaching, the addition of bacteria to geological materials, has been applied to sludge to remove metals and improve upon sludge dewaterability. This paper investigates the effect of using different quantities of inoculum (bacteria) during bioleaching on sludge dewaterability. The analysis was based on bioleaching experiments conducted in a 20 L bio-reactor using different quantities of inoculum (20%, 10%, 5%, 2%, 0%). Changes in pH, oxidation reduction potential (ORP), capillary suction time (CST), specific resistance to filtration (SRF) and extracellular polymeric substances (EPS) were determined to gauge sludge dewatering. Results indicate that sludge dewaterability during the 2%, 10%, and 20% inoculum experiments declined through time. Decreased dewaterability is attributed to increases in the quantity of proteins and polysaccharides in slime EPS. Dewaterability improved during the 5% inoculum experiment, and reached a maximum when pH was 2.3. During this latter experiment, CST and SRF were reduced by 74% and 62%, respectively, in comparison to control conditions, while total EPS content decreased by 71%. The decrease in total EPS was primarily due to a decrease in proteins associated with tightly bound EPS (TB-EPS). Thus, changes in the amount of proteins in TB-EPS and sludge pH played a crucial role in sludge dewaterability.

Fibrin Formation: The Role of the Fibrinogen-Fibrin Monomer Complex

1976 ◽  
Vol 36 (01) ◽  
pp. 037-048 ◽  
Author(s):  
Eric P. Brass ◽  
Walter B. Forman ◽  
Robert V. Edwards ◽  
Olgierd Lindan
Keyword(s):  
Particle Size ◽  
Induction Period ◽  
Fibrin Clot ◽  
Clot Formation ◽  
Appreciable Amount ◽  
Buffer System ◽  
Homeostatic Mechanism ◽  
Fibrin Formation ◽  
Fibrin Monomer

SummaryThe process of fibrin formation using highly purified fibrinogen and thrombin was studied using laser fluctuation spectroscopy, a method that rapidly determines particle size in a solution. Two periods in fibrin clot formation were noted: an induction period during which no fibrin polymerization occurred and a period of rapid increase in particle size. Direct measurement of fibrin monomer polymerization and fibrinopeptide release showed no evidence of an induction period. These observations were best explained by a kinetic model for fibrin clot formation incorporating a reversible fibrinogen-fibrin monomer complex. In this model, the complex serves as a buffer system during the earliest phase of fibrin formation. This prevents the accumulation of free polymerizable fibrin monomer until an appreciable amount of fibrinogen has reacted with thrombin, at which point the fibrin monomer level rises rapidly and polymerization proceeds. Clinically, the complex may be a homeostatic mechanism preventing pathological clotting during periods of elevated fibrinogen.

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