Regimes for zone settling of waste activated sludges

Chen, G.W.; Chang, In-Soung; Hung, W. T.; Lee, D.J.

doi:10.1016/0043-1354(95)00322-3

Cited by 52 publications

(27 citation statements)

References 15 publications

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“…6 provides ample evidence that the settling rate during underdose range accelerates. This "self-speed up" phenomenon was also reported by Chen et al [6] who pointed out that the activated sludge zone settling curve (interfacial height vs. settling time)…”

Section: Fig 5 [Here]mentioning

confidence: 59%

“…The ratios () between the settling cylinder tube diameter to the floc mean diameter d 50 [5] for the conditions of this study are listed in Table 3. Although there is no standard value of , from literature Chen et al [6] pointed out that  should be in the range of 200 -1000 in which the wall effect might be negligible. For such a case, Jaara [7] reported the range of  in 50 -100.…”

Section: Fig 5 [Here]mentioning

confidence: 99%

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Settling behaviour of polymer flocculated water-treatment sludge I: analyses of settling curves

Zhao

2004

Separation and Purification Technology

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Publication informationSeparation and Purification Technology, 35 (1): 71-80Publisher ElsevierLink to online version http://dx.doi.org/10.1016/S1383-5866(03)00132-1 Item record/more information http://hdl.handle.net/10197/3182 Publisher's statementThis is the author's version of a work that was accepted for publication in Separation and Purification Technology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Separation and Purification Technology, 35 (1): 71-80 DOI:10.1016/S1383-5866(03)00132-1 Publisher's version (DOI)http://dx.doi.org/10.1016/S1383-5866(03)00132-1Some rights reserved. For more information, please see the item record link above.--1-- **************************************************************** AbstractSettling behaviour of polymer conditioned water-treatment sludge was investigated in this study for the purpose of a better understanding of a so-called "CML30 method", which was developed in previous study to evaluate the optimum polymer dosage in sludge conditioning.The "CML30 method" is on the basis of a 30 min settling test in 100 ml measuring cylinders.In this study, the series of settling tests in 100, 500 and 1000 ml measuring cylinders were respectively performed and the settling curves (interfacial height to dose and time) were the main focuses for presentation and analyses in great detail in this paper. According to the experimental data presented in this study, settling behaviour may be controlled by both the growth of large sized floc and progressively decreased viscosity. The "speed-up" phenomenon in small polymer dose range obviously enhances the settlement and plays a critical role for the settling set in a 100 ml measuring cylinder at a special dose and at the settling time interval 5-30 min. It is such special observation that leads to the success of socalled ad hoc "CML30 method". However, sludge settling behaviour could be controlled by the formation of networked structure which is involved in excess polymer during the large --2--range (say over 10 mg/l for the case tested) of polymer doses. The higher liquid viscosity values derived from excess polymer will increase the drag force for the resistance of the settlement. In addition, wall effects are likely to interplay with the internal networked structure in large dosed region.

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Section: Fig 5 [Here]mentioning

confidence: 59%

Section: Fig 5 [Here]mentioning

confidence: 99%

Settling behaviour of polymer flocculated water-treatment sludge I: analyses of settling curves

Zhao

2004

Separation and Purification Technology

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“…Although this kind of settling has been examined in many studies [3,4,5], knowledge of the effect of polymer conditioning on thickening behaviour is still lacking. In particular, the interaction between polymer and water treatment sludge, commonly known as alum sludge, is complex and the settling behaviour of this suspension is a physicochemical process.…”

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confidence: 99%

Settling behaviour of polymer flocculated water-treatment sludge II: effects of floc structure and floc packing

Zhao

2004

Separation and Purification Technology

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“…Settlability test can be used to investigate the sludge-water separation behavior (Chen, et al, 1996). The settlability test was done to investigate the sludge-water separation behavior.…”

Section: Methodsmentioning

confidence: 99%

Effects of aeration rate and detention time on thermophilic aerobic digestion of mixed sludge and its dewaterability

Attar

Bina

Moeinian

2005

Int. J. Environ. Sci. Technol.

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Thermophilic aerobic digestion (TAD) is a possible alternative for rapid sludge degradation and producing Class A biosolids. Aeration rate and detention time are two of the important parameters in TAD processes due to rapidly growing thermophilic bacteria population, limited solubility of oxygen at high temperatures and the need to prevent cooling of TAD process. Also the current knowledge and understanding of dewatering TAD biosolids are limited and incompelet.The objectives of this study were to investigate the effects of various aeration rates and detention time on some characteristics of mixed sewage sludge. Four glass-cylindrical digesters with 7 liters of sludge in each, placed in a water bath and were operated at 55 º C with the aeration rates of 2.14, 3.00, 3.86 and 4.71 volume of air per volume of sludge per hours. It was found the increase in aeration rate decreased the required detention time in order to meet the Class A sludge regulations to reduce vector attraction. The values of Oxidation-Reduction Potential (ORP) were changed from negative values to positiv ones and the values of pH were increased from around neutral to slightly basic, but this increases were occured at different detention times. TAD affected dewaterability of mixed sewage sludge and produced biosolids with higher specific resistance to filtration (lower dewaterability) than undigested sludge. Thermophically digested sludge has a good setteling behavior and air drying on sand bed. Key words: Sludge processing, thermophilic aerobic digestion, Class A biosolid, oxidation-reduction potential (ORP), sludge dewaterability, specific resistance to filtration (SRF) AbstractThermophilic aerobic digestion (TAD) is a possible alternative for rapid sludge degradation and producing Class A biosolids. Aeration rate and detention time are two of the important parameters in TAD processes due to rapidly growing thermophilic bacteria population, limited solubility of oxygen at high temperatures and the need to prevent cooling of TAD process. Also the current knowledge and understanding of dewatering TAD biosolids are limited and incompelet. The objectives of this study were to investigate the effects of various aeration rates and detention time on some characteristics of mixed sewage sludge. Four glass-cylindrical digesters with 7 liters of sludge in each, placed in a water bath and were operated at 55 º C with the aeration rates of 2.14, 3.00, 3.86 and 4.71 volume of air per volume of sludge per hours. It was found the increase in aeration rate decreased the required detention time in order to meet the Class A sludge regulations to reduce vector attraction. The values of oxidation-reduction potential (ORP) were changed from negative values to positiv ones and the values of pH were increased from around neutral to slightly basic, but this increases were occured at different detention times. TAD affected dewaterability of mixed sewage sludge and produced biosolids with higher specific resistance to filtration (lower dewaterability) than undi...

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Regimes for zone settling of waste activated sludges

Cited by 52 publications

References 15 publications

Settling behaviour of polymer flocculated water-treatment sludge I: analyses of settling curves

Settling behaviour of polymer flocculated water-treatment sludge I: analyses of settling curves

Settling behaviour of polymer flocculated water-treatment sludge II: effects of floc structure and floc packing

Effects of aeration rate and detention time on thermophilic aerobic digestion of mixed sludge and its dewaterability

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