Floc breakup in activated sludge plants

Das, Debankur; Keinath, Thomas M.; Parker, Denny; Wahlberg, Eric J.

doi:10.2175/wer.65.2.6

Cited by 39 publications

(26 citation statements)

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“…When the turbulent dissipation rate of the main part was 2.45×10 -3 m 2 /s 3 and other part was 7.75×10 -6 m 2 /s 3 , the minimal SVI and maximal ZSV were achieved. The best root-mean-square velocity gradient in 180r/min stirring speed was 110s -1 through calculation, which is similar with the Das's [11]. It's also an evidence for the result of turbulence optimizing.…”

Section: A Distribution Of Turbulent Dissipation Rate Under Differensupporting

confidence: 78%

Sedimentation of Activated Sludge Under Different Shear Conditions

Feng

Chao

2009

2009 3rd International Conference on Bioinformatics and Biomedical Engineering

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Laboratory experiments were carried out using five identical sequencing batch reactors (SBR) to investigate the effect of shear conditions on sedimentation of activated sludge in wastewater treatment. All of the aerated stirred bioreactors, which volume was 2L each and were seeded with activated sludge, were fed at the same rate with synthetic wastewater. Shear conditions were changed by adjustment of stirring paddle in SBR and were analyzed by the technology of PIV (Particle Image Velocimetry). Based on analysis, the turbulent dissipation rate of specific area was used to evaluate the shear conditions in aerated stirred bioreactors. Attempts were made to relate the settlement characteristics of activated sludge with turbulent dissipation rate. The results showed that using the turbulent dissipation rate in specific area to evaluate the shear conditions in stirred bioreactors was effective. Sedimentation of activated sludge in bioreactors is sensitive to variable shear condition. As the stirring speed rose, the turbulent energy dissipation of different parts in bioreactor increased gradually, the settleability of activated sludge was improved first and then deteriorated. The best indexes of turbulent dissipation rate in the experiment were 2.45×10 -3 m 2 /s 3 of main part and 7.75×10 -6 m 2 /s 3 of other part. Settleability of activated sludge can be improved in practice by declining the turbulent dissipation rate of main part and raising that of main part.

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Section: A Distribution Of Turbulent Dissipation Rate Under Differensupporting

confidence: 78%

Sedimentation of Activated Sludge Under Different Shear Conditions

Feng

Chao

2009

2009 3rd International Conference on Bioinformatics and Biomedical Engineering

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“…The root mean square velocity gradient (G) has been used as a measure of turbulence in several activated sludge studies (Das et al, 1993, Parker 1970. The G value for the SMBR and CAS reactors was calculated from:…”

Section: Measurement Of Turbulencementioning

confidence: 99%

Physical, Chemical and Biological Properties of Submerged Membrane Bioreactor and Conventional Activated Sludges

Merlo¹,

Trussell²,

Hermanowicz

et al. 2004

proc water environ fed

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A pilot-scale submerged membrane bioreactor (SMBR) and two bench-scale conventional activated sludge (CAS) reactors were operated on municipal primary effluent over a range of mean cell residence times (MCRTs) from 2-10 d. The reactors had different turbulence levels. The root mean square velocity gradient (G) of the SMBR was 632 s -1 ; for the CAS reactors the G values were 72 s -1 and 250 s -1 . The sludges from all systems were analyzed for particle size distribution (PSD), colloidal material, extracellular polymer substances (EPS) and filamentous microorganisms. Capillary suction time (CST) and time to filter (TTF) analyses were also performed. The SMBR sludges had the highest amount of small particles and higher levels of colloidal material than the CAS sludges. This was attributed to its higher G value and the use of a membrane for solids-liquid separation. The SMBR sludge contained the higher levels of total filamentous organisms attributable largely to its higher nocardioform level. This resulted from more efficient foam trapping by the SMBR. The normalized CST values of the SMBR sludge were lower than for the CAS sludges. This was attributed to its lower EPS content. There was no significant difference between the normalized TTF values of the SMBR and the CAS sludges. This was attributed to the offsetting effects of colloidal material and EPS contents. KEYWORDSSubmerged membrane bioreactor (SMBR), particle size distribution (PSD), extracellular polymeric substances (EPS), filamentous microorganisms, nocardioform organisms, capillary suction time (CST), time to filter (TTF) BACKGROUND

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“…Hence, the ability of an SST to act successfully as a clarifier is highly dependent on the potential of the microorganisms to form a flocculent biomass which settles and compacts well, producing a clear effluent (Das et al, 1993). The aim of the flocculation process is to combine individual flocs into large and dense flocs that settle rapidly and to incorporate discrete particles that normally would not settle alone.…”

Section: Measuring Flocculation State Of Activated Sludgementioning

confidence: 99%

“…Distinguishing between flocculation problems and poor hydrodynamics is more challenging but can be accomplished by means of a Dispersed Suspended Solids/Flocculated Suspended Solids (DSS/FSS) test (Wahlberg et al, 1995) 6.3.1 DSS/FSS test 6.3.1.1 Goal and application Wahlberg et al (1995) proposed a procedure that makes it possible to distinguish between hydraulic and flocculation problems in a given SST, the so-called DSS/FSS test. Using the DSS and/or FSS test has been proven to be a useful technique in several studies: it makes it possible (i) to assess the flocculation and deflocculation processes in transmission channels (Das et al, 1993;Parker and Stenquist, 1986;Parker et al, 1970), (ii) to determine the influence of hydraulic disturbances in the aeration basin on the effluent nonsettleable sludge particles (Das et al, 1993;Parker et al, 2000Parker et al, , 1970 and (iii) to determine the benefits of a flocculation procedure in decreasing effluent suspended solids in a WWTP (Parker et al, 2000;Wahlberg et al, 1994). …”

Section: Measuring Flocculation State Of Activated Sludgementioning

confidence: 99%

Experimental Methods in Wastewater Treatment

Loosdrecht¹,

Nielsen²,

López-Vázquez³

et al. 2016

Water Intelligence Online

143

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PrefaceWastewater treatment is a core technology for water resources protection and reuse, as is clearly demonstrated by the great success of its consequent implementation in many countries worldwide. During the last decennia scientific research has made vast progress in understanding the complex and interdisciplinary aspects of the biological, biochemical, chemical and mechanical processes involved. It can be concluded that the global application of existing knowledge and experience in wastewater treatment technology will represent a cornerstone in future water management, as expressed in the Strategic Development Goals accepted by the UN in September 2015.Only about one fifth of the wastewater produced globally is currently being adequately treated. To achieve the goal for sustainable water management by 2030 would require extra wastewater treatment facilities for about 600,000 people each day. I am convinced that this book will make its own significant contribution to meeting this ambitious goal.In the near future, most of the global population will live in cities and in low and middle-income countries, where most wastewater is not adequately treated. Probably the most limiting factor in achieving the goals for sustainable water management is the lack of qualified, well-trained professionals, able to comprehend the scientific research results and transfer them into practice. It is therefore of prime importance to make currently available scientific advances and proven experiences in wastewater treatment technology applications easily accessible worldwide. This was one of the drivers for the development of this book, which represents an innovative contribution to help overcome such a capacity development challenge. The book is most definitely expected to contribute to bridging the gaps between the science and technology, and their practical applications.The great collection of authors and reviewers represents an interdisciplinary team of globally acknowledged experts. The book will therefore make a major contribution to establishing a common professional language, enhancing global communication between wastewater professionals. In addition, the authors have linked the description of the scientific basis for wastewater treatment processes with a video-based online course for the training of students, researchers, engineers, laboratory technicians and treatment plant operators, demonstrating commonly accepted experimentation procedures and their application for lab-, pilot-, and full-scale treatment plant operation.From the perspective of the IWA this book also has the great potential to enhance the development of a new generation of researchers and enable them to communicate on a global scale and beyond their specific field of expertise. Both aspects are urgently needed to develop adapted solutions for specific local conditions and to make them globally available for implementation.There has been a trend for some time that scientific research and practice have been growing apart from each other. Part of the rea...

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Floc breakup in activated sludge plants

Cited by 39 publications

References 0 publications

Sedimentation of Activated Sludge Under Different Shear Conditions

Sedimentation of Activated Sludge Under Different Shear Conditions

Physical, Chemical and Biological Properties of Submerged Membrane Bioreactor and Conventional Activated Sludges

Experimental Methods in Wastewater Treatment

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