Sludge characteristics, system performance and microbial kinetics of ultra-short-SRT activated sludge processes

Conventional and oxygen bleaching effluents from hardwood kraft pulp mills were treated in laboratory-scale activated sludge processes. The main interest was the fate of organochlorine compounds in the activated sludge process. In the treatment of conventional bleaching wastewaters the BOD7-reduction was 80-91 % and in oxygen bleaching wastewaters 86-93 %. The respective CODCr removals were about 40 % and about 50 %. The AOX reductions were on average 22 % and 40 % in the treatment of conventional and oxygen bleaching effluents, respectively. The reductions of chlorinated phenols, guajacols and catecols were usually more than 50 % in both reactors. Very little accumulation of AOX into the sludge was observed. The stripping of AOX from aeration unit was insignificant.

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Small Activated Sludge Performance and Viability Characteristics under Intermittent and Reduced Flows

Water Science & Technology ◽

10.2166/wst.1993.0248 ◽

1993 ◽

Vol 28 (10) ◽

pp. 309-316

Author(s):

Bilsen Beler Baykal

Keyword(s):

Activated Sludge ◽

System Performance ◽

Treatment Plant ◽

Generation Model ◽

Transient States ◽

Stepwise Manner ◽

Seasonal Basis ◽

Soluble Substrate ◽

House Site ◽

Activated Sludge Systems

Small activated sludge systems operate in transient states under intermittent and variable flows. Simulations for such a treatment plant in a summer house site operating on a seasonal basis is investigated for system performance and viability using the five component inert soluble substrate generation model. The results have revealed that the viability drops to zero within the first month after the cessation of the feed for intermittently loaded systems that are fed during the summer months, while it never reaches that value for systems operating all year round with reduced flows off season. Restartup is compulsory for the intermittent loadings while the system adapts itself in a stepwise manner for the year round operation. Other factors being comparable, conventional operation with shorter sludge ages may be preferable since viability of the sludge is higher and the effluent COD is comparable.

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Design and Operational Analyses of Activated Sludge Processes Using Respirometrically Calibrated Models

Water Science & Technology ◽

10.2166/wst.1992.0456 ◽

1992 ◽

Vol 26 (3-4) ◽

pp. 753-762 ◽

Cited By ~ 5

Author(s):

A. F. Rozich

Keyword(s):

Activated Sludge ◽

Model Calibration ◽

Process Model ◽

Process Analysis ◽

Case Histories ◽

Model Case ◽

Operational Strategies ◽

Analysis Methodology ◽

Technical Basis ◽

Activated Sludge Processes

The purpose of this paper is to present the background and examples of methodology which enable environmental engineers and scientists to analyze activated sludge processes much more effectively than is otherwise possible with conventional approaches. Good process analyses are key for devising optimal design and operational strategies. The key features to the technique presented herein are the field-proven predictability of the model and the methodology for collecting data needed for calibrating the process model. Case histories prove the predictability of the model that is associated with the process analysis approach. The advantage of the approach advocated herein is the use of respirometric techniques to calibrate the model. These methods enable the process analyst to collect the requisite data for model calibration in twenty-four hours or less. This feature enables one to use this process analysis methodology for both design and operational applications. The paper will present the technical basis for the process model and how respirometric methods are utilized to compute biokinetic constants in a manner which is consistent with kinetic theory. Case histories will be discussed that demonstrate the predictability of the modeling approach and demonstrate the utility of this tool for process analysis.

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Automatic monitoring of denitrification rates and capacities in activated sludge processes using fluorescence or redox potential

Water Science & Technology ◽

10.2166/wst.1998.0519 ◽

1998 ◽

Vol 37 (12) ◽

pp. 121-129 ◽

Cited By ~ 3

Author(s):

S. Isaacs ◽

Terry Mah ◽

S. K. Maneshin

Keyword(s):

Biological Activity ◽

Activated Sludge ◽

Redox Potential ◽

Treatment Plant ◽

Automatic Monitoring ◽

Organic Substrate ◽

Anoxic Zone ◽

Optimal Dosing ◽

Denitrifying Microorganisms ◽

Activated Sludge Processes

A novel method is described to automatically estimate several key parameters affecting denitrification in activated sludge processes: the nitrate concentration, the denitrification capacity, and the maximum (substrate unlimited) and actual denitrification rates. From these, the concentration of active denitrifying microorganisms and the quality of available organic substrate pool can be estimated. Additionally, a modification of the method allows the determination of the efficacy of various carbon substrates to enhance denitrification, and this can be used to determine optimal dosing rates of an external carbon source. The method is based on measurements of either fluorescence or redox potential (ORP) in an isolated mini-reactor, the Biological Activity Meter (BAM), situated in the anoxic zone of the wastewater treatment plant. Advantages of the method are that it is in situ, operating at the same temperature as in the measured anoxic zone, requires no pumps or pipes for mixed liquor sampling, consumes little or no reagents, and uses measurement signals which are instantaneous and low maintenance, one of which provides a direct measure of biological activity.

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Floc size distribution and bacterial activities in membrane separation activated sludge processes for small-scale wastewater treatment/reclamation

Water Science & Technology ◽

10.2166/wst.1997.0241 ◽

1997 ◽

Vol 35 (6) ◽

pp. 37-44 ◽

Cited By ~ 38

Author(s):

Boran Zhang ◽

Kazuo Yamamoto ◽

Shinichiro Ohgaki ◽

Naoyuki Kamiko

Keyword(s):

Wastewater Treatment ◽

Activated Sludge ◽

Municipal Wastewater ◽

Membrane Separation ◽

Small Scale ◽

Nitrification Rate ◽

Floc Size ◽

Denitrification Activity ◽

Concentration Changes ◽

Activated Sludge Processes

Activated sludges taken from full-scale membrane separation processes, building wastewater reuse system (400m3/d), and two nightsoil treatment plants (50m3/d) as well as laboratory scale membrane separation bioreactor (0.062m3/d) were analyzed to characterize membrane separation activated sludge processes (MSAS). They were also compared with conventional activated sludges(CAS) taken from municipal wastewater treatment plants. Specific nitrification activity in MSAS processes averaged at 2.28gNH4-N/kgMLSS.h were higher than that in CAS processes averaged at 0.96gNH4-N/kgMLSS.h. The denitrification activity in both processes were in the range of 0.62-3.2gNO3-N/kgMLSS.h without organic addition and in the range of 4.25-6.4gNO3-N/kgMLSS.h with organic addition. The organic removal activity in nightsoil treatment process averaged at 123gCOD/kgMLSS.h which was significantly higher than others. Floc size distributions were measured by particle sedimentation technique and image analysis technique. Flocs in MSAS processes changed their sizes with MLSS concentration changes and were concentrated at small sizes at low MLSS concentration, mostly less than 60 μm. On the contrary, floc sizes in CAS processes have not much changed with MLSS concentration changes and they were distributed in large range. In addition, the effects of floc size on specific nitrification rate, denitrification rate with and without organic carbon addition were investigated. Specific nitrification rate was decreased as floc size increased. However, little effect of floc size on denitrification activity was observed.

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Minimization of activated sludge production by chemically stimulated energy spilling

Water Science & Technology ◽

10.2166/wst.2000.0269 ◽

2000 ◽

Vol 42 (12) ◽

pp. 189-200 ◽

Cited By ~ 32

Author(s):

G.-H. Chen ◽

H.-K. Mo ◽

S. Saby ◽

W.-k. Yip ◽

Y. Liu

Keyword(s):

Activated Sludge ◽

Growth Yield ◽

Dry Weight ◽

Staining Technique ◽

Microbial Culture ◽

Dapi Staining ◽

E Coli ◽

Energy Spilling ◽

Activated Sludge Processes ◽

Sludge Production

Minimization of excess sludge production in activated sludge processes has been pursued around the world in order to meet stringent environmental regulations on sludge treatment and disposal. To achieve this goal, physical, chemical, and biological approaches have been proposed. In this paper, a chemical compound, 3,3′,4′,5-tetrachlorosalicylanilide (TCS) was tested for enhancing microbial energy spilling of the sludgeso as to minimize its growth. In order to examine this, an exploratory study was conducted using both batch and continuous activated sludge cultures. Batch experiments with these two cultures were carried out at different initial concentrations of TCS. It has been confirmed that an addition of TCS is effective in reducing the production of both the sludge cultures, particularly the continuous culture where the observed growth yield was reduced by around 70%, when the initial TCS concentration was 0.8 ppm. Meanwhile, the substrate removal activity of this culture was found not to be affected at this TCS concentration. To further evaluate the TCS effect, a pure microbial culture of E. coli was employed. Batch experiment results with this culture implied that TCS might be able to reduce the cell density of E. coli drastically when an initial TCS concentration was greater than 0.12 ppm. It was also found that TCS was not toxic to this type of bacteria. Microscopic examinations with a 4′, 6-diamidino-2-phenylindole (DAPI) staining technique revealed that TCS neither affected the cell division nor altered the cell size of E. coli. However, both the cell ATP content and the cell dry weight were reduced significantly with the addition of TCS.

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