A methodological approach for direct quantification of the activated sludge floc size distribution by using different techniques

2009 ◽  
Vol 60 (7) ◽  
pp. 1857-1867 ◽  
Author(s):  
R. Govoreanu ◽  
H. Saveyn ◽  
P. Van der Meeren ◽  
I. Nopens ◽  
P. A. Vanrolleghem
Keyword(s):  
Activated Sludge ◽  
Size Distribution ◽  
Methodological Approach ◽  
Measurement Techniques ◽  
Spherical Particles ◽  
Experimental Conditions ◽  
Detection Range ◽  
Floc Size ◽  
In Series ◽  
High Concentrations

The activated sludge floc size distribution (FSD) is investigated by using different measurement techniques in order to gain insight in FSD assessment as well as to detect the strengths and limitations of each technique. A second objective was to determine the experimental conditions that allow a representative and accurate measurement of activated sludge floc size distributions. Laser diffraction, Time Of Transition (TOT) and Dynamic Image Analysis (DIA) devices were connected in series. The sample dilution liquid, the dilution factor and hydraulic flow conditions avoiding flocculation proved to be important. All methods had certain advantages and limitations. The MastersizerS has a broader dynamic size range and provides accurate results at high concentrations. However, it suffers from an imprecise evaluation of small size flocs and is susceptible to particle shape effects. TOT suffers less from size overestimation for non-spherical particles. However, care should be taken with the settings of the transparency check. Being primarily a counting technique, DIA suffers from a limited size detection range but is an excellent technique for process visualization. All evaluated techniques turned out to be reliable methods to quantify the floc size distribution. Selection of a certain method depends on the purpose of the measurement.

Simultaneous determination of activated sludge floc size distribution by different techniques

2004 ◽  
Vol 50 (12) ◽  
pp. 39-46 ◽  
Author(s):  
R. Govoreanu ◽  
H. Saveyn ◽  
P. Van der Meeren ◽  
P.A. Vanrolleghem
Keyword(s):  
Image Analysis ◽  
Activated Sludge ◽  
Size Distribution ◽  
Bimodal Distribution ◽  
Pilot Scale ◽  
Automated Image Analysis ◽  
Image Analysis System ◽  
Floc Size ◽  
In Series ◽  
Log Normal

The activated sludge floc size distribution (FSD) is investigated by using different techniques and the results are compared against each other in order to gain insight into the FSD characteristics, as well as to detect the limitations of each measurement technique. The experimental set-up consisted of three devices coupled in series: a MastersizerS, an automated image analysis system (IMAN) and a CIS-100. The latter instrument has two measurement channels, based on time of transition (TOT), and image analysis (SHAPE) principles. In order to minimise the variability between successive measurements, the activated sludge samples collected from a pilot-scale SBR were flocculated until steady state was achieved. The results show that the MastersizerS and SHAPE devices yield similar volume weighted FSD. In contrast, the IMAN overestimated the floc size and TOT frequently showed a bimodal distribution. The number distributions from TOT and SHAPE were in agreement, while those generated by the MastersizerS were mainly located in the submicron range and those of IMAN corresponded to larger sizes. The experimental distributions show a good fit to the log-normal model. It is shown that the measurement principle is of utmost importance and results transformation may lead to data misinterpretation.

scholarly journals Simulation of Floc Size Distribution in Flocculation of Activated Sludge Using Population Balance Model with Modified Expressions for the Aggregation and Breakage

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Zhenliang Li ◽  
Peili Lu ◽  
Daijun Zhang ◽  
Fuzhong Song
Keyword(s):  
Activated Sludge ◽  
Size Distribution ◽  
Velocity Gradient ◽  
Population Balance ◽  
Balance Model ◽  
Population Balance Model ◽  
Collision Efficiency ◽  
Volume Percentage ◽  
Floc Size ◽  
Breakage Rate

The floc size distribution of activated sludge was simulated successfully by population balance model in the previous study (Population Balance Model and Calibration Method for Simulating the Time Evolution of Floc Size Distribution of Activated Sludge Flocculation. Desalination and Water Treatment, 67, 41-50). However, nonignorable errors exist in the simulation for the volume percentage of large flocs. This paper describes the application of a modified population balance model in the simulation of the time evolution of floc size distribution in activated sludge flocculation process under shear-induced conditions. It was found that the application of modified size dependent collision efficiency, modified breakage rate expression by assuming a maximum value, and binominal daughter-particles distribution function could improve the population balance model for activated sludge flocculation and successfully predict the dynamic changes in volume percentage distribution and mean floc size of activated sludge under different shear conditions. The results demonstrate that the maximum breakage rate was independent on the velocity gradient, and both the collision efficiency and breakage rate coefficient show a power-law relationship with the average velocity gradient; the former decreases while the latter increases with the rise of the average velocity gradient. These findings would help to understand the dynamics of activated sludge flocculation.

Study of kinetics of degradation of cyclohexane carboxylic acid by acclimated activated sludge

2016 ◽  
Vol 73 (10) ◽  
pp. 2552-2558 ◽  
Author(s):  
Chunhua Wang ◽  
Shuian Shi ◽  
Hongyan Chen
Keyword(s):  
Carboxylic Acid ◽  
Activated Sludge ◽  
Degradation Kinetics ◽  
Experimental Conditions ◽  
First Order Kinetics ◽  
Effects Of Ph ◽  
High Concentrations ◽  
Cyclohexane Carboxylic Acid ◽  
Kinetics Of ◽  
Acclimated Activated Sludge

Activated sludge contains complex microorganisms, which are highly effective biodegrading agents. In this study, the kinetics of biodegradation of cyclohexane carboxylic acid (CHCA) by an acclimated aerobic activated sludge were investigated. The results showed that after 180 days of acclimation, the activated sludge could steadily degrade >90% of the CHCA in 120 h. The degradation of CHCA by the acclimated activated sludge could be modeled using a first-order kinetics equation. The equations for the degradation kinetics for different initial CHCA concentrations were also obtained. The kinetics constant, kd, decreased with an increase in the CHCA concentration, indicating that, at high concentrations, CHCA had an inhibiting effect on the microorganisms in the activated sludge. The effects of pH on the degradation kinetics of CHCA were also investigated. The results showed that a pH of 10 afforded the highest degradation rate, indicating that basic conditions significantly promoted the degradation of CHCA. Moreover, it was found that the degradation efficiency for CHCA increased with an increase in temperature and concentration of dissolved oxygen under the experimental conditions.

Linking floc structure and settling properties to activated sludge population dynamics in an SBR

2003 ◽  
Vol 47 (12) ◽  
pp. 9-18 ◽  
Author(s):  
R. Govoreanu ◽  
D. Seghers ◽  
I. Nopens ◽  
B. De Clercq ◽  
H. Saveyn ◽  
...  
Keyword(s):  
Microbial Community ◽  
Activated Sludge ◽  
Size Distribution ◽  
Community Dynamics ◽  
16S Rrna Genes ◽  
Volume Index ◽  
Rrna Genes ◽  
Filamentous Bacteria ◽  
Floc Size ◽  
Stable Conditions

Over a period of 227 days properties of activated sludge grown in an aequencing batch reactor (SBR) operated under stable conditions were analyzed. Settling properties (sludge volume index (SVI)) of the activated sludge were compared with on-line measurements of floc size and size distribution obtained by using a laser light scattering technique (Malvern Mastersizer/S, Malvern, UK), and with measurements of microbial community dynamics analyzed by denaturing gradient gel electrophoresis (DGGE) patterns of 16S rRNA genes. In addition, microscopical observations were used to confirm the results. Three distinct stages in the SBR evolution were observed. In the first stage the structural floc properties showed predominant presence of floc-forming bacteria in the activated sludge. A good correlation between floc size, settling properties and microbial community evolution was observed. The second stage showed a good balance between floc-forming and filamentous bacteria, with good settling properties and a highly dynamic community in the SBR. In the third stage, an increase in the filamentous bacteria, which became predominant in the system was observed. Again, a good correlation between settling properties and floc size distribution was obtained and a new dominant species was observed in the DGGE patterns, which can be assumed to be a filamentous organism.

Predator grazing effect on bacterial size distribution and floc size variation in membrane-separation activated sludge

2000 ◽  
Vol 42 (3-4) ◽  
pp. 211-217 ◽  
Author(s):  
B.S. Luxmy ◽  
F. Nakajima ◽  
K. Yamamoto
Keyword(s):  
Activated Sludge ◽  
Size Distribution ◽  
Membrane Separation ◽  
Bacterial Species ◽  
Treatment Plant ◽  
Size Variation ◽  
Predator Population ◽  
Predator Species ◽  
Floc Size ◽  
Grazing Effect

In this study the role of higher organisms and the effect of their predation on bacterial size distribution as well as on floc size variation were investigated in the membrane-separation activated sludge system. The pilot plant study was conducted by setting a membrane-separation bioreactor (MBR) in a wastewater treatment plant in Tokyo, Japan. A large number of predator organisms were observed in the MBR dominated by ciliated protozoa. The dispersed bacterial size distribution was obtained by using the combination of florescent in situ hybridization (FISH) and image analysis technique. With the increase of predator species especially sessile ciliates and free-swimming ciliates, reduction of smaller bacterial population (1 μm or so) was significant. It was found that, bacteria and predators are negatively correlated i.e. with increasing number of predator organisms the number of dispersed bacteria decreased. This effect of predation was confirmed while observing the floc size distribution with an automatic particle distribution measuring instrument simultaneously. It was observed that when the higher predator organisms (protozoa and metazoa) were high in number, the percentage of floc groups less than 10 μm (optimum prey size for most of the ciliate species) were less and vice versa. From this study it can be concluded that, mainly the smaller flocs which mostly consist of small (<1 μm) dispersed bacterial species, were grazed heavily by the predator population in the membrane-separation activated sludge.

Validation of a monetary Taylor Aggression Paradigm: Associations with trait aggression and role of provocation sequence

2020 ◽  
Author(s):  
J Konzok ◽  
L Kreuzpointner ◽  
GI Henze ◽  
L Wagels ◽  
C Kärgel ◽  
...  
Keyword(s):  
Random Sequence ◽  
Reactive Aggression ◽  
Reaction Time Task ◽  
Competitive Reaction ◽  
Experimental Conditions ◽  
Fixed Sequence ◽  
Taylor Aggression Paradigm ◽  
Trait Aggression ◽  
Significant Difference ◽  
In Series

© 2020 Elsevier Inc. The Taylor Aggression Paradigm (TAP) is widely used to measure reactive aggression in laboratory settings. While modified versions (mTAPs) with various stimulus characteristics (shocks, noise, pressure, heat) have already been established, a modified version with monetary stimuli has only been introduced very recently. In this experiment, 209 young healthy participants (104 males, 105 females) completed a mock Competitive Reaction Time Task (CRTT) with a fictional opponent with preprogrammed 40 win and 60 lose trials. In lose trials, participants were provoked by subtracting a low (0–20 euro cents), medium (30–60 cents) or high (70–90 cents) amount of money from their fictitious account. Provocation stimuli were either presented randomly or in a fixed sequence (experimental conditions). In contrast to a random sequence, the fixed sequence was generated by repeating trials from the same provocation category in series of three. Linear mixed models (LMMs) considering aggression trajectories revealed significant effects of provocation (low, medium, high) and trait aggression (K-FAF) on reactive aggression. Men showed significantly higher reactive aggression levels than women. In regard to provocation sequence, we found no significant difference in reactive aggression between the random vs. fixed stimulus sequences. The findings provide new evidence supporting the view that the monetary mTAP is able to induce as well as capture reactive aggression in the laboratory. Additionally, we found no advantage of a fixed sequence as the level of reactive aggression in a given trial appeared to be mainly predicted by the preceding provocation trial.

Pond Treatment of Rettery Wastewaters

1987 ◽  
Vol 19 (12) ◽  
pp. 79-83
Author(s):  
K. Bartoszewski ◽  
A. Bilyk
Keyword(s):  
Activated Sludge ◽  
Treatment Process ◽  
New Technology ◽  
Treatment Plant ◽  
Anaerobic Treatment ◽  
Cod Removal ◽  
Experimental Results ◽  
Aerobic Conditions ◽  
Aerobic Stabilization ◽  
In Series

Rettery wastewaters were treated in anaerobic and aerobic ponds. Anaerobic treatment yielded efficiencies of BOD5 and COD removal as low as 20%. The treatment process conducted under aerobic conditions in aerated and stabilizing ponds arranged in series took from 18 to 20 days and gave efficiencies of BOD5 and COD removal amounting to 90%. The experimental results were interpreted by virtue of the Eckenfelder equation. Excess activated sludge was subjected to aerobic stabilization in a separate tank. A new technology was suggested for the existing obsolete industrial treatment plant.

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