Effects of Activated Sludge Properties on Water Flux of Ultrafiltration Membrane Used for Human Excrement Treatment

1991 ◽  
Vol 23 (7-9) ◽  
pp. 1601-1608 ◽  
Author(s):  
Takeshi Sato ◽  
Yasuhiko Ishii
Keyword(s):  
Activated Sludge ◽  
Water Flux ◽  
Stable State ◽  
Transmembrane Pressure ◽  
Test Plant ◽  
Average Pressure ◽  
Filtration Resistance ◽  
State Water ◽  
Sludge Properties ◽  
The Relationship

We studied the relationship between water flux of a UF membrane with MLSS, soluble COD, and the viscosity of activated sludge suspension in a human excrement treatment test plant utilizing UF membrane. The bench-scale plate and frame UF membrane test unit was operated for activated sludge suspension of 20~29 kg/m3 MLSS, 500-730 g/m3 soluble COD and 0.38-1.3 Pa·s viscosity under the conditions of 0.2-0.24 MPa average pressure and 2 m/s recirculating velocity. As a result, stable-state water flux was 0.55-1.65 m/D at 25°C. The relationship between filtration resistance R to transmembrane pressure drop ∆P, MLSS, COD, and viscosity η was expressed by the following equation: From this equation, we were able to predict R with an accuracy of ±24%. Soluble COD had the largest effect on water flux followed by MLSS. The effect of viscosity was relatively small.

Study of Flocculation Mechanisms by Observing Effects of a Complexing Agent on Activated Sludge Properties

1991 ◽  
Vol 24 (7) ◽  
pp. 21-28 ◽  
Author(s):  
L. Eriksson ◽  
B. Alm
Keyword(s):  
Activated Sludge ◽  
Metal Ions ◽  
Electrostatic Interactions ◽  
Wastewater Treatment Plants ◽  
Sedimentation Velocity ◽  
Complexing Agent ◽  
Extracellular Polymers ◽  
Filtration Resistance ◽  
Polyvalent Metal ◽  
Sludge Properties

Electrostatic interactions between bacterial surfaces, extracellular polymers (ECP) and polyvalent metal ions are important in activated sludge flocculation. An indirect study of these mechanisms was done by adding different concentrations of EDTA to activated sludge samples from 6 Swedish wastewater treatment plants. The effects on sludge properties were studied with sedimentation and filtration tests as well as analysis of released extracellular polymers. EDTA had a significant effect on sedimentation velocity in all investigated sludges. This shows that charged polymers are important for the properties of the floc surfaces and in building up the sludge macroflocs. The effect on filtration resistance where the bulk properties of the primary flocs are more important varied considerably for the different sludges. Thus, both electrostatic and other interactions are involved to a varying extent in building up the primary flocs in the sludges investigated. Variations in sedimentation velocity, residual turbidity, filtration resistance and release of ECP with variations in EDTA concentrations could be explained by effects of polyvalent metal ions on ECP binding and conformation.

Evaluation of Sludge Properties at an Activated Sludge Plant

1992 ◽  
Vol 25 (6) ◽  
pp. 251-265 ◽  
Author(s):  
Leif Eriksson ◽  
Inga Steen ◽  
Marta Tendaj
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Extracellular Polymers ◽  
Filtration Resistance ◽  
Water Composition ◽  
Floc Structure ◽  
History Of ◽  
Floc Strength ◽  
Sludge Properties ◽  
One Year

Composition of pre-settled water, sludge properties in two different lines of an activated sludge plant, and suspended solids (SS) content in outgoing water were followed three times a week during one year. Sludge characteristics were: settling properties, residual turbidity, floc strength, filtration resistance, amount of extracellular polymers, microscope appearance and total length of filamentous organisms. The outgoing SS could be related to residual turbidity and sludge volume. These factors depended on the floc structure and the filament length. These were determined by sludge load or sludge age, water composition and the hydrodynamic history of the sludge. On basis of these and earlier findings a general model for properties of flocs built by floc-forming organisms in activated sludge is proposed.

Role of Glycogen as an Intracellular Carbon Reserve of Activated Sludge in the Competitive Growth of Filamentous and Non-Filamentous Bacteria

1991 ◽  
Vol 23 (4-6) ◽  
pp. 899-905 ◽  
Author(s):  
Y. Matsuzawa ◽  
T. Mino
Keyword(s):  
Activated Sludge ◽  
Feeding Pattern ◽  
Filamentous Bacteria ◽  
Competitive Growth ◽  
Maximum Capacity ◽  
Intermittent Feeding ◽  
Feeding Type ◽  
Continuous Feeding ◽  
The Relationship

Activated sludge mixed cultures were cultivated with a glucose containing substrate in order to investigate the relationship between the feeding pattern (continuous or intermittent feeding) and the glycogen reservation capacity of activated sludge. An experimental method to measure the maximum capacity of glycogen reservation in the sludge was developed. Sludge with higher glycogen reservation capacity has an ability to synthesize glycogen faster, which ensures the higher glucose uptake. Therefore, sludge which has high glycogen reservation capacity becomes predominant in intermittently fed reactors. When the feeding pattern was changed from continuous feeding to intermittent feeding, a filamentous bacterium, Type 1701, started to decrease and a gram positive tetrad coccus became predominant. When the feeding pattern was returned to continuous feeding, Type 1701 re-appeared. Type 1701 has lower glycogen reservation capacity than the tetrad coccus. Therefore, the former cannot dominate over the latter in intermittently fed reactors.

Filtration resistance induced by ammonia oxidizers accumulating on the rotating membrane disk

1998 ◽  
Vol 38 (4-5) ◽  
pp. 443-452
Author(s):  
Katsuki Kimura ◽  
Yoshimasa Watanabe ◽  
Naoki Ohkuma
Keyword(s):  
Membrane Filtration ◽  
Extracellular Polymeric Substances ◽  
Drinking Water Treatment ◽  
Treatment Method ◽  
Operating Conditions ◽  
Transmembrane Pressure ◽  
Ammonia Oxidizers ◽  
Filtration Resistance ◽  
Rotating Membrane Disk ◽  
Membrane Disk

Membrane filtration and oxidation of ammonia were simultaneously performed by using a rotating membrane disk module. Nitrification performance, composition of the accumulated cakes on the membrane and the filtration resistances were investigated under five different operating conditions. The filtration resistance due to the accumulated cake on the membrane was found to be dominant in this treatment method, compared to the resistance due to the micropore plugging or irreversible adherence. The cake consisted mainly of iron, humic substances and bacteria. The possibility that extracellular polymeric substances were related to the cake resistance was also shown. The composition of the cake depended on the length and the condition of operation. Accumulation of ammonia oxidizers caused by oxidation of low concentrations of ammonia (less than 1 mg/l) did not increase transmembrane pressure significantly. Therefore, the application of this treatment method for drinking water treatment is feasible. Filtration resistance due to the micropore plugging or irreversible adherence to the membrane was caused by organic substances.

Evolutionary game analysis of information sharing by institutional investors

2021 ◽  
pp. 1-9
Author(s):  
Hua Li ◽  
Qingqing Lou ◽  
Qiubai Sun ◽  
Bowen Li
Keyword(s):  
Information Sharing ◽  
Institutional Investors ◽  
Information Exchange ◽  
Evolutionary Game ◽  
Stable State ◽  
Point Of View ◽  
Game Model ◽  
Game Analysis ◽  
Relationship Network ◽  
The Relationship

In order to solve the conflict of interests of institutional investors, this paper uses evolutionary game model. From the point of view of information sharing, this paper discusses four different situations. Only when the sum of risk and cost is less than the penalty of free riding, the evolution of institutional investors will eventually incline to the stable state of information sharing. That is, the phenomenon of hugging. The research shows that the institutional investors are not independent of each other, but the relationship network of institutional investors for the purpose of information exchange. The content of this paper enriches the research on information sharing of institutional investors.

Effect of activated sludge properties and membrane operation conditions on fouling characteristics in membrane bioreactors

Chemosphere ◽  
2006 ◽  
Vol 63 (10) ◽  
pp. 1699-1708 ◽  
Author(s):  
Hyeok Choi ◽  
Kai Zhang ◽  
Dionysios D. Dionysiou ◽  
Daniel B. Oerther ◽  
George A. Sorial
Keyword(s):  
Activated Sludge ◽  
Membrane Bioreactors ◽  
Operation Conditions ◽  
Sludge Properties ◽  
Fouling Characteristics

On the 3D Correlation between Myofibroblast Shape and Contraction

2021 ◽  
Author(s):  
Alex Khang ◽  
Emma Lejeune ◽  
Ali Abbaspour ◽  
Daniel Howsmon ◽  
Michael Sacks
Keyword(s):  
Cell Shape ◽  
Interstitial Cell ◽  
Stable State ◽  
Stress Fiber ◽  
Poly Ethylene Glycol ◽  
Critical Feature ◽  
Peg Hydrogels ◽  
Poly Ethylene ◽  
And Function ◽  
The Relationship

Abstract Cell shape is known to correlate closely with stress-fiber geometry and function, and is thus a critical feature of cell biophysical state. However, the relationship between myofibroblast shape and contraction is complex, even as well in regards to steady-state contractile level (basal tonus). At present, the relationship between myofibroblast shape and basal tonus in 3D is poorly understood. Herein, we utilize the aortic valve interstitial cell (AVICs) as a representative myofibroblast to investigate the relationship between basal tonus and overall cell shape. AVICs were embedded within 3D poly (ethylene glycol) (PEG) hydrogels containing degradable peptide crosslinkers, adhesive peptide sequences, and sub-micron fluorescent micro-spheres to track the local displacement field. We then developed a methodology to evaluate the correlation between overall AVIC shape and basal tonus induced contraction. We computed a volume averaged stretch tensor <U> for the volume occupied by the AVIC, which had three distinct eigenvalues (1.08, 0.99, and 0.89), suggesting that AVIC shape is a result of anisotropic contraction. Furthermore, the direction of maximum contraction correlated closely with the longest axis of a bounding ellipsoid enclosing the AVIC. As gel--imbedded AVIC are known to be in a stable state by three days of incubation used herein, this finding suggests that the overall quiescent AVIC shape is driven by the underlying stress-fiber directional structure and possibly contraction level.

Effects of potassium ion on sludge settling, dewatering and effluent properties

1998 ◽  
Vol 37 (4-5) ◽  
pp. 317-324 ◽  
Author(s):  
Sudhir N. Murthy ◽  
John T. Novak
Keyword(s):  
Activated Sludge ◽  
Field Studies ◽  
Potassium Ion ◽  
Potassium Ions ◽  
Nutrient Requirements ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Sludge Flocs ◽  
Sludge Properties ◽  
Sludge Settling

Potassium ions appear to play an important role in determining the nature of activated sludge flocs. Relative to sodium, the concentration of potassium ions in most industrial activated sludge is typically low. Laboratory and field studies were conducted to examine the influence of potassium on activated sludge properties. The concentration of potassium affected the concentration of readily extractable (slime) proteins in the floc and the proteins in the surrounding solution. In laboratory tests, an increase in this cation's concentration beyond nutrient requirements impeded sludge dewatering properties as measured by capillary suction time (CST) and specific resistance to filtration (SRF) and associated with an increase in soluble protein. An increase in effluent total organic carbon and effluent turbidity was observed at higher concentrations of this ion. Conversely, an increase in concentration of potassium ion improved the settling properties of sludge with low equivalent monovalent to divalent cation ratio.

Simultaneous Removal of Nitrogen and Phosphorus in Intermittently Aerated 2-Tank Activated Sludge Process Using DO and ORP-Bending-Point Control

1993 ◽  
Vol 28 (11-12) ◽  
pp. 513-521 ◽  
Author(s):  
Kousei Sasaki ◽  
Yasuji Yamamoto ◽  
Kazushi Tsumura ◽  
Shigeru Hatsumata ◽  
Masahiro Tatewaki
Keyword(s):  
Control System ◽  
Activated Sludge ◽  
Phosphorus Uptake ◽  
Material Balance ◽  
Phosphorus Release ◽  
Test Plant ◽  
Activated Sludge Process ◽  
Time Sharing ◽  
Nitrogen And Phosphorus ◽  
Time Control

The 2-tank intermittent aeration method is an anaerobic-aerobic activated sludge process of time-sharing type in which 2 complete mixing reaction tanks are connected in series, and aeration and agitation are periodically repeated in each tank. We have developed a new control system for the process which can secure anaerobic, anoxic and aerobic conditions through a combination of DO and ORP-Bending-point (corresponding to termination of denitrification) emergence time control. In the 1st tank, nitrification and phosphorus uptake occur in the aeration period, followed by denitrification and phosphorus release in the agitation. The 2nd tank performs nitrification and phosphorus uptake in the aeration and denitrification in the agitation. One cycle of aeration and agitation is approximately 2 hours. This control system was applied to the test plant (influent flow rate: 225 I/day) for two months under the conditions of HRT 16 hours and temperature 20 ±2 °C. We achieved stable and high removal ratios: TOC 94.9 %, T-N 89.4 %, and T-P 95.5 %. We also investigated the mechanisms of nitrogen and phosphorus removal and their material balance.

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