A Simple morphologically structured model describing the growth of filamentous microorganisms

1993 ◽  
Vol 41 (7) ◽  
pp. 715-727 ◽  
Author(s):  
Jens Nielsen
Keyword(s):  
Structured Model ◽  
Filamentous Microorganisms ◽  
Morphologically Structured Model

A morphologically structured model for penicillin production

2002 ◽  
Vol 77 (5) ◽  
pp. 538-552 ◽  
Author(s):  
Gülnur Birol ◽  
Cenk Ündey ◽  
Satish J. Parulekar ◽  
Ali Çınar
Keyword(s):  
Penicillin Production ◽  
Structured Model ◽  
Morphologically Structured Model

Variation in Sludge Settleability with Temperature

1980 ◽  
Vol 15 (1) ◽  
pp. 73-82 ◽  
Author(s):  
J.G. Henry ◽  
E.E. Salenieks
Keyword(s):  
Activated Sludge ◽  
Effect Of Temperature ◽  
Organic Load ◽  
Limiting Factor ◽  
Appreciable Effect ◽  
Loading Rates ◽  
Bench Scale ◽  
Filamentous Bulking ◽  
Filamentous Microorganisms ◽  
Sludge Settleability

Abstract This study examined the effect of temperature on the settleabi1ity of activated sludge at various organic loading rates. Five completely mixed, bench-scale, activated sludge plants, operating under similar conditions at 5, 10 and 19°C, were continuously fed diluted, settled sewage supplemented with carbohydrate (sucrose). Hydraulic loading rates, MLSS and pH were maintained at constant levels during the experiments to eliminate these factors are variables. Dissolved oxygen was kept in excess of 3 mg/1 so that it would not be a limiting factor. Sludge Volume Indices (SVI ) and zone settling velocities were used to indicate changes in sludge settleability. Microscopic examination of the activated sludge indicated significant differences in the morphological features of filamentous microorganisms present at the two temperature extremes. At 19°C, the predominant forms were characterized by long curving trichomes, occasionally falsely branching, containing short cylindrical cells. At 5 °C, much smaller straight filaments, composed of long, narrow, rod-shaped cells appeared to be the principal microorganisms responsible for bulking. Various other filamentous forms were always present at each of the temperatures studied. Stirred sludge settling tests of moderately bulking sludges generally exhibited much higher settling velocities and lower SVI's than unstirred bulking samples. However, extremely filamentous bulking sludge exhibited comparable stirred and unstirred settling velocity and SVI values. The standard SVI test was found to be an inadequate indicator of the extent of bulking when trying to correlate the SVI failures from bench-scale performance with the results from continuous units. Lower temperature had no appreciable effect on COD removal efficiency as long as bulking did not cause a loss of solids in the effluent. However, results suggested that less than half the organic load could be accepted at 5°C, that could be handled at 19°C, before filamentous bulking occurred. A plot of loading versus temperature for various SVI's provided a visual indication of the safe loading limit below which bulking was unlikely to occur. The study clearly demonstrated that temperature can have a significant effect on sludge settleability.

Two-stage chemical-biological treatment at Thessaloniki greater area WWTP - experiences and potentials

1995 ◽  
Vol 32 (9-10) ◽  
pp. 75-84 ◽  
Author(s):  
A. D. Andreadakis ◽  
G. H. Kristensen ◽  
A. Papadopoulos ◽  
C. Oikonomopoulos
Keyword(s):  
Biological Treatment ◽  
Treatment Plant ◽  
Cost Effective ◽  
Primary Treatment ◽  
Effective Control ◽  
Two Stage ◽  
Effluent Quality ◽  
Filamentous Microorganisms ◽  
Sludge Settling ◽  
The City

The wastewater from the city of Thessaloniki is discharged without treatment to the nearby inner part of the Thessaloniki Gulf. The existing, since 1989, treatment plant offers only primary treatment and did not operate since the expected effluent quality is not suitable for safe disposal to the available recipients. Upgrading of the plant for advanced biological treatment, including seasonal nitrogen removal, is due from 1995. In the mean time, after minor modifications completed in February 1992, the existing plant was put into operation as a two-stage chemical-biological treatment plant for 40 000 m3 d−1, which corresponds to about 35% of the total sewage flow. The operational results obtained during the two years operation period are presented and evaluated. All sewage and sludge treatment units of the plant perform better than expected, with the exception of the poor sludge settling characteristics, due to severe and persistent bulking caused by excessive growth of filamentous microorganisms, particularly M. Parvicella. Effective control of the bulking problem could lead to more cost-effective operation and increased influent flows.

Experiences with sludge settleability in different process alternatives for nutrient removal

1996 ◽  
Vol 33 (12) ◽  
pp. 137-146 ◽  
Author(s):  
Kjær Andreasen ◽  
Lars Sigvardsen
Keyword(s):  
Nutrient Removal ◽  
Plant Layout ◽  
Filamentous Microorganisms ◽  
Positive Effect ◽  
Sludge Settleability ◽  
Settling Characteristics ◽  
P Removal

SVI and DSVI were measured three times at almost 100 Danish nutrient removal plants and the filamentous microorganisms were subsequently characterized in the laboratory. Information about the plant layout and the operation was collected by means of a questionnaire. In general, the sludge settleability index becomes worse by the introduction of nutrient removal. Among nutrient removal plants the best settling characteristics are found among plants with biological P removal and the poorest among the plants that perform simultaneous denitrification. When compared to iron products, aluminium products in some cases seem to reduce the filament number and improve the settling characteristics in plants that apply simultaneous precipitation for P removal. Selectors may have a positive effect on the filament number but the effect may not be enough to prevent bulking.

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