Effects of Various Additives on the Solidification of Oily Sludges: A Bench-Scale Study

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.

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Can Aerobic Granular Reactors help a Land-locked Plant Upgrade to BNR? From Bench-scale testing to Full-scale Conceptual Design

Proceedings of the Water Environment Federation ◽

10.2175/193864715819539759 ◽

2015 ◽

Vol 2015 (16) ◽

pp. 2760-2783

Author(s):

Roland Jezek ◽

Ed Kobylinski ◽

Belinda Sturm ◽

Mark Steichen ◽

James L Barnard

Keyword(s):

Conceptual Design ◽

Full Scale ◽

Bench Scale

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Bench-Scale Evaluation of the Genifuel Hydrothermal Processing Technology for Wastewater Solids

Proceedings of the Water Environment Federation ◽

10.2175/193864717822157702 ◽

2017 ◽

Vol 2017 (9) ◽

pp. 3032-3061 ◽

Cited By ~ 1

Author(s):

P.A Marrone ◽

D.C Elliott ◽

J.M Billing ◽

R.T Hallen ◽

T.R Hart ◽

...

Keyword(s):

Processing Technology ◽

Hydrothermal Processing ◽

Scale Evaluation ◽

Bench Scale

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