Evaluation of ozonation and cryptic growth for biosolids management in wastewater treatment

The ultimate disposal of biosolids has been and continues to be one of the most expensive problems faced by wastewater utilities. The objective of this research is to develop a process configuration for reducing the waste sludge generation in an activated sludge plant by promoting cryptic growth conditions (i.e., biomass growth on intracellular products). For this purpose, excess biosolids from a continuous flow activated sludge system were solubilized using ozone as the cell lysis agent, and then returned to the aeration tank. It is hypothesized that growth under such cryptic conditions will result in low net microbial yields, and hence, minimal net solids wastage. The results of these preliminary studies indicate that the proposed process configuration has the potential to reduce the waste sludge production by 40% to 60%.

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Evaluation of an ozonation system for reduced waste sludge generation

Water Science & Technology ◽

10.2166/wst.2001.0800 ◽

2001 ◽

Vol 44 (2-3) ◽

pp. 445-452 ◽

Cited By ~ 49

Author(s):

E. Egemen ◽

J. Corpening ◽

N. Nirmalakhandan

Keyword(s):

Activated Sludge ◽

Growth Conditions ◽

Aeration Tank ◽

Excess Sludge ◽

Waste Sludge ◽

Process Configuration ◽

Solids Concentration ◽

Expensive Problems ◽

Ozonation Time ◽

Ozonation Process

The ultimate disposal of biosolids has been and continues to be one of the most expensive problems faced by wastewater utilities. Previous work has shown that the waste sludge generation in an activated sludge plant can be reduced by promoting cryptic growth conditions (i.e., biomass growth on intracellular products). For this purpose, excess biosolids from a continuous flow activated sludge system were solubilized using ozone as the cell lysing agent, and then returned to the aeration tank. The results of these preliminary studies indicate that the proposed process configuration has the potential to reduce the waste sludge production by 40% to 60%. In the present research, the details of the ozonation process is further investigated to determine the maximum solubilization efficiency. For this purpose, a number of variables such as the solids concentration in the excess sludge, ozonation time, and ozonation dosage rate are studied.

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Nitrification Kinetics in Activated Sludge with Both Suspended and Attached Biomasses

Water Science & Technology ◽

10.2166/wst.1994.0339 ◽

1994 ◽

Vol 29 (7) ◽

pp. 181-184 ◽

Cited By ~ 5

Author(s):

P. Chudoba ◽

M. Pannier

Keyword(s):

Activated Sludge ◽

Aeration Tank ◽

Continuous Systems ◽

Biomass Growth ◽

Batch Tests ◽

Activated Sludge System ◽

Nitrification Kinetics ◽

Kinetic Tests ◽

Suspended Biomass ◽

Kinetics Of

A series of nitrification kinetic tests was carried out with both suspended and fixed biomasses originated from a combined activated sludge system with a plastic support for biomass growth introduced into the aeration tank (Experimental combined unit - ECU). The results of these batch tests were compared with kinetics calculated from continuously run pilot plant. It was concluded that nitrification kinetics of both suspended and attached biomasses were similar and, consequently, it was assumed that the percentage of autotrophs is the same in both biomasses. The kinetics determined in both batch and continuous systems were comparable. Kinetic constants measured for suspended biomass of the ECU were higher than those reported by the literature, which was attributed to an overaeration of the ECU and an energetic mixing

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REDUCTION BY SONICATION OF EXCESS SLUDGE PRODUCTION IN A CONVENTIONAL ACTIVATED SLUDGE SYSTEM: CONTINUOUS FLOW AND LAB‐SCALE REACTOR

Environmental Technology ◽

10.1080/09593330802379649 ◽

2008 ◽

Vol 29 (12) ◽

pp. 1307-1320 ◽

Cited By ~ 13

Author(s):

S. Vaxelaire ◽

E. Gonze ◽

G. Merlin ◽

Y. Gonthier

Keyword(s):

Activated Sludge ◽

Continuous Flow ◽

Excess Sludge ◽

Conventional Activated Sludge ◽

Activated Sludge System ◽

Scale Reactor ◽

Sludge Production

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Removal and fate of estrogens in an anaerobic-anoxic-oxic activated sludge system

Water Science & Technology ◽

10.2166/wst.2011.008 ◽

2011 ◽

Vol 63 (1) ◽

pp. 51-56 ◽

Cited By ~ 18

Author(s):

Y. M. Li ◽

Q. L. Zeng ◽

S. J. Yang

Keyword(s):

Activated Sludge ◽

Removal Efficiency ◽

Laboratory Scale ◽

Dominant Mechanism ◽

Waste Sludge ◽

Activated Sludge System ◽

17Β Estradiol ◽

Solid Phases ◽

Final Effluent

Laboratory-scale experiments were conducted to investigate the removal and fate of estrogens 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) in an anaerobic-anoxic-oxic (AAO) activated sludge system. Estrogen concentrations in the aqueous and solid phases in each reactor of AAO system were analyzed separately. E2 was not detected in the final effluent. The anaerobic, anoxic and oxic reactors accounted for 71%, 7% and 22% of the overall E2 removal, respectively. The overall EE2 removal efficiency was about 80%, and the anaerobic, anoxic and oxic reactors were responsible for 44%, 8% and 48% of the overall EE2 removal, respectively. In anaerobic unit, sorption was the dominant mechanism for the removal of E2 and EE2. While E2 was degraded in all the three units of the AAO system, EE2 was only degraded in the anoxic and aerobic units. Biodegradation is important for the fate of E2 compared to sorption. Of the total influent E2 in the AAO system, 99.99% was biodegraded and 0.01% remained in the waste sludge. Nevertheless, both sorption and biodegradation play important roles in the removal of EE2. Of the total influent EE2, 79.1% was degraded by activated sludge, 19.9% was discharged in the effluent and 1% remained in the waste sludge.

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A Pilot-Plant Study to Salvage a Full-Scale Treatment Plant

Water Science & Technology ◽

10.2166/wst.1992.0014 ◽

1992 ◽

Vol 25 (1) ◽

pp. 93-98 ◽

Cited By ~ 1

Author(s):

Y. H. Yu ◽

K. S. L. Lo

Keyword(s):

Activated Sludge ◽

Pilot Plant ◽

Settling Tank ◽

Treatment Plant ◽

Chemical Precipitation ◽

Aeration Tank ◽

Treatment Unit ◽

Activated Sludge System ◽

High Metal ◽

Pilot Plant Study

Kwei-Shan Wastewater Treatment Plant is the second oldest treatment plant ever designed and operated in Taiwan, to treat the combined industrial wastewater collected from various kinds of factories located in Kwei-Shan Industrial Park. From the beginning the treatment plant has been suffering from influents containing a spectrum of various pollutants harmful to the activated-sludge system of the plant. Extreme pH measurements (1.4-12.0), jumpy organic contents (COD 104-6660 mg/l), high metal concentrations (Cu up to 19 mg/l, Zn up to 37 mg/l), and high grease concentrations (up to 470 mg/l) were unbelievably found in tne plant influents, while a traditional plain primary settling tank was the only shield to protect the aeration basin from damage. In a dilemma like this, a pilot-plant study was undertaken to save the efficiency of the existing biological treatment plant from those various fatal influent constituents. A flow equalization tank and a chemical treatment unit were first built to damp out pH and COD variations, Ca(OH)2 was added to remove the toxic metals as well as part of the grease. The effluent after the above treatment was then neutralized and sent to the downscaled activated sludge system containing one aeration tank and one settling tank. The results indicated that equalization and chemical precipitation by using the existing space of the roughing filter and the sedimentation tank could produce much safer influents to the activated sludge system.

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Denitrification kinetics in an activated sludge system

Water Science & Technology ◽

10.2166/wst.1995.0699 ◽

1995 ◽

Vol 32 (9-10) ◽

pp. 323-330

Author(s):

M. Roš

Keyword(s):

Activated Sludge ◽

Closed System ◽

Open Systems ◽

Aeration Tank ◽

Activated Sludge System ◽

Denitrification Kinetics ◽

Closed Systems ◽

Nitrate And Nitrite ◽

Sludge Concentration

For all water bodies especially for sea, lakes, and ground waters it is very important that nutrient pollution is the least possible (minimal). From municipal and industrial waste waters where considerable amount of nutrients is expected it is possible to remove nutrients with biological treatment. The first step is usually aerobic activated sludge treatment and the second step is combined anaerobic-anoxic-aerobic step in different combinations. A very effective process for nitrogen removal is anoxic activated sludge system. It is very important that in the first aerobic step complete nitrification is achieved. In our laboratory denitrification kinetics was studied. The objective of this study was determination of denitrification velocity and attendance of different parallel phenomena such as nitrite, disappearance of nitrate and nitrite, sulphide formation, etc. Denitrification process was studied in two systems, in closed system (such as in closed reactors for denitrification) and in open systems (such as in open denitrification tanks). We found out that denitrification rate in closed systems was from about 8 to 52 mg/l.h and was dependent on activated sludge type, sludge concentration, and temperature of the system. In open system (such as in an anoxic aeration tank) the rate of denitrification was lower than in closed system; it was from 4 to 15 mg/l.h dependent on activated sludge type, sludge concentration, and temperature of the system. Experiments were carried out in the range of temperature from 20° to 30°C.

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