Degasification of mixed liquor improves settling and biological nutrient removal

2010 ◽  
Vol 5 (1) ◽  
Author(s):  
M. Maciejewski ◽  
J. A. Oleszkiewicz ◽  
A. Golcz ◽  
A. Nazar
Keyword(s):  
Nutrient Removal ◽  
Gas Bubbles ◽  
Biological Nutrient Removal ◽  
Surface Loading ◽  
Nitrogen Gas ◽  
Mixed Liquor ◽  
Loading Rates ◽  
Dissolved Nitrogen ◽  
Solids Separation ◽  
Sludge Settling

Degasification of mixed liquor by subjecting it to vacuum is a physical process used in biological nutrient removal (BNR) to improve settleability and allow for achieving higher mixed liquor suspended solids (MLSS). Vacuum degassing installation is located between the last cell of the bioreactor and secondary clarifiers. In this process two operations are performed: gas bubbles contained in mixed liquor leaving the bioreactor are removed and concentration of gasses (mainly nitrogen gas) dissolved in the liquid is reduced. Lack of gas bubbles and concentration of dissolved nitrogen gas below saturation in mixed liquor significantly improved sludge settling in secondary clarifiers and eliminated floating scum formation. Presented settleability tests of degasified MLSS and return activated sludge (RAS) from various BNR facilities showed continued settling and/or thickening for over 3 h at room temperature, without exhibiting any solids separation. Settleability tests of biomass that was not degasified typically led to flotation of portion of the sludge after about 1.5 h. Plants equipped with vacuum degasification consistently operate at larger than typically recommended final clarifier sludge surface loading rates. Rates as high as 180-220 kg TSS/m2d and deep sludge blankets have been employed. Such plants were shown to maintain operational levels of MLSS at 4500 to 6000 mg/L and higher.

Settling Characteristics of Activated Sludge in Danish Treatment Plants with Biological Nutrient Removal

1994 ◽  
Vol 29 (7) ◽  
pp. 157-165 ◽  
Author(s):  
Gert Holm Kristensen ◽  
Per Elberg Jørgensen ◽  
Per Halkjær Nielsen
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Volume Index ◽  
Biological Nutrient Removal ◽  
Sludge Volume Index ◽  
Filamentous Microorganisms ◽  
Best Parameter ◽  
One Year ◽  
Sludge Settling ◽  
Settling Characteristics

In 1989-91, a study was performed to investigate the settling characteristics of activated sludge in Danish treatment plants with biological nutrient removal. The study included three screening series on 38 treatment plants. Furthermore, the study included investigations during one year on seasonal variations in sludge settling characteristics at three treatment plants. The screening investigations were performed in November 1989 and May and September, 1990. Results showed that in the May-screening, 35-45% of the plants had a filament index of 2-2.5 or above, corresponding to a sludge volume index above 150 ml/g. When comparing data for diluted and non-diluted sludge volume indices, a SVI value of 150 ml/g seemed parallel to a DSVI of 110 ml/g. In the November- and September-screenings, some 30% of the plants had activated sludge showing a filament index in or above the critical area. Dominating filamentous microorganisms were found to be (in decreasing order): Microthrix parvicella, Type 0041, Type 021N, Type 0092, Type 0914, and Type 1851. A distinct variation over the year in sludge settling characteristics was found for the three plants. Sludge settling characteristics improved during summer, and deteriorated during winter. For activated sludge with a high content of filamentous microorganisms, the best parameter to follow the variations in sludge settling properties was the filament number. If the activated sludge concentration, the MLSS, varied significantly, the specific filament number was to be applied.

The hydrodynamic filter separator for removal of urban storm runoff

2006 ◽  
Vol 53 (7) ◽  
pp. 243-252 ◽  
Author(s):  
J.H. Lee ◽  
K.W. Bang ◽  
Y.J. Cho ◽  
S.J. Joh
Keyword(s):  
Particle Size ◽  
Loading Rate ◽  
Solid Particles ◽  
Storm Runoff ◽  
Surface Loading ◽  
Loading Rates ◽  
Operation Conditions ◽  
Solids Separation ◽  
Series Of Experiments ◽  
Urban Storm

The majority of storm runoff pollution is trapped in particles smaller than 100 μm in diameter. Solid particles smaller than 100 μm in diameter are not easily separated by conventional types of hydrodynamic separator, and remain in suspension in overflow. To overcome this problem, a HDFS (hydrodynamic filter separator) has been developed for treatment of the microparticles in urban storm runoff. We conducted a laboratory scale study on treatable potential of microparticles using HDFS that combined HDS with perlite filter. To determine the efficiency for various operation conditions, a series of experiments was performed with different solids concentrations and surface loading rate. The operation ranges of surface loading rates were 100 to 2,800 m3/m2/day, and influent solids concentrations were varied from 800 to 1,900 mg/L. Also, the particle size distribution was monitored to investigate the effects of surface loading rates on the particle size. Results indicated that the HDFS-Inside type showed greater efficiency at solids separation than the other type.

Effects of integrated fixed film activated sludge media on activated sludge settling in biological nutrient removal systems

2010 ◽  
Vol 44 (5) ◽  
pp. 1553-1561 ◽  
Author(s):  
Hyun-su Kim ◽  
James W. Gellner ◽  
Joshua P. Boltz ◽  
Robert G. Freudenberg ◽  
Claudia K. Gunsch ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Biological Nutrient Removal ◽  
Fixed Film ◽  
Sludge Settling

scholarly journals Inducing granulation within a full-scale activated sludge system to improve settling

2021 ◽  
Author(s):  
Isaac Avila ◽  
Dan Freedman ◽  
Joel Johnston ◽  
Blair Wisdom ◽  
James McQuarrie
Keyword(s):  
Particle Size ◽  
Nutrient Removal ◽  
Full Scale ◽  
Cold Climate ◽  
Biological Nutrient Removal ◽  
Secondary Treatment ◽  
Entire Study ◽  
Mixed Liquor ◽  
Settling Behaviour ◽  
And Control

Abstract Most cold-climate biological nutrient removal facilities experience poor settling mixed liquor during winter resulting in treatment capacity throughput limitations. The Metro Wastewater Reclamation District in Denver, Colorado operated two full-scale secondary treatment trains to compare the existing biological nutrient removal configuration (Control) to one that was modified to operate with an anaerobic selector and with hydrocyclone selective wasting (Test) to induce granulation. Results from this evaluation showed that the Test achieved significantly better settling behaviour than the Control. The difference in the mean diluted SVI30 between the Test and Control were statistically significant (P < 0.05), with values of 77 ± 17 and 135 ± 25 mL/g observed for the Test and Control respectively. These settling results were accompanied by differences in the particle size distribution with notably higher settling velocities commensurate with increasing particle size. The degree of granulation observed in the Test train was between 32 and 56% of the mass greater than ≥250 μm in particle size whereas 16% of the mixed liquor in the Control was ≥250 μm over the entire study period. The improved settling behaviour of the Test configuration may translate into an increase of secondary treatment capacity during winter by 32%.

Settling of Nutrient Removal Activated Sludges

1985 ◽  
Vol 17 (4-5) ◽  
pp. 493-504 ◽  
Author(s):  
A. R. Pitman
Keyword(s):  
Nutrient Removal ◽  
Biological Nutrient Removal ◽  
Easy Method ◽  
Sludge Settling

This paper surveys the settling properties of activated sludges from four biological nutrient removal plants. Empirically derived constants used in the settling flux theory are correlated with more traditional measures of settling properties such as the SVI. An easy method of using the settling flux approach to clarifier design and operation is presented and a new parameter describing the settling properties of sludges is proposed. Typical values of constants describing the settling properties of nutrient removal sludges are presented. It was found that the factor most influencing sludge settling properties was the degree of aeration in these plants.

Nitrification Kinetics in Single-Sludge Biological Nutrient Removal Activated Sludge Systems

1992 ◽  
Vol 25 (6) ◽  
pp. 195-214 ◽  
Author(s):  
C. W. Randall ◽  
V. M. Pattarkine ◽  
S. A. McClintock
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Municipal Wastewater ◽  
Biomass Concentration ◽  
Biological Nutrient Removal ◽  
Mixed Liquor ◽  
Nitrification Kinetics ◽  
Anoxic Zones ◽  
Complete Nitrification ◽  
Activated Sludge Systems

Nitrification kinetics as a function of mixed liquor temperature were compared for a conventional fully-aerobic activated sludge system and a system accomplishing biological nutrient removal (BNR) by incorporation of anaerobic and anoxic zones using the UCT configuration. The systems treated the same municipal wastewater and both had flow rates of 151 L/day. The nitrification rates were greater in the nutrient removal system compared to the conventional system as long as the aerobic MCRT was above the minimum for complete nitrification. It was concluded that BNR systems require less aerobic volume than fully aerobic systems to accomplish nitrification because the aerobic biomass concentration is greater in the BNR systems, particularly if the UCT configuration is used. Nonetheless, BNR systems require more total volume to accomplish complete nitrification than fully aerobic systems, and the volume differential increases as mixed liquor temperatures decrease.

Bulking sludge solved?!

2002 ◽  
Vol 46 (1-2) ◽  
pp. 457-464 ◽  
Author(s):  
J. Kruit ◽  
J. Hulsbeek ◽  
A. Visser
Keyword(s):  
Nutrient Removal ◽  
Wastewater Treatment Plants ◽  
Plug Flow ◽  
Biological Nutrient Removal ◽  
Ammonium Concentration ◽  
Strictly Anaerobic ◽  
Flow Conditions ◽  
Anaerobic Reactor ◽  
Aerobic Reactor ◽  
Sludge Settling

At present there is still no final theory explaining the bulking of activated sludge. Previous investigations showed that the sludge settling properties become better and more stable when more plug flow conditions are implemented in wastewater treatment plants for biological nutrient removal. In this research the effect of the process configuration (4 wwtps with fully biological nutrient removal) on the sludge settling properties has been investigated. The results show that a separate anoxic reactor can not avoid the presence of LCFA for the growth of M. parvicella in the anaerobic reactor. A SVI < 120 ml/g could be achieved by: implementation of a separate anoxic reactor with plug flow conditions, introducing of a strictly anaerobic reactor (UCT-modification), implementation of an extra anoxic/aerobic reactor, maintaining a high oxygen concentration (> 1.5 mg/l) and creating a low ammonium concentration (< 1 mg/l) in the aerobic reactor.

Supersaturation of Nitrogen in Water During Passage Through Hydroelectric Turbines at Mactaquac Dam

1973 ◽  
Vol 30 (9) ◽  
pp. 1392-1394 ◽  
Author(s):  
J. Rod Macdonald ◽  
R. A. Hyatt
Keyword(s):  
Dissolved Oxygen ◽  
New Brunswick ◽  
Salmo Salar ◽  
Hydroelectric Station ◽  
Gas Bubbles ◽  
Anguilla Rostrata ◽  
Fish Kills ◽  
Nitrogen Gas ◽  
Dissolved Nitrogen ◽  
Generating System

Two fish kills occurred at the Saint John River, New Brunswick, below the Mactaquac Hydroelectric Station in the summer of 1968. Gas bubbles, commonly associated with nitrogen supersaturation, were observed on dead and dying salmon (Salmo salar) and eels (Anguilla rostrata). Tests showed that the concentrations of dissolved oxygen and nitrogen gases were substantially increased when water passed through the turbine generating system at low generating levels. Concentrations of dissolved nitrogen gas increased by as much as 20% above atmospheric equilibrium.

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