Activated sludge flocculation: direct determination of the effect of calcium ions

2001 ◽  
Vol 43 (11) ◽  
pp. 75-82 ◽  
Author(s):  
C. A. Biggs ◽  
A. M. Ford ◽  
P. A. Lant
Keyword(s):  
Activated Sludge ◽  
Direct Determination ◽  
Rate Of Change ◽  
Valuable Insight ◽  
Floc Size ◽  
Sludge Flocs ◽  
On Line ◽  
Flocculation Process ◽  
Insight Into

The effect of calcium on activated sludge flocculation dynamics is investigated using a unique experimental technique. The technique allows on-line analysis of the size of activated sludge flocs during flocculation and provides valuable insight into the mechanisms of flocculation. Activated sludge samples were firstly sonicated for 3 minutes at 50W and then stirred at 100 rpm. The floc size was subsequently measured on-line using a Malvern Mastersizer/E. For concentrations of calcium less than 4 meq/L no significant increase in final floc size was observed even though an increase in the initial rate of change of floc size could be seen. Addition of calcium greater than 4 meq/L resulted in a dramatic increase in floc size. Results from this investigation support the theory that cations are involved in flocculation through cationic bridging, and will be used in ongoing investigations to model the flocculation process.

Automation in sludge dewatering by novel on-line characterisation of flocculation

2003 ◽  
Vol 47 (2) ◽  
pp. 157-164 ◽  
Author(s):  
M. Sievers ◽  
C. Schroeder ◽  
H. Bormann ◽  
T.I. Onyeche ◽  
O. Schlaefer ◽  
...  
Keyword(s):  
Image Processing ◽  
Size Distribution ◽  
Experimental Period ◽  
Filter Press ◽  
Sludge Dewatering ◽  
Floc Size ◽  
Sludge Flocs ◽  
Extended Range ◽  
On Line ◽  
Flocculation Process

A novel on-line method and system for characterisation of sludge flocs in view of improving sludge dewatering has been developed. The characterisation of sludge flocs was carried out after the conditioning or the flocculation process. The system uses a conventional CCD-line scan camera providing an on-line monitoring of the relative floc size distribution by image processing procedures. The image processing procedure has been re-evaluated and adapted to the practical dewatering results, obtained from a chamber filter press of 250 × 250 mm size. A good correlation between the calculated sensor signal and the sludge dewaterability of digested sludge in terms of the up-concentration factor was found. Although different sludge compositions and flocculation systems have been tested within the whole experimental period of six months, a good reproducibility of this correlation was also found. A well balanced floc size distribution is necessary showing that not too many but still some fine flocs and also not too large but compact flocs lead to improved dewaterability. This has been illustrated by an extended range of floc size measurements ranging between 50 mm and 29 mm. The conditioning monitoring system would be suitable for the control of production of good size-balanced flocs to compensate fluctuations in sludge characteristics of the sludge to be conditioned.

Effect of floc size and structure on biosolids capillary suction time

2003 ◽  
Vol 47 (12) ◽  
pp. 255-260 ◽  
Author(s):  
J. Guan ◽  
R. Amal ◽  
T.D. Waite
Keyword(s):  
Activated Sludge ◽  
Fractal Dimensions ◽  
Scattering Method ◽  
Capillary Suction ◽  
Floc Size ◽  
Sludge Flocs ◽  
Floc Structure ◽  
Small Angle Light Scattering ◽  
Size And Structure

Both size and structure of wastewater solids (biosolids) have been hypothesised to have an impact on the dewaterability of these solids yet very little data exists to validate this hypothesis or to elucidate the relative effects of size and structure. We have recently undertaken studies in which the size and structure of activated sludge flocs were altered in a controlled manner and the dewaterability of resultant flocs examined using the well established capillary suction time (CST) test. A small angle light scattering method was applied for the determination of activated sludge floc size and structure. The results obtained in this work show that floc structure is a major determinant of capillary suction time. In some instances, flocs have almost double the median (D(4,3)) size but possess similar fractal dimensions and similar CST values.

Respirometry for determination of the influents SS-concentration

1996 ◽  
Vol 33 (1) ◽  
pp. 311-323 ◽  
Author(s):  
A. Witteborg ◽  
A. van der Last ◽  
R. Hamming ◽  
I. Hemmers
Keyword(s):  
Experimental Design ◽  
Activated Sludge ◽  
Substrate Concentration ◽  
Full Scale ◽  
Activated Sludge Process ◽  
Respiration Rates ◽  
On Line ◽  
Large Measurement ◽  
Set Up

A method is presented for determining influent readily biodegradable substrate concentration (SS). The method is based on three different respiration rates, which can be measured with a continuous respiration meter which is operated in a cyclic way. Within the respiration meter nitrification is inhibited through the addition of ATU. Simulations were used to develop the respirometry set-up and decide upon the experimental design. The method was tested as part of a large measurement programme executed at a full-scale plant. The proposed respirometry set-up has been shown to be suitable for a semi-on-line determination of an influent SS which is fully based on the IAWQ #1 vision of the activated sludge process. The YH and the KS play a major role in the principle, and should be measured directly from the process.

Study of factors affecting simultaneous nitrification and denitrification (SND)

1999 ◽  
Vol 39 (6) ◽  
pp. 61-68 ◽  
Author(s):  
Klangduen Pochana ◽  
Jürg Keller
Keyword(s):  
Carbon Source ◽  
Activated Sludge ◽  
Physical Phenomenon ◽  
Treatment Plant ◽  
Batch Reactors ◽  
Sequencing Batch Reactors ◽  
Factors Affecting ◽  
Floc Size ◽  
Sludge Flocs ◽  
Activated Sludge Systems

Experiments have been performed to gain an understanding of the conditions and processes governing the occurrence of SND in activated sludge systems. Sequencing batch reactors (SBRs) have been operated under controlled conditions using the wastewater from the first anaerobic pond in an abattoir wastewater treatment plant. Under specific circumstances, up to 95% of total nitrogen removal through SND has been found in the system. Carbon source and oxygen concentrations were found to be important process parameters. The addition of acetate as an external carbon source resulted in a significant increase of SND activity in the system. Stepwise change of DO concentration has also been observed in this study. Experiments to determine the effect of the floc size on SND have been performed in order to test the hypothesis that SND is a physical phenomenon, governed by the diffusion of oxygen into the activated sludge flocs. Initial results support this hypothesis but further experimental confirmation is still required.

Rapid quantification of polyhydroxyalkanoates (PHA) concentration in activated sludge with the fluorescent dye Nile blue A

2011 ◽  
Vol 64 (3) ◽  
pp. 747-753 ◽  
Author(s):  
M. Oshiki ◽  
H. Satoh ◽  
T. Mino
Keyword(s):  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Nile Blue ◽  
Maximum Level ◽  
Fluorescence Measurement ◽  
Batch Reactors ◽  
Floc Size ◽  
Nile Blue A ◽  
On Line ◽  
Rapid Quantification

The present study was conducted (1) to develop a rapid quantification method of polyhydroxyalkanoates (PHA) concentration in activated sludge by Nile blue A staining and fluorescence measurement and (2) to perform on-line monitoring of PHA concentrations in activated sludge. Activated sludge samples collected from laboratory scale sequencing batch reactors and full-scale wastewater treatment plants were stained with Nile blue A and their fluorescence intensities were determined. There was a high correlation (R2 > 0.97) between the fluorescence intensities of Nile blue A and PHA concentrations in activated sludge determined by gas chromatography. The Nile blue A staining and fluorescence measurement method allows us to determine PHA concentrations in activated sludge within only five minutes and up to 96 samples can be measured at once by using microplate reader. On-line monitoring of PHA concentrations in activated sludge was achieved by using a fluorometer equipped with a flow cell and the time point at which PHA concentration in activated sludge reached the maximum level could be identified. In addition, we examined the influence of pH, floc size and co-existing chemicals in activated sludge suspension on the fluorescence intensities of Nile blue A.

On-line determination of nitrite in wastewater treatment by use of a biosensor

2002 ◽  
Vol 45 (4-5) ◽  
pp. 69-76 ◽  
Author(s):  
M. Nielsen ◽  
N.P. Revsbech ◽  
L.H. Larsen ◽  
A. Lynggard-Jensen
Keyword(s):  
Activated Sludge ◽  
Mechanical Damage ◽  
Operating Conditions ◽  
Bacterial Populations ◽  
Operational Lifetime ◽  
On Line ◽  
Low Levels ◽  
In The Beginning

A newly developed biosensor for nitrite having a 90% response time of about 1 min was used to monitor nitrite concentration in activated sludge exposed to oxic/anoxic cycles. The NO2− biosensor contains bacteria that reduce NO2−, but not NO3−, to N2O that is subsequently monitored by a built-in electrochemical sensor. Nitrite plus nitrate (NOx−) was simultaneously monitored by a NOx− biosensor. The maximum operational lifetime of the NO2− biosensor was 6 weeks, but much longer lifetimes can be expected as malfunctioning by the 3 sensors used for longer periods was due to either mechanical damage or ineffective internal sterilization during the construction. Insufficiently sterilized sensors became sensitive also to NO3− after some time due to development of NO3−-reducing bacterial populations within the sensor. The fraction of NO2− as compared to NO3− in the activated sludge was very dependent on prehistory, actual loading, and aeration. During balanced operation with NH4+ being exhausted during the later parts of the aerobic cycle, NO2− increased in concentration up to about 50 μM during the early part of the aeration cycle until NH4+ became limiting. At that time the NO2− concentration decreased to low levels. Under some operating conditions a peak of NO2− also appeared in the beginning of the anoxic period. NO2− and NO3− were depleted simultaneously during the anoxic period.

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