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.

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.

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.

Effects of potassium ion on sludge settling, dewatering and effluent properties

1998 ◽  
Vol 37 (4-5) ◽  
pp. 317-324 ◽  
Author(s):  
Sudhir N. Murthy ◽  
John T. Novak
Keyword(s):  
Activated Sludge ◽  
Field Studies ◽  
Potassium Ion ◽  
Potassium Ions ◽  
Nutrient Requirements ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Sludge Flocs ◽  
Sludge Properties ◽  
Sludge Settling

Potassium ions appear to play an important role in determining the nature of activated sludge flocs. Relative to sodium, the concentration of potassium ions in most industrial activated sludge is typically low. Laboratory and field studies were conducted to examine the influence of potassium on activated sludge properties. The concentration of potassium affected the concentration of readily extractable (slime) proteins in the floc and the proteins in the surrounding solution. In laboratory tests, an increase in this cation's concentration beyond nutrient requirements impeded sludge dewatering properties as measured by capillary suction time (CST) and specific resistance to filtration (SRF) and associated with an increase in soluble protein. An increase in effluent total organic carbon and effluent turbidity was observed at higher concentrations of this ion. Conversely, an increase in concentration of potassium ion improved the settling properties of sludge with low equivalent monovalent to divalent cation ratio.

scholarly journals Tailing propensity in the ultraviolet disinfection of trickling filter and activated sludge wastewater treatment processes

2017 ◽  
Vol 76 (3) ◽  
pp. 623-632 ◽  
Author(s):  
Thiam C. Tan ◽  
Yaldah Azimi ◽  
Ramin R. Farnood
Keyword(s):  
Activated Sludge ◽  
Suspended Particle ◽  
Uv Disinfection ◽  
Distribution Data ◽  
Trickling Filter ◽  
Floc Size ◽  
Sludge Flocs ◽  
Filter System ◽  
Secondary Effluents ◽  
Wastewater Samples

In this paper, the effect of suspended flocs on the tailing of ultraviolet (UV) disinfection kinetics of secondary effluents was examined. To achieve this goal, final effluents produced in two processes for treating wastewater; namely, a trickling filter system and an activated sludge system, were collected and their UV disinfection were compared. Tailing of the UV dose response curve was controlled by the fraction of flocs that are both culturable and UV-resistant, referred to as the ‘tailing propensity’. Using this parameter, the contribution of various floc size fractions in reducing the UV disinfection efficiency of wastewater samples was quantified. Activated sludge flocs larger than 125 μm exhibited as much as 35 times greater tailing propensity than smaller flocs in the range of 20–25 μm. Within a fixed size range, the tailing propensity of flocs generated in the trickling filter system was 3 to 8 times higher than that of activated sludge flocs, and this difference increased with the floc size. A mathematical model was developed to predict the UV disinfection of secondary effluents from suspended particle size distribution data. The model showed good agreement with experimental results.

Bacterial composition of activated sludge - importance for floc and sludge properties

2004 ◽  
Vol 49 (10) ◽  
pp. 51-58 ◽  
Author(s):  
P.H. Nielsen ◽  
T.R. Thomsen ◽  
J.L. Nielsen
Keyword(s):  
Activated Sludge ◽  
Sludge Flocs ◽  
Floc Structure ◽  
Culture Independent ◽  
In Situ Methods ◽  
Sludge Properties ◽  
And Function ◽  
Biological Methods ◽  
Dominant Bacteria

Activated sludge flocs consist of numerous constituents which, together with other factors, are responsible for floc structure and floc properties. These properties largely determine the sludge properties such as flocculation, settling and dewaterability. In this paper we briefly review the present knowledge about the role of bacteria in relation to floc and sludge properties, and we present a new approach to investigate the identity and function of the bacteria in the activated sludge flocs. The approach includes identification of the important bacteria and a characterization of their physiological and functional properties. It is carried out by use of culture-independent molecular biological methods linked with other methods to study the physiology and function, maintaining a single cell resolution. Using this approach it was found that floc-forming properties differed among the various bacterial groups, e.g. that different microcolony-forming bacteria had very different sensitivities to shear and that some of them deflocculated under anaerobic conditions. In our opinion, the approach to combine identity with functional analysis of the dominant bacteria in activated sludge by in situ methods is a very promising way to investigate correlations between presence of specific bacteria, and floc and sludge properties that are of interest.

Early warning-system for operation-failures in biological stages of WWTPs by on-line image analysis

2002 ◽  
Vol 46 (4-5) ◽  
pp. 117-124 ◽  
Author(s):  
W. Heine ◽  
I. Sekoulov ◽  
H. Burkhardt ◽  
L. Bergen ◽  
J. Behrendt
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Biological Parameter ◽  
Chemical Parameters ◽  
Floc Size ◽  
Sludge Flocs ◽  
Operation Conditions ◽  
Physico Chemical ◽  
Microscopic Picture

By the observation and evaluation of the microscopic picture of activated sludge samples it is possible to introduce another biological parameter additional to conventional physico-chemical parameters for the control of biological stages of waste water treatment plants. Considering the fact that parameters like floc size and floc size distribution, structure of the flocs (compact/open), shape of the flocs (round/irregular) allow perceptions of the adjusted operation conditions of the biological stages, evidence for changing operation conditions or threatening operation disturbances can be recognised. This recognition takes place at a very early phase, because the morphology of activated sludge flocs reacts very fast to changing conditions. An automatic image analysis of activated sludge floc pictures would enable the introduction of a new sum parameter to enhance operation control of aeration tanks. By a statistical evaluation of the processed sludge images several parameters can be used to describe the alteration of activated sludge flocs characteristics. With these biological parameters it is possible to detect altered operation conditions or threatening or existing operation problems at an early phase. Thus it is possible to plan suitable countermeasures. Furthermore, the microscopic picture is the only parameter, that gives important information about the structure of the activated sludge flocs and the biozenosis. In comparison with the mainly used physico-chemical parameters, that just give information about the inlet and outlet of the wastewater treatment plants, the microscopic picture is the only parameter that gives information about the biology of the wastewater treatment process. By means of this biological parameter an improved control and regulation of the biological stages of wastewater treatment plants can be obtained.

scholarly journals Influence of road salt thawing peaks on the inflow composition and activated sludge properties in municipal wastewater treatment

2021 ◽  
Author(s):  
J. Tauber ◽  
B. Flesch ◽  
V. Parravicini ◽  
K. Svardal ◽  
J. Krampe
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Road Salt ◽  
Volume Index ◽  
Municipal Wastewater Treatment ◽  
Floc Size ◽  
Floc Structure ◽  
Autotrophic Biomass

Abstract Operational data over 2 years from three large Austrian wastewater treatment plants (WWTPs) with design capacities of 4 million, 950,000 and 110,000 population equivalent (PE) were examined. Salt peaks, due to thawing road salt were detected and quantified by electrical conductivity, temperature and chloride measurement in the inflow of the WWTPs. Daily NaCl inflow loads up to 1,147 t/d and PE-specific loads of 0.26–0.5 kg NaCl/(PE · y) were found. To mimic the plants' behaviour in a controlled environment, NaCl was dosed into the inflow of a laboratory-scale activated sludge plant. The influence of salt peaks on important activated sludge parameters such as sludge volume index, settling velocity and floc size were investigated. Influent and effluent were sampled extensively to calculate removal rates. Respiration measurements were performed to quantify activated sludge activity. Particle size distributions of the activated sludge floc sizes were measured using laser diffraction particle sizing and showed a decrease of the floc size by approximately two-thirds. The floc structure was examined and documented using light microscopy. At salt concentrations below 1 g/L, increased respiration was found for autotrophic biomass, and between 1 and 3 g NaCl/L respiration was inhibited by up to 30%.

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