A one-dimensional model for a secondary settling tank including density current and short-circuiting

1995 ◽  
Vol 31 (2) ◽  
pp. 215-224 ◽  
Author(s):  
René Dupont ◽  
Claus Dahl
Keyword(s):  
Settling Tank ◽  
Treatment Plant ◽  
Density Current ◽  
One Dimensional ◽  
Solids Concentration ◽  
Primary Particles ◽  
Flux Model ◽  
Secondary Settling ◽  
Soluble Components ◽  
Sludge Concentration

This paper presents a dynamic one-dimensional flux model for the secondary settling tank which is suitable for use with the latest innovations in models for activated sludge tanks, and which takes into account observed effects of density current and short-circuiting. The components of the influent to the settling tank are divided into three fractions. Soluble components, non-settleable particulate components (primary particles), and settleable particulate components. (macroflocs). Soluble components and primary particles are considered to follow the hydraulic flow in the settling tank. The transport of macroflocs in the settling tank is modelled according to the traditional flux theory on a layer model of the settling tank extended with a model for density current and short-circuiting. For modelling of the density current in the inlet region of the settler a dynamic inlet height is introduced. The short-circuiting is modelled by the introduction of a factor which accounts for the dilution in the suspended solids concentration at the bottom of the settling tank down to the concentration in the return sludge flow. Settling velocities of the macroflocs for both free and hindered sedimentation are measured, and a new model for the settling velocity is proposed. The model is validated with data from the wastewater treatment plant Lynetten, Copenhagen, Denmark. It was found that the suspended sludge concentration profile and the suspended sludge concentration in the return sludge were predicted well with the model.

Cost-effective upgrading of a biological wastewater treatment plant by using lamella separators with bypass operation

2008 ◽  
Vol 57 (10) ◽  
pp. 1619-1625 ◽  
Author(s):  
N. Jardin ◽  
L. Rath ◽  
A. Schönfeld ◽  
T. Grünebaum
Keyword(s):  
Activated Sludge ◽  
Biological Treatment ◽  
Settling Tank ◽  
Treatment Plant ◽  
Optimal Solution ◽  
Cost Effective ◽  
A Value ◽  
Solids Concentration ◽  
Treatment Stage ◽  
Secondary Settling

Based on a comprehensive cost analysis for the expansion of the Finnentrop WWTP, integration of lamella separators in the biological treatment stage was given priority as optimal solution to increase the solids concentration. The overall expansion project included the reconstruction of the former primary clarifier into a primary settling tank with short retention times and the use of the remaining volume for pre-denitrification. Four lamella separators were positioned in the existing carousel-type activated sludge tank. With the lamella assemblies ensuring it was possible to continue operation of the existing secondary settling tanks. To control an adequate solids concentration in the activated sludge tank and to avoid any overloading of the secondary settling tank, a newly developed bypass strategy was applied. With a controlled mixing of direct effluent from the lamella separators and the contents of the activated sludge tank, the solids concentration of the influent to the secondary settling tank could be maintained at a value of 2.2 kg/m3. The lamella separator concept did not account for any significant changes in the sludge characteristics, and the overall elimination of nutrients and organic carbon was found to be excellent upon optimisation of the operational lamella strategy.

Monitoring On-Line and Control of Sludge Concentration in Sewage Treatment System

2013 ◽  
Vol 373-375 ◽  
pp. 897-901
Author(s):  
Lian Qing Yin ◽  
Chun Xiao Yin ◽  
Xue Zhou ◽  
Jia Liu
Keyword(s):  
Water Treatment ◽  
Sewage Treatment ◽  
Settling Tank ◽  
Great Influence ◽  
Treatment Plant ◽  
Water Treatment Plant ◽  
Treatment System ◽  
On Line ◽  
And Control ◽  
Sludge Concentration

The reuse of industrial waste and urban sewage is a vital method for solving the shortage of water resource in China. Settling tank as a processing link in water treatment system widely used exercises a great influence on sewage treatment efficiency, and sludge emissions have a great influence on the operation of water treatment plant. Manual mud and mechanical dredge are widely used in most of the water treatment plants from the current domestic. The design used ultrasonic as a method for determination of sludge concentration, developped corresponding application control software, and finally completed a reasonable and feasible for settling tank intermittent discharge of sludge monitoring and emission control system.The result of our simulation system shows that the program operation is stable and maneuverability, and this set of monitoring on-line and control system has good application and development foreground.

Influence of sludge properties and hydraulic loading on the performance of secondary settling tanks - full-scale operational results

2004 ◽  
Vol 50 (7) ◽  
pp. 179-186 ◽  
Author(s):  
R.J. Vestner ◽  
F. Wolfgang Günthert
Keyword(s):  
Suspended Solids ◽  
Loading Rate ◽  
Settling Tank ◽  
Full Scale ◽  
Volume Loading ◽  
Solids Concentration ◽  
Sludge Properties ◽  
And Performance ◽  
Secondary Settling ◽  
Flocculation Time

Full-scale investigations at a WWTP with a two-stage secondary settling tank process revealed relationships between significant operating parameters and performance in terms of effluent suspended solids concentration. Besides common parameters (e.g. surface overflow rate and sludge volume loading rate) feed SS concentration and flocculation time must be considered. Concentration of the return activated sludge may help to estimate the performance of existing secondary settling tanks.

Accounting of External Factors for Sewage Disinvasion

2018 ◽  
Vol 931 ◽  
pp. 996-1000
Author(s):  
Natalia V. Yudina ◽  
Lidiya A. Dolzhenko
Keyword(s):  
Biological Treatment ◽  
Sewage Treatment ◽  
Settling Tank ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Municipal Sewage ◽  
Helminth Eggs ◽  
Sand Trap ◽  
Treatment Facilities ◽  
Secondary Settling

The results of a survey of the background parasitic characteristics on individual structures of the municipal sewage treatment plant are given. It is established that 27% of the grids and sand trap are retained, the effectiveness of the retention in the biological treatment facilities after the secondary settling tank corresponded to 61.9%. Helminth eggs are mostly concentrated in sewage sludge, to a large extent maintaining their viability (90%). An imitating model of the process of disinvasion of sewage and sediments was developed, represented by a network diagram for sewage treatment fa-cilities. In production conditions, an experiment was performed to determine the influence of exter-nal factors on the efficiency of dehelmintization by the plant reagent.

scholarly journals Experience from the Implementation and Operation of the Biological Membrane Reactor (MBR) at the Modernized Wastewater Treatment Plant in Wydminy

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3410 ◽  
Author(s):  
Iwona Skoczko ◽  
Pawel Puzowski ◽  
Ewa Szatyłowicz
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Biological Membrane ◽  
Sewage Treatment ◽  
Settling Tank ◽  
Treatment Plant ◽  
Membrane Reactors ◽  
Northeastern Poland ◽  
Secondary Settling

Biological membrane reactors or membrane bioreactors (MBRs) based on pressure separation techniques are placed among the latest and most modern methods of wastewater treatment. Currently, this method is becoming more and more popular and is being implemented in smaller and larger wastewater treatment plants (WWTPs). However, technologists, operators, and managers of small WWTPs often do not understand the MBR technology installed in their sites and need extensive professional and technological information. The aim of this study was to analyze the modernized WWTP in a small town of Wydminy, located in northeastern Poland in the Great Masurian Lakes region, where the traditional secondary settling tank was replaced by an MBR. The effectiveness of wastewater treatment before modernization and after installation of the membrane module was compared. On the basis of the conducted research, it was noted that the operation of the plant after modernization is more cost-intensive. There were additional electricity costs due to ensuring adequate pressure on the membrane. Nevertheless, the obtained results of the removal of contaminants place the plant in Wydminy in the group of the most effective Polish sewage treatment plants, as compared to the results obtained in other facilities. The MBR operation also places high demands on the exploiters, prompting them to observe even the smallest changes. The conducted research is a type of a case study, which could give the readers an understanding of the necessity of traditional WWTP modernization with MBR.

Effect of Activated Sludge Processes on Secondary Settling Tank Efficiencies

1988 ◽  
Vol 20 (4-5) ◽  
pp. 153-163 ◽  
Author(s):  
Z. Koníček ◽  
J. Burdych
Keyword(s):  
Settling Tank ◽  
Standard Test ◽  
Density Current ◽  
Secondary Settling ◽  
Final Settlement ◽  
Activated Sludge Processes ◽  
Harmful Effects ◽  
Current Zone ◽  
Better Than ◽  
Number Of Particles

Some calculations and experimental work on the turbulence in aeration tanks using different aeration systems and its effect on floc cohesion are presented. Vigorous aeration causes floc dispersion and it can be quantified in standard test conditions using velocity gradient calculations and comparing these with the numbers of particles in the supernatant liquor after 30 minutes settlement of the sludge. Tests on final settlement tanks indicated that the density current is of prime importance and that the harmful effects of this can be overcome by installing deep inlets and arranging to have the outlet weir inset and as near to the inlet as possible. Mixing calculations also indicated that circular tanks are more efficient than rectangular and that if the latter were used transverse flow is better than longitudinal flow. A test on a full scale plant indicated that flocculation occurred in the density current zone of the final tank so that the number of particles in the supernatant decreased to an extent similar to that produced by mild agitation.

Dynamic one-dimensional modeling of secondary settling tanks and system robustness evaluation

2014 ◽  
Vol 69 (11) ◽  
pp. 2339-2349 ◽  
Author(s):  
Ben Li ◽  
M. K. Stenstrom
Keyword(s):  
Numerical Methods ◽  
Numerical Technique ◽  
Settling Tank ◽  
Operating Conditions ◽  
Parabolic Partial Differential Equation ◽  
Engineering Practice ◽  
Time To Failure ◽  
One Dimensional ◽  
Secondary Settling ◽  
The Yrd

One-dimensional secondary settling tank models are widely used in current engineering practice for design and optimization, and usually can be expressed as a nonlinear hyperbolic or nonlinear strongly degenerate parabolic partial differential equation (PDE). Reliable numerical methods are needed to produce approximate solutions that converge to the exact analytical solutions. In this study, we introduced a reliable numerical technique, the Yee–Roe–Davis (YRD) method as the governing PDE solver, and compared its reliability with the prevalent Stenstrom–Vitasovic–Takács (SVT) method by assessing their simulation results at various operating conditions. The YRD method also produced a similar solution to the previously developed Method G and Enquist–Osher method. The YRD and SVT methods were also used for a time-to-failure evaluation, and the results show that the choice of numerical method can greatly impact the solution. Reliable numerical methods, such as the YRD method, are strongly recommended.

The evaluation of a density current experiment as a verification tool of a secondary clarifier model

2003 ◽  
Vol 47 (12) ◽  
pp. 113-118 ◽  
Author(s):  
J. Kim ◽  
S. Kim ◽  
J. Yoon
Keyword(s):  
Steady State ◽  
Activated Sludge ◽  
Gravity Current ◽  
Settling Tank ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Bottom Layer ◽  
Density Current ◽  
Density Currents ◽  
The Impact

The prediction of the spatial and temporal flow regime is important for the efficient design and operation of the settling tank. The impact of the gravity current has been investigated by the temperature difference or artificial glass particles. This experimental study is designed to obtain the steady state of stratified flow with the consideration of the heavy density flow. Two different approaches were performed at lab scale considering the hydraulic similarity. One is the investigation of a heavy density current of saline water intrusion. The characteristics of the internal hydraulics are monitored using Particle Image Velocimetry (PIV). As a result of the saline intrusion, the internal flow established a continual density stratification of 3-layers in steady state. The other is the movement of activated sludge from a sewage treatment plant. The video image is captured to analyze the behavior of activated sludge in the settling tank. The experiments with various inlet baffle conditions suggest that the hydraulic characteristics of the two experiments are significantly different. As the distance between the baffle and inlet point was decreased, significant strength of saline density currents in the bottom layer was observed. However, the strength of the velocity in the bottom density currents appeared to be the opposite in the case of the activated sludge. The reason for the slower density current in the bottom layer is associated with the compressibility of activated sludge characteristics.

Dynamic loading tests for final settling tanks

1996 ◽  
Vol 34 (3-4) ◽  
pp. 267-274 ◽  
Author(s):  
Patrik Baumer ◽  
Peter Volkart ◽  
Peter Krebs
Keyword(s):  
Suspended Solids ◽  
Flow Direction ◽  
Settling Tank ◽  
Treatment Plant ◽  
Pilot Scale ◽  
Solids Concentration ◽  
Dynamic Experiments ◽  
Main Flow Direction ◽  
Loading Tests ◽  
Removal System

Dynamic experiments conducted in a pilot scale settling tank at Zurich's wastewater treatment plant (WWTP) are presented. The experiments were carried out with real activated sludge. They showed that vertical perforated walls transverse to the main flow direction are very beneficial particularly for wet-weather flow. The increase of the effluent suspended solids concentration is significantly dampened with dynamic hydraulic loading. Installing several perforated walls enables uniform velocity profiles to be attained, enhancing flocculation. The total sludge mass stored in the final settling tank may be increased by this system and requires special attention when the removal system is designed.

Sign in / Sign up

Export Citation Format

Share Document