scholarly journals A sensitivity and model reduction analysis of one-dimensional secondary settling tank models under wet-weather flow and sludge bulking conditions

2016 ◽  
Vol 288 ◽  
pp. 813-823 ◽  
Author(s):  
Ben Li ◽  
Michael K. Stenstrom
Keyword(s):  
Model Reduction ◽  
Settling Tank ◽  
One Dimensional ◽  
Sludge Bulking ◽  
Wet Weather ◽  
Wet Weather Flow ◽  
Secondary Settling

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.

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.

Wet-Weather Flow Management in the Great Lakes Areas of Concern

2004 ◽  
Vol 39 (4) ◽  
pp. 319-330 ◽  
Author(s):  
Sandra Kok
Keyword(s):  
Great Lakes ◽  
Municipal Wastewater ◽  
Flow Management ◽  
Beneficial Uses ◽  
Wet Weather ◽  
Areas Of Concern ◽  
Municipal Wastewaters ◽  
Wet Weather Flow ◽  
The Government ◽  
Government Of Canada

Abstract Under the Government of Canada's Great Lakes Program, the Great Lakes Sustainability Fund and its predecessor programs (the Great Lakes Cleanup Fund and the Great Lakes 2000 Cleanup Fund) were established to implement cleanup actions and strategies that would contribute to the restoration of beneficial uses in environmentally degraded areas (known as Areas of Concern) in the Great Lakes basin. The Great Lakes Sustainability Fund is administered by Environment Canada on behalf of eight Government of Canada departments. Contributing to impaired beneficial uses are municipal wastewaters generated from the urban centres in the Great Lakes Areas of Concern. These municipal wastewaters include treated sewage and wetweather discharges of combined sewer overflows and stormwater runoff. This paper provides an overview of the Municipal Wastewater Program of the federal government's Great Lakes Sustainability Fund and highlights the progress made to date under the program towards wet-weather flow management and the Program's role in developing and demonstrating sustainable approaches and technologies in the Great Lakes Areas of Concern.

An equation for the empirical design of anoxic zones used to eliminate rising sludges at nitrifying activated sludge plants

1996 ◽  
Vol 33 (3) ◽  
pp. 185-194 ◽  
Author(s):  
M. Sarioglu ◽  
N. Horan
Keyword(s):  
Activated Sludge ◽  
Empirical Equation ◽  
Nitrate Nitrogen ◽  
Critical Concentration ◽  
Settling Tank ◽  
Limited Information ◽  
Batch Experiments ◽  
Anoxic Zone ◽  
Secondary Settling ◽  
Anoxic Zones

Anoxic zones are designed for the removal of nitrogen in nitrifying activated sludge plants. This can be carried out either to achieve a nitrogen discharge consent or to eliminate the problem of rising sludges. The rising sludge problem is mostly encountered in medium and small size plants in warm conditions and there is limited information as to the appropriate design of anoxic zones to protect against rising sludges in the secondary sedimentation tanks. Therefore a series of batch experiments were undertaken in order to establish the critical concentration of nitrate-nitrogen which causes rising sludge in the secondary settling tank and the effect of environmental factors such as temperature (15°C to 30°C) and residual carbon source (100 to 600 mg/1 COD) were examined. Based on the results of these experiments an empirical equation was presented which can be used to size an anoxic zone to eliminate rising sludges. The application of this equation at full-scale plants is discussed.

Origins and characteristics of urban wet weather pollution in combined sewer systems: the experimental urban catchment “Le Marais” in Paris

1998 ◽  
Vol 37 (1) ◽  
pp. 35-43 ◽  
Author(s):  
Marie-Christine Gromaire-Mertz ◽  
Ghassan Chebbo ◽  
Mohamed Saad
Keyword(s):  
Waste Water ◽  
Sewer System ◽  
Urban Catchment ◽  
Rainfall Events ◽  
Sources Of Pollution ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Wet Weather ◽  
Wet Weather Flow ◽  
Different Sources

An experimental urban catchment has been created in the centre of Paris, in order to obtain a description of the pollution of urban wet weather flows at different levels of the combined sewer system, and to estimate the contribution of runoff, waste water and sewer sediments to this pollution. Twenty-two rainfall events were studied from May to October 1996. Dry weather flow was monitored for one week. Roof, street and yard runoff, total flow at the catchment outlet and waste water were analysed for SS, VSS, COD and BOD5, on both total and dissolved fraction. Results show an evolution in the characteristics of wet weather flow from up to downstream: concentrations increase from the catchment entry to the outlet, as well as the proportion of particle-bound pollutants and the part of organic matter. A first evaluation of the different sources of pollution establishes that a major part of wet weather flow pollution originates from inside the combined sewer, probably through erosion of sewer sediments.

Accurate Wet-Weather Flow Characterization and Dynamic Modeling Help Optimize Treatment Designs and Operations

2012 ◽  
Vol 2012 (14) ◽  
pp. 2339-2357
Author(s):  
J. D. Fitzpatrick ◽  
N. J. Tetrick ◽  
S. Sengupta ◽  
D. Martin ◽  
A. Gelderloos ◽  
...  
Keyword(s):  
Dynamic Modeling ◽  
Flow Characterization ◽  
Wet Weather ◽  
Wet Weather Flow ◽  
Treatment Designs

A Physics-Based Dynamic Model for Boilers: Part 2 — Model Reduction in a Cogeneration Application

2017 ◽  
Author(s):  
Matthew J. Blom ◽  
Michael J. Brear ◽  
Chris G. Manzie ◽  
Ashley P. Wiese
Keyword(s):  
Model Reduction ◽  
Gas Turbine ◽  
Dynamic Model ◽  
Reduction Process ◽  
Singular Perturbation Theory ◽  
Reduced Order Models ◽  
Reduced Order ◽  
One Dimensional ◽  
Time Scale Separation ◽  
Modelling Framework

This paper is the second part of a two part study that develops, validates and integrates a one-dimensional, physics-based, dynamic boiler model. Part 1 of this study [1] extended and validated a particular modelling framework to boilers. This paper uses this framework to first present a higher order model of a gas turbine based cogeneration plant. The significant dynamics of the cogeneration system are then identified, corresponding to states in the gas path, the steam path, the gas turbine shaft, gas turbine wall temperatures and boiler wall temperatures. A model reduction process based on time scale separation and singular perturbation theory is then demonstrated. Three candidate reduced order models are identified using this model reduction process, and the simplest, acceptable dynamic model of this integrated plant is found to require retention of both the gas turbine and boiler wall temperature dynamics. Subsequent analysis of computation times for the original physics-based one-dimensional model and the candidate, reduced order models demonstrates that significantly faster than real time simulation is possible in all cases. Furthermore, with systematic replacement of the algebraic states with feedforward maps in the reduced order models, further computational savings of up to one order of magnitude can be achieved. This combination of model fidelity and computational tractability suggest suggests that the resulting reduced order models may be suitable for use in model based control of cogeneration plants.

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