Solids separation efficiency of combined sewer overflows

2005 ◽  
Vol 51 (2) ◽  
pp. 71-78 ◽  
Author(s):  
G. Luyckx ◽  
G. Vaes ◽  
J. Berlamont
Keyword(s):  
Velocity Distribution ◽  
Settling Velocity ◽  
Separation Efficiency ◽  
Efficiency Curve ◽  
Combined Sewer Overflows ◽  
Combined Sewer ◽  
Different Types ◽  
Solids Separation ◽  
Settling Velocity Distribution ◽  
The One

The removal of sewer solids at combined sewer overflow locations depends on the flow patterns inside the overflow structure on the one hand and on the sediment characteristics on the other hand. Flow conditions can be described by the residence time distribution; sewer sediments can be characterised by their settling velocity distribution. The combination of both distributions leads to a dimensionless efficiency curve, which gives the removal efficiency as a function of the Hazen number. For field conditions this efficiency curve is mainly influenced by the settling velocity distribution of the sewer sediments and, as a consequence, nearly identical efficiency curves are found for different types of prototype CSO structure. For design purposes, a methodology using return frequency analysis is proposed.

A Water Elutriation Apparatus for Measuring Settling Velocity Distribution of Suspended Solids in Combined Sewer Overflows

2004 ◽  
Vol 39 (4) ◽  
pp. 432-438 ◽  
Author(s):  
Bommanna G. Krishnappan ◽  
Jiri Marsalek ◽  
Kirsten Exall ◽  
Robert P. Stephens ◽  
Quintin Rochfort ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Suspended Solids ◽  
Settling Velocity ◽  
Settling Chamber ◽  
Combined Sewer Overflows ◽  
Polymer Addition ◽  
Combined Sewer ◽  
Sewer Overflows ◽  
Settling Velocity Distribution ◽  
Chemical Distribution

Abstract An elutriation apparatus has been proposed for determining the settling velocity distributions of suspended solids in combined sewer overflows (CSOs). The apparatus consisted of a series of interconnected cylindrical settling chambers, through which the sample was drawn using a peristaltic pump attached to the outlet of the last settling chamber. Since the diameters of the cylinders were progressively increasing, sediment with different settling velocities settled in different cylinders. By measuring the amount of sediment in each cylinder, the settling velocity distribution was deduced. The apparatus was tested using samples from a CSO outfall in Hamilton, Ontario, Canada. The test results showed that the apparatus performed well for determining settling characteristics of suspended solids and chemical distribution in different settling fractions. The effectiveness of polymer addition to enhance flocculation and settling of CSOs was also tested in this apparatus. The elutriation apparatus proposed here offers several advantages over the traditional methods (i.e., settling columns) of measurements of settling velocity distributions. The main advantage is its ability to measure the distributions under dynamic conditions, i.e., in the presence of flow. Consequently, the elutriation apparatus reproduces flow conditions in actual settling tanks better than conventional settling columns.

Characterisation of retention tank water quality: particle settling velocity distribution and retention time

2013 ◽  
Vol 48 (4) ◽  
pp. 321-332 ◽  
Author(s):  
Thibaud Maruéjouls ◽  
Peter A. Vanrolleghem ◽  
Geneviève Pelletier ◽  
Paul Lessard
Keyword(s):  
Velocity Distribution ◽  
Retention Time ◽  
Settling Velocity ◽  
Oxygen Demand ◽  
Combined Sewer Overflows ◽  
Particle Settling ◽  
Wastewater Systems ◽  
Receiving Waters ◽  
Settling Velocity Distribution ◽  
Settling Performance

Retention tanks (RTs) are commonly used to reduce combined sewer overflows, management of which is an important way of reducing the impacts of urban development on receiving waters. However, overflow characteristics and the processes affecting them are not yet fully understood. In a context of integrated urban wastewater systems, the management of RTs is mainly done to satisfy hydraulic constraints even if the idea behind such structures is to limit the discharge of pollutants to the environment. This study reports new insights in the settling processes and the pollutant behaviour occurring in an off-line RT. The authors first focus on the total suspended solids (TSS) and the total chemical oxygen demand (CODt) dynamics at the inlet and the outlet of a RT. Secondly, they focus on the possible relationship between the variation of the particle settling velocity distribution of particles and the TSS concentration dynamics. Finally, analyses of the TSS and CODt concentration evolution during tank emptying give information on the interaction between wastewater retention time and the settling performance.

Vortex Separation Technology

1997 ◽  
Vol 32 (1) ◽  
pp. 185-214 ◽  
Author(s):  
Richard Field ◽  
David Averill ◽  
Thomas P. O'Connor ◽  
Paula Steel
Keyword(s):  
Settling Velocity ◽  
Combined Sewer Overflows ◽  
Reliable Determination ◽  
Major Function ◽  
Solids Concentration ◽  
Combined Sewer ◽  
Vortex Separation ◽  
Settling Velocity Distribution ◽  
Stormwater Pollution

Abstract Several types of vortex separators have been developed during the last 30 years. Their major function has been to provide both flow regulation and settleable solids concentration for the control of combined sewer overflows (CSOs). A variety of opinions have developed regarding the application of these technologies, ranging from overwhelming support to reservations of their effectiveness. The performance of vortex devices depends on the settling velocity distribution of the particles in the wastewater. When correctly installed with other controls in combined sewer or separate stormwater systems, vortex devices can play an important role in the control of pollution from CSO and stormwater discharge. Reliable determination of performance depends principally upon accurate sampling techniques, suspended solids and other pollutant analyses, and the settling velocity distributions of the influent and effluent. Simultaneous flow rate measurement, synchronized to sampling time, is also necessary. This paper discusses design, application and evaluation of swirl/vortex technologies as part of CSO and stormwater pollution control systems.

Methodology of Calculation the Terminal Settling Velocity Distribution of Irregular Particles for High Values of the Reynold’s Number/Metodologia Wyliczania Rozkładu Granicznej Prędkości Opadania Ziaren Nieregularnych Dla Wysokich Wartości Liczb Reynoldsa

2014 ◽  
Vol 59 (2) ◽  
pp. 553-562 ◽  
Author(s):  
Agnieszka Surowiak ◽  
Marian Brożek
Keyword(s):  
Velocity Distribution ◽  
Settling Velocity ◽  
Random Variables ◽  
Independent Random Variables ◽  
Calculation Algorithm ◽  
Shape Coefficient ◽  
Geometrical Properties ◽  
Size And Shape ◽  
Physical Density ◽  
Settling Velocity Distribution

Abstract Settling velocity of particles, which is the main parameter of jig separation, is affected by physical (density) and the geometrical properties (size and shape) of particles. The authors worked out a calculation algorithm of particles settling velocity distribution for irregular particles assuming that the density of particles, their size and shape constitute independent random variables of fixed distributions. Applying theorems of probability, concerning distributions function of random variables, the authors present general formula of probability density function of settling velocity irregular particles for the turbulent motion. The distributions of settling velocity of irregular particles were calculated utilizing industrial sample. The measurements were executed and the histograms of distributions of volume and dynamic shape coefficient, were drawn. The separation accuracy was measured by the change of process imperfection of irregular particles in relation to spherical ones, resulting from the distribution of particles settling velocity.

Field testing CFD-based predictions of storage chamber gross solids separation efficiency

1999 ◽  
Vol 39 (9) ◽  
pp. 161-168 ◽  
Author(s):  
Virginia R. Stovin ◽  
Adrian J. Saul ◽  
Andrew Drinkwater ◽  
Ian Clifforde
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Settling Velocity ◽  
Separation Efficiency ◽  
Flow Patterns ◽  
Total Efficiency ◽  
Separation Performance ◽  
Storage Chamber ◽  
Solids Separation ◽  
Simulated Flow

The use of computational fluid dynamics-based techniques for predicting the gross solids and finely suspended solids separation performance of structures within urban drainage systems is becoming well established. This paper compares the result of simulated flow patterns and gross solids separation predictions with field measurements made in a full size storage chamber. The gross solids retention efficiency was measured for six different storage chambers in the field and simulations of these chambers were undertaken using the Fluent computational fluid dynamics software. Differences between the observed and simulated flow patterns are discussed. The simulated flow fields were used to estimate chamber efficiency using particle tracking. Efficiency results are presented as efficiency cusps, with efficiency plotted as a function of settling velocity. The cusp represents a range of efficiency values, and approaches to the estimation of an overall efficiency value from these cusps are briefly discussed. Estimates of total efficiency based on the observed settling velocity distribution differed from the measured values by an average of ±17%. However, estimates of steady flow efficiency were consistently higher than the observed values. The simulated efficiencies agreed with the field observations in identifying the most efficient configuration.

Hydrodynamic Water Quality Simulation - An Approximative Solution

1991 ◽  
Vol 24 (6) ◽  
pp. 157-163
Author(s):  
E. Ristenpart ◽  
D. Wittenberg
Keyword(s):  
Water Quality ◽  
Drainage System ◽  
Urban Drainage ◽  
Flow Conditions ◽  
Nonstationary Flow ◽  
Combined Sewer Overflows ◽  
Water Quality Simulation ◽  
Combined Sewer ◽  
Receiving Waters ◽  
The One

Impacts from combined sewer systems on receiving waters are heavily polluting a lot of small river ecosystems. A simulation model which can be used to predict the development of water quality after combined sewer overflows and other impacts from the urban drainage system has been developed. This model works with hydrodynamic flow calculation because it is applied in a system of small wetland creeks with nonstationary flow conditions. The numerical solution of the differential equations is described as well as calibration results. It is shown that water quality simulation based on the one-dimensional mass transport equation is possible for nonstationary flow conditions and is going to become very useful in urban drainage planning.

A method for measuring the settling velocity distribution of large biotic particles

Aerobiologia ◽  
2007 ◽  
Vol 23 (3) ◽  
pp. 159-169 ◽  
Author(s):  
B. Loubet ◽  
N. Jarosz ◽  
S. Saint-Jean ◽  
L. Huber
Keyword(s):  
Velocity Distribution ◽  
Settling Velocity ◽  
Settling Velocity Distribution
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