Experimental abatement data of underflow baffles for removal of floatables in the CSOs of the Greater Montréal (Canada) area

2005 ◽  
Vol 51 (2) ◽  
pp. 65-70 ◽  
Author(s):  
John F. Cigana ◽  
Martin Couture
Keyword(s):  
Pilot Scale ◽  
Horizontal Velocity ◽  
Design Criteria ◽  
Operational Cost ◽  
Flow Conditions ◽  
Combined Sewer Overflows ◽  
Follow Up Study ◽  
Combined Sewer ◽  
Rapid Flow

Underflow baffles have gained in popularity over the years as a viable mean to intercept floatables in Combined Sewer Overflows (CSOs). This choice was mainly justified by the extremely low capital cost (CAPEX) and operational cost (OPEX) of this solution, although the efficiency of underflow baffles has never been clearly proven. The only similar application to underflow baffles are scum boards in grit chambers and clarifier. However, the flow conditions at CSOs vary considerably from those in grit chambers and clarifier. For this reason, review of the behavior of floatables in a rapid flow is paramount. Only then can comprehensive design criteria for underflow baffles and overflow chambers be suggested. Pilot scale tests, performed in a 17 metres long basin at various flowrates, had already shown that a critical horizontal velocity for floatables (Vcr) may develop in the overflow chambers. In this follow up study, the fate of intercepted floatables was investigated. It appears from this latest data that permanent capture of floatables decreases rapidly with an increase in the horizontal velocity of the flow, no matter what the baffle depth. Baffle depth increases capture at lower velocities (0.17 m/s) but become irrelevant at higher velocities (0.61 m/s). This data suggests that capture efficiency of existing underflow baffles in overflow chambers can be, at best, very low whenever the horizontal velocity increases above 0.30 m/s or 1 ft/s.

Design criteria of underflow baffles for control of floatables

1998 ◽  
Vol 38 (10) ◽  
pp. 57-63 ◽  
Author(s):  
J. Cigana ◽  
G. Lefebvre ◽  
C. Marche ◽  
M. Couture
Keyword(s):  
Preliminary Analysis ◽  
Pilot Scale ◽  
Design Criteria ◽  
Efficient Design ◽  
Combined Sewer Overflows ◽  
Combined Sewer ◽  
Sewer Overflows

Underflow baffles have gained in popularity over the last few year as a viable means to intercept floatables in Combined Sewer Overflows (CSOs). This has happened although the efficiency of underflow baffles has never been clearly proven. Furthermore, there are no guidelines helping planners in the correct and efficient design of underflow baffles. This article proposes design criteria deduced from pilot scale essays performed in a 17 meters basin at various flowrates. These new informations can be used in two different ways. First, these criteria can be used to correctly design a new overflow chamber. Secondly, these criteria can be used to evaluate the efficiency of existing overflow chambers. Preliminary analysis of existing chambers show that interception efficiency of floatables can be very low.

Critical velocity of floatables in Combined Sewer Overflow (CSO) chambers

2001 ◽  
Vol 44 (2-3) ◽  
pp. 287-294 ◽  
Author(s):  
J. Cigana ◽  
G. Lefebvre ◽  
C. Marche
Keyword(s):  
Critical Velocity ◽  
Vertical Velocity ◽  
Pilot Scale ◽  
Horizontal Velocity ◽  
Combined Sewer Overflow ◽  
Combined Sewer Overflows ◽  
Combined Sewer ◽  
Sewer Overflows ◽  
Sewer Overflow

Although the efficiency of underflow baffles has never been clearly proven, these underflow baffles have gained in popularity over the last few years as a viable means to intercept floatables in Combined Sewer Overflows (CSOs). These pilot scale essays, performed in a 17.0 metres basin at various flowrates, show that a critical horizontal velocity (VCR) may develop in the overflow chamber. Whenever this critical velocity is exceeded, floatables that would normally rise to the surface are kept within the flow and never intercepted, thus rendering the underflow baffle ineffective. The equation relating the critical horizontal velocity to the vertical velocity is found to be: VCR = 16 w RH1/6.

Pilot-Scale Study of Satellite Treatment Options for the Control of Combined Sewer Overflows

1997 ◽  
Vol 32 (1) ◽  
pp. 169-184 ◽  
Author(s):  
J. SCHMIDT ◽  
P. SETO ◽  
D. Averill
Keyword(s):  
Treatment Options ◽  
Cost Effective ◽  
Pilot Scale ◽  
Combined Sewer Overflows ◽  
International Joint Commission ◽  
Pollution Problem ◽  
Combined Sewer ◽  
Vortex Separator ◽  
Sewer Overflows ◽  
Screen Performance

Abstract Combined sewer overflows (CSOs) have been recognized for many years as a pollution problem within the Great Lakes ecosystem. CSOs were identified as a source of contamination in 10 of the 17 Canadian “Areas of Concern” designated by the International Joint Commission, and were considered a major problem in Hamilton Harbour and the Metropolitan Toronto Waterfront. Satellite treatment systems (located upstream in the sewerage system) were identified as being significantly more cost effective than other CSO control options in a feasibility study conducted for Metropolitan Toronto. Consequently, a multi-agency initiative was established in 1993 to examine the treatment of CSOs at a pilot-scale facility in the City of Scarborough. The technologies evaluated during two experimental seasons in 1994 and 1995 included a vortex separator, a circular clarifier, a horizontal-flow plate clarifier and an inclined rotary drum screen. Performance of the technologies is being assessed against a draft policy proposed by the Ontario Ministry of Environment and Energy. Results to date have indicated that the vortex separator and the plate clarifier under “best conditions” were capable of 50% TSS removal and 30% BOD5 removal and should be capable of satisfying the policy.

High-Rate Retention Treatment Basins for CSO Control in Windsor, Ontario

2004 ◽  
Vol 39 (4) ◽  
pp. 449-456 ◽  
Author(s):  
Jian Guo Li ◽  
Harold Horneck ◽  
David Averill ◽  
J. Alex McCorquodale ◽  
Nihar Biswas
Keyword(s):  
Empirical Relationship ◽  
Pilot Scale ◽  
High Rate ◽  
Experimental Investigations ◽  
Combined Sewer Overflows ◽  
Column Tests ◽  
Dosage Range ◽  
Loading Rates ◽  
Combined Sewer ◽  
Removal Efficiencies

Abstract Experimental investigations were conducted to evaluate the effectiveness of a retention treatment basin (RTB) with polymer coagulation for the treatment of combined sewer overflows (CSO) at high hydraulic loading rates. The TSS removal efficiency of the pilot-scale RTB at a surface overflow rate (SOR) of 11 m/h was approximately 35% without chemical addition, and 80% with a polymer dosage range of 5 to 10 milligrams per gram of influent TSS. The results demonstrated that the use of polymer coagulation significantly improved TSS removal and allowed the SOR in the RTB to be significantly increased, resulting in smaller treatment units. An empirical relationship was established to estimate removal efficiencies as a function of overflow rate. The results also compared settling characteristics of CSO, obtained from long column tests, to removal efficiencies in the high-rate RTB.

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.

Field facility for research and demonstration of CSO treatment technologies

1997 ◽  
Vol 36 (8-9) ◽  
pp. 391-396
Author(s):  
D. Averill ◽  
D. Mack-Mumford ◽  
J. Marsalek ◽  
R. Andoh ◽  
D. Weatherbe
Keyword(s):  
Pilot Scale ◽  
High Rate ◽  
Uv Disinfection ◽  
Combined Sewer Overflows ◽  
Combined Sewer ◽  
Treatment Technologies ◽  
Test Threshold ◽  
Vortex Separator ◽  
Solid Liquid ◽  
Solid Liquid Separation

A pilot scale study of options for the treatment combined sewer overflows is being conducted in Ontario, Canada. The objective is to achieve primary clarification equivalency in simple, high-rate satellite treatment systems. Effluent disinfection will also be required where bathing beaches are to be protected. Long column settling tests conducted with CSO suspensions indicated that approximately 40% of the suspended solids was non-settleable at the test threshold of 0.3 m/h. The use of a cationic polymer as the sole coagulant in a three metre diameter vortex separator achieved at least 50% TSS removal at surface loads up to approximately 40 m/h. The effluents from solid/liquid separation operations using the polymer coagulation strategy were more amenable to UV disinfection than those produced with metal-based coagulants. This document has been updated to include experimental results to mid-1997.

The vortex concentrator for suspended solids treatment

2003 ◽  
Vol 47 (7-8) ◽  
pp. 335-341 ◽  
Author(s):  
J. Lee ◽  
K. Bang ◽  
J. Choi ◽  
L.H. Ketchum ◽  
Y. Cho
Keyword(s):  
Removal Efficiency ◽  
Retention Time ◽  
Suspended Solids ◽  
Combined Sewer Overflows ◽  
Surface Loading ◽  
Solids Concentration ◽  
Coagulant Dosage ◽  
Combined Sewer ◽  
Retention Basin

The use of vortex concentrators is becoming increasingly popular for suspended solids reduction in combined sewer overflows and stormwater. This study is a laboratory investigation of the use of vortex concentrators to reduce the solids concentration of synthesized stormwater. The synthesized stormwater was made with water and addition of particles; sand, granular activated carbon, and sewer sediments. The vortex concentrator was made of acryl resin 300 mm in diameter. To determine the efficiency for various influent suspended solids (SS) concentrations, tests were performed with different SS concentrations. The samples were taken simultaneously at the influent storage tank and effluent tank, and measured SS concentrations. The range of surface loading rates were 120 to 850 m3/m2/day, and influent SS concentrations were varied from 300 to 5,000 mg/L. To determine the optimum coagulant dosage, jar tests were conducted with coagulants such as PAM and PAC. It was found that optimum coagulant and its dosage were PAM and 2 mg/L. The overall SS removal efficiency of the vortex concentrator for typical stormwater was estimated at about 65%. With an increase of SS concentration, the removal efficiency was increased. Since the SS concentration of stormwater was higher than 1,000 mg/L, the removal efficiency of the vortex concentrator for stormwater could be estimated to be 65-70%. The SS removal efficiency was increased with an increase of retention time, and the optimum retention time was 0.15-1.0 minutes. With an increase of the foul to overflow QF/Qo, a key parameter for vortex concentrator operation, the removal efficiency was increased. An alternative solution to improve treatment efficiency might be to set a follow-up retention basin. Based on a series of settling tests on the treated overflow water from the vortex concentrator, 5 to 10 minutes hydraulic retention time in a follow-up retention basin would substantially improve the results.

Modelling, Design and Optimization of a Combined Sewer Overflow Treatment System

1997 ◽  
Vol 32 (1) ◽  
pp. 139-154 ◽  
Author(s):  
B. Gall ◽  
D. Averill ◽  
D. Weatherbe
Keyword(s):  
Treatment Options ◽  
Model Development ◽  
Pilot Scale ◽  
Development Work ◽  
Preliminary Design ◽  
Treatment Facility ◽  
Combined Sewer Overflows ◽  
Design And Optimization ◽  
Treatment Processes ◽  
Combined Sewer

Abstract A process modelling and simulation program is being developed as part of a pilot-scale study of satellite treatment options for the control of combined sewer overflows (CSOs). The initial objectives are (1) the development of mathematical models for satellite wastewater treatment processes; (2) the implementation of these models in a computer simulator; and 3) the application of these models to provide a preliminary design of a full-scale CSO treatment facility that will satisfy the local regulatory agency. Results to date show that the models and simulation algorithms constitute a useful planning level tool for investigating CSO control options. The results also indicate the direction of further model development work.

Improved formulations for rapid erosion of diverse solids in combined sewers

2005 ◽  
Vol 52 (5) ◽  
pp. 143-150 ◽  
Author(s):  
T.D. McIlhatton ◽  
R.M. Ashley ◽  
S.J. Tait
Keyword(s):  
Urban Areas ◽  
Suspended Sediment Concentration ◽  
Peak Flow ◽  
Initial Period ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Storm Event ◽  
Flow Conditions ◽  
Combined Sewer Overflows ◽  
Combined Sewer

For more than a decade, research carried out in Scotland has investigated the movement of sediment in sewers and the associated pollutant release. Pollution by discharges from combined sewer overflows can adversely affect watercourses, particularly those in urban areas. Solids and dissolved contaminants, many derived from in-sewer deposits during a storm event, can be especially significant. This phenomenon can occur during events known as ‘foul flushes’. In combined sewers these typically occur in the initial period of storm flows, when the concentration of suspended sediments and other pollutants is significantly higher than at other times. It has become apparent that much of the suspended load originates from solids eroded from the bed. The ‘near bed solids’ which are re-entrained into the flow, together with solids eroded from the bulk bed, account for large changes in the suspended sediment concentration under time varying flow conditions. This paper describes some of the methods employed to investigate the solids eroding in combined sewers during peak flow events. The work examined the potential for sediment re-suspension under high flow conditions both in the laboratory and in the field.

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