Methods to accompany and evaluate planning of combined sewer overflow treatment concepts for complex sewer systems

Simulation tools are in common use to evaluate combined sewer overflow (CSO) treatment concepts in complex sewer systems. However, the planning of CSO structures in a sewer system is a matter of local constraints, expert knowledge and trial and error. Common standards only provide general recommendations to plan CSO structures and work out management strategies. Additionally, modelling the emissions of complex sewer systems tends to result in comprehensive findings. Although, it is essential to understand local behaviour and interaction of CSO structures in a system to improve local and overall performance there is a lack of tools to illustrate comprehensive simulation results in a simple way. In this context the methods presented here are developed. These include clear illustrations of the as-is state in the catchment using Sankey diagrams to show relevant volume and pollutant flows. Furthermore, loading and treatment indicators are suggested to illustrate local loading conditions and treatment capabilities of CSO structures in relation to the overall system. Additional emission indicators provide information on local emissions and show interactions of CSO structures. The results indicate that the suggested methods contribute to an efficient evaluation of interactions and performances to improve treatment strategies in the planning phase.

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Innovative monitoring of combined sewer overflow (CSO) quality in the Liguori catchnment (Cosenza, Italy)

Water Quality Research Journal ◽

10.2166/wqrjc.2012.035 ◽

2012 ◽

Vol 47 (2) ◽

pp. 178-185 ◽

Cited By ~ 3

Author(s):

Patrizia Piro ◽

Marco Carbone ◽

Giuseppina Garofalo

Keyword(s):

Chemical Oxygen Demand ◽

Treatment Plant ◽

Treatment Strategies ◽

Oxygen Demand ◽

Combined Sewer Overflow ◽

Planning Approach ◽

Combined Sewer ◽

Wet Weather ◽

Wet Weather Flow ◽

Sewer Overflow

Estimates of urban wet-weather flow pollutant loads are required to assess their impact on receiving waters and optimize wastewater treatment plant (WWTP) and combined sewer overflow (CSO) operations. In particular, a quantitative characterization of flow quality by means of fairly accurate monitoring is required for developing a rational planning approach and preferential treatment strategies. The main aim of this paper is to examine the qualitative–quantitative characteristics of wet-weather flow in an urbanized test catchment in Cosenza, Italy, and to compare three studied water quality constituent concentrations (total suspended solids (TSS), total chemical oxygen demand (CODt) and filtered chemical oxygen demand (CODf)) obtained by laboratory analyses to those measured by a UV/Vis spectrometer (‘spectrolyzer scan’), which represents a most modern and efficient spectrometric instrument requiring little maintenance. The results of such comparisons indicated the feasibility of using in situ spectroscopy to provide fairly accurate concentrations of the constituents studied, particularly in the case of CODt and CODf.

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Combined sewer overflow over an oblique weir at Rat Creek in Edmonton, Alberta

Canadian Journal of Civil Engineering ◽

10.1139/l09-177 ◽

2010 ◽

Vol 37 (3) ◽

pp. 477-488

Author(s):

Elizabeth Valentine ◽

Kurt Kronebusch ◽

David Z. Zhu ◽

N. Rajaratnam ◽

Sid Lodewyk ◽

...

Keyword(s):

Urban Drainage ◽

Combined Sewer Overflow ◽

Rating Curve ◽

Flow Conditions ◽

Sewer System ◽

Sewer Systems ◽

Model Study ◽

Combined Sewer ◽

Sewer Overflow

Oblique weirs are commonly used in urban drainage systems to remove excess flow from a sewer, in particular, a combined sewer system that has limited conveyance capacity. It is important to understand the hydraulics of these weirs to properly monitor the amount of the overflows as well as to design and improve sewer systems. The Rat Creek structure in Edmonton, Alberta, is a combined sewer overflow structure with a weir at an oblique alignment to the centerline of the sewer. A physical model study of the structure was conducted. The results show that both the approach flow conditions and the chamber geometry can significantly affect the hydraulic performance of the weir and invalidate the application of standard weir equations. A unique flow regime with a linear head–discharge rating curve was observed. The effects of modifying the weir and the hanging baffle wall downstream of the weir were also studied and reported. The results of this case study help to improve the understanding of the hydraulics of oblique weirs in sewer systems.

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Laboratory investigation on the performances of baffles for the capture of sewer floatables

Water Science & Technology ◽

10.2166/wst.2009.295 ◽

2009 ◽

Vol 60 (1) ◽

pp. 29-36 ◽

Cited By ~ 3

Author(s):

A. Campisano

Keyword(s):

Water Treatment ◽

Laboratory Investigation ◽

Dimensional Analysis ◽

Limit Equilibrium ◽

Combined Sewer Overflow ◽

Equilibrium Conditions ◽

Sewer Systems ◽

Water Treatment Plants ◽

Combined Sewer ◽

Sewer Overflow

The use of baffles in sewer systems enables the capture of floatables, which could be responsible for both malfunctioning of water treatment plants and aesthetic pollution of receiving bodies when discharges through combined sewer overflow devices occur. An experimental contribution to the understanding of capturing processes of floatable elements by means of baffle devices is presented in this paper. Experiments were carried out using different baffle configurations. The limit equilibrium conditions of various types of floatables, i.e the condition beyond which upstream intercepted floatables start to escape the baffle, were investigated. The dimensional analysis was used in order to generalise the results of the experiments and to compare the capturing performances of analysed baffle configurations.

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Estimating inflow to a combined sewer overflow structure with storage tank in real time: evaluation of different approaches

Water Science & Technology ◽

10.2166/wst.2014.331 ◽

2014 ◽

Vol 70 (7) ◽

pp. 1143-1151 ◽

Cited By ~ 9

Author(s):

G. Leonhardt ◽

M. D'Oria ◽

M. Kleidorfer ◽

W. Rauch

Keyword(s):

Water Level ◽

Bayesian Approach ◽

Measurement Errors ◽

Combined Sewer Overflow ◽

Online Application ◽

Storage Model ◽

Sewer Systems ◽

Combined Sewer ◽

Sewer Overflow ◽

The Bayesian Approach

The performance assessment of storage tanks and combined sewer overflow (CSO) structures in sewer systems requires knowledge of the total inflow from the catchment during rainfall events. Many structures are, however, only equipped with sensors to measure water level and/or outflows. Based on the geometry of the tank, expressed as a level-storage relationship, inflow can be calculated from these data using a simple conceptual storage model. This paper compares a deterministic and a Bayesian approach for estimating the inflow to a CSO structure from measurements of outflows and water level. The Bayesian approach clearly outperforms the deterministic estimation which is very sensitive to measurement errors. Although computationally more demanding, the use of a simple linear storage model allows the online application of the Bayesian approach to repeatedly estimate inflow in short time intervals of a few minutes. The method could thus be used as an online software sensor for inflow to storage structures in sewer systems.

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Foreword: Stormwater Management and Abatement of Combined Sewer Overflow Pollution

Water Quality Research Journal ◽

10.2166/wqrj.1997.001 ◽

1997 ◽

Vol 32 (1) ◽

pp. 1-228 ◽

Cited By ~ 10

Author(s):

J. Marsalek ◽

S. Kok

Keyword(s):

Stormwater Management ◽

Combined Sewer Overflow ◽

Combined Sewer ◽

Sewer Overflow

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Experience with Vortex Separators for Combined Sewer Overflow Control

Water Science & Technology ◽

10.2166/wst.1993.0489 ◽

1993 ◽

Vol 27 (5-6) ◽

pp. 93-104 ◽

Cited By ~ 6

Author(s):

H. Brombach ◽

C. Xanthopoulos ◽

H. H. Hahn ◽

W. C. Pisano

Keyword(s):

Separation Efficiency ◽

Operational Reliability ◽

Second Phase ◽

Combined Sewer Overflow ◽

Specific Storage ◽

Impervious Area ◽

Evaluation Phase ◽

Combined Sewer ◽

Sewer Overflow ◽

Overflow Control

In 1987 the first vortex solids separator facility in Germany was installed for combined sewer overflow (CSO) control. The separation efficiency was optimized in the hydraulic laboratory using scaled down models with artificial tracers to simulate typical sewage particulates. The station has two parallel operating vortex separators and serves a connected and impervious area of about 11 hectares (ha) and 1,500 people. The specific storage volume of the station is 7.2 m3 per ha. Two evaluation programs were conducted. The first evaluation phase noted the operational reliability, hydraulic loads, overflow frequencies and water mass balances. The second phase monitored separation efficiencies. The evaluation showed that vortex solids separators are now ready for use in CSO control.

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