Separate and combined sewer systems: a long-term modelling approach

2009 ◽  
Vol 60 (3) ◽  
pp. 555-565 ◽  
Author(s):  
Giorgio Mannina ◽  
Gaspare Viviani
Keyword(s):  
Cost Benefit Analysis ◽  
Treatment Plant ◽  
Cost Benefit ◽  
Sewer System ◽  
Sewer Systems ◽  
System Versus ◽  
Combined Sewer ◽  
Wet Weather ◽  
Wet Weather Flow

Sewer systems convey mostly dry weather flow, coming from domestic and industrial sanitary sewage as well as infiltration flow, and stormwater due to meteoric precipitations. Traditionally, in urban drainage two types of sewer systems are adopted: separate and combined sewers. The former convey dry and wet weather flow separately into two different networks, while the latter convey dry and wet weather flow together. Which is the best solution in terms of cost-benefit analysis still remains a controversial subject. The present study was aimed at comparing the pollution loads discharged to receiving bodies by Wastewater Treatment Plant (WWTP) and Combined Sewer Overflow (CSO) for different kinds of sewer systems (combined and separate). To accomplish this objective, a comparison between the two systems was carried out using results from simulations of catchments characterised by different dimensions, population densities and water supply rate. The analysis was based on a parsimonious mathematical model able to simulate the sewer system as well as the WWTP during both dry and wet weather. The rain series employed for the simulations was six years long. Several pollutants, both dissolved and particulate, were modelled. The results confirmed the uncertainties in the choice of one system versus the other, emphasising the concept that case-by-case solutions have to be undertaken. Further, the compared systems showed different responses in terms of effectiveness in reducing the discharged mass to the RWB in relation to the particular pollutant taken into account.

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.

Sewer rehabilitation strategy in Berlin

2002 ◽  
Vol 46 (6-7) ◽  
pp. 379-387
Author(s):  
D. Jacobi ◽  
K.-J. Sympher
Keyword(s):  
Structural Integrity ◽  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
Remaining Useful Life ◽  
Sewer System ◽  
Sewer Systems ◽  
Catchment Areas ◽  
Sewer Rehabilitation ◽  
Useful Life ◽  
Rehabilitation Strategy

Berlin Wasserbetriebe is in need of a significant and longterm investment in the rehabilitation of its sewer system. With ratification of the European Standard EN 752 Part 5, comprehensive rules have been set out for the rehabilitation of drain and sewer systems: hydraulic performance, environmental impact and structural integrity of complete catchment areas are given equal consideration. Taking this into account, Berliner Wasserbetriebe has developed a sewer rehabilitation strategy. Economic aspects are integrated with a cost-benefit-analysis; the significance of the remaining useful life of a pipe section is examined.

The Erosion and Movement of Sediments and Associated Pollutants in Combined Sewers

1992 ◽  
Vol 25 (8) ◽  
pp. 101-114 ◽  
Author(s):  
R. M. Ashley ◽  
D. J. J. Wotherspoon ◽  
B. P. Coghlan ◽  
I. McGregor
Keyword(s):  
Field Data ◽  
Bed Load ◽  
Surficial Sediments ◽  
Sediment Erosion ◽  
Weak Layer ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Wet Weather ◽  
Wet Weather Flow

The complex and inhomogeneous nature of sediments in sewers, and the variability of the particles and dissolved substances flowing in dry and wet weather combined sewage, make the prediction of sediment erosion and pollutant release a difficult proposition. It is apparent that the erosion of sediments in sewers can release pollutants in concentrations which exceed by many times the levels found in the various contributing sources of the sediments and pollutants, and whilst this release is normally in the form of an initial highly polluting foul flush at the start of wet weather flow, the occurrence of foul flushes has not been found to be ubiquitous, even from event to event in the same sewer. The origins of foul flushes may be attributable to the speedy erosion of a weak layer of highly concentrated surficial sediments (or bed-load) at the start of wet weather flows. Various models have been proposed, and some successfully applied to field data, to simulate the erosion and movement of sediments and associated pollutants in combined sewer systems.

Field campaign on sediment transport behaviour in a pressure main from pumping station to wastewater treatment plant in Berlin

2017 ◽  
Vol 75 (9) ◽  
pp. 2025-2033
Author(s):  
M. Gunkel ◽  
E. Pawlowsky-Reusing
Keyword(s):  
Wastewater Treatment ◽  
Sediment Transport ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Weather Conditions ◽  
Sewer System ◽  
Field Campaign ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Transport Behaviour

As part of the project KURAS, the Berliner Wasserbetriebe realized a field campaign in 2015 in order to increase the process knowledge regarding the behaviour of transported sediment in the pressure main leading from the pumpstation to the wastewater treatment plant. The field campaign was conducted because of a lack of knowledge about the general condition of the pressure main due to its bad accessibility and the suspicion of deposits caused by hydraulic underload. The practical evidence of the sediment transport performance of this part of the sewer system, dependent on different load cases, should present a basis for further analysis, for example regarding flushing measures. A positive side-effect of the investigation was the description of the amount of pollutants caused by different weather conditions in combined sewer systems and the alterations of the sewage composition due to biogenic processes during transport. The concept included the parallel sampling of the inflow at the pumpstation and the outflow at the end of the pressure main during different weather conditions. By calculating the inflow to the pressure main, as well as its outflow at different flow conditions, it was possible to draw conclusions in regard to the transport behaviour of sediment and the bioprocesses within an 8.5 km section of the pressure main. The results show clearly that the effects of sedimentation and remobilization depend on the flow conditions. The balance of the total suspended solids (TSS) load during daily variations in dry weather shows that the remobilization effect during the run-off peak is not able to compensate for the period of sedimentation happening during the low flow at night. Based on the data for dry weather, an average of 238 kg of TSS deposits in the pressure main remains per day. The remobilization of sediment occurs only due to the abruptly increased delivery rates caused by precipitation events. These high pollution loads lead to a sudden strain at the wastewater treatment plant. It was found that the sediment transport behaviour is characterized by sedimentation up to a flow velocity of 0.35 m/s, while remobilization effects occur above 0.5 m/s. The assumption of bad sediment transport performance in the pressure main was confirmed. Therefore, the results can be used as a basis for further analysis, for example regarding periodical flushing as a means of cleaning the pressure main. The findings, especially regarding the methods and processes, are transferable and can be applied to other pressure mains in combined sewer systems. Besides the outlined evaluation of the sediment transport behaviour of the pressure main, the collected data were used in the project to calibrate a sewer system model, including a water quality model for the catchment area, and as a contribution towards an early physically based sediment transport modelling in InfoWorks CS.

Infiltration and inflow in combined sewer systems: long-term analysis

2002 ◽  
Vol 45 (7) ◽  
pp. 11-19 ◽  
Author(s):  
G. Weiß ◽  
H. Brombach ◽  
B. Haller
Keyword(s):  
Surface Runoff ◽  
Treatment Plant ◽  
Drainage System ◽  
Polluted Water ◽  
Special Focus ◽  
Stormwater Treatment ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Insight Into

A study was conducted on 34 German combined sewer systems including combined sewer overflow (CSO) tanks and treatment plant to show up actual hidden reserves and bottlenecks in stormwater treatment. The study gave also a general insight into the water pathways in urban hydrology. A special focus was given to undesired non-polluted water infiltrating into the sewer, labelled infiltration and inflow (I/I) or infiltration inflows, which is widely underestimated. It leads to a bad performance of the drainage system although the parasite waters are themselves non-polluted. In existing combined systems, pollution control can be considerably improved by reducing I/I. It is equivalent to the reduction of surface runoff e.g. by a separate drainage as frequently proposed alternative. Artificial infiltration of surface runoff may even increase infiltration inflows.

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

2012 ◽  
Vol 47 (2) ◽  
pp. 178-185 ◽  
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.

Urban Storm Water Discharges: Effects upon Communities of Sessile Diatoms and Macro-Invertebrates

1990 ◽  
Vol 22 (10-11) ◽  
pp. 147-154 ◽  
Author(s):  
G. D. Willemsen ◽  
H. F. Gast ◽  
R. O. G. Franken ◽  
J. G. M. Cuppen
Keyword(s):  
Organic Pollution ◽  
Constant Flow ◽  
Combined Sewer Overflows ◽  
Sewer System ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Receiving Waters ◽  
Sewer Overflows ◽  
Urban Storm

From 1985 to 1987, long-term and more or less permanent effects of discharges from combined or separate sewer systems on communities of sessile diatoms and macro-invertebrates in receiving waters have been studied. Sessile diatoms and/or macro-invertebrates have been investigated on 46 locations, spread all over The Netherlands. The results were related to the type of sewer system, the discharges, and the characteristics of the receiving water, and compared with results from sample(s) taken from a corresponding water not influenced by sewer overflows, the reference water. In general, communities of sessile diatoms and macro-invertebrates indicate a more severe organic pollution and disturbance of receiving waters compared with reference waters. In the immediate vicinity of the overflows these communities were more disturbed than at some distance. In small ditches, effects were more pronounced compared with large waterbodies and waters with a constant flow regime. Finally, effects of combined sewer overflows were more pronounced than effects of discharges from separate sewer systems, except for locations in industrial areas.

Methods for Calculation of Annual and Extreme Overflow Events from Combined Sewer Systems

1984 ◽  
Vol 16 (8-9) ◽  
pp. 311-325 ◽  
Author(s):  
N B Johansen ◽  
P Harremoës ◽  
M Jensen
Keyword(s):  
Extreme Event ◽  
Short Term ◽  
Sewer Systems ◽  
Extreme Load ◽  
Combined Sewer ◽  
Receiving Waters ◽  
Water Problems ◽  
Source Of Pollution ◽  
Receiving Water

Overflow from combined systems constitute an increasing source of pollution of receiving waters, as compared to daily wastewater discharges which undergo treatment to a still higher extent. The receiving water problems from overflows are significant both in a long term scale (mean annual load) and in a short term scale (extreme event load). A method for computation of both annual and extreme load is presented. It is based on historical rain series and the use of a time-area model and simple pollutant mixing model in runoff calculation. Statistical calculations for both mean annual load and extreme events have been applied to the computed overflow series. Based on the computerized method simple manual calculations methods have been developed, resulting in graphs and tables for annual load and extreme load.

Sediment transport under dry weather conditions in a small sewer system

1998 ◽  
Vol 37 (1) ◽  
pp. 155-162
Author(s):  
Flemming Schlütter ◽  
Kjeld Schaarup-Jensen
Keyword(s):  
Sediment Transport ◽  
Field Data ◽  
Field Measurements ◽  
Weather Conditions ◽  
Sewer System ◽  
Transport Models ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Initial Results

Increased knowledge of the processes which govern the transport of solids in sewers is necessary in order to develop more reliable and applicable sediment transport models for sewer systems. Proper validation of these are essential. For that purpose thorough field measurements are imperative. This paper renders initial results obtained in an ongoing case study of a Danish combined sewer system in Frejlev, a small town southwest of Aalborg, Denmark. Field data are presented concerning estimation of the sediment transport during dry weather. Finally, considerations on how to approach numerical modelling is made based on numerical simulations using MOUSE TRAP (DHI 1993).

An application of Austrian legal requirements for CSO emissions

2011 ◽  
Vol 64 (5) ◽  
pp. 1081-1088 ◽  
Author(s):  
Manfred Kleidorfer ◽  
Wolfgang Rauch
Keyword(s):  
Model Calibration ◽  
Model Building ◽  
Treatment Plant ◽  
Cost Effective ◽  
Combined Sewer Overflows ◽  
Sewer System ◽  
Legal Requirements ◽  
Innovative Methods ◽  
Combined Sewer

The Austrian standard for designing combined sewer overflow (CSO) detention basins introduces the efficiency of the combined sewer overflows as an indicator for CSO pollution. Additionally criteria for the ambient water quality are defined, which comprehend six kinds of impacts. In this paper, the Austrian legal requirements are described and discussed by means of hydrological modelling. This is exemplified with the case study Innsbruck (Austria) including a description for model building and model calibration. Furthermore an example is shown in order to demonstrate how – in this case – the overall system performance could be improved by implementing a cost-effective rearrangement of the storage tanks already available at the inflow of the wastewater treatment plant. However, this guideline also allows more innovative methods for reducing CSO emissions as measures for better usage of storage volume or de-centralised treatment of stormwater runoff because it is based on a sewer system simulation.

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