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.

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.

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.

Removal of the organic surface layer in combined sewer sediment using a flushing gate

2003 ◽  
Vol 47 (4) ◽  
pp. 19-26 ◽  
Author(s):  
D. Laplace ◽  
C. Oms ◽  
M. Ahyerre ◽  
G. Chebbo ◽  
J. Lemasson ◽  
...  
Keyword(s):  
Surface Layer ◽  
Organic Layer ◽  
First Flush ◽  
Pollution Load ◽  
Water Flows ◽  
Sources Of Pollution ◽  
Combined Sewer ◽  
Wet Weather ◽  
Different Sources ◽  
Sediment Interface

Recent research identified the different sources of pollution of wet weather Combined Sewers Overflows (CSOs): it appeared that the deposits in sewers, and especially an organic layer situated at the water-sediment interface, may contribute 40-70% to the total pollution load of CSOs. Using the cyclic flush Hydrass gate, we generated increased water flows during dry weather. The effects of flushing the deposits have been analysed: the eroded particles sampled during the first flush wave show pollutant characteristics similar to characteristics measured in the organic layer. The organic layer that has formed on the surface of deposits can thus be washed off before rainstorms occur using the cyclic flushing technique.

Spatial variability of characteristics and origins of urban wet weather pollution in combined sewers

2005 ◽  
Vol 52 (3) ◽  
pp. 53-62 ◽  
Author(s):  
M. Kafi-Benyahia ◽  
M.G. Gromaire ◽  
G. Chebbo
Keyword(s):  
Heavy Metals ◽  
Organic Matter ◽  
Suspended Solids ◽  
Spatial Scales ◽  
Urban Runoff ◽  
Urban Catchment ◽  
Rainfall Events ◽  
Wet Weather ◽  
Wet Weather Flow ◽  
Dry Weather Flow

An experimental on-site observatory of urban pollutant loads in combined sewers was created in the centre of Paris to quantify and characterise the dry and wet weather flow in relation to spatial scale. Eight rainfall events were studied from April 2003 to May 2004. Samples were analysed for suspended solids, organic matter, nitrogen and heavy metals. Results confirm the extent of wet weather pollution. They have shown the relative homogeneity of SS and organic matter characteristics from one urban catchment area to another. Two groups of heavy metals were identified. The first one concerns Cu, which has a higher concentration in wet weather flow (WWF) than in dry weather flow (DWF), and runoff. The second includes Cd, Pb and Zn, where higher concentrations were measured in urban runoff than in WWF and DWF. A first evaluation of contribution of wastewater, urban runoff and sewer deposit erosion sources to wet weather pollution was established and has highlighted the contribution of wastewater and sewer deposits to this pollution. However, it has shown that sewer deposit erosion remains an important source of wet weather pollution at different spatial scales.

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).

Quantification of sewer system infiltration using δ18O hydrograph separation

2009 ◽  
Vol 60 (3) ◽  
pp. 727-735 ◽  
Author(s):  
V. Prigiobbe ◽  
M. Giulianelli
Keyword(s):  
Sampling Strategy ◽  
Infiltration Rate ◽  
Hydrograph Separation ◽  
Catchment Scale ◽  
Sewer System ◽  
Urban Catchment ◽  
Sewer Systems ◽  
Conservative Tracer ◽  
Effective Water ◽  
Sewer Networks

The infiltration of parasitical water into two sewer systems in Rome (Italy) was quantified during a dry weather period. Infiltration was estimated using the hydrograph separation method with two water components and δ18O as a conservative tracer. The two water components were groundwater, the possible source of parasitical water within the sewer, and drinking water discharged into the sewer system. This method was applied at an urban catchment scale in order to test the effective water-tightness of two different sewer networks. The sampling strategy was based on an uncertainty analysis and the errors have been propagated using Monte Carlo random sampling. Our field applications showed that the method can be applied easily and quickly, but the error in the estimated infiltration rate can be up to 20%. The estimated infiltration into the recent sewer in Torraccia is 14% and can be considered negligible given the precision of the method, while the old sewer in Infernetto has an estimated infiltration of 50%.

Settleable Solids in a Combined Sewer System, Settling Characteristics, Heavy Metals, Efficiency of Storm Water Tanks

1993 ◽  
Vol 27 (5-6) ◽  
pp. 153-164 ◽  
Author(s):  
S. Michelbach ◽  
C. Wöhrle
Keyword(s):  
Heavy Metals ◽  
Settling Velocity ◽  
Urban Runoff ◽  
Stormwater Treatment ◽  
Sewer System ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Combined Sewer System ◽  
Water Tanks ◽  
The Relationship

Sedimentation and transportation of mineral and organic pollutions in combined sewer systems are not completely understood. For better understanding, samples of sediment, slime and urban runoff were taken from the combined sewer system of Bad Mergentheim. The settling velocity of settleable solids was measured with a settling apparatus. Typical settling curves for sediment, slime and wastewater were put together. Some of the samples were analysed for heavy metals and organic micro-pollution. By this the relationship between settling velocity and the load of heavy metals can be shown. The gained data are of interest for the design of clarifier tanks for stormwater treatment.

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