Technical solutions envisaged in managing solids in combined sewer networks

1996 ◽  
Vol 33 (9) ◽  
pp. 237-244 ◽  
Author(s):  
Ghassan Chebbo ◽  
Dominique Laplace ◽  
André Bachoc ◽  
Yves Sanchez ◽  
Benoit Le Guennec
Keyword(s):  
Large Scale ◽  
Suspended Solids ◽  
Drainage Area ◽  
Bed Load ◽  
Urban Drainage ◽  
Combined Sewer ◽  
Wet Weather ◽  
Technical Solutions ◽  
Dry Weather Flow ◽  
Sewer Networks

Solids in combined sewer networks represent two important technical questions: - the clogging of man-entry sewers, and - pollution in urban wet weather discharges, whose main vectors are generally suspended solids. In this paper, we shall present first, curative technical solutions which avoid or remove deposits in man-entry sewers. We shall discuss the partial extraction of the largest solids; selective trapping of bed load solids, which form deposits; and the displacement of deposits using dry weather flow flushing waves. We shall then examine technical solutions to control pollution in urban wet weather discharges. This will show that decantation is an efficient means of fighting pollution. However, it is not always feasible because it involves large scale investments. Complementary methods should, therefore, be developed and used at different points in the water's passage through an urban drainage area.

The transfer of solids in combined sewer networks

1995 ◽  
Vol 31 (7) ◽  
pp. 95-105 ◽  
Author(s):  
G. Chebbo ◽  
A. Bachoc ◽  
D. Laplace ◽  
B. Le Guennec
Keyword(s):  
Organic Matter ◽  
Suspended Solids ◽  
Rainfall Event ◽  
Bed Load ◽  
Surface Slope ◽  
Rainfall Events ◽  
Sediment Deposits ◽  
Combined Sewer ◽  
Stress Variations ◽  
Sewer Networks

Suspended solids are the main vectors of pollution in combined sewer wet weather flows. In spite of being very fine, they decant rather quickly except in the case of light rainfall events rich in organic matter. The part originating from sewer sediment deposits provides a large proportion of organic matter mass. By analysing the content and the volume of sewer deposits at different points from upstream to downstream, it emerges that the main source of this contribution is probably located in man-entry sewers. In one of these, sewer trunk no. 13 in Marseilles, five hundred metres of which were monitored continuously for sediment build-up over three years, the deposit volume grows mainly during certain rainfall events and its surface slope tends to an equilibrium with the (millimetric) particle size. Theoretical bed-load and suspension thresholds have been validated, then analysed for various situations and sections. A typology of the vulnerable areas, in several networks, has been drawn up, as well as a study of shear stress variations during a rainfall event. The sediment deposits seem to occur in particular hydraulic discontinuity zones where transport capacities can drop sharply.

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.

CSO treatment strategy based on constituent index relationships in a highly urbanised catchment

2007 ◽  
Vol 56 (12) ◽  
pp. 85-91 ◽  
Author(s):  
P. Piro ◽  
M. Carbone ◽  
G. Garofalo ◽  
J. Sansalone
Keyword(s):  
Chemical Oxygen Demand ◽  
Suspended Solids ◽  
Treatment Effectiveness ◽  
Oxygen Demand ◽  
Biological Unit ◽  
Unit Operations ◽  
Physical Unit ◽  
Combined Sewer ◽  
Hydrologic Controls ◽  
Wet Weather

In urbanising catchments the variability of particulate matter (solids) and oxygen demanding constituents of wet weather and dry weather characteristics result in variable treatment effectiveness from physical unit operations and biological unit processes. Higher organic concentrations during dry weather flow are more amenable to biological unit processes while the higher inorganic loads generated largely by urban wet weather constituents and much larger flows can be more effectively treated or conditioned by physical unit operations, including ideally preceded by hydrologic controls. This study examines the relationships between total chemical oxygen demand (COD)t, dissolved chemical oxygen demand (COD)d, particulate chemical oxygen demand (COD)p and solids, measured as total suspended solids (TSS). Results also provide an index for selection and optimisation of treatment operations for combined sewer overflow (CSO) loads.

scholarly journals Relationship between turbidity and total suspended solids concentration within a combined sewer system

2011 ◽  
Vol 64 (12) ◽  
pp. 2445-2452 ◽  
Author(s):  
A. Hannouche ◽  
G. Chebbo ◽  
G. Ruban ◽  
B. Tassin ◽  
B. J. Lemaire ◽  
...  
Keyword(s):  
Suspended Solids ◽  
Total Suspended Solids ◽  
Weather Conditions ◽  
Sewer System ◽  
Calibration Dataset ◽  
Solids Concentration ◽  
Sampling Campaign ◽  
Combined Sewer ◽  
Wet Weather ◽  
Strong Linear Relationship

This article confirms the existence of a strong linear relationship between turbidity and total suspended solids (TSS) concentration. However, the slope of this relation varies between dry and wet weather conditions, as well as between sites. The effect of this variability on estimating the instantaneous wet weather TSS concentration is assessed on the basis of the size of the calibration dataset used to establish the turbidity – TSS relationship. Results obtained indicate limited variability both between sites and during dry weather, along with a significant inter-event variability. Moreover, turbidity allows an evaluation of TSS concentrations with an acceptable level of accuracy for a reasonable rainfall event sampling campaign effort.

Cluster analysis for characterization of rainfalls and CSO behaviours in an urban drainage area of Tokyo

2013 ◽  
Vol 68 (3) ◽  
pp. 544-551 ◽  
Author(s):  
Yang Yu ◽  
Keisuke Kojima ◽  
Kyoungjin An ◽  
Hiroaki Furumai
Keyword(s):  
Urban Areas ◽  
Drainage Area ◽  
Distributed Model ◽  
Urban Drainage ◽  
Strong Correlations ◽  
Rainfall Events ◽  
Combined Sewer ◽  
Pollutant Source ◽  
Receiving Waters ◽  
Rainfall Patterns

Combined sewer overflow (CSO) from urban areas is recognized as a major pollutant source to the receiving waters during wet weather. This study attempts to categorize rainfall events and corresponding CSO behaviours to reveal the relationship between rainfall patterns and CSO behaviours in the Shingashi urban drainage areas of Tokyo, Japan where complete service by a combined sewer system (CSS) and CSO often takes place. In addition, outfalls based on their annual overflow behaviours were characterized for effective storm water management. All 117 rainfall events recorded in 2007 were simulated by a distributed model InfoWorks CS to obtain CSO behaviours. The rainfall events were classified based on two sets of parameters of rainfall pattern as well as CSO behaviours. Clustered rainfall and CSO groups were linked by similarity analysis. Results showed that both small and extreme rainfalls had strong correlations with the CSO behaviours, while moderate rainfall had a weak relationship. This indicates that important and negligible rainfalls from the viewpoint of CSO could be identified by rainfall patterns, while influences from the drainage area and network should be taken into account when estimating moderate rainfall-induced CSO. Additionally, outfalls were finally categorized into six groups indicating different levels of impact on the environment.

Sewer Sediment and its Relation with the Quality Characteristics of Combined Sewer Flows

1990 ◽  
Vol 22 (10-11) ◽  
pp. 247-257 ◽  
Author(s):  
M. Verbanck
Keyword(s):  
Suspended Solids ◽  
Particulate Material ◽  
Main Trunk ◽  
Rainfall Events ◽  
Combined Sewer ◽  
First Results ◽  
Sandy Material ◽  
Complex Phenomena ◽  
Pollution Emissions ◽  
Dry Weather Flow

Combined sewer lines in the centre of Brussels are laid at very slack gradients, resulting during dry-weather in a systematic deficit of the load of particulate material at the outlet. The first results of a data collection programme are documented, with regard to the influence of in-sewer deposits upon pollution emissions. The monitoring of suspended solids load in the Main Trunk showed the extent of sediment deposition/resuspension processes in the system. Over a long period of time, the accumulation of deposits on sewer inverts is clearly noticeable. The total volume of deposition in the network also appears to be much more influenced by rainfall events than by human sewer-cleaning practices. Particle size analyses of sewer sediment samples have shown that most deposits in running sewers are composed of sandy material, which reduces the hydraulic capacity, but is suspected to have only slight adverse pollutional impact. Samples with finer material and higher organic contents were however found in some protected locations, not submitted to continuous dry-weather flow. From the experience gained in this study, it is strongly believed that the acquisition of detailed field data is essential in order to assess correctly the complex phenomena involved.

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.

Survey monitoring results on the reduction of micropollutants, bacteria, bacteriophages and TSS in retention soil filters

2013 ◽  
Vol 68 (5) ◽  
pp. 1004-1012 ◽  
Author(s):  
Katharina Tondera ◽  
Stefan Koenen ◽  
Johannes Pinnekamp
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
Suspended Solids ◽  
Total Suspended Solids ◽  
Cleaning Efficiency ◽  
Surface Water Pollution ◽  
Reduction Processes ◽  
Combined Sewer ◽  
Limiting Efficiency ◽  
Median Rate

A main source of surface water pollution in Western Europe stems from combined sewer overflow. One of the few technologies available to reduce this pollution is the retention soil filter. In this research project, we evaluated the cleaning efficiency of retention soil filters measuring the concentration ratio of standard wastewater parameters and bacteria according to factors limiting efficiency, such as long dry phases or phases of long-lasting retention. Furthermore, we conducted an initial investigation on how well retention soil filters reduce certain micropollutants on large-scale plants. There was little precipitation during the 1-year sampling phase, which led to fewer samples than expected. Nevertheless, we could verify how efficiently retention soil filters clean total suspended solids. Our results show that retention soil filters are not only able to eliminate bacteria, but also to retain some of the micropollutants investigated here. As the filters were able to reduce diclofenac, bisphenol A and metoprolol by a median rate of almost 75%, we think that further investigations should be made into the reduction processes in the filter. At this point, a higher accuracy in the results could be achieved by conducting bench-scale experiments.

Investigations on the filtration of natural aquatic suspensions supported by dosing small amounts of Fe(III)-salts (βFe ≤ 0.1 mg.L-1): mode of action and basic design criteria

2002 ◽  
Vol 2 (2) ◽  
pp. 91-98
Author(s):  
R. Winzenbacher ◽  
R. Schick ◽  
H.-H. Stabel ◽  
M. Jekel
Keyword(s):  
Large Scale ◽  
Suspended Solids ◽  
Iron Hydroxides ◽  
Essential Step ◽  
Iron Salts ◽  
Alkaline Earths ◽  
Co Precipitation ◽  
Solid Liquid ◽  
Solid Liquid Separation

Improved removal of particles during the treatment of natural aquatic suspensions has been achieved by pre-ozonation and the addition of small quantities of iron salts (βFe ≤ 0.1 mg.L-1; “Fe(III)-assisted filtration”) followed by rapid filtration. As shown by investigations on a large-scale installation at Lake Constance Water Supply, this procedure reliably reduces suspended solids by at least 2-3 powers of ten in long-term use. However, the high efficacy of Fe(III)-assisted filtration cannot be explained on the basis of known coagulation mechanisms (like adsorption-charge neutralization, co-precipitation). Instead, the essential step was found to be the conditioning of the filter medium by coating it with colloids containing Fe(OH)3, and this “Fe coating” process occurs only in the presence of alkaline earths (especially Ca2+). According to further experiments, the enhanced solid-liquid separation was ultimately traced to chemical interactions such as the formation of calcium-organic association structures between the iron hydroxides and other solids. For design of Fe(III)-assisted filtration steps, finally, a βCa/DOC ratio above 40 mg.mg-1 and pre-oxidation with ozone dosages not exceeding 2 mg O3/mg DOC was recommended.

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