The feasibility of flocculation in a storage sedimentation basin

1999 ◽  
Vol 39 (2) ◽  
pp. 75-83 ◽  
Author(s):  
W. De Cock ◽  
P. Blom ◽  
G. Vaes ◽  
J. Berlamont
Keyword(s):  
Numerical Model ◽  
Velocity Gradient ◽  
Settling Velocity ◽  
Pollution Load ◽  
Combined Sewer Overflows ◽  
Combined Sewer ◽  
Efficiency Increase ◽  
Receiving Waters ◽  
Sedimentation Basins ◽  
The Impact

For the Flemish situation, storage sedimentation basins are one of the best ‘end-of-pipe’ solutions to reduce the impact of combined sewer overflows on the receiving waters. In some cases, when the spilled pollution load is too high, the settling efficiency of the basin has to be improved. Adding coagulants could be a reasonable alternative for building larger basins. To estimate the effect of enhancing the settling by flocculation, a floc growth and break-up model is worked out and is implemented in the numerical model Phoenics. The evolution of the floc dimensions and the sedimentation behaviour of the particles in the basin is calculated for different inflow rates and initial settling velocity profiles. Finally, the efficiency increase by mixing (creating a higher velocity gradient) in the agitation chamber or by adding coagulants in the trunk sewer upstream of the basin is also investigated.

Estimation of Combined Sewer Overflow Discharge From the City of Malmö

1984 ◽  
Vol 15 (4-5) ◽  
pp. 333-340
Author(s):  
W. Hogland ◽  
R. Berndtsson ◽  
M. Larson
Keyword(s):  
Urban Areas ◽  
Point Of View ◽  
Water Volume ◽  
Pollution Load ◽  
Combined Sewer Overflows ◽  
Storm Water Management Model ◽  
Continuous Simulation ◽  
Combined Sewer ◽  
Receiving Waters ◽  
The City

The function of combined sewer overflows (CSO) from both a quantitative and a qualitative point of view is often little known in the Nordic communities. Since large pollution loads are discharged from urban areas by CSO, it is important to consider this problem when rehabilitation plans are established. A study aiming at the estimation of yearly volumes of CSO and yearly quantities of pollution load from CSO has been carried out in the city of Malmö, Sweden. The CSO discharges into four different types of receiving waters: the channel, the harbour, the Sege River and the Öresund. Registration of frequency, duration and water volume was made at about 30 weirs at different time periods. Storm Water Management Model (SWMM) was used both to simulate single SCO events and for continuous simulation. The results from these simulations were compared with actual measurements. The total pollution load was estimated from mean concentration of pollutants from more than 100 samples taken at different weirs and CSO events. Through analysis of the occurrence of CSO in time and space, a program of priorities for the rehabilitation of the CSO-system was established.

Development of a Methodology to Determine the Pollution Discharged by a Combined Sewer Network

1990 ◽  
Vol 22 (10-11) ◽  
pp. 15-22 ◽  
Author(s):  
M. Cherrered ◽  
B. Chocat
Keyword(s):  
Urban Runoff ◽  
Pollution Source ◽  
Relative Effect ◽  
Actual State ◽  
Combined Sewer Overflow ◽  
Combined Sewer Overflows ◽  
Combined Sewer ◽  
Receiving Waters ◽  
Sewer Overflow ◽  
The Impact

Until a few years ago, there was not much research in France into Combined Sewer Overflow phenomena in storm weather. The water of urban runoff has always been considered “clean” and one considered that the dilution of dry weather flows in storm water decreased the impact of the pollution generated by overflows. Now, with increased urban development and realization of the importance of pollution caused by urban runoff, the problem can be considered differently. Indeed, some quality studies of receiving waters show that combined sewer networks represent an important pollution source for the natural environment, due to the increasing relative effect of combined sewer overflow discharge into receiving waters. Thus, combined sewer overflows have until recently been the least known part of the sewer system. In this present communication, methodology to estimate combined overflows has been elaborated after exploitation of data resulted from ten French real case studies where such problems were observed. This study has been realized in four steps:- A bibliography study to discover the actual state of the problem in terms of existent methods concerning both experimentation and modelling and to define the needs of the research.- Ten French studies have been selected, analysed, and used to define the different methods used, and to show methodological lacunas from the observations and results realized. Elements of improvement have been proposed.- Methods and new propositions have been defined and a coherent methodological diagram has been realized to compare and test these methods.- Computer tools have been conceived and tested in the ten study cases.

Considering the impact of intermittent discharges when modelling overflows

1998 ◽  
Vol 38 (10) ◽  
pp. 23-30
Author(s):  
Sarah Jubb ◽  
Philip Hulme ◽  
Ian Guymer ◽  
John Martin
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Preliminary Investigation ◽  
Oxygen Demand ◽  
Sediment Oxygen Demand ◽  
Combined Sewer Overflows ◽  
River Hydraulics ◽  
Combined Sewer ◽  
The Impact ◽  
Curve Equation

This paper describes a preliminary investigation that identified factors important in the prediction of river water quality, especially regarding dissolved oxygen (DO) concentration. Intermittent discharges from combined sewer overflows (CSOs) within the sewerage, and overflows at water reclamation works (WRW) cause dynamic conditions with respect to both river hydraulics and water quality. The impact of such discharges has been investigated under both wet and dry weather flow conditions. Data collected from the River Maun, UK, has shown that an immediate, transient oxygen demand exists downstream of an outfall during storm conditions. The presence of a delayed oxygen demand has also been identified. With regard to modelling, initial investigations used a simplified channel and the Streeter-Phelps (1925) dissolved oxygen sag curve equation. Later, a model taking into account hydrodynamic, transport and dispersion processes was used. This suggested that processes other than water phase degradation of organic matter significantly affect the dissolved oxygen concentration downstream of the location of an intermittent discharge. It is proposed that the dynamic rate of reaeration and the sediment oxygen demand should be the focus of further investigation.

Review of Rainfall Data Application for Design and Analysis

1984 ◽  
Vol 16 (8-9) ◽  
pp. 1-45 ◽  
Author(s):  
V Arnell ◽  
P Harremoës ◽  
M Jensen ◽  
N B Johansen ◽  
J Niemczynowicz
Keyword(s):  
Statistical Prediction ◽  
Dynamic Flow ◽  
Combined Sewer Overflows ◽  
Statistical Characterization ◽  
Data Application ◽  
Combined Sewer ◽  
Dynamic Flow Model ◽  
Receiving Waters ◽  
Rain Fall

This review has been prepared for the international seminar: Rain fall as the basis for urban runoff design and analysis, held in Copenhagen, 24'26 Aug. 1983. The purpose of the review is to bring a state of the art within, 1) the statistical characterization of rain fall in time and space, 2) the development of synthetic design storms and, 3) the application of both synthetic design storms and historical storms to pipe design, flooding prediction, design of detention basins and calculation of the yearly or extreme pollutiona1 load on receiving waters from combined sewer overflows. The main conclusion, primarily related to item 3), is that more attention in this context should be put on statistical analysis of the detrimental effects: flooding and pollution. This analysis is best performed by applying historical rain records. Realistic flooding prediction is believed only to be possible with a fully dynamic flow model, whereas pollution may be studied by means of simpler models like the time area approach. The outstanding problem in the statistical prediction is the distribution in space of the historical rains.

The influence of biodegradability of sewer solids for the management of CSOs

2005 ◽  
Vol 51 (2) ◽  
pp. 89-97 ◽  
Author(s):  
R. Sakrabani ◽  
R.M. Ashley ◽  
J. Vollertsen
Keyword(s):  
Weather Conditions ◽  
Bulk Water ◽  
Combined Sewer Overflows ◽  
Sediment Erosion ◽  
Combined Sewer ◽  
Utilisation Rate ◽  
Laboratory Device ◽  
Receiving Waters ◽  
Oxygen Utilisation ◽  
Wet Weather

The re-suspension of sediments in combined sewers and the associated pollutants into the bulk water during wet weather flows can cause pollutants to be carried further downstream to receiving waters or discharged via Combined Sewer Overflows (CSO). A typical pollutograph shows the trend of released bulk pollutants with time but does not consider information on the biodegradability of these pollutants. A new prediction methodology based on Oxygen Utilisation Rate (respirometric method) and Erosionmeter (laboratory device replicating in-sewer erosion) experiments is proposed which is able to predict the trends in biodegradability during in-sewer sediment erosion in wet weather conditions. The proposed new prediction methodology is also based on COD fractionation techniques.

scholarly journals Intensive monitoring of conventional and surrogate quality parameters in a highly urbanized river affected by multiple combined sewer overflows

2018 ◽  
Vol 19 (3) ◽  
pp. 953-966 ◽  
Author(s):  
D. Copetti ◽  
L. Marziali ◽  
G. Viviano ◽  
L. Valsecchi ◽  
L. Guzzella ◽  
...  
Keyword(s):  
Total Phosphorus ◽  
Laboratory Data ◽  
Quality Parameters ◽  
Nutrient Concentrations ◽  
Combined Sewer Overflows ◽  
Continuous Measurements ◽  
Combined Sewer ◽  
Early Peak ◽  
Sewer Overflows ◽  
The Impact

Abstract The paper reports results of four intensive campaigns carried out on the Seveso River (Milan metropolitan area, Italy) between 2014 and 2016, during intense precipitation events. Laboratory analyses were coupled with on-site, continuous measurements to assess the impact of pollutants on water quality based on both conventional and surrogate parameters. Laboratory data included total suspended solids, caffeine, total phosphorus and nitrogen, and their dissolved forms. Screening of trace metals (Cr, Cu, Pb, Ni, Cd) and PBDEs (polybromodiphenylethers) was carried out. Continuous measurements included water level, physico-chemical variables and turbidity. Nutrient concentrations were generally high (e.g. average total phosphorus > 1,000 μg/L) indicating strong sewage contributions. Among monitored pollutants Cr, Cu, Pb, and Cd concentrations were well correlated to TSS, turbidity and discharge, being bound mostly to suspended particulate matter. A different behavior was found for Ni, that showed an early peak occurring before the flow peak, as a result of first flush events. PBDEs correlated well to nutrient concentrations, showing the highest peaks soon after activation of the combined sewer overflows, likely because of its accumulation in sewers. In addition to showing the existing correlations between quality parameters, the paper highlights the importance of surrogate parameters as indicators of anthropic pollution inputs.

Characterisation of retention tank water quality: particle settling velocity distribution and retention time

2013 ◽  
Vol 48 (4) ◽  
pp. 321-332 ◽  
Author(s):  
Thibaud Maruéjouls ◽  
Peter A. Vanrolleghem ◽  
Geneviève Pelletier ◽  
Paul Lessard
Keyword(s):  
Velocity Distribution ◽  
Retention Time ◽  
Settling Velocity ◽  
Oxygen Demand ◽  
Combined Sewer Overflows ◽  
Particle Settling ◽  
Wastewater Systems ◽  
Receiving Waters ◽  
Settling Velocity Distribution ◽  
Settling Performance

Retention tanks (RTs) are commonly used to reduce combined sewer overflows, management of which is an important way of reducing the impacts of urban development on receiving waters. However, overflow characteristics and the processes affecting them are not yet fully understood. In a context of integrated urban wastewater systems, the management of RTs is mainly done to satisfy hydraulic constraints even if the idea behind such structures is to limit the discharge of pollutants to the environment. This study reports new insights in the settling processes and the pollutant behaviour occurring in an off-line RT. The authors first focus on the total suspended solids (TSS) and the total chemical oxygen demand (CODt) dynamics at the inlet and the outlet of a RT. Secondly, they focus on the possible relationship between the variation of the particle settling velocity distribution of particles and the TSS concentration dynamics. Finally, analyses of the TSS and CODt concentration evolution during tank emptying give information on the interaction between wastewater retention time and the settling performance.

Occurrence and fate of organic pollutants in combined sewer systems and possible impacts on receiving waters

2007 ◽  
Vol 56 (10) ◽  
pp. 141-148 ◽  
Author(s):  
A. Welker
Keyword(s):  
Organic Pollutants ◽  
Wastewater Treatment Plants ◽  
Combined Sewer Overflows ◽  
Sewer Systems ◽  
Flow Surface ◽  
Combined Sewer ◽  
Polycyclic Aromatic ◽  
Receiving Waters ◽  
First Time ◽  
Receiving Water

Selected organic pollutants are classified based on an intensive literature survey. Two wastewater parameters (COD and ammonium) and six selected organic pollutants (polycyclic aromatic hydrocarbons (PAH), diethylhexylphthalate (DEHP), estradiol (E2), ethinylestradiol (EE2), ethylenediamine tetraacetic acid (EDTA) and nitrilo triaceticacid (NTA)) are specified. As a result, for the first time representative concentrations in dry weather flow, surface runoff and effluent of wastewater treatment plants (WWTPs) in combined sewer systems (CSS) are stated. The second part of the paper presents a first estimation of main emission out of a combined sewer system and possible receiving water impacts in terms of (1) annual discharged loads calculated by pollution load simulations in a hypothetical catchment and (2) concentrations calculated in combined sewer overflows (CSO) discharges and resulting receiving water concentrations.

scholarly journals The importance of pollutional loads during wet weather

2019 ◽  
pp. 271-282
Author(s):  
Oddvar Georg Lindholm ◽  
Lars Aaby
Keyword(s):  
Time Series ◽  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
The Other ◽  
Combined Sewer Overflows ◽  
Combined Sewer ◽  
Receiving Waters ◽  
Wet Weather ◽  
Annual Discharge

Wet weather discharges consist mainly of washed out surface pollution in separate sewered areas, but in combined sewered areas; resuspended pipe deposits, surface washoff and sewage, discharging via combined sewer overflows (CSOs). Of the three mentioned sources, resuspended pipe solids is dominating over the other two and may contribute as much as 50 to 90 % of the total amount of the CSO. The CSO in a normal catchment may also on an annual bases be of the same amount, or even twice as much as the effluent from the wastewater treatment plant (WWTP). If the receiving waters are vulnerable to shock loads on a daily base, it is important to be aware that the amount of CSO might, at its most adverse be up to I 00 times more than the effluent from the WWTP during a day. The annual discharge via CSOs in a catchment may easily vary with a factor of up to 8 from the driest to the wettest year, during time series of 20 to 40 years.

scholarly journals Ecological aspect in combined sewer overflows chamber design

2013 ◽  
Vol 8 (3-4) ◽  
pp. 409-416
Author(s):  
J. Pollert
Keyword(s):  
Ecological Engineering ◽  
Combined Sewer Overflows ◽  
Reinforced Plastic ◽  
Combined Sewer ◽  
New Type ◽  
Receiving Waters ◽  
Sewer Overflows ◽  
The Cost ◽  
Floating Objects ◽  
Receiving Water

In 2005 one of major Czech manufacturers of glass reinforced plastic pipes asked the Department of Sanitary and Ecological Engineering to develop a new type of combined sewer overflows (CSO) chamber that could become a part of their manufacturing programme. The main requirements were economy of production, easy and fast installation on the field and increased protection of receiving waters. A simple object consisting of a pipe placed above another one was designed. The object begins with a stilling chamber formed by a conical expansion of the inlet pipe. It is separated from the overflow object itself by a downflow baffle designed to trap floating objects. The CSO chamber is equipped by a flow regulation device (e.g. vortex valve or throttle pipe) at the end. Excess water flows through a slit in the top of the bottom pipe into the upper pipe and from there to the receiving water. More than 15 prototypes were already installed in the Czech and Slovak Republics and more than 20 are planned to be built in Europe. We hope this type of CSO CHAMBER will help to decrease the cost of construction of new sewers and reconstruction of old ones. Its higher efficiency of separation of suspended particles might also contribute to the improvement of the quality of receiving water bodies according to Water Framework Directive 2000/60/EC.

Sign in / Sign up

Export Citation Format

Share Document