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1
Carleton, M. G. "Comparison of Overflows from Separate and Combined Sewers – Quantity and Quality." Water Science and Technology 22, no. 10-11 (1990): 31–38. http://dx.doi.org/10.2166/wst.1990.0285.
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The use of separate sewerage systems to solve pollution problems associated with combined systems is examined. Overflows from combined stormwater-sewer systems have been found to be one of the major causes of receiving water pollution. Experiences in two countries which have predominantly one system or the other provided a basis for comparison. Wet weather overflow was found to be a major problem with similar quality of overflow produced for both systems. Minimising overflows was feasible, however proper and integrated control of stormwater and sewage flows, related to receiving water impacts, is indicated as the best solution. The use of separate sewerage systems to solve pollution problems may not be justified.
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Rechenburg, A., Ch Koch, Th Claßen, and Th Kistemann. "Impact of sewage treatment plants and combined sewer overflow basins on the microbiological quality of surface water." Water Science and Technology 54, no. 3 (2006): 95–99. http://dx.doi.org/10.2166/wst.2006.454.
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In a small river catchment, microbiological quality of different sewage treatment plants under regular conditions and in case of heavy rainfall, when combined sewage overflow basins (CSOs) are activated, was examined regarding microbial indicators and pathogens. In the watercourse, no self-cleaning effects could be observed. Small compact treatment plants discharge treated wastewater with a poor microbiological quality compared to river water quality and the quality of treated wastewater of larger plants. During storm water events, concentrations of microorganisms downstream of sewer overflows were approximately two logs higher than during dry weather conditions. Concentrations of parasites decreased slowly during the overflow, in parallel to filterable matter and particle-bound substances. The annual load of microorganisms originating from CSOs significantly exceeds the load from treated effluent of the sewage plants. Thus, an improved hygienic quality of the water course could be achieved by preventing overflows and by enhancing sewage treatment plants.
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Yomtovian, Isaac. "OPTIMUM ALTERNATIVES FOR CONTROLLING COMBINED SEWAGE OVERFLOWS - A CASE STUDY1." JAWRA Journal of the American Water Resources Association 15, no. 3 (2007): 628–43. http://dx.doi.org/10.1111/j.1752-1688.1979.tb00384.x.
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Guderian, Joachim, Andreas Durchschlag, and Jürgen Bever. "Evaluation of total emissions from treatment plants and combined sewer overflows." Water Science and Technology 37, no. 1 (1998): 333–40. http://dx.doi.org/10.2166/wst.1998.0079.
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Based upon the connection of a simulation program for combined sewer systems with the IAWQ-Activated Sludge Model No.1 the new simulation tool GEMINI was developed, which allows the calculation of sewer and sewage treatment plant as a unit. Some obtained results are presented in an example. They suggest, that for every treatment plant a rate of inflow is determinable, which leads to a minimum of total emissions out of sewer and treatment plant. The optimal value of sewage treatment plant inflow in the example is distinctly greater than the design flow rate fixed in German design rules. So it is recognizable that a rigid flow management for sewer and treatment plant does not always fulfil the aim of minimization of total emissions.
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Mielczarek, Szymon, and Jerzy M. Sawicki. "Dimensioning of vortex storm overflows." Water Science and Technology 78, no. 2 (2018): 259–65. http://dx.doi.org/10.2166/wst.2018.291.
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Abstract Vortex storm overflow is an interesting and useful technical solution, especially important in storm and combined sewage systems. However, there are no methods of this device dimensioning, which would be mathematically simple and properly precise physically. Such a method has been proposed in this paper, on the basis of investigations performed for the vortex separators and vortex flow controls. The essence of this method relies on the kinematic model of the velocity field and energy balance of the inflowing stream and dissipation. The procedure enables specialists to calculate the rise of the liquid free surface caused by the inlet stream energy and the hydraulic resistance of the bottom outlet. These mathematical relations are completed by two formulae: for the bottom ‘morning glory’ sink and for the upper overflow. The model has been positively verified during the laboratory measurements, so can be used during the technical dimensioning of the vortex storm overflows.
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Rutsch, M., I. Müller, and P. Krebs. "Dynamics of rain-induced pollutographs of solubles in sewers." Water Science and Technology 52, no. 5 (2005): 169–77. http://dx.doi.org/10.2166/wst.2005.0131.
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When looking at acute receiving water impacts due to combined sewer overflows the characteristics of the background diurnal sewage flux variation may influence the peak loads from combined sewer overflows (CSO) and wastewater treatment plant (WWTP) effluent significantly. In this paper, effects on the dynamic compounds transported in the sewer, on CSO discharges and WWTP loading are evaluated by means of hydrodynamic simulations. The simulations are based on different scenarios for diurnal dry-weather flow variations induced by different infiltration rates.
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Korving, H., M. Geise, and F. Clemens. "Failure of sewage pumps: statistical modelling and impact assessment." Water Science and Technology 54, no. 6-7 (2006): 119–26. http://dx.doi.org/10.2166/wst.2006.577.
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Sewage pumping stations are directly responsible for affecting performance, i.e. failing pumps may result in combined sewer overflows or flooding. However, failures of sewage pumps are not yet incorporated in sewer assessments due to lack of knowledge and data. This paper presents the analysis of pump failure data provided by two sewer management authorities in The Netherlands. Pump failures have been studied accounting for the nature of the failures, the operation and maintenance procedures of the management authority, the ageing of the pumps and the changes in the environment of pumps. The analysis shows that sewage pumps fail relatively often due to the composition of sewage and the discontinuous operation of the pumps. The interarrival time and the duration of failures are highly variable and independent of the pump type and the specific function of the pump. The results also indicate that the serviceability of sewer systems is significantly affected by failing pumps. As a consequence, part of the environmental damage due to CSOs (combined sewer overflows) can be avoided by improving maintenance of pumping stations.
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Hansen, O. B., C. Jacobsen, and P. Skat Nielsen. "Storm Water Loading of Greater Copenhagen Sewage Treatment Plant." Water Science and Technology 27, no. 12 (1993): 183–86. http://dx.doi.org/10.2166/wst.1993.0297.
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Copenhagen's plans to cut pollution loads from combined sewer overflows involves increased storage capacity in the sewer system, real time control of that system, and increased hydraulic loading for the treatment plant. Modelling studies have been used to examine the consequences.
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Schilling, W., and D. T. Kollatsch. "Reduction of Combined Sewer Overflow Pollution Loads by Detention of Sanitary Sewage." Water Science and Technology 22, no. 10-11 (1990): 205–12. http://dx.doi.org/10.2166/wst.1990.0306.
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For mixed combined/separate sewer systems it is proposed, in times of combined sewage overflows (CSO), to store sanitary sewage at the inlet point to the combined system. Thereby, sanitary sewage (with high strength) is kept in the system for further treatment after the storm whereas less-polluted CSO are diverted to the receiving water. By using data of an existing catchment different scenarios are evaluated and the potential benefit of sanitary sewage detention is quantified. This approach is compared to current German CSO regulations. It is more effective than conventional CSO detention if more than 60 % of the population upstream of the CSO diversion are served by a separate system. A key problem of this concept is the control strategy that determines when to activate and empty the storage tanks. A number of criteria are compared. Considerations are also made on operational aspects such as chemical transformations in stored sewage, maximum allowable detention time, and cleansing of storage tanks.
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Capodaglio, Andrea G. "INTEGRAL CONTROL REQUIREMENTS FOR SEWERAGE SYSTEMS." Water Science and Technology 30, no. 1 (1994): 131–38. http://dx.doi.org/10.2166/wst.1994.0014.
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Sewerage systems and sewage treatment plants are often planned, designed and operated as totally separate entities. As a result, sewage treatment efficiency is subject to considerable variability, depending both on general hydrologic conditions in the urban watershed (wet versus dry periods), and on specific “instantaneous” operating conditions. It has been postulated that the integration of design and operation in urban drainage and wastewater treatment could allow minimization of the harmful effects of discharges from treatment plants, combined sewer overflows and surface runoff. This “ideal condition” can be achieved through the introduction of so-called “Real-Time Control” technology in sewerage collection and treatment operations. This paper examines the requirements of a hypothetical integrated sewer flow and sewage treatment model, the mathematical tools used to design and operate Real-Time Control systems, and the issues emerging from an integration of the conveyance and disposal aspects of the sewerage cycle.
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Hedges, Peter D. "The Prediction of Combined Sewer Overflow Performance from Models – A Case Study." Water Science and Technology 29, no. 1-2 (1994): 373–82. http://dx.doi.org/10.2166/wst.1994.0685.
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Hydrodynamic separators have been employed as combined sewer overflows (CSOs) in the UK since the early 1960s. Since little was known of their operating characteristics, Severn Trent Water Authority contracted Aston University to monitor the performance of a separator constructed during 1986-87 at James Bridge, Walsall, UK. Unfortunately only three overflow events were fully documented during the monitoring period, which was particularly dry. One separator was therefore artificially charged by pumping from the adjacent river to simulate storm flow conditions. A model study was not included in the original proposal, but one was established to complement the main programme since the characteristics of hydrodynamic separators were poorly understood. The arrangement of the field site is described, and the results from the monitored storm events, pump tests and model studies are summarised. Characteristics derived from the model study are combined with sewage settling velocity grading curves to predict the performance of the prototype hydrodynamic separator for one of the observed storm events. Given the limitations inherent in the sewage data used, a comparison of the predicted and observed separator efficiencies demonstrates the potential of this approach for the design and selection of CSOs for specific locations.
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Stirrup, M. "Implementation of Hamilton-Wentworth Region’s Pollution Control Plan." Water Quality Research Journal 31, no. 3 (1996): 453–72. http://dx.doi.org/10.2166/wqrj.1996.026.
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Abstract The Regional Municipality of Hamilton-Wentworth operates a large combined sewer system which diverts excess combined sewage to local receiving waters at over 20 locations. On average, there are approximately 23 combined sewer overflows per year, per outfall. The region’s Pollution Control Plan, adopted by Regional Council in 1992, concluded that the only reasonable means of dealing with large volumes of combined sewer overflow in Hamilton was to intercept it at the outlets, detain it and convey it to the wastewater treatment plant after the storm events. The recommended control strategy relies heavily on off-line storage, with an associated expansion of the Woodward Avenue wastewater treatment plant to achieve target reductions of combined sewer overflows to 1–4 per year on average. The region has begun to implement this Pollution Control Plan in earnest. Three off-line detention storage tanks are already in operation, construction of a fourth facility is well underway, and conceptual design of a number of other proposed facilities has commenced. To make the best possible use of these facilities and existing in-line storage, the region is implementing a microcomputer-based real-time control system. A number of proposed Woodward Avenue wastewater treatment plant process upgrades and expansions have also been undertaken. This paper reviews the region's progress in implementing these control measures.
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Saul, A. J., and R. C. Thornton. "Hydraulic Performance and Control of Pollutants Discharged from a Combined Sewer Storage Overflow." Water Science and Technology 21, no. 8-9 (1989): 747–56. http://dx.doi.org/10.2166/wst.1989.0278.
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The development of the Wallingford Procedure WASSP (1981) and the MOSQITO (Moys 1987) models will provide the sewerage engineer with design tools to assess the quantitative and qualitative performance of sewer systems. As part of the development of such a quality model, the University of Manchester, financed by the Water Research centre and North West Water, have undertaken a fieldwork program of research to monitor the hydraulic performance and the temporal variation of pollutants in the inflow and the overflow at five combined sewage overflows in the North West of England. These projects are integrated into the program of research co-ordinated by the River Basin Management group at WRc Engineering. This paper describes the instrumentation used at a typical field site and illustrates the monitored temporal variation of pollutants for a number of storm events. These results show the complexity of the monitored pollutographs and highlight the large number of variables which influence combined sewer quality. Using data monitored in 1986, it is hypothesised that the long term impact of combined sewer discharges on receiving waters may be estimated from the flow retention performance and some estimate of annual average pollutant concentration. To predict the short term impact on river quality it is necessary to consider the complex processes associated with combined sewer flow and to include the separation performance of the overflow structure.
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Milina, J., S. Sægrov, J. Lei, et al. "Improved interception of combined sewage in the Trondheim-Høvringen wastewater system." Water Science and Technology 39, no. 2 (1999): 159–68. http://dx.doi.org/10.2166/wst.1999.0111.
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This paper describes some results of an integrated model development and its application to the Høvringen wastewater system in Trondheim, Norway. Major model development needs concern the integration of sewage production, transport and treatment simulation, the interface with existing databases and the possibility of simulating processes that are controlled in real time. The developed integrated model has been used to design the treatment process as well as static and dynamic measures in both the catchment and the sewer system. These measures include extended pumping, adjustment of overflows, separation of storm water runoff from “non-effective separate systems”, retention and real-time control of the sewer tunnel volume.
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Rodríguez, Roberto A., Patricia M. Gundy, Geeta K. Rijal, and Charles P. Gerba. "The Impact of Combined Sewage Overflows on the Viral Contamination of Receiving Waters." Food and Environmental Virology 4, no. 1 (2012): 34–40. http://dx.doi.org/10.1007/s12560-011-9076-3.
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Georgaki, Sofia, Dejan Vernon, Rodrigo Baur, Donal Black, and David Crawford. "Extended CSO control storage: what could possibly go wrong?" Water Practice and Technology 13, no. 1 (2018): 184–90. http://dx.doi.org/10.2166/wpt.2018.025.
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Abstract The Thames Tideway Tunnel (TTT), is one of the main components of the London Tideway Improvements Programme, designed to capture combined sewer overflows (CSOs) which currently discharge untreated combined sewage into the tidal river Thames. CSO discharges would be stored in the tunnel until there is capacity at Beckton sewage treatment works (STW), to accept, for treatment, pumped sewage from the tunnel system. There is at present limited literature information on odour generation from stored combined sewage in CSO control systems; on sampling methods of actual combined sewage and continuous monitoring and sampling of gas and liquid phases of stored combined sewage. To better understand the relationship between odour and stored combined sewage, the TTT project team have designed and operated a septicity rig to evaluate the aspects of odour generation from the tunnel system during storage conditions. The key areas of research include: 1. Odour monitoring to measure the emission rates of H2S during tunnel storage conditions, 2. Assessment of the potential for the development of septic conditions and the generation of sulphide compounds that could cause odour problems, 3. Extensive investigation of the impact of biofilm formation and slime growth on the tunnel lining. The findings of the study have determined the levels of sulphide that could potentially be generated from the CSO tunnel system, during storage operations, to ensure adequate consideration in the design of the air management system and tunnel lining and potential for adverse impact on STW operations.
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Bergman, W. A., and D. H. Kapadia. "Tunnel and reservoir plan solution to Chicago's combined sewer overflow, basement flooding, and pollution." Canadian Journal of Civil Engineering 15, no. 3 (1988): 389–96. http://dx.doi.org/10.1139/l88-054.
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In 1890, the Metropolitan Sanitary District of Greater Chicago was formed to permanently protect the region's drinking water supply from devastating contamination by sewage. The solution was to excavate a massive canal across the continental divide and to thus reverse the flow of the Chicago River, causing it to flow into the tributaries of the Mississippi River and away from Lake Michigan. Later, sewage treatment works were constructed to treat dry weather flows.Each time rainfall exceeds 8.4 mm, the combined sewers' capacities are exceeded, and they discharge directly to the canal system on the average of 100 times per year without benefit of treatment. When the sewers and canal system are overtaxed, raw sewage backs up the sewers in Chicago and 51 suburbs, flooding streets, businesses, and home basements.In order to solve these problems on a regional basis, the Sanitary District in 1972 adopted the tunnel and reservoir plan (TARP). TARP is a second river system which is being constructed by boring tunnels up to 11 m in diameter in rock as much as 100 m under the city. When the surface sewers' capacities are exceeded, the excess flows will drop into TARP. Huge reservoirs totalling 157 000 000 m3 capacity will store the sewage until it can be gradually pumped back to the treatment works. Key words: sewage, combined sewers, overflows, water pollution, water quality, stream pollution, flood control, tunneling.
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Fong, Theng-Theng, Mantha S. Phanikumar, Irene Xagoraraki, and Joan B. Rose. "Quantitative Detection of Human Adenoviruses in Wastewater and Combined Sewer Overflows Influencing a Michigan River." Applied and Environmental Microbiology 76, no. 3 (2009): 715–23. http://dx.doi.org/10.1128/aem.01316-09.
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ABSTRACT Enteric viruses are important pathogens found in contaminated surface waters and have previously been detected in waters of the Great Lakes. Human adenoviruses were monitored because of their high prevalence and persistence in aquatic environments. In this study, we quantified adenoviruses in wastewater, surface water, and combined sewer overflows (CSOs) by real-time PCR. Between August 2005 and August 2006, adenovirus concentrations in raw sewage, primary-treated effluent, secondary-treated effluent, and chlorinated effluent from a wastewater treatment plant in Michigan were examined. CSO samples (n = 6) were collected from a CSO retention basin in Grand Rapids, MI. Adenoviruses were detected in 100% of wastewater and CSO discharge samples. Average adenovirus DNA concentrations in sewage and CSOs were 1.15 × 106 viruses/liter and 5.35 × 105 viruses/liter, respectively. Adenovirus removal was <2 log10 (99%) at the wastewater treatment plant. Adenovirus type 41 (60% of clones), type 12 (29%), type 40 (3%), type 2 (3%), and type 3 (3%) were isolated from raw sewage and primary effluents (n = 28). Six of 20 surface water samples from recreational parks at the lower Grand River showed virus concentrations above the real-time PCR detection limit (average, 7.8 × 103 viruses/liter). This research demonstrates that wastewater effluents and wastewater-impacted surface waters in the lower Grand River in Michigan contain high levels of viruses and may not be suitable for full-body recreational activities. High concentrations of adenovirus in these waters may be due to inefficient removal during wastewater treatment and to the high persistence of these viruses in the environment.
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Oh, Hye Cheol, Seog Ku Kim, Sung Won Kang, Sang Leen Yun, and Jae Hwan Ahn. "The Development of Solid Fabric Filter for CSOs Treatment." Materials Science Forum 658 (July 2010): 288–91. http://dx.doi.org/10.4028/www.scientific.net/msf.658.288.
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The cost for nonpoint source in urban area tends to increase as it's distanced farther from the pollution source. Thus it's more effective to dispose of the pollution at the pollution source. It becomes more difficult when nonpoint source is flowed into the surface water by stormwater. In case of combined sewer, increasing stormwater on impermeable surface causes the Combined Sewer Overflows (CSOs) containing the high level of pollutants which runs into the water system through the storm overflow diverging tank without treatment process. A huge amount of CSOs is generated instantly and as it carries the pollutants on impermeable surface as well as the deposits in sewage pipe, it's necessary to develop the technology for treatment of CSOs. This study was intended to develop the solid fabric filter which will be suitable for treatment of CSOs and the characteristic and performance of solid fabric filter were evaluated.
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Mignosa, Paolo, and Alessandro Paoletti. "Pollution Loads Discharged from Combined Sewer Overflows: Theoretical Approach and Long Term Numerical Assessment." Hydrology Research 23, no. 1 (1992): 27–48. http://dx.doi.org/10.2166/nh.1992.0003.
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The paper describes a theoretical analysis and a numerical assessment of pollutant loads discharged from Combined Sewer Overflows (CSOs) - with or without stormwater tanks – into the environment. The theoretical approach was based on certain simple assumptions, reasonably valid if the time scale of the problem involved is long enough (month/ year), in that single-event simulation is not interesting at all. Two main parameters related to the rainfall regime were found to be significant: the total volume of water discharged from the structure and the effective mixing factor between sanitary sewage and storm runoff. A numerical assessment of these two parameters was then made, on an annual basis, by means of a long-term rainfall series recorded in Milan, Italy. Both the “simple” CSO structure and the CSO coupled with stormwater tanks (on-line or off-line) were considered. The resulting graphs make it possible to evaluate the total annual load discharged from CSOs into the environment and the potential reduction obtained by adding a storage capacity to the overflow. This estimation could be of interest for persistent pollutants (phosphorus, heavy metals) discharged into low-recirculation bodies (lakes, estuaries, lagoons, closed seas).
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Brzezińska, Agnieszka, Grażyna Sakson, and Marek Zawilski. "Predictive model of pollutant loads discharged by combined sewer overflows." Water Science and Technology 77, no. 7 (2018): 1819–28. http://dx.doi.org/10.2166/wst.2018.050.
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Abstract Effective protection of receiving waters on urbanized areas requires knowledge about the amount of pollutants contained in discharged wastewater, inter alia by combined sewer overflows (CSOs). This involves the need to conduct long-lasting, costly and technically complex studies on the quantity and quality of discharged sewage. Loads of pollutants emitted by CSOs depend on many factors, inter alia on very variable characteristics of precipitations. This paper attempts to develop a simplified predictive model of pollutant loads for two basic parameters: total suspended solids (TSS) and chemical oxygen demand (COD). Studies were conducted in Lodz (Poland) between 2012 and 2015 on an urban catchment. Obtained data were analysed using the Pearson's correlation and principal component analysis method which enabled selection of the key parameters forming the model (depth and maximum intensity of rainfall and CSO volume). A good fit for the developed model was obtained (R2 = 0.79 for TSS and R2 = 0.80 for COD). The model was verified for two other catchments in the same city. Results indicate that the load of TSS and COD can be sufficiently precisely determined by using the proposed model for the studied city without the need to perform long-term continuous quality research of wastewater.
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Lessard, Paul, and Pierre Lavallée. "Caractérisation des eaux usées de débordements de réseau unitaire." Canadian Journal of Civil Engineering 12, no. 3 (1985): 527–37. http://dx.doi.org/10.1139/l85-060.
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In 1981, the City of Québec signed a protocol with the Québec Ministry of Environment permitting the study of the impact of combined sewer overflows (CSO) during rain periods on the St-Charles River. One of the main study objectives was to characterize CSO, both quantitatively and qualitatively. Five main drainage basins, representative of the study area, were selected and sampled during nine rain events. Certain appraisals were made to explain the importance of the water quality variations during rain events in combined sewers, dry weather period influence on runoff quality, and "first-flush" phenomenon. Two principal conclusions have been drawn from these data: (1) the major part of the pollutant load routed through a combined sewer network during a rain event is generated by surface runoff and dragging of sewage deposits and (2) the overall water quality of CSO doesn't seem to vary much from one basin to another, even if the percentages associated with different types of land use (residential, commercial, industrial, etc.) are different. Key words: urban runoff, combined sewer overflow, rainfall, quality, concentration, load.
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Kay, Paul, Stephen R. Hughes, James R. Ault, Alison E. Ashcroft, and Lee E. Brown. "Widespread, routine occurrence of pharmaceuticals in sewage effluent, combined sewer overflows and receiving waters." Environmental Pollution 220 (January 2017): 1447–55. http://dx.doi.org/10.1016/j.envpol.2016.10.087.
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Jefferies, C., C. L. Allinson, and J. McKeown. "The performance of a novel combined sewer overflow with perforated conical screen." Water Science and Technology 37, no. 1 (1998): 243–50. http://dx.doi.org/10.2166/wst.1998.0058.
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Increasing concern over the discharge of sewer solids from combined sewer overflows (CSOs) has encouraged the introduction of installations which incorporate either mesh or bar screen arrangements, or both. Gross solids create visual and aesthetic pollution if they reach watercourses. An entirely new arrangement for a CSO with a perforated screen of 6 mm diameter apertures is described in the paper. The arrangement is circular, with tangential flow across the screen to facilitate its cleaning. High velocities across the screen holes ensure that solids which have been prevented from discharging are swept clear from the screen. As a result, a sufficient screen area remains free from trapped solids to permit discharge of flow. The device has been designed to meet all anticipated performance criteria for the removal of solids, and to require a minimum of maintenance. A thorough testing programme in different conditions is described. Laboratory testing utilised a wide range of gross solids and flows to determine efficiencies of solids removal under all anticipated operating conditions. The performance of the CSO in a sewer environment was evaluated at a sewage treatment works with flows up to 1801/s using both raw and treated sewage to simulate storm sewage of different strengths. Both the device and its testing are described, together with the results of the testing programme.
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Exall, K., J. Marsalek, and B. G. Krishnappan. "Hydraulic fractionation of conventional water quality constituents in municipal dry- and wet-weather flow samples." Water Science and Technology 59, no. 6 (2009): 1159–67. http://dx.doi.org/10.2166/wst.2009.101.
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The effective design of treatment processes for combined sewer overflows (CSOs) requires understanding of the CSO characteristics and treatability. Environment Canada partnered with four municipalities to evaluate water quality and treatability of wet- and dry-weather flows at local sewage or CSO treatment facilities. Chemical characterization of the samples indicates that the municipal sewage at all of the sites is of relatively weak strength, with several differences between the water quality data for dry-weather and wet-weather flows (assumed to represent CSOs). Hydraulic separation of constituents with an elutriation apparatus illustrated the removals that can be expected with conventional settling techniques and differences in settling of various constituents.
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Michelbach, Steven, and Gebhard J. Weiß. "Settleable sewer solids at stormwater tanks with clarifier for combined sewage." Water Science and Technology 33, no. 9 (1996): 261–67. http://dx.doi.org/10.2166/wst.1996.0226.
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A six-year study of CSO problems showed that in most cases the settleable sewer solids are responsible for poor water quality. This is the reason why the settling behaviour of settleable solids should be taken into account at stormwater treatment to a greater degree than it is done up to now. New efficiency measurements at stormwater tanks with clarifier overflows for combined sewage showed two important results: 1) The annual mean surface loading qA of a clarifier-type CSO tank is only about 25 % of the design surface loading of 10 m3/(m·h) recommended by the German guideline A 128. 2) The settling process in stormwater tanks is effective: - The median settling velocity vs of sewer solids is reduced from about 0,21 cm/s to vs = 0,035 cm/s. - The concentration of settleable solids is reduced about 80 %, that of total solids about 65% and COD concentration about 50 %. With this efficiency, well designed stormwater tanks will be a good measure in many cases to reduce significantly CSO impacts on receiving water quality.
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Seager, J., and R. G. Abrahams. "The Impact of Storm Sewage Discharges on the Ecology of a Small Urban River." Water Science and Technology 22, no. 10-11 (1990): 163–71. http://dx.doi.org/10.2166/wst.1990.0301.
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Intermittent discharges of storm sewage from combined sewer overflows continue to be one of the principal causes of poor water quality in many urban rivers in the UK. Despite the persistent nature of this problem, very little attention has been given to the study of how discharges of varying magnitude, duration and frequency affect the ecological quality of receiving waters. This information is of critical importance for deriving meaningful water quality criteria for the control of intermittent pollution. This paper describes the results of a study which has been carried out on Pendle Water, a river which flows through the urban catchment of Burnley, Lancashire, UK. Both the chemical and biological quality of Pendle Water are adversely affected by storm sewage discharges during heavy rainfall events. The ecological investigation has been primarily concerned with impact of these episodic discharges on benthic invertebrate communities and physiological responses in fish. Quantitative sampling of macroinvertebrates has indicated that storm sewage discharges may have a significant impact on the structure and diversity of benthic communities in receiving waters. Physico-chemical properties of habitats appear to be altered in a way which tends to favour the proliferation of certain pollution-tolerant species and decrease the abundance of taxa intolerant of organic pollution. Insitu bioassays, including the WRc Mark III Fish Monitor, have been deployed to investigate physiological responses to storm events of different magnitude, duration and frequency. Results are discussed in relation to their application in the field validation of proposed water quality criteria for the control of intermittent pollution from combined sewer overflows.
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Calhoun, Lisa M., Raymond King, Karina Gunarto, et al. "Combined Sewage Overflows (CSO) Are Major Urban Breeding Sites for Culex quinquefasciatus in Atlanta, Georgia." American Journal of Tropical Medicine and Hygiene 77, no. 3 (2007): 478–84. http://dx.doi.org/10.4269/ajtmh.2007.77.478.
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Lijklema, L., A. F. M. Meuleman, and H. M. M. Bosgoed. "Fluxes of Oxygen Equivalents and Nutrients across the Sediment-Water Interface after Combined Sewer Overflows." Water Science and Technology 22, no. 10-11 (1990): 111–18. http://dx.doi.org/10.2166/wst.1990.0295.
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The fluxes of oxygen into sediments and the release rate of COD, methane and nitrogen after deposition of fresh sewage sludge were measured in an experimental laboratory apparatus. Effects of the initial surface loading revealed a progressive contribution of COD release to the flux of oxygen equivalent to increased loading. Lower oxygen concentrations had the same effect. The actual conversion rate of the organics in the sediments was lower than the potential maximal aerobic degradation rate and higher than the anaerobic rate of hydrolysis. Preferential oxidation of soluble organics at the sediment interface over particulate material limits the release of COD except for high-loaded systems or at low DO concentrations.
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Helness, H., C. Sun, S. Damman, et al. "High rate filtration for local treatment of combined sewer overflow." Water Science and Technology 79, no. 6 (2019): 1206–13. http://dx.doi.org/10.2166/wst.2019.121.
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Abstract Combined sewer overflows (CSOs) pollute receiving waters and have a negative impact on ecosystem services. In urban areas rehabilitation of the sewer system to avoid CSOs is associated with high investment costs. Furthermore, not all CSOs can be closed due to the need for hydraulic reliability of the system. Local treatment of CSO with high rate filtration offers an alternative to rehabilitation of the sewer system that is flexible with respect to design and has lower investment cost than separating sewage and storm water runoff. Results from DESSIN, a 4-year EU demonstration project, are presented. The results showed on average 50% removal of particulate matter during CSO events, with higher removal (80%) in the initial first flush period. Other constituents, for example heavy metals, were removed through their association with particles. Potential impacts on ecosystem services in the catchment and the sustainability of the solution were assessed.
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Ellis, J. Bryan, and Yu Wang. "Bacteriology of urban runoff: the combined sewer as a bacterial reactor and generator." Water Science and Technology 31, no. 7 (1995): 303–10. http://dx.doi.org/10.2166/wst.1995.0246.
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Combined Sewer Overflows (CSOs) are widely recognised as being a primary source of faecal pollution indicator bacteria and pathogens to urban receiving waters. The discharge and in-stream accumulation of sediments from CSOs have also been considered to constitute a bacterial reservoir yielding a continuous inoculation to the receiving water. This paper reports the findings of a microbiological study of CSO discharges and sediments within a N London urban catchments focusing on bacterial indicators (Total and Faecal Coliforms, Faecal Streptococci and pathogens) and the role of somatic coliphages in typing sewage pollution. Evidence is provided for both extended in-stream bacterial survival and bacterial generation in the presence of nutrified organic sediment.
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Chambers, P. A., M. Allard, S. L. Walker, et al. "Impacts of Municipal Wastewater Effluents on Canadian Waters: a Review." Water Quality Research Journal 32, no. 4 (1997): 659–714. http://dx.doi.org/10.2166/wqrj.1997.038.
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Abstract Domestic sewage is a major threat to receiving waters throughout the world. In Canada, a high proportion of the population (81%) is served by municipal wastewater treatment facilities. Nevertheless, discharges from wastewater treatment plants, stormwater sewers and combined sewers have caused adverse impacts on some lakes, rivers and coastal waters. The most publicly recognized impacts are shellfish harvesting restrictions and beach closures resulting from microbial contamination. Habitat degradation and contamination also occur and these, in turn, have altered the abundance and diversity of aquatic organisms. Our findings on the effects of municipal wastewater discharge suggest that there is a need to review sewage treatment requirements in Canada. Further research is also required on the interactive and cumulative responses to habitat degradation and to long-term exposure to persistent and bioaccumula-tive pollutants. Finally, an integrated approach to wastewater management is needed that addresses loadings from treatment plants, stormwater sewers, combined sewer overflows and other wastewater sources.
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Korving, H., and E. C. Ottenhoff. "Analysis of the causes of pump failure and differences of failure characteristics." Water Science and Technology 57, no. 8 (2008): 1271–76. http://dx.doi.org/10.2166/wst.2008.304.
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It is generally accepted that sewage pumping stations are directly responsible for affecting sewer system performance in terms of combined sewer overflows and flooding. However, the specific causes of pump failure are unknown. This paper presents the analysis of pump failure data provided by four sewer management authorities in The Netherlands. Pump failures have been studied accounting for the nature of failures, operation and maintenance procedures of the management authority, ageing of the pumps and changes in the environment of pumps. Pumps have been clustered on the basis of specific characteristics of their ‘environment’, including pump age, operating time, pump capacity and degree of pollution of the sewage. The analysis shows that the well known ‘bathtub’ type failure rate curve can describe failures of sewage pumps. The impact of the degree of pollution of the sewage, however, is less clear. Operating time and total pumping capacity show no correlation with failure rate. Consequently, further research using data mining techniques is needed to separate the impact of the different aspects of the environment of a pump.
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De Keyser, W., V. Gevaert, F. Verdonck, et al. "Combining multimedia models with integrated urban water system models for micropollutants." Water Science and Technology 62, no. 7 (2010): 1614–22. http://dx.doi.org/10.2166/wst.2010.475.
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Integrated urban water system (IUWS) modeling aims at assessing the quality of the surface water receiving the urban emissions through sewage treatment plants, combined sewer overflows (CSOs) and stormwater drainage systems. However, some micropollutants tend to appear in more than one environmental medium (air, water, sediment, soil, groundwater, etc.). In this work, a multimedia fate and transport model (MFTM) is “wrapped around” a dynamic IUWS model for organic micropollutants to enable integrated environmental assessment. The combined model was tested on a hypothetical catchment using two scenarios: on the one hand a reference scenario with a combined sewerage system and on the other hand a stormwater infiltration pond scenario, as an example of a sustainable urban drainage system (SUDS). A case for Bis(2-ethylhexyl) phthalate (DEHP) was simulated and resulted in reduced surface water concentrations for the latter scenario. However, the model also showed that this was at the expense of increased fluxes to air, groundwater and infiltration pond soil. The latter effects are generally not included in IUWS models, whereas MTFMs usually do not consider dynamic surface water concentrations,; hence the combined model approach provides a better basis for integrated environmental assessment of micropollutants' fate in urban environments.
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Mouri, Goro, and Taikan Oki. "Modelling sewer sediment deposition, erosion, and transport processes to predict acute influent and reduce combined sewer overflows and CO2 emissions." Water Science and Technology 62, no. 10 (2010): 2346–56. http://dx.doi.org/10.2166/wst.2010.249.
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Understanding of solids deposition, erosion, and transport processes in sewer systems has improved considerably in the past decade. This has provided guidance for controlling sewer solids and associated acute pollutants to protect the environment and improve the operation of wastewater systems. Although measures to decrease combined sewer overflow (CSO) events have reduced the amount of discharged pollution, overflows continue to occur during rainy weather in combined sewer systems. The solution lies in the amount of water allotted to various processes in an effluent treatment system, in impact evaluation of water quality and prediction technology, and in stressing the importance of developing a control technology. Extremely contaminated inflow has been a serious research subject, especially in connection with the influence of rainy weather on nitrogen and organic matter removal efficiency in wastewater treatment plants (WWTP). An intensive investigation of an extremely polluted inflow load to WWTP during rainy weather was conducted in the city of Matsuyama, the region used for the present research on total suspended solid (TSS) concentration. Since the inflow during rainy weather can be as much as 400 times that in dry weather, almost all sewers are unsettled and overflowing when a rain event is more than moderate. Another concern is the energy consumed by wastewater treatment; this problem has become important from the viewpoint of reducing CO2 emissions and overall costs. Therefore, while establishing a prediction technology for the inflow water quality characteristics of a sewage disposal plant is an important priority, the development of a management/control method for an effluent treatment system that minimises energy consumption and CO2 emissions due to water disposal is also a pressing research topic with regards to the quality of treated water. The procedure to improve water quality must make use of not only water quality and biotic criteria, but also modelling systems to enable the user to link the effect of changes in urban sewage systems with specific quality, energy consumption, CO2 emission, and ecological improvements of the receiving water.
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Hall, Ken J., Donald W. McCallum, Kathy Lee, and Ronald Macdonald. "Characterization and aquatic impacts of combined sewer overflows in greater vancouver British Columbia." Water Science and Technology 38, no. 10 (1998): 9–14. http://dx.doi.org/10.2166/wst.1998.0368.
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The Greater Vancouver Regional District has been assessing the environmental concerns and management problems associated with combined sewer overflows (CSOs) as part of their long range liquid waste management plan. There are currently 52 CSO outfalls in the region with some of the major outfalls having 100-150 discharge events/yr concentrated in the winter months. Physical/chemical/microbiological characterization studies of CSO discharge has been investigated at 7 sites. Statistical analysis of these quality data have demonstrated that it can be segregated into three groups based on land use characteristics, namely residential, light industrial, and heavy industrial. These quality characteristics were used along with land use characterization of the 52 collection areas and discharge data to determine the loading of contaminants to the different waterways in the region. The contaminant loading in the region is dominated by the Clark Drive CSO since it contributes 40% of the annual discharge volume to the inner harbor of Burrard Inlet. Contaminant loading calculations from other sources demonstrates that, the sewage treatment plant predominates in the outer harbor, while the CSO and stormwater predominate in the inner and central harbor respectively. At the large Clark Drive outfall, dye tracer and numerical modelling were used to characterize the dispersion plume. Ecological effects of the contaminants were determined using the sediment quality triad. Silver sediment contamination, toxicity bioassays, and benthic invertebrate community structure analysis were useful indicators of the environmental effects of this discharge. Similar studies at the English Bay CSO, which only has 1/90 of the Clark Drive discharge, found sediment contamination levels that exceeded sediment contaminant criteria, but ecological impacts were less severe.
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Locatelli, Luca, Maria Guerrero, Beniamino Russo, Eduardo Martínez-Gomariz, David Sunyer, and Montse Martínez. "Socio-Economic Assessment of Green Infrastructure for Climate Change Adaptation in the Context of Urban Drainage Planning." Sustainability 12, no. 9 (2020): 3792. http://dx.doi.org/10.3390/su12093792.
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Green infrastructure (GI) contributes to improve urban drainage and also has other societal and environmental benefits that grey infrastructure usually does not have. Economic assessment for urban drainage planning and decision making often focuses on flood criteria. This study presents an economic assessment of GI based on a conventional cost-benefit analysis (CBA) that includes several benefits related to urban drainage (floods, combined sewer overflows and waste water treatment), environmental impacts (receiving water bodies) and additional societal and environmental benefits associated with GI (air quality improvements, aesthetic values, etc.). Benefits from flood damage reduction are monetized based on the widely used concept of Expected Annual Damage (EAD) that was calculated using a 1D/2D urban drainage model together with design storms and a damage model based on tailored flood depth–damage curves. Benefits from Combined Sewer Overflows (CSO) damage reduction were monetized using a 1D urban drainage model with continuous rainfall simulations and prices per cubic meter of spilled combined sewage water estimated from literature; other societal benefits were estimated using unit prices also estimated from literature. This economic assessment was applied to two different case studies: the Spanish cities of Barcelona and Badalona. The results are useful for decision making and also underline the relevancy of including not only flood damages in CBA of GI.
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Arnone, Russell D., and Joyce Perdek Walling. "Waterborne pathogens in urban watersheds." Journal of Water and Health 5, no. 1 (2006): 149–62. http://dx.doi.org/10.2166/wh.2006.001.
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A serious concern for managers of water resources, pathogens in the urban environment easily enter waters through a number of pathways, including discharge of inadequately treated sewage, stormwater runoff, combined sewer overflows and sanitary sewer overflows. Pathogens in US ambient water bodies are regulated under the Clean Water Act (CWA), while pathogens in drinking water supplies are regulated under the Safe Drinking Water Act. Total maximum daily loads (TMDLs) are developed in accordance with CWA regulations for ambient water bodies with bacterial concentrations exceeding the water quality standard, which generally is a measure of a bacterial indicator organism. However, developing a TMDL for a supplementary indicator or pathogen is also required if a use impairment would still exist even after the water body is in compliance with the standard. This occurs because indicator organisms do not reflect the presence of pathogen contamination with complete certainty. The evaluation of pathogen indicators and summary of epidemiological studies presented are resources for those developing TMDLs to achieve water quality standards and restore water bodies to their intended uses.
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Green, M. B., J. R. Martin, and P. Griffin. "Treatment of Combined Sewer Overflows at Small Wastewater Treatment Works by Constructed Reed Beds." Water Science and Technology 40, no. 3 (1999): 357–64. http://dx.doi.org/10.2166/wst.1999.0182.
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The performance of constructed reed beds is illustrated by examination of results of surveys from a sewage treatment works with storm treatment reed beds and another site with a combined storm and tertiary treatment reed bed. During surveys of the first system the average hydraulic loads were between 25 and 40 cm d−1 and removals of between 6.7 to 15.4 g m−2 d BOD5, 17.7 to 38.6 g m−2 d TSS, 0.43 to 0.99 g m−2 d NH4N and 0.63 to 0.76 g m−2 d TON were observed. A survey during a storm at the combined storm and tertiary treatment reed bed showed a hydraulic loading of 98 cm d−1 in the first 24 hr and removals of 12.6 g m−2 d BOD5, 29.9 g m−2 d TSS, 0.49 g m−2 d NH4N and a small increase in TON. The sustainability of the high rate of removal during storm events is ascribed to the longer intervals in which loadings are much lower. Samples taken by the regulator from the time of commissioning of 20 sites with combined storm and tertiary treatment reed beds, up to the end of May 1998 are examined. Three of these had operational problems not associated with storm treatment. The aggregate data for the remaining 17 sites (n=906 to 911) illustrate a level of performance matching that of sites with tertiary treatment systems, with averages of 2.2 mg l−1 BOD5, 3.0 mg l−1 TSS, 1.25 mg l−1 NH4N and 12.2 mg l−1 TON.
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Nguyen, An T., Amanda J. Williams-Newkirk, Uriel D. Kitron, and Luis F. Chaves. "Seasonal Weather, Nutrients, and Conspecific Presence Impacts on the Southern House Mosquito Oviposition Dynamics in Combined Sewage Overflows." Journal of Medical Entomology 49, no. 6 (2012): 1328–38. http://dx.doi.org/10.1603/me12090.
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Roldin, Maria, Ole Fryd, Jan Jeppesen, et al. "Modelling the impact of soakaway retrofits on combined sewage overflows in a 3km2 urban catchment in Copenhagen, Denmark." Journal of Hydrology 452-453 (July 2012): 64–75. http://dx.doi.org/10.1016/j.jhydrol.2012.05.027.
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O'Keefe, B., B. J. D'Arcy, J. Davidson, B. Barbarito, and B. Clelland. "Urban diffuse sources of faecal indicators." Water Science and Technology 51, no. 3-4 (2005): 183–90. http://dx.doi.org/10.2166/wst.2005.0590.
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Increasing concern about bathing water quality in Scotland has led to renewed interest in diffuse sources, as well as the already closely monitored municipal sewage effluents and combined sewer overflows (CSOs) that have been the subject of multi-million pound capital expenditure schemes for several years. Early investigations of diffuse sources focused on rural land uses. This paper is an initial effort to consider the possible significance of urban diffuse sources. A review of the potential for diffuse urban sources includes consideration of sewage pollution in surface water sewers, as well as non-human sources such as pigeon and other bird roosts, and faecal material from pets such as dogs and cats. Portobello beach in Edinburgh is the case study selected, because of earlier work done by Scottish Water and SEPA. The Figgate Burn crosses Edinburgh to discharge onto the beach at Portabello, and pollution sources in its catchment are described. Additional information is reported from Dunfermline, where the sewer network has provided examples of three ways in which sewage pollution can occur in urban streams, and also Scottish examples of measures to control some non-human sources (e.g. SUDS).
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Balasa, Gabriella, Enjolie S. Levengood, Joseph M. Battistelli, and Rima B. Franklin. "Diversity of Multidrug-Resistant Bacteria in an Urbanized River: A Case Study of the Potential Risks from Combined Sewage Overflows." Water 13, no. 15 (2021): 2122. http://dx.doi.org/10.3390/w13152122.
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Wastewater contamination and urbanization contribute to the spread of antibiotic resistance in aquatic environments. This is a particular concern in areas receiving chronic pollution of untreated waste via combined sewer overflow (CSO) events. The goal of this study was to expand knowledge of CSO impacts, with a specific focus on multidrug resistance. We sampled a CSO-impacted segment of the James River (Virginia, USA) during both clear weather and an active overflow event and compared it to an unimpacted upstream site. Bacteria resistant to ampicillin, streptomycin, and tetracycline were isolated from all samples. Ampicillin resistance was particularly abundant, especially during the CSO event, so these isolates were studied further using disk susceptibility tests to assess multidrug resistance. During a CSO overflow event, 82% of these isolates were resistant to five or more antibiotics, and 44% were resistant to seven or more. The latter statistic contrasts starkly with the upstream reference site, where only 4% of isolates displayed resistance to more than seven antibiotics. DNA sequencing (16S rRNA gene) revealed that ~35% of our isolates were opportunistic pathogens, comprised primarily of the genera Stenotrophomonas, Pseudomonas, and Chryseobacterium. Together, these results demonstrate that CSOs can be a significant source of viable clinically-relevant bacteria to the natural environment and that multidrug resistance is an important understudied component of the environmental spread of antibiotic resistance.
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Khelil, Amar, and Stefan Schneider. "Development of a Control Strategy to Reduce Combined Sewerage Overflows: The Case of Bremen – Left of the Weser." Water Science and Technology 24, no. 6 (1991): 201–8. http://dx.doi.org/10.2166/wst.1991.0158.
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In recent years, the population and authorities in West Germany have become very concerned with water pollution. In this respect, combined sewage discharges have been pointed out as a major source. Various measures can be considered, which can be ordered into three categories: a redefinition of the objectives of the Urban Drainage System (UDS), the reshaping of the UDS (e.g. extension of the storage capacity) or the modification of its operation. Among the latter measures, Real-Time Control (RTC) constitutes the main option. It aims at a better exploitation of the existing storage potential. As the city of Bremen (Germany) decided, several years ago, to renew the on-line survey and monitoring system of its UDS, the determination of on-line strategies to operate the pumps came to the fore. Methods and tools to investigate the possibility to reduce the pollution loads through improved control strategies have been developed. Some results are presented.
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Crabtree, B., W. Earp, and P. Whalley. "A demonstration of the benefits of integrated wastewater planning for controlling transient pollution." Water Science and Technology 33, no. 2 (1996): 209–18. http://dx.doi.org/10.2166/wst.1996.0050.
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The Urban Pollution Management (UPM) Research Programme has been the UK Water Industry's response to the need to limit the risk of transient pollution of receiving waters resulting from intermittent discharges, such as combined sewer overflows. Demonstrating that the UPM tools, such as MOSQITO, STOAT and MIKE 11, can be used to produce cost-effective and reliable solutions to practical problems is considered to be a major element in promoting the benefits of the UPM Procedure approach by eliminating the uncertainty of water quality impact associated with more traditional approaches. A demonstration of the full UPM Procedure for inland situations has been carried out in the city of Derby, in the UK, where high levels of investment are planned for both sewerage and sewage treatment. Detailed simulation models were calibrated and verified and then used with the simplified pollution modelling tool, SIMPOL, to evaluate the integrated environmental impact of a possible sewerage upgrading option. The results indicated that this option would meet wet-weather water quality requirements at a reduced cost compared to alternatives derived from traditional planning procedures which had a high degree of uncertainty in meeting water quality objectives.
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Masseroni, Daniele, Giulia Ercolani, Enrico Antonio Chiaradia, et al. "Exploring the performances of a new integrated approach of grey, green and blue infrastructures for combined sewer overflows remediation in high-density urban areas." Journal of Agricultural Engineering 49, no. 4 (2018): 233–41. http://dx.doi.org/10.4081/jae.2018.873.
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Most sewage collection systems designed between 19th and early to mid-20th century use single-pipe systems that collect both sewage and urban runoff from streets, roofs and other impervious surfaces. This type of collection system is referred to as a combined sewer system. During storms, the flow capacity of the sewers may be exceeded and the overflow discharged into a receiving water body (RWB) through spillways without any control and remediation. Combined sewer overflows (CSOs) may, therefore, produce serious water pollution and flooding problems in downstream RWBs. Methodologies for a rational management of CSOs quantity and quality share many commonalities, and these two aspects should be considered together in order to maximize benefits and promote local distributed actions, especially in high urban density areas where the space availability for the construction of CSO storage tanks is often a limiting factor. In this paper, a novel strategy to control downstream flow propagation of a CSO as well as to improve its quality is tested on a real case study in the area of the metropolitan city of Milan. The approach is based on the combination of grey, green and blue infrastructures and exploits the integrated storage and self-depuration capacities of a firstflush tank, a constructed wetland and a natural stream to obtain admissible flow rates and adequate water quality in the RWB. The results, evaluated through a modelling framework based on simplified equations of water and pollutants dynamics, show excellent performances for the integrated system, both in terms of flow control and pollution mitigation. The pollution, using biological oxygen demand concentration as a proxy of the whole load, was decreased by more than 90% and downstream flooding situations were avoided, despite the spillway was not regulated. Concerning the economic point of view, from a rough estimate of the costs, the system allows reducing the investment of 30 to 50% in respect to the traditional CSO controls based solely on flow detention tanks. The proposed approach, as well as the modelling framework for its effective implementation, appear strongly scalable in different world contexts and aim to fill the gap between urban and rural environments in the management of stormwater and CSOs, promoting the involvement of the water managers, the irrigation-reclamation agencies and regional authorities.
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Reda, A. L. L., and M. B. Beck. "Simulation model for real-time decision support in controlling the impacts of storm sewage discharges." Water Science and Technology 39, no. 9 (1999): 225–33. http://dx.doi.org/10.2166/wst.1999.0483.
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The impacts of combined sewage discharges on river water quality are studied using the MCSTR (Multiple Continuously Stirred Tank Reactor) dynamic model. The potential for applying this model in a real-time context is demonstrated as a tool to support decisions regarding treatment plant operating during storm events, when it is often not possible to sustain full treatment of the incoming sewage flow. Discharges to the River Cam of treated and untreated urban wastewaters from Cambridge and the Cambridge Sewage Works are addressed as a hypothetical case study. Alternative treatment strategies are defined for improving receiving water quality and assessed through simulated water quality downstream of the discharge; the state variables of the model include the concentrations of biochemical oxygen demand, ammoniacal- and nitrate-nitrogen, and dissolved oxygen (chlorophyll-a concentrations are also calculated, but not considered herein). Strategies are assessed and ranked according to the reduction in maximum pollutant concentration (or the increase in minimum concentration, in the case of dissolved oxygen) promoted by each alternative, relative to conventional operation. The consequences of discharging overflows at an alternative position in the river, rather than together with the treatment-plant effluent, are also evaluated. Run times fr the MCSTR model are of the order of just a few minutes (at most), thus allowing the potential for its use in real time as a decision-support aid.
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Parente, Mario, and Kenneth E. Stevens. "Evaluation of a Combined Sewer Overflow Tank Cleaning System in the City of Sarnia." Water Quality Research Journal 32, no. 1 (1997): 215–26. http://dx.doi.org/10.2166/wqrj.1997.014.
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Abstract The International Joint Commission has identified the St. Clair River in Sarnia as an area of concern requiring a remedial action plan in order to restore and protect the water quality. To attain this objective, the City of Sarnia has completed a Pollution Control Plan in March 1993 to develop the approach in resolving the pollution problems along the City of Sarnia waterfront and the St. Clair River. The Pollution Control Plan identified the following three areas for improvement: (1) upgrade the water pollution control plant to provide secondary treatment for three times the average dry weather flow; (2) install four tanks to intercept combined sewer overflows; and (3) intercept storm runoff discharges along the waterfront and provide their treatment through sedimentation and/or flow through a wetland. The City of Sarnia is presently installing the first of the CSO control tanks at Devine Street. During the operation of combined sewage or stormwater detention facilities, settling of solids will occur along the invert of the facility. These sediments have to be removed after every storage event to minimize future problems such as caking and/or odour. This paper presents the evaluation and selection process carried out in developing a cost effective cleaning system for the Devine Street detention tank.
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Sakson, Grażyna, Marek Zawilski, and Agnieszka Brzezińska. "Analysis of Combined Sewer Flow Storage Scenarios Prior to Wastewater Treatment Plant." Ecological Chemistry and Engineering S 25, no. 4 (2018): 619–30. http://dx.doi.org/10.1515/eces-2018-0041.
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Abstract Combined sewer systems in cities are increasingly equipped with additional storage facilities or other installations necessary for keeping the wastewater treatment plants from overloading during wet weather and reducing combined sewer overflows into receiving waters. Effective methods for reducing such negative phenomena include the temporary storage of wet weather flow in an end-of-pipe separate tank or in a sewer system. In this paper, four scenarios of wastewater storage for the Group Wastewater Treatment Plant (GWWTP) in Lodz (Poland) have been analysed: a storage in a separate single tank located in GWWTP, a storage in the bypass channel in GWWTP, in-sewer storage, and a combination of the aforementioned variants, also with real time control (RTC) system introduced. The basic calculations were performed using the EPA’s SWMM software for the period of 5 years (2004-2008). The chosen solution - storage in a separate storage tank - has been verified based on the inflow dataset from the years 2009-2013. The specific volume of the separate storage tank should be at least 22 m3 per hectare of impervious catchment area, but it could be reduced if additional in-sewer storage with RTC were introduced. Both options allow the effective protection of receiving waters against discharge of untreated sewage during wet weather.
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Weiß, Gebhard J., and Steven Michelbach. "Vortex separator: dimensionless properties and calculation of annual separation efficiencies." Water Science and Technology 33, no. 9 (1996): 277–84. http://dx.doi.org/10.2166/wst.1996.0229.
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Vortex separators as new devices for combined sewer overflows (CSOs) claim good efficiencies which can be confirmed by laboratory tests. Such model tests are usually performed in reduced scale and under steady-flow conditions. This paper describes a possible way to transfer model test results to the prototype scale. As a first step, the most essential parameters must be accounted for using a proper dimensional analysis which also considers scale effects. It will result in dimensionless efficiency curves which allow prediction of prototype efficiencies, yet valid for steady flow only. To take into account the variability of annual inflow as well as dynamic effects like filling and emptying of a particular separator, the efficiency characteristics of the separator are combined with a quantity-quality simulation model. Such a numerical model is able to compute inflow and outflow hydrographs and pollutographs and to account for the catchment data at the given site. It allows the computation of annual pollutant loads as well as of the percentage of sewage sediment fed to the treatment plant, i.e. an annual separation efficiency.