Is combined sewer overflow spill frequency/volume a good indicator of receiving water quality impact?

Combined sewer overflow (CSO) water introduces pathogens to receiving waters. To control pathogenic releases, chlorine may be added to disinfect CSO water. The added chlorine may react with water constituents to form oxidative species known as chlorine-produced oxidants (CPO). CPO are the sum of free and combined oxidative species that form upon adding free chlorine-bearing compounds (e.g. gaseous chlorine or hypochlorite) to water. CPO discharge is often regulated by governing agencies. Current methods to model CPO behavior do not account for CPO decay and dilution simultaneously in receiving water. This study creates a novel model for CPO demand and dilution in receiving water from chlorinated effluent in order to determine site-specific practices for implementation of a CSO water disinfection regime. To do this, representative receiving water was collected and dosed with 1, 2, and 4 mg/L chlorine. The residual chlorine was measured at intervals up to 30 min after dosing. The immediate and subsequent chlorine demand was calculated, with the subsequent demand modeled by simultaneous application of dilution and decay using pseudo-first-order decay kinetics. A comparison of model calculations indicates that application of dilution before decay underestimates CPO demand, while application of decay before dilution overestimates CPO demand.

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A study on vortex separator technology to control combined sewer overflow

10.32920/ryerson.14661471 ◽

2021 ◽

Author(s):

Nawshin Rummnan

Keyword(s):

Pilot Project ◽

Rain Event ◽

Combined Sewer Overflow ◽

Niagara Falls ◽

Combined Sewer ◽

Receiving Waters ◽

Vortex Separator ◽

Sewer Overflow ◽

Receiving Water

A combined-sewer overflow (CSO) is a significant contributor of contamination to surface waters. During a rain event, the flow in a combined sewer system (CSS) may exceed the capacity of the intercepting sewer leading to a wastewater treatment plant, thus releasing a mixture of storm water and raw sanitary wastewater into the receiving water. As CSOs contain untreated domestic, commercial, and industrial wastes, as well as surface runoff, many different types of contaminants can be present. Because of these contaminants and the volume of the flows, CSOs can cause a variety of adverse impacts on the physical characteristics of surface water, impair the viability of aquatic habitats, and pose a potential threat to drinking water supplies. The resulting short-term problems are poor aesthetics (floatables, turbidity, oil and grease), and beach closure due to increased harmful bacteria levels. The long term impacts include reduced dissolved oxygen in receiving waters, eutrophication and sediment contamination. Since CSO is considered to be a major source of water quality impairment for the receiving waters, much attention has been directed to reducing the quantity and quality of CSO discharged to meet the Ministry of Environment guidelines. There are several approaches to control the quantity and quality of CSO. The selection of a particular treatment technology depends on various factors such as site conditions, CSO characteristics, receiving water requirements. One of the emerging options is the vortex separator technology for High Rate Treatment (HRT) facilities at overflow location. There are many devices for CSO control in different trade names where vortex separator technology has been used (e.g. EPA Swirl Concentration, FluidSep(TM), Storm King(TM), CDS®). This study articulates the different CSO control technologies with emphasized [sic] on vortex separator technology. The City of Niagara Falls HRT pilot project for CSO control to the Niagara River is presented as a case study in this report. The performance of two HRT devices - Storm King(TM) and CDS® are evaluated in the pilot project. Analytical Probabilistic Model has been used a a tool in this study to evaluate the potential pollution reduction at the Niagara Falls CSO system.

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A study on vortex separator technology to control combined sewer overflow

10.32920/ryerson.14661471.v1 ◽

2021 ◽

Author(s):

Nawshin Rummnan

Keyword(s):

Pilot Project ◽

Rain Event ◽

Combined Sewer Overflow ◽

Niagara Falls ◽

Combined Sewer ◽

Receiving Waters ◽

Vortex Separator ◽

Sewer Overflow ◽

Receiving Water

A combined-sewer overflow (CSO) is a significant contributor of contamination to surface waters. During a rain event, the flow in a combined sewer system (CSS) may exceed the capacity of the intercepting sewer leading to a wastewater treatment plant, thus releasing a mixture of storm water and raw sanitary wastewater into the receiving water. As CSOs contain untreated domestic, commercial, and industrial wastes, as well as surface runoff, many different types of contaminants can be present. Because of these contaminants and the volume of the flows, CSOs can cause a variety of adverse impacts on the physical characteristics of surface water, impair the viability of aquatic habitats, and pose a potential threat to drinking water supplies. The resulting short-term problems are poor aesthetics (floatables, turbidity, oil and grease), and beach closure due to increased harmful bacteria levels. The long term impacts include reduced dissolved oxygen in receiving waters, eutrophication and sediment contamination. Since CSO is considered to be a major source of water quality impairment for the receiving waters, much attention has been directed to reducing the quantity and quality of CSO discharged to meet the Ministry of Environment guidelines. There are several approaches to control the quantity and quality of CSO. The selection of a particular treatment technology depends on various factors such as site conditions, CSO characteristics, receiving water requirements. One of the emerging options is the vortex separator technology for High Rate Treatment (HRT) facilities at overflow location. There are many devices for CSO control in different trade names where vortex separator technology has been used (e.g. EPA Swirl Concentration, FluidSep(TM), Storm King(TM), CDS®). This study articulates the different CSO control technologies with emphasized [sic] on vortex separator technology. The City of Niagara Falls HRT pilot project for CSO control to the Niagara River is presented as a case study in this report. The performance of two HRT devices - Storm King(TM) and CDS® are evaluated in the pilot project. Analytical Probabilistic Model has been used a a tool in this study to evaluate the potential pollution reduction at the Niagara Falls CSO system.

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Impact of an intense combined sewer overflow event on the microbiological water quality of the Seine River

Water Research ◽

10.1016/j.watres.2010.09.024 ◽

2011 ◽

Vol 45 (2) ◽

pp. 893-903 ◽

Cited By ~ 128

Author(s):

Julien Passerat ◽

Nouho Koffi Ouattara ◽

Jean-Marie Mouchel ◽

Vincent Rocher ◽

Pierre Servais

Keyword(s):

Water Quality ◽

Combined Sewer Overflow ◽

Seine River ◽

Combined Sewer ◽

Microbiological Water Quality ◽

Sewer Overflow

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Effectiveness of combined sewer overflow treatment for dissolved oxygen improvement in the Chicago Waterways

Water Science & Technology ◽

10.2166/wst.2007.455 ◽

2007 ◽

Vol 56 (1) ◽

pp. 215-222 ◽

Cited By ~ 11

Author(s):

E. Alp ◽

C.S. Melching ◽

H. Zhang ◽

R. Lanyon

Keyword(s):

Water Quality ◽

Dissolved Oxygen ◽

Pollutant Removal ◽

Combined Sewer Overflow ◽

Pumping Stations ◽

Short Period ◽

Combined Sewer ◽

High Pollution ◽

Wet Weather ◽

Sewer Overflow

An Use Attainability Analysis (UAA) has been initiated to evaluate what water-quality standards can be achieved in the Chicago Waterway System (CWS). There are nearly 200 combined sewer overflow (CSO) locations discharging to the CWS by gravity. Three CSO pumping stations also drain approximately 140 km2. Because of the dynamic nature of the CWS the DUFLOW model that is capable of simulating hydraulics and water-quality processes under unsteady-flow conditions was used to evaluate the effectiveness of water-quality improvement techniques identified by the UAA including CSO treatment. Several CSO treatment levels were applied at gravity flow CSOs to evaluate improvement in dissolved oxygen (DO). The results show that pollutant removal at CSOs improves DO to a certain degree, but it still was not sufficient to bring DO concentrations to 5 mg/L or higher for 90% of the time during wet weather at most locations on the CWS. Flow from the pumping stations results in substantial stress on DO since a huge amount of un-treated water with a high pollution load is discharged into the CWS in a short period of time at a certain location. The simulation results indicate that CSO treatment does not effectively improve DO during wet-weather periods on the CWS.

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