A study on vortex separator technology to control combined sewer overflow

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.

A study on vortex separator technology to control combined sewer overflow

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.

Performance evaluation of Hydrodynamic Vortex Separator at different hydraulic retention times applied in Recirculating Biofloc Technology system

Recirculating biofloc technology (RBFT) has been gradually acknowledged for its positive effect on the control of biofloc concentration using a hydrodynamic vortex separator (HDVS). To operate an RBFT system at maximum performance, the removal efficiency of an HDVS at different hydraulic retention times (HRTs) must be fully predictable. Hence, a numerical study of the fluid flow and particle dynamics was performed to characterize the performance of an HDVS at varying HRTs. First, flow simulation was conducted to determine an economical mesh size at an HRT of 248 s. Then, with respect to the total suspended solids (TSS) in the RBFT system and the physical properties of the flocs, two-way coupling of the dense discrete phase model (DDPM) and discrete element model (DEM) methods was used to predict floc tracking in an HDVS. Additionally, the Reynolds averaged Navier-Stokes (RANS) equations with the Reynolds stress turbulence model (RSM) were solved using the finite volume method based on the semi-implicit method pressure-linked equations (SIMPLE) pressure correction algorithm in the computational domain. Finally, pilot-scale studies were conducted to verify the simulation models. Based on the simulation results, floc management in an RBFT system is briefly discussed. Due to limited research on the numerical simulation and operating conditions of an HDVS in an RBFT system, this article describes an original investigation of the modeling approach. Keywords: Computational fluid dynamics, Dense discrete phase model, Discrete element model, Floc management, Flow field, Removal efficiency, Total suspend solids.