Combined sewer overflow chamber analysis based on CFD modelling.

The paper deals with CFD simulation of a real combined sewer overflow chamber using Ansys fluent software. Simulations are created for various structural modifications. Within the results, the hydraulic parameters of the individual are evaluated with a proposal for optimal operation of the given relief chamber.

Alternatives how to mitigate urban flooding and CSO in urbanized areas used in European cities and towns

Urban flooding and combined sewer overflow in city, or town areas represents potential risk in environmental, economic, or social aspects. The goal of this study is to process and evaluate efficiency of individual solutions to reduce occurrence of flooding in urban areas caused by intense rainfall events. The known conventional solutions are stormwater chambers, or storage drains. The new trend in reduction of stormwater drainage into combined sewer system are parts of blue-green infrastructure. Blue-green infrastructure represents environmental urban infrastructure which consists of sensitively selected urban vegetation combined with ingenious hydrological elements of urban city drainage. The study also deals with experimental usage of decentralized real time control, based on a gossip-based algorithm of moveable gates in sewage network. Experiment was proposed for drainage system of the city of Cosenza in Italy. Evaluation will assess application value of individual proposed solutions for the reduction of combined sewer overflow for Slovak republic and its urban cities, or towns.

Citizens' Perception of Combined Sewer Overflow Spills into Bathing Coastal Areas

Once a wastewater treatment plant (WWTP) exceeds its capacity, it is necessary to discharge a proportion of the flow to watercourses through combined sewer overflow (CSO) structures. In coastal urban areas, CSO spills may occur in seawaters. The present study analyses the effects of these spills into urban coastal bathing areas, through a qualitative survey-based analysis in Badalona and Barcelona, focusing on stakeholders' reputation and image involved in the sewer system and beaches management (i.e. intangible damages) and the consequences for the economy (i.e. tangible damages). The direct relation between CSO spills and impacts on restaurants’ revenues is not observed since business owners in Badalona and Barcelona do not perceive any economic impact due to these events. Their main concern is the municipality’s image, which might affect the citizens’ view of the management of the responsible agents and indirectly, the tourist sector, especially in Barcelona. Residents perception in this matter is remarkably different in both cities. In Badalona, residents know the problem and even the body responsible for setting the red flag and the beaches closure (i.e. the municipality). In Barcelona, though, residents are quite confused about this. The complexity in terms of competencies in sewer systems management requires a better communication campaign for the citizens to avoid misunderstandings and unnecessary loss of trust in the City Council. Decision-makers and stakeholders should be interested in understanding the perception of affected users upon these events to take appropriate measures to enhance awareness programs or measures to reduce overflows.

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.