a novel model for sewer ventilation
DESCRIPTION
A Novel model for sewer ventilation. Emil Dietz Fuglsang Department of civil engineering Aalborg university , denmark. Motivation – why are we interested in sewer ventilation?. Broken covers leed to discharge of air. Corrosion of concrete and metal. - PowerPoint PPT PresentationTRANSCRIPT
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A NOVEL MODEL FOR SEWER VENTILATION
E M I L D I E T Z F U G L S A N GD E PA R T M E N T O F C I V I L E N G I N E E R I N G
A A L B O R G U N I V E R S I T Y, D E N M A R K
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Motivation – why are we interested in sewer ventilation?
Broken covers leed to discharge of air Corrosion of concrete and metal
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Methodology - how to use CO2 as a natural tracer
Wastewater is always super saturated with CO2
For example at pH 7.5 water in equilibrium with atmospheric CO2: • 0.2 mM CO2 -equivalents in the wastewater
BUT:
• Biological processes in wastewater produce 0.5-1mM CO2 –eq. per hour• Furthermore, potable water is often CO2 -super saturated
Wastewater is always super saturated with CO2
𝐶𝑂𝐷+𝑂2→𝐶𝑂2
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Sewer ventilation CO2 is continuously released from the water to the sewer gas and diluted by
the sewer ventilationAlternating water levels can furthermore cause in- and outflow of sewer gasBalancing production and release allows determination of ventilation
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Methodology – in the field
• Length profile CO2 + pH
Inspected the sewer for openings to the atmosphere
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Methods – computer simulations
• Full dynamic transient hydraulic model• Upper boundary conditions: intermittent operated pump station• Resulting in rapid water level changes in the pipe…
• WATS sewer process model• Full dynamic simulation of chemical and biological transformations
• Quasi stationary friction-drag gas flow model
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Results two hours in the upstream and downstream pointMeasured Simulated
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Length profile of CO2
• Large effect of pump starts at the top of the system
• Continuing release further downstream
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Conclusions
Combining CO2 as a natural tracer and an in-sewer process model it is possible to predict levels and dynamics of ventilation in an intercepting sewer
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QUESTIONS?