a novel model for sewer ventilation

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A NOVEL MODEL FOR SEWER VENTILATION EMIL DIETZ FUGLSANG DEPARTMENT OF CIVIL ENGINEERING AALBORG UNIVERSITY, DENMARK

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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 Presentation

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Page 1: A  Novel  model for  sewer  ventilation

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

Page 2: A  Novel  model for  sewer  ventilation

Motivation – why are we interested in sewer ventilation?

Broken covers leed to discharge of air Corrosion of concrete and metal

Page 3: A  Novel  model for  sewer  ventilation

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

Page 4: A  Novel  model for  sewer  ventilation

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

Page 5: A  Novel  model for  sewer  ventilation

Methodology – in the field

• Length profile CO2 + pH

Inspected the sewer for openings to the atmosphere

Page 6: A  Novel  model for  sewer  ventilation

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

Page 7: A  Novel  model for  sewer  ventilation

Results two hours in the upstream and downstream pointMeasured Simulated

Page 8: A  Novel  model for  sewer  ventilation

Length profile of CO2

• Large effect of pump starts at the top of the system

• Continuing release further downstream

Page 9: A  Novel  model for  sewer  ventilation

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

Page 10: A  Novel  model for  sewer  ventilation

QUESTIONS?