A dynamic ventilation model for gravity sewer networks

Abstract

To implement any effective odour and corrosion control technology in the sewer network, it is imperative that the airflow through gravity sewer airspaces be quantified. This paper presents a full dynamic airflow model for gravity sewer systems. The model, which is developed using the finite element method, is a compressible air transport model. The model has been applied to the North Head Sewerage Ocean Outfall System (NSOOS) and calibrated using the air pressure and airflow data collected during October 2008. Although the calibration is focused on forced ventilation, the model can be applied to natural ventilation as well.

Airflow in Gravity Sewers – Determination of Wastewater Drag Coefficient

“…This is a substantial simplification of the reality, and the models have poor accuracy when applied to real sewer systems (Ward et al, 2011), in which the airflow can also have a significant variation in time during presumably equal conditions (Madsen et al, 2006). To overcome this, a force balance model formulation integrated with a hydraulic model of the wastewater flow has been proposed by Wang et al (2012). They presented a fully dynamic ventilation model for a forced ventilated sewer system, which included in-and outflow across manholes and vent inducts.…”

“…where W is the width of the air-water interface, U w is the mean water velocity and f D and f C is a drag and friction coefficient, respectively, of which both was assigned a constant value (Wang et al, 2012). Their model was able to fit measurements in a convincing way, and the model formulation can, in principle, be applied to natural ventilation as well (Wang et al, 2012).…”

Corrosion and odor management in sewer systems

“…Dynamic ventilation models have been developed and evaluated to predict airflow in gravity sewers under natural or forced ventilation conditions [60,61]. These models, though based upon fundamentals, are empirical in nature as a number of factors affecting the airflow are lumped together as the coefficients in the model.…”

“…These models, though based upon fundamentals, are empirical in nature as a number of factors affecting the airflow are lumped together as the coefficients in the model. Moreover, the model requires solving complex partial differential equations for the prediction of the dynamics of airflow [60]. Integration of such a model with a sewer model therefore poses significant challenges.…”

Modeling Odors and Hydrogen Sulfide in the Sewers of San Francisco

“…The resulting gas flow velocity is found assuming stationary and uniform gas flow conditions in a pipe and hence balancing the drag imparted by the flowing water and the friction at the pipe wall. The concept is based on work done by Ward et al (2011) and Wang et al (2012), and the detailed approach for determining drag and friction is given by Bentzen et al (2014). The network is simulated open to the urban atmosphere at nodes.…”