Effect of Pump Operation on Headspace Air Pressure Variation in Sanitary Sewer Systems

Modeling air flow movement in the headspace of sanitary sewers is important for municipalities for sewer corrosion control and odor mitigation. This paper presents the results of field-measured air pressure and H2S variations affected by the operation of pump stations in a prototype sanitary sewer system. A total of five locations near four pump stations were monitored along a 5-km trunk sewer. It was found that the air pressure in the vicinity of the pump stations showed an oscillation pattern in response to the pumping cycles. This is mainly due to the change in the headspace air volume resulting in air pressure fluctuations. A simple model is proposed to estimate the magnitude of the pressure fluctuation. Pump operations also have a direct impact on the H2S level downstream of the discharge manhole with relatively long forcemains.