Characterization of Natural Ventilation in Municipal Wastewater Collection Systems

This paper presents findings of the WERF Collection System Ventilation Research project. The purpose of the study was to measure air ventilation within full-scale gravity collection system components and simultaneously measure parameters related to ventilation. Experiments were completed at four different locations within the Los Angeles and King County wastewater collection systems. Subject components were concrete gravity pipes ranging in diameter from 33 to 96 inches. Air velocity was measured within each pipe using a carbon monoxide pulse tracer method. Air velocity was measured entering or exiting the components at vents using a stand pipe and hotwire anemometer arrangement. Ambient wind speed, temperature, and relative humidity; headspace temperature and relative humidity; and wastewater flow and temperature were measured. The field experiments resulted in a large database of measured ventilation and related parameters characterizing ventilation in full-scale gravity sewers. Ultimately, the results will be used to develop an advanced ventilation model.