Characterization of Natural Ventilation in Wastewater Collection Systems

Abstract

The purpose of the study was to characterize natural ventilation in full-scale gravity collection system components while measuring other parameters related to ventilation. Experiments were completed at four different locations in the wastewater collection systems of Los Angeles County Sanitation Districts, Los Angeles, California, and the King County Wastewater Treatment District, Seattle, Washington. The subject components were concrete gravity pipes ranging in diameter from 0.8 to 2.4 m (33 to 96 in.). Air velocity was measured in each pipe using a carbon-monoxide pulse tracer method. Air velocity was measured entering or exiting the components at vents using a standpipe 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. Measured ventilation rates ranged from 23 to 840 L/s. The experimental data was used to evaluate existing ventilation models. Three models that were based upon empirical extrapolation, computational fluid dynamics, and thermodynamics, respectively, were evaluated based on predictive accuracy compared to the measured data. Strengths and weaknesses in each model were found and these observations were used to propose a concept for an improved ventilation model. Water Environ. Res., 83, 265 (2011).

The Ecology of Acidophilic Microorganisms in the Corroding Concrete Sewer Environment

“…The sewer RH typically ranges between 60 and 100% (Ward et al, 2011; Wells et al, 2012). In addition, the tidal regions in sewer walls are frequently wetted by wastewater flooding, which will increase the water content of the concrete in those regions.…”

Municipal sewer networks as sources of nitrous oxide, methane and hydrogen sulphide emissions: A review and case studies

“…(Supporting information 1) For a more detailed description of 57 the sewer elements and biological processes leading to emissions, 58 we recommend [9,11,12]. 59 Emissions of CH 4 and H 2 S from sewers have received a lot more 60 attention than N 2 O and CO 2 given their safety, toxicity, and 61 corrosion issues [13][14][15][16][17][18][19]. According to the IPCC, CH 4 has a Global 62 Warming Potential (GWP) 25 times higher than CO 2 in a 100-year 63 time horizon [20].…”

Use of Flow Regulation in Manhole Odor Control Devices to Reduce Maintenance and Frequency of Media Replacement

“…To further clarify performance characteristics and better understand appropriate system design criteria, data on flow rates of gases vented from manholes and other potential influential constituents should be collected. In a study by Ward et al (2011), data on lateral and vented gas flow rates within sanitary sewer collection systems indicated that the flow rates were variable and bi-directional.…”

“…Previous attempts using such an approach have been marred by the short service life of the installed adsorptive filter media, which quickly reaches its capacity to retain hydrogen sulfide (H 2 S) and other odorous constituents. Gas flow rates within in the headspace of collection systems can be significant while the vented flow rates are orders of magnitude lower (Ward et al, 2011).…”