AROMATIC VOC EMISSIONS FROM A MUNICIPAL SEWER INTERCEPTOR

Municipal and industrial sewers have come under increased regulatory s crutiny as sources of volatile organic compound (VOC) emissions to the ambient atmosphere. A well-ventilated municipal sewer interceptor tha t receives significant quantities of VOC-laden industrial wastewater w as studied to quantify VOC emissions. Headspace outgassing rates acros s four manhole covers were as high as 2300 m(3)/h. Emissions were grea test for toluene, approaching 100 g/h from a single manhole cover at t he mid-point of the 24-hour event. Significant diurnal and weekday/wee kend trends were observed. Emissions from a single manhole cover rival ed or exceeded those summed over aerated grit chambers and aeration ba sins at four large municipal wastewater treatment facilities in Southe rn Ontario, The primary source of VOC stripping was observed to be a s eries of large drop structures, with aromatic VOC stripping efficienci es ranging from 25 to 38% across two drops. Finally, an existing model that predicts VOC emissions from sewers was observed to reasonably pr edict measured stripping efficiencies. An important conclusion of this study is that large fractions of VOCs may be removed from wastewater and emitted to the ambient atmosphere prior to entering a downstream t reatment facility.