Dispersion of Hydrogen Sulfide from Wastewater Lagoons at a Kraft Pulp Mill, Missoula, Montana: Including the 2000 Wildfire Season, 2003 Environmental Conference Proceedings

Wastewater from Smurfit-Stone Container’s Missoula mill is retained in an 800-acre landscape of ponds for treatment and subsequent release during spring runoff conditions. Anaerobic respiration by pond microbes leads to the emission of H2S. The mill’s operating permit limits H2S emissions to 50 ppb on a continuous monitoring basis (1-hour averaging period). During the summer of 2000, a bloom of sulfurreducing bacteria gave rise to increased H2S emissions from the wastewater ponds. Normal circulation of air in the Missoula Valley would typically have been able to disperse the H2S below the aesthetic permit limit. Smoke from wildland fires, however, created summertime inversions that prevented effective attenuation of H2S emissions. Hourly averages of H2S exceeded 50 ppb for a total of 158 times. Time/date charted data are presented to demonstrate typical H2S dispersion, and the stagnant H2S emissions seen in the summer of 2000. PM-10 data (measured simultaneously at a site 15 km SE) are also presented to illustrate the extent of the inversions.