Sources and Fate of TRS Compounds in a Pulp Mill ASB

Abstract

The source and treatability of TRS emissions at a mill in the Southeastern USA was studied in connection with potential capital upgrades in response to recently promulgated regulations. The front-end of the lagoon is anoxic, and is associated with odor, which drops markedly beyond the onset of the aerated zone. Laboratory work with wastewater from two mills showed that the rate of H2S degradation corresponded to that of oxygen consumption, confirming that the two processes were related. The rates were biphasic; the initial decrease was rapid, and then a slower process took over. The rate of the slower process equaled the degradation rate of H2S in distilled water, suggesting that it originated from the uncatalyzed oxidation of H2S. Hence, H2S oxidation appears to be initially catalyzed by a wastewater component that is inactivated before the process goes to completion. Subsequent degradation of H2S then occurs through the uncatalyzed step. Wastewater taken from the lagoon showed the presence of the transition metals necessary for sulfide catalysis. A dissolved oxygen level of 1 ppm was sufficient to suppress H2S generation.