PrOlor: a Modelling Approach for Environmental Odor

Odor episodes control due to low threshold perception odorants, as H2S, is extremely difficult, as they are detected in very low concentrations. Even low odorants emissions without any health effects can derive in odor episodes, highly dependent on the changeable meteorology. PrOlor system is an environmental odor forecast system based in WRF/CALMET/CALPUFF models. WRF model settings includes four one-way nested grids, with 1x1 km(2) horizontal resolution for the innermost grid, and initial and boundary conditions from GFS model forecast. CALMET horizontal resolution is 250x250 m(2) to provide meteorological input to CALPUFF dispersion model. CALPUFF odorants dispersion modelling includes not only mixing, but also first order chemical decay. In addition, in order to estimate short odor events (minutes) from hourly CALPUFF concentrations peak-to-mean approach was adopted. Finally, chemical odorant peak concentrations were converted to odor intensity and odor concentration applying the Steven's law. Traditionally, pulp paper mills using Kraft process produce TRS (Total Reduced Sulphur) odorants emissions, so their environment can be affected by odors. ENCE-Pontevedra pulp paper mill, located at the NW of the Iberian Peninsula, developed significant improvements to avoid any odor impact. Particularly, PrOlor system was developed and applied in order to prevent any odor event. Around the paper mill environment, both wind and temperature WRF and CALMET models results were compared and validated against four surface meteorological sites, using Openair software. About CALPUFF results, after several months under operation, PrOlor forecasted most of the sporadic short odor events registered as qualitative observations around the paper pulp mill.