In response to complaints from nearby residents, a biofilter was designed installed, and tested for treating odors in one of three odorous emission streams from an asphalt plant pl producing polymer-modified asphalt. The biofilters bed became increasingly acidified during the plant's 1997 operating season producing a pH gradient through the bed ranging from a high of 6.6 to a low of 3.1. Bed acidification did not impart the biofilter's H2S removal efficiency.
Plans are to implement biofiltration for odor control at all of the facility's emission points.