ODOR AND VOC REMOVAL IN A BIOTRICKLING FILTER SYSTEM AT HYPERION

To investigate odor control for collection system application, a 6,800 m3 h−1 (4,000 cfm) Bioway Purspring™ biotrickling filter (BTF) was installed at the Hyperion Treatment Plant as first-stage treatment for ventilated sewer air. For second-stage treatment, three types of biofilter media, Biorem, Envirogen, and compost, were evaluated along with two types of activated carbon media, virgin and Midas™. The BTF provided 98 percent removal with inlet H2S as high as 100 ppm. The bulk of the H2S removal occurred in the lower media with an average H2S loading rate 24 g m−3h−1 and maximum of 76g m−3 h−1. When air flow was increased 50 percent, H2S removal decreased to 94 percent. The BTF erformed well with reduced irrigation and with recycled drainage water, but the amount of acid was onstant, so neutralization chemical requirements remain unchanged.The BTF provided minimal reduction of the toxic VOCs detected except for toluene. For the Hyperion influent source, the BTF outlet odor averaged about 3,500 D/T, so in addition to being mandated for air quality, second-stage treatment is also needed for odor control. Over the nine-month testing period, there was only one partial loss of treatment, lasting just two days, which was attributed to toxic compounds in the incoming air stream.Biofilters were initially preferred for second-stage treatment, but the testing showed that none of the units yielded acceptable outlet odor. The biofilters reduced BTF odor by about 90 percent, but the final outlet odor of 300 to 500 D/T was not acceptable. The biofilters provided no significant reduction of the toxic VOCs measured with the exception of toluene, which was reduced by 70 percent in the Envirogen and compost media units. The virgin carbon maintained excellent odor control over a nine-month period with a final outlet of 133 D/T and a third-stage outlet of 69 D/T. The virgin carbon media provided good VOC removal except for chloroform and methylene chloride. The second-stage Midas™ carbon provided excellent odor reduction to 107 D/T and good VOC removal except for chloroform.As a result of the Hyperion testing, the final collection system design was modified from a Bioway BTF followed by a biofilter to a Bioway BTF followed by two stages of virgin carbon.