PRACTICAL EXPERIENCES WITH BIOLOGICAL TREATMENT SYSTEMS FOR ODOR AND VOC REMOVAL AT THE HYPERION TREATMENT PLANT

Odor control is a severe problem common to many wastewater treatment operations and is particularly significant at urban treatment plants. The most commonly reported odorous compound in POTW off-gases is hydrogen sulfide (H2S), which has a very low odor threshold. In addition, most POTW off-gases contain low concentrations (ppb levels) of air toxics and volatile organic compounds (VOCs). Hence the objective of this study was to investigate the removal of H2S and other odors in combination with VOCs. A pilot biofilter (bed volume of 0.29 m3) and a pilot biotrickling filter (3.7 m3) were installed at the headworks of the Hyperion Treatment Plant in Los Angeles and operated for a period of 10 months under a range of selected operating conditions. The nominal empty bed contact time was 20–50 s for the biofilter and 15–25 s for the biotrickling filter. Monitoring included H2S, VOC, and odor removal. Overall, the study revealed that H2S was very well removed under the conditions tested. VOC removal was moderate in the biofilter and very low in the biotrickling filter. Attempts to increase the elimination of the VOCs failed. Cost estimation for the replacement of conventional scrubbers with biofilters or biotrickling filters revealed that both biofilters and biotrickling filters show very good perspective for effective odor control.