BIOFILTRATION DESIGN, OPERATIONAL DETAILS, AND CASE STUDIES

Biofiltration is a process whereby odorous air is forced through a bed of organic or inorganic material. In this process, the odorous contaminants, including sulfides and VOCs, are removed from the gas phase through biological and chemical oxidation. The innocuous by-products of the biofiltration process are cell mass, water, salts, and carbon dioxide.Industrial, municipal, and federal agencies are increasingly using biofilters to treat process air and odors. While there are differences from site to site, some general design criteria can be followed. Critical to the design are the type of media used and the residence time of the air stream through the media bed. A number of configurations are available, from pre-fabricated enclosed modules to custom-designed open organic media beds. Economics usually favor enclosed packaged biofilters in the lower airflow range or high strength air stream, while custom-engineered biofilters are indicate in the higher airflow, lower strength airstreams, such as for wastewater treatment plants.At the US Naval Station Everett, Washington, odorous air from the Master Pump Station has been successfully treated with an open bed biofilter since early spring 2002. The biofilter treats 1,000 scfm of foul air and is contained in concrete walls. Another organic media biofilter treats odors generated in a King County, Washington, interceptor sewer. This biofilter, in operation since January 2002, treats 5,000 scfm of foul air contaminated with hydrogen sulfide. Probably the largest biofilte treating municipal wastewater treatment plant odors in North America is at the St Paul, Minnesota, wastewater treatment plant and has been operational since November 2002. This biofilter treats 127,000 scfm of foul air emanating from the plant's processes. These operating biofilters will be described in the presentation, together with design data, cost information, start up details, and operational and maintenance guidance.