In order to maintain the pH of the vessel around neutral, or a pH of 7, buffering material may be added to the organic media. The media used in biofilters can include peat, heather, bark, composted sewage sludge, granular carbon or other suitable materials. Generally, the media should be capable of providing nutrients to the microorganisms and minimizing pressure drop. In addition to humidifying the airflow, sprinkler systems are frequently installed inside the biofilter that can be controlled to maintain a suitable bed moisture. Pressure drop across the biofilter reactor vessel should be minimized since an increase in pressure drop requires more blower power and can result in air channeling through the media.
Pressure drop is directly related to the moisture content in the media and the media pore size.
Increased moisture and decreased pore size result in increased pressure drop. Consequently, media filter selection and watering is critical to biofilter performance and energy efficiency. For a typical biofilter pressure drops range between 1 and 10 hPa. The operation and maintenance of the biofiltration system would require weekly site visits during initiation of operations for emiss. However, after acclimation and all system problems are resolved the frequency of site visits could be reduced to the biweekly or monthly.