Evaluation of full-scale biofilter media performance

The objective of this study was to characterize the key physical, chemical and biological properties of compost media from a full-scale biofiltration system used to control VOC emissions. Results of media characterization wer e used to assess the need for operational changes and media replacement. Bi ofilter media properties evaluated included: moisture content, pH, total or ganic carbon (TOC) and nitrogen content in water extracts and solid matrix, oxygen uptake rates, and microbial plate counts including total heterotrop hs, oligotrophs, actinomycetes and fungi. Samples were taken from various l ocations and depths in the biofilter after three and five years of system o peration. Media moisture content was highly variable, with samples from dee per in the bed dryer than surface samples. Low moisture contents were assoc iated with low pH values values and low oxygen uptake rates. Total organic carbon contents in water extracts were higher than typical biosolids compos t in samples near the inlet to the biofilter, possibly due to extracellular polysaccharides. After five years of use, total nitrogen and organic carbo n contents in the solid matrix did not significantly differ from initial le vels or those in typical biosolids compost.