scope:

This guideline VDI 3477 covers the treatment of waste gas/exhaust air containing gaseous air pollutants, aerosols and notably odorants. Biodegradation of the pollutants is accomplished under aerobic conditions by micro-organisms colonizing on solid support media.

This guideline gives an overview of waste gas streams that have been successfully treated and/or pollutants that have been effectively degraded in biofilter systems. It addresses the criteria to be considered for the proper design of the biofilter system, discusses performance evaluation criteria and presents production processes in which biofilters have become successfully established for waste gas treatment. For the sake of simplicity, this guideline does not distinguish between waste gas and exhaust air but uses the term "waste gas" throughout. Depending on the context, the term waste gas may therefore also relate to exhaust air.

Volumetric gas rates indicated normally relate to standard temperature and pressure conditions. An exception applies to the biofilter area and space loading rates where the associated volumetric gas flow rates relate to the actual operating conditions.

Where applicable, reference is made to the statutory regulations [G1 to G15] and technical rules [T1 to T53] to be observed.

This guideline describes the state of the art in biofiltration technology for biological waste gas treatment. Despite the numerous practical applications of biofilters, the applicability of biofiltration to the specific waste gas stream should be confirmed by field pilot studies in all cases where no application-specific empirical data are available. Moreover, a comparison with other waste gas cleaning processes is recommended before opting for a biofilter.

At the time this guideline was published, biofilters were being successfully employed in the production plants and disposal facilities listed in Table 1 [T23; L12; L33; L46; L61].

Table 2 lists the individual substances and substance groups for which biodegradation results are available from biofiltration tests. Depending on the specific waste gas composition, the individual substances may exhibit a biodegradation behaviour differing from that shown in Table 2. It should be noted that this list is based on experience available so far (e.g. as per [L1; L11; L14]) and that there are no clear cut-off points between the individual categories. Table 2 may serve as a decision-making basis to determine whether prior treatability tests in a biofilter pilot plant will be needed (see Section 5.3) to establish the design basis for a biofilter.