MULTI-LAYERED BIOREACTORS: THE NEW STANDARD IN MANAGING ODORS-Design considerations, Implementation issues and Operating experiences

Polluted air streams nearly always contain a mixture of many compounds. These compounds are
usually different in, for example, water solubility and biodegradability, which result in important
consequences for its removal potential.
To remove all pollutants from an air stream using biotechnology, a mix of micro-organisms is
required. Micro-organisms differ from each other by their capacities to use energy, carbon and
nutrients sources. In addition, the optimal environmental conditions for the micro-organisms
required are unfortunately not the same for all micro-organisms.
Therefore, depending on the many compounds in the air stream, a mix of micro-organisms is
required and different environmental conditions for the micro-organisms result in a more
efficient biological air treatment system.
Multi-layered bioreactors can provide these different environmental conditions, which are
difficult to obtain and maintain in conventional biofilter systems. High odor removal efficiencies
(>98%) and low outlet odor concentrations (<1000 OU) have been obtained in full-scale
applications at a relatively small footprint. Reactor design, however, as well as operating strategy
is critical for success as outlined in this paper.