Performance Validation of the First North American Shell-Based Biological Air Treatment System

A range of biological technologies have been employed in North America over the last several decades for the treatment odorous reduced sulfur compounds (RSCs) and volatile organic compounds (VOCs) emitted from wastewater collection and treatment facilities. Technologies including wet scrubbers, activated carbon, thermal oxidizers, and biological treatment systems, among others, have been used as stand alone solutions or in combination in order to address odor challenges. Among these solutions, biological treatment has more recently gained validity due to improved processes yielding effective treatment at relatively low operating costs. Biotrickling filters typically function based on a fixed-film biomass on plastic media or foam, where odorous compounds are absorbed into the film and biologically oxidized by microorganisms. Biofilters are differentiated by use of a natural filter media such as soil, peat, compost, or woodchips (among others).This paper evaluates the performance of the first North American shell-based biological air treatment system, which functions similarly to a biotrickling filter in that it treats high and variable levels of H2S, yet with a media similar to that of a biofilter in that it is naturally occurring and provides high removal efficiencies of organic sulfides. While the shell-based process is widely applied in Europe and further abroad, results here report its first use in North America. The performance of a system treating emissions from a mixed sludge storage tank at a Greensboro, NC water reclamation facility was evaluated over a period of eleven months with performance in the last five months of the trial period evaluated by a third party (NC State University, Dept. of Soil Sc.). The study results show that the system combines the treatment capabilities of biotrickling filters and biofilters in that high concentrations of H2S, as well as non-H2S RSCs, were effectively treated in one stand-alone unit without the use of nutrient addition or chemical addition for pH balancing.