Attempted biofiltration of reduced sulphur compounds from a pulp and paper mill in northern Sweden

The objective of this study was to identify the reduced sulphur compounds (RSCs) present in waste gas from a specific deaerator at a pulp and paper mill in northern Sweden, and to investigate the feasibility of a multi-stage biofilter to treat these compounds in an industrial setting. Two filter media, rockwool mats and an organic peat and compost mixture, were used as biofilter media. A mixed population of heterotrophs and a strain of Hypomicrobium were examined for DMS and DMDS degradation. Two experimental periods were performed for 45 days each, in the fall and winter in cold climate. Process parameters as well as the number of viable cells of the filter were monitored during operation. Results were inconsistent due to the fluctuations of the system, and a number of operational problems were identified, differing from those developed under controlled, laboratory set-ups. Process conditions varied greatly, that is, fluctuating temperatures, pollutant concentrations, and airflows that led to insufficient residence times. Both biological and mass transfer limitations are possible explanations for the poor treatment results. This study can contribute to assessing the feasibility of biofilters in the pulp and paper industry, and help reduce the knowledge gap between laboratory studies and field conditions. (c) 2006 American Institute of Chemical Engineers Environ Prog.