Removal efficiency of dust and bacteria by multi-stage air scrubbers in pig houses

Emissions of aerial pollutants from animal houses may raise environmental problems and pose hazards to public health. Some of these emissions, such as NH3 and odor, can be reduced effectively by installing well-designed air scrubbers at the air outlets of animal houses. The aim of this study was to evaluate and compare the removal efficiency of three multi-stage scrubbers on dust (PM10 and PM2.5) and airborne bacteria. The multi-stage scrubbers used in this study were: 1) a double-stage scrubber (acid stage - biofilter, ABF); 2) a double-stage scrubber (acid stage ¿ bio-scrubber, ABS); and 3) a triple-stage scrubber (water stage - acid stage - biofilter, WABF). Dust and bacteria concentrations, including ammonia (NH3) and carbon dioxide (CO2), were measured in the incoming and outgoing air of three scrubbers installed at three different pig houses. Measurements were done during a winter period (from Dec, 2006 to Feb, 2007). Results showed that multi-stage scrubbers reduced concentrations of PM10 with 62%-93%, concentrations of PM2.5 with 47%-90%, concentrations of airborne total bacteria with 46%-85%, and concentrations of NH3 with 70.3%-99.7%. CO2 concentrations were not affected. The WABF had the highest reduction of dust and NH3. From this study it can be concluded that the multi-stage air scrubbers achieve a satisfactory efficiency for removal of PM10, PM2.5, and NH3. Although airborne bacteria were reduced, as well, the reduction is insufficient to disinfect the air. It should be noticed that all measurements were performed in the winter time at relatively low ventilation rates, thus at low loading rates of the multi-stage air scrubbers. 2