Influence of the frequency of emptying wash waters on the efficiency of a bioscrubber in reducing ammonia, odours and dust emitted by fattening pig units

This study was conducted on two successive batches of 120 pigs each between 25-110kg live weight, divided into two rooms equipped with identical bioscrubbers. In both rooms, sixty pigs were group-housed in 6 pens on fully slatted floor. Slurry was stored in pit underneath during the whole fattening period. Fresh air entered via a ceiling of perforated plastic sheet-ing. The set-point temperature was fixed at 24°C during the whole period. For both rooms, air exhaust air was entirely treated by bioscrubber. During the first batch, a partial emptying of wash water (&‡76;50%) was carried out twice for the first bioscrubber while the emptying was complete for the second one. For the second batch, a complete emptying was carried out four times for the first bioscrubber while no emptying was applied for the second one. During both batches, ammonia, odours and dust were measured in the air before and after each bioscrubber. The gas concentrations were continuously measured by photoacoustic infrared absorption spectrometry using a gas analyser (Innova 1412) coupled to a sampler dosimeter (Innova 1303) sampling air before/after the bioscrubber and outside. Air samples for olfacto-metric analyses were conducted in the extraction duct for each room and odour concentra-tions were determined in accordance with the European standard (CEN 13725). After each emptying, wash water samplings were achieved for analyses (dry matter, pH, total and am-monium nitrogen). Ammonia, odour and dust emissions measured in exhaust air before be-ing treated by the bioscrubber were in accordance with previously published data. Efficiency of bioscrubbers on ammonia, dust and odours emissions varied depending on the emptying modalities applied. A partial emptying compared to a complete emptying led to a higher effi-ciency of the bioscrubber on odours and ammonia. No difference was observed on ammonia and dust emissions between the four-time emptying and no emptying modalities. Conversely, the efficiency on odours was sharply deteriorated. Data collected during this study led us to determine the part played by the biological action in bioscrubbing the ammonia, enabling us to confirm the biological action of scrubbing on odours.