Control of biotrickling filter efficiency on NH3 emitted by piggeries

E. Dumont (IMT Atlantique) et al., 70th Annual Meeting of the European Federation Animal Science (EAAP), 26-30 août 2019, Ghent, Belgique, p. 319, poster

Ammonia emitted by piggeries can be removed using biotrickling filtration. As ammonia is a very soluble compound in water, removal efficiency (RE) around 70-80% can be expected. However, the accumulation of nitrogen salts in water leads to a decrease in RE. Consequently, there is need to improve the management of equipment by controlling the amount of water which has to be discharged and replaced by fresh water in order to limit the accumulation of nitrogen salts. Such an improvement is based on the knowledge of the nitrogen mass balance between the gas phase and the liquid phase. The objective of this study was to establish the nitrogen mass balance of a pilot-scale biotrickling filter treating ammonia emitted by a pig house. The experiment was carried out for 14 weeks on a French pig farm.
The biotrickling filter installed to treat the polluted air generated by 54 fattening pigs was filled with a structured plastic packing WAT NET 150 NC 20/48 (0.9×0.9×0.45 m). The airflow rate was of 1,350 m3/h corresponding to an Empty Bed Residence Time (EBRT) of 1 s. In the gas phase, temperature, relative humidity, ammonia and nitrous oxide concentration were hourly measured. In the liquid phase, temperature, pH, electrical conductivity, and concentration of nitrogen salts (NH4+, NO2-, NO3-) were weekly measured. Results showed that nitrogen mass balances carried out on both phases are in agreement (5% difference). A steady transfer rate of ammonia from the gas phase to the liquid phase was obtained (3.22 gN/h corresponding to 10.0 gN/pig/week). From the measured concentrations of nitrogen salts in the liquid phase, it was calculated that the nitrogen mass transfer was 9.5 gN/ pig/week. Moreover, it was also evidenced that the amount of nitrogen salts dissolved in water could be correlated to the water conductivity. As a result, the measurement of this parameter could be a useful tool to determine the amount of ammonia removed from the gas phase.