Enrichment and screening of nitrifying bacteria and application in a biotrickling filter

Nitrifying bacteria, comprising ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), were enriched and screened from activated sludge and cattle manure. Removal efficiency of NH₃ in exhaust composting gases by a biotrickling filter (BTF) which was non-inoculated and inoculated with the nitrifying bacteria was compared. The results shows that the nitrifying bacteria continuously oxidized NH₄⁺ to NO₃^-, which decreased the NH₃ vapor pressure outside the biofilm and benefited NH₃ shift from the gas phase to the liquid phase. When the biofilm was inoculated with the nitrifying bacteria, NH₃ removal efficiency was 15% on the average higher than that of non-inoculation with nitrifying bacteria. The BTF could completely remove NH₃ during composting at the inlet NH₃ of 3~197 mg/m³ and empty bed retention time of 96 s. The pressure drop was always lower than 30 Pa, and the BTF was absent from any indication of clogging suggesting that it could effectively and stably eliminate NH₃ released from composting.