Elimination of NH₃ and odor from composting by biotrickling filter and preliminary exploration on molecular biology

A biotrickling filter was focused on treatment of odorous NH₃ gas, along with volatile organic compounds (VOCs) and other odorous gases during cattle manure composting. The biotrickling filter could treat NH₃, the main composition, with removal efficiencies of close to 100% because NH₄⁺ was bio-oxidized in the biofilm to NO₃⁻ resulting final NO₃⁻ concentrations of about 1000 mg/L. Results of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) revealed that ammonia-oxidizing bacteria, Nitrosospira sp, and nitrite-oxidizing bacteria, Nitrococcus mobilis, coexisted in the biofilm. There were 23 kinds of VOCs detected in the exhaust gas. A significant observation was that the biofilm itself of the biotrickling biofilter released VOCs. The odor concentrations of inlet and outlet gases were 1425 and 110, respectively, with removal efficiency of 92.2%, suggesting that the biotrickling filter was effective for treatment of odorous gases during composting.