Biofiltration of WWTP sludge composting emissions at contact times of 2–10 s by structured/unstructured packing materials

Abstract

The performance of a biotrickling filter for the abatement of composting emissions was evaluated at short gas contact times of 2–10 s with a structured and an unstructured packing material. The effect of the gas contact time, pH control and water make-up flowrate were also evaluated during 8 months. The average elimination capacity was 13 g N m-3 h-1 and 3.3 g C m-3 h-1 for NH3 and VOCs, respectively. Maximum capacities obtained during an inlet concentration spiking experiment were 45 g N m-3 h-1 and 20 g C m-3 h-1 at a removal efficiency of 92.5 and 46.7%, respectively. A decrease of 40% was detected in the nitrification capacity when the hydraulic residence time increased from 2 to 5 h. Thus, water renewal was identified as a critical parameter to avoid substrate inhibition by nitrite and NH3 accumulation. Results demonstrate that significant NH3 and VOCs removal efficiencies can be achieved for composting emissions in a biotrickling filter operated at short gas contact times, which entails a substantial reduction of operational and investment costs in comparison to traditional techniques.