STRATEGIES AGAINST BREAKTHROUGH OF AMMONIA PEAK LOADS IN NITRIFYING BIOLOGICAL AERATED FILTERS (BAF)

Biofiltration is a meanwhile well established and proven technology for the full treatment of municipal and industrial wastewaters. The combination of filtration with high rate biofilm processes results in comparably small WWTP sizes and footprints. However, this small reactor size combined with plug flow hydraulics results in a limited hydraulic buffering capacity which may cause increased effluent concentrations under peak loading conditions incase of nitrification due to the zero to half order degradation kinetics. In order to cope with ammonia peak loads this study shows that by adding pure oxygen to the aeration air the nitrification performance can be doubled within minutes. It is also demonstrated that the use of carrier materials with sorption properties for ammonia (e.g. zeolite) can dampen concentration peaks efficiently with subsequent release under normal conditions within one day. The results can help to design BAF plants more efficiently and avoid common problems with under loaded plants.