Experimental study on enhancing nitrogen removal by effluent recirculation in a BAF reactor with crushed lava packed as carriers
- Received Date: 28/08/2008
- Accepted Date: 24/04/2008
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Key words:
- BAFs /
- effluent recirculation /
- enhancing nitrogen removal /
- denitrification /
- crushed lava /
- DO
Abstract: It was demonstrated in a pilot experiment that crushed lava was good carriers in an up-flow biological aerated filter (UBAF). The removal efficiencies of COD, SS, and turbidity were not affected by effluent recirculation, and moreover the efficiency of nitrification was not enhanced too much due to the effect of low temperature during the experiment, but the removal efficiency of total nitrogen (TN) was indeed enhanced by effluent recirculation. Up to effluent recirculation at R=150%, NO-3 converted from nitrification could be fully removed by denitrification. Due to limited nitrification at low temperatures, however, the removal efficiency of TN was enhanced at a limited extent (from 43.8% at R=0 to 69.1% at R=150%). The valley-type DO profile along the bed height （the DO valley at 50 cm）revealed that the DO valley was a turning point for denitrification and also was a boundary of nitrification and denitrification.
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