Hydrogen Sulfide Effects on Ammonia Removal by a Biofilter Seeded with Earthworm Casts

Ammonia (NH 3 ) removal efficiencies were evaluated when hydrogen sulfide (H 2 S) and NH 3 in binary mixture gases were supplied to a ceramic biofilter seeded with earthworm ( Lumbricus terrestris ) casts. The effect of inlet H 2 S concentration and space velocity (SV) on the removal of NH 3 was investigated after the acclimation of the biofilter with NH 3 gas. When NH 3 was singly supplied to the biofilter, NH 3 removal was maintained at almost 100% until inlet NH 3 concentration was increased up to 600 μL L −1 and SV up to 330 h −1 , at which the elimination capacity of NH 3 was 148 g N m −3 h −1 When H 2 S was supplied simultaneously, however, the accumulation of toxic sulfide ions showed dual effects on NH 3 removal efficiencies. First, no effects were observed at inlet H 2 S loading below 60 g S m −3 h −1 ; however, inhibition by H 2 S at higher loading was observed above 60 g S m −3 h −1 The point at which loading achieved a maximum of more than 99% NH 3 removal efficiency was 139 g N m −3 h −1 , when inlet H 2 S concentration was held under 100 μL L −1 , but it dropped to 76 and 30 g N m −3 h −1 when the inlet H 2 S concentration increased to 220 and 460 μL L −1 , respectively. The critical points of inlet H 2 S loading that guaranteed over 99% NH 3 removal were determined as 100, 100, 60, and 40 g S m −3 h −1 at inlet NH 3 concentrations of 100, 200, 400, and 600 μL L −1 , respectively. Inlet NH 3 loading had synergic effects of increasing the inhibition of inlet H 2 S loading on the NH 3 removability of the biofilter.