The effects of Tween-20 and Zn(II)on ethylbenzene removal were evaluated using two biotrickling filters(BTFs),BTF1 and BTF2.Only BTF1 was fed with Tween-20 and Zn(II).Results show that ethylbenzene removal decreased from 94%to 69%for BTF1 and from 74%to 54%for BTF2 with increased organic loading from 64.8 to 189.0 g ethylbenzene/(m3·hr)at EBRT of 40 sec.The effect of EBRT(60–15 sec)at a constant ethylbenzene inlet concentration was more significant than that of EBRT(30–10 sec)at a constant organic loading.Biomass accumulation rate within packing media was reduced significantly.