Performance of anaerobic thermophilic fluidized bed in the treatment of cutting-oil wastewater

This paper examines the effect of organic loading rate on the removal efficiency of COD and TOC anaerobic thermophilic fluidized bed reactor (AFBR) in the treatment of cutting-oil wastewater at different hydraulic retention time (HRT) conditions. The essays are development at laboratory scale using a porous support medium. The AFBR reactor was subjected to a programme of steady-state operation over a range of hydraulic retention times, HRTs, in the range 12–2 h and organic loading rates, OLRs, between 11.9 and 51.3 kg COD/m3 d. The highest efficiency was 95.9% for an OLR of 13 kg COD/m3 d and HRT of 11 h. Over an operating period of 92 days, an OLR of 51.3 kg COD/m3 d was achieved with 67.1% COD removal efficiency (71.3% TOC) in the experimental AFBR reactor. Although the level of biogas generation was not high, the anaerobic fluidized bed technology provided significant advantages over the conventional physico-chemical treatment applied in the factory. The effluent had a better quality (lower organic loading) and it was possible to reuse it in different applications in the factory (e.g., irrigation of gardens). The biological treatment did not lead to the generation of oily sludge, which is considered as hazardous waste by legislation. Furthermore, a continuous stream is produced and this reduced the impact of large flows discharged 4–5 times per week to the urban collector and MWWTP (municipal wastewater treatment plant).