This paper evaluated the effect of hydraulic retention time (HRT) on the performance of three upflow aerobic reactors, with polyurethane foam as support material, inoculated with Aspergillus niger AN400, used for the treatment of petroleum refinery wastewater. Each reactor was operated with a different HRT: 4, 8 and 12 hours, during 152 days. The performance was evaluated based on pH; phenols; COD, nitrate and nitrite. The results show that for the COD removal, it is more reasonable to operate the reactor with HRT of eight hours. However, there was no difference among results of phenol removal efficiency of the different HRTs. During steady state condition, nitrite was removed in approximately 99%, but there was no reduction on the nitrate concentration. Ammonia was produced in all reactors, probably due to ammonification of nitrite.
wastewater; petroleum refinery wastewater; aerobic biological treatment; filamentous fungi; hydraulic retention time
