An Integrated Bioremediation Approach for Wastewater Treatment and Contaminated Soil Remediation in a Used Oil Recycling Plant

Abstract This work focused on the biotreatment of wastewater and contaminated soil in a used oil recycling plant located in Bizerte. A Continuous Stirred Tank Reactor (CSTR) and a Trickling Filter (TF) were used to treat stripped and collected wastewater, respectively. The CSTR was started up and stabilized for 90 days. Over the following 170 days, the operational organic loading rates (OLR) of the TF and the CSTR were around 1200 and 3000 mg chemical oxygen demand (COD) L-1 day-1, respectively. The treatment efficiency was 94% for total petroleum hydrocarbons (TPH), 89.5% for COD, 83.34% for biological oxygen demand (BOD5) and 91.25% for phenol. Treated industrial wastewater from the TF was used for bioaugmentation (BA) of contaminated soil. The BA strategy was compared with natural attenuation (NA) based on the use of tap water. The assessment of the soil took 24 weeks to complete. The effectiveness of the soil bioaugmentation strategy was confirmed by monitoring of phenolic compounds, aliphatic and polycyclic aromatic hydrocarbons (AH and PAH), heavy metals and germination index (GI). The biodegradation rate of contaminants was improved and the time required for their removal was reduced. The soil bacterial communities were dominated by species of the genera Mycobacterium, Proteiniphilum, Nocardioides, Luteimicrobium and Azospirillum, which were identified as hydrocarbon and phenol degrading bacteria. The bioremediation of polluted soils by the treated industrial effluents seems to be an interesting approach for the conservation of water and soil resources.