Wastewater biotreatment and bioaugmentation for remediation of contaminated sites at an oil recycling plant

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 of the TF and the CSTR were around 1,200 and 3,000 g chemical oxygen demand (COD) m^-3 day^-1, respectively. The treatment efficiency was 94% for total petroleum hydrocarbons (TPHs), 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 assessment of the soil took 24 weeks to complete. The effectiveness of the soil BA strategy was confirmed by monitoring phenolic compounds, aliphatic and polycyclic aromatic hydrocarbons, heavy metals, and germination index. 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 <i>Mycobacterium, Proteiniphilum, Nocardioides, Luteimicrobium</i>, and <i>Azospirillum</i>, which were identified as hydrocarbon and phenol-degrading bacteria.