Background: Biodegradation of hydrocarbon compounds is a great environmental concern due to their toxic nature and ubiquitous occurrence. In this study, biodegradation potential of oily soils was investigated in an oil field using indigenous bacterial consortium.
Methods: The bacterial strains present in the contaminated and non-contaminated soils were identified via DNA extraction using 16S rDNA gene sequencing during six months. Furthermore, total petroleum hydrocarbons (TPH) were removed from oil-contaminated soils. The TPH values were determined using a gas chromatograph equipped with a flame ionization detector (GC-FID).
Results: The bacterial consortium identified in oil-contaminated soils (case) belonged to the families Halomonadaceae (91.5%) and Bacillaceae (8.5%), which was significantly different from those identified in non-contaminated soils (control) belonging to the families Enterobacteriaceae (84.6%), Paenibacillaceae (6%), and Bacillaceae (9.4%). It was revealed that the diversity of bacterial strains was less in oil-contaminated soils and varied significantly between case and control samples. Indigenous bacterial consortium was used in oil-contaminated soils without need for amplification of
heterogeneous bacteria and the results showed that the identified bacterial strains could be introduced as a sufficient consortium for biodegradation of oil-contaminated soils with similar texture, which is one of the innovative aspects of this research.
Conclusion: An oil-contaminated soil sample with TPH concentration of 1640 mg/kg was subjected to bioremediation during 6 months using indigenous bacterial consortium and a TPH removal efficiency of 28.1% was obtained.

Background: Wastewater treatment plants are important sources of emissions of greenhouse gases (GHSs) such as carbon dioxide and methane in the atmosphere. Also, energy consumption in the wastewater treatment process causes indirect carbon dioxide emissions.
Methods: One hundred thirty-three operating wastewater treatment plants in Iran treat municipal wastewater. The carbon dioxide and methane emissions from the wastewater treatment plants for the year 2022 were estimated by establishing a calculation model according to the methods recommended
by the Intergovernmental Panel on Climate Change for National Greenhouse Gas Inventories (2006) and United States Environmental Protection Agency (USEPA) guidelines.
Results: Based on the Intergovernmental Panel on Climate Change guideline, the total methane emission was 158.63 tons. Based on the USEPA guideline, the total emissions of methane and carbon dioxide were 47.61 and 351.47 tons, respectively. This amount is 3.2% of all the methane and carbon dioxide emissions of Iran. Isfahan and Tehran provinces have the highest emissions rates of methane at 31.85 and 22.91 tons, respectively. While South Khorasan and Kerman provinces have the lowest methane emissions rates of 0.46 and 0.67 tons, respectively.
Conclusion: The results will provide a scientific basis and effective strategies for policymakers to reduce the methane and carbon dioxide emissions from the wastewater treatment plants of Iran.