Humification Process and Total Petroleum Hydrocarbons Assessment During Oily Sludge Composting

The petroleum sludge composting in a bioreactor with green wastes was made in interest to assess the organic matter biotransformation, the total petroleum hydrocarbons biodegradation and the maturity of the final product. During the composting process the C/N and NH4+/NO3− ratios decreased to reach values of maturity for the second test B. Otherwise, the decomposition rate was found to be high for test B, as the maximal temperature reached 52 °C for test B while it was only 40 °C for test A. The humification process was monitored by the increase of the humic substance and the HA/FA ratio, and by the FTIR which demonstrated the decrease of the aliphatic group bands and the persistence of the aromatic group bands. The three analysis methods revealed a similarity in the assessment of total petroleum hydrocarbons removal, which reached a rate of 94%. The composting process had also led to a reduction of the phytotoxicity by increasing the germination index.