Comparison of Composting and Vermicomposting Processes in Refining Drill Cutting Mud from Ahvaz Oil Field in the Presence of Biosolids

Cutting and drilling mud contains significant amounts of petroleum hydrocarbons that are detrimental to both the environment and public health. The objective of this study was to remove the hazardous components of drill cutting mud using the two biological processes of sewage sludge vermicomposting and biocomposting. In an experimental laboratory research, two pilot composting and vermicomposting processes, each over a period of two months with 2 repetitions, were conducted using the the same biological sludge mixed with drill cuttings contaminated with total petroleum hydrocarbon (TPH) along with sawdust and yard waste. The GC-FID unit was used to determine the residual total petroleum hydrocarbon concentrations. Results showed that the vermicomposting pilot had a higher TPH removal efficiency than did the composting one so that TPH concentration in the mixed waste mass declined after 60 days from its original value of 42.004 g/kg to 11.316 g/kg. In other words, TPH removal in the pilots A (vermicomposting) and B (biocomposting) were 73/06% and 55/3%, respectively. Moreover, the TPH levels in the two composting and vermicomposting pilots on the 45th and 60th days showed significant differences (p < 0.05). The study showed that the vermicomposting process enjoys a higher capability than the composting one in removing TPH from oil-based drill cutting waste.