Effect of immature and mature compost addition on petroleum contaminated soils composting: kinetics.

Abstract

The kinetic studies and effect of amendment addition on the performance of the composting process in reduction of total petroleum hydrocarbons (TPH) from petroleum contaminated soils (PCS) were investigated in the present research. Seven composting experiments containing various mixing ratios of PCS to unfinished compost (UC) and finished compost (FC) were set up and operated for 14weeks. The mixing rations consisted of 1:0 (as control experiment), 1:0.3, 1:0.6, and 1:1. The initial C/N/P and moisture contents of the composting piles were adjusted to 100/5/1 and 50-55%, respectively. Results showed that 50.09-79.49% of TPH was removed in the composting experiments after 14weeks. The highest and lowest removal rates were achieved in the ratios of 1:1 and 1:0.3, respectively. Moreover, application of UC as amendments and bulking agent is more efficient than FC. The biodecomposition of TPH was fitted to the first-order kinetic with the half lives and rate constants of 5.63-11.55days and 0.060-0.123 d-1, respectively. The bacteria detected from the composting treatments were Staphylococcus sp., Bacillus sp., and Pseudomonas sp. The study confirmed the suitability of composting process for PCS bioremediation and superiority of UC than FC as bulking agent.