Clean up of petroleum-hydrocarbon contaminated soils using enhanced bioremediation system: laboratory feasibility study

The objective of this study was to assess the potential of applying enhanced bioremediation on the treatment of petroleumhydrocarbon contaminated soils. Microcosm experiments were conducted to determine the optimal biodegradation conditions. The control factors included oxygen content, nutrient addition, addition of commercially available mixed microbial inocula, addition of wood chip and rice husk mixtures (volume ratio = 1 : 1) as bulking agents, and addition of organic amendments (chicken manures). Results indicate that the supplement of microbial inocula or chicken manures could significantly increase the microbial populations in soils, and thus enhance the efficiency of total petroleum hydrocarbon (TPH) removal (initial TPH=5,500 mg/kg). The highest first-order TPH decay rate and removal ratio were approximately 0.015 [day.sup.-1] and 85%, respectively, observed in microcosms containing microbial inocula (mass ratio of soil to inocula=50:1), nutrient, and bulking agent (volume ratio of soil to bulking agent= 10 to 1) during 155 days of incubation. Results indicate that the first-order TPH decay rates of 0.015 and 0.0142 [day.sup.-1] can be obtained with the addition of microbial inocula and chicken manures, respectively, compared with the decay rate of 0.0069 [day.sup.-1] under intrinsic conditions. Thus, chicken manures have the potential to be used as substitutes of commercial microbial inocula. The decay rate and removal ratio can be further enhanced to 0.0196 [day.sup.-1] and 87%, respectively, with frequent soil shaking and air replacement. Results will be useful in designing an ex situ soil bioremediation systems (e.g., biopile and land farming) for practical application. DOI: 10.1061/(ASCE)EE.1943-7870.0000166 CE Database subject headings: Soil pollution; Hydrocarbons; Biological processes; Soil treatment; Laboratory tests. Author keywords: Soil contamination; Total petroleum hydrocarbon; Enhanced bioremediation.