Performance and Kinetics of Bioaugmentation, Biostimulation, and Natural Attenuation Processes for Bioremediation of Crude Oil-Contaminated Soils

Cevat Yaman

doi:10.3390/pr8080883

Abstract

Bioremediation of contaminated sites is usually limited due to the inadequate availability of nutrients and microorganisms. This study was conducted to assess the impact of bioaugmentation (BA) and biostimulation (BS) on petroleum hydrocarbon degradation efficiency. In addition, treatment performance and kinetics of different remediation processes were investigated. For this purpose, four tanks containing oil-contaminated soils were tested. Tank 1 was operated as the natural attenuation process. Then, a microbial inoculum and nutrients were added to tank 2 to promote BA and BS. In tank 3, only the BA process was adopted, whereas in tank 4, only the BS process was adopted. After 63 days of operation, the total petroleum hydrocarbon (TPH) in tank 2 was reduced from 1674 to 430 mg/kg, with 74% reduction. Tank 1, tank 3, and tank 4 indicated TPH reductions of 35%, 41%, and 66%, respectively. Microbiological analysis of the inoculum indicated that Alcanivorax was the dominant bacterium. The population of TPH degrader bacteria in tank 2 soil was two orders of magnitude higher than in the control tank. Reaction rate data were fitted with a first-order reaction rate model. The Monod kinetic constants, maximum specific growth rate (µmax), and substrate concentration at half-velocity constant (Ks) were also estimated. This study showed that the TPH removal efficiency in the combined BA and BS process was higher than in other processes tested. The populations of TPH degrading microorganisms in soil tanks were positively related to TPH removal efficiency during bioremediation of petroleum-contaminated soils.

Highlights

Petroleum contamination in subsurface environments has become a serious global environmental hazard
Microbial analysis showed that an active microbial population of 1 × 105 (1.0E+05) colony forming units (CFU).g−1 was initially present in the soils prior to treatment
This study confirmed that it is possible to enhance the biodegradation of total petroleum hydrocarbon (TPH) in soil by using different treatment methods such as bioaugmentation and biostimulation alone or in combination

Summary

Introduction

Petroleum contamination in subsurface environments has become a serious global environmental hazard. Some of the main sources of this contamination are crude oil, refineries, and underground storage tanks (UST). Some of the chemicals in fossil fuels tend to remain in the environment for a long period of time. These persistent contaminants have several health risks to humans, animals, and other living organisms. Bioremediation is recognized as a cost-effective treatment technology for oil-contaminated soils [2]. Bioaugmentation (BA) and biostimulation (BS) are the two main bioremediation technologies commonly used for soil clean-up [3,4,5,6,7,8]. Bioaugmentation works by introduction of exogenous microbial population to the contaminated environment [9,10,11]

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