Abstract
The purpose of this study is to investigate and evaluate the effects of natural bioattenuation, bioventing, and brewery waste effluents amendment as biostimulation-bioaugmentation agent on biodegradation of diesel oil in unsaturated soil. A microcosm system was constructed consisting of five plastic buckets containing 1 kg of soil, artificially contaminated or spiked with 10% w/w of diesel oil. Biodegradation was monitored over 28 days by determining the total petroleum hydrocarbon content of the soil and total hydrocarbon degrading bacteria. The results showed that combination of brewery waste effluents amendment and bioventing technique was the most effective, reaching up to 91.5% of diesel removal from contaminated soil; with the brewery waste effluents amendment (biostimulation-bioaugmentation), the percentage of diesel oil removal was 78.7%; with bioventing, diesel oil percentage degradation was 61.7% and the natural bioattenuation technique resulted in diesel oil removal percentage be not higher than 40%. Also, the total hydrocarbon-degrading bacteria (THDB) count in all the treatments increased throughout the remediation period. The highest bacterial growth was observed for combined brewery waste effluents amendment with bioventing treatment strategy. A firstorder kinetic model was fitted to the biodegradation data to evaluate the biodegradation rate and the corresponding half-life time was estimated. The model revealed that diesel oil contaminated-soil microcosms under combined brewery waste effluents amendment with bioventing treatment strategy had higher biodegradation rate constants, k as well as lower half-life times, t1/2 than other remediation systems. This study showed that the microbial consortium, organic solids, nitrogen and phosphorus present in the brewery waste effluents proved to be efficient as potential biostimulation-bioaugmentation agents for bioremediation processes of soils contaminated with diesel oil.
Highlights
Petroleum-based products are the major source of energy for industry and daily life
Diesel oil is a complex mixture of alkanes and aromatic compounds that are frequently reported as soil contaminants leaking from storage tanks and pipelines or released in accidental spills [Gallego et al, 2001]
The value of the kinetic parameter showed that the degree of effectiveness of these treatment strategies in the clean-up of soil contaminated with diesel oil is in the following order: brewery waste effluents amendment with bioventing > brewery waste effluents amendment > bioventing > natural bioattenuation
Summary
Petroleum-based products are the major source of energy for industry and daily life. Leakages and accidental spills occur regularly during the exploration, production, refining, transport, and storage of petroleum and petroleum products. The technology commonly used for Journal of Ecological Engineering vol 16(2), 2015 soil remediation includes mechanical, burying, evaporation, dispersion, and washing. These technologies are expensive and can lead to incomplete decomposition of contaminants [Das and Chandra, 2011]. For this reason an increasing attention has been directed toward the research of new strategies and environmental-friendly technologies to be applied for the remediation of soil contaminated by petroleum hydrocarbons. Bioremediation technology which involves the use of microorganisms to detoxify or remove pollutants through the mechanisms of biodegradation has been found to be an environmentally-friendly, noninvasive and relatively cost-effective option [April et al, 2000]
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