Laboratory study on the bioremediation of diesel oil contaminated soil from a petrol station

Abstract

The purpose of the present study was to investigate possible methods to enhance the rate of aerobic biodegradation of hydrocarbons (ex-situ treatments). In this work, the bioremediation processes were applied to a sandy soil with a high level of contamination originated from the leakage of a diesel oil underground storage tank at a petrol station. Laboratory scale experiments (Bartha biometer flasks) were used to evaluate the biodegradation of the diesel oil. Enhancement of biodegradation was carried out through biostimulation (addition of nitrogen and phosphorus solutions or Tween 80 surfactant) and bioaugmentation (bacterial consortium isolated from a landfarming system). To investigate interactions between optimizing factors, and to find the right combination of these agents, the study was based on full factorial experimental design. Efficiency of biodegradation was simultaneously measured by two methods: respirometric (microbial CO2 production) and gas chromatography. Acute toxicity tests with Daphnia similis were applied for examination of the efficiency of the processes in terms of the generation of less toxic products. Results showed that all bioremediation strategies enhanced the natural bioremediation of the contaminated soil and the best results were obtained when treatments had nutritional amendment. Respirometric data indicated a maximum hydrocarbon mineralization of 19.8%, obtained through the combination of the three agents, with a total petroleum hydrocarbons (TPH) removal of 45.5% in 55 days of treatment. At the end of the experiments, two predominant bacteria species were isolated and identified (Staphylococcus hominis and Kocuria palustris).

Investigation about the efficiency of the bioaugmentation technique when applied to diesel oil contaminated soils

“…Soil samples were separately homogenized by a thorough mixing and divided into three aliquots, in which the amendment solution of each treatment was added. The nitrogen and phosphorus correction was performed, respectively, using (NH 4 ) 2 SO 4 and KH 2 PO 4 solutions to obtain a nutrient ratio (C:N:P) of 100:15:1 (Mariano et al, 2007). The bacterial consortium (Staphylococcus hominis and Kocuria palustris) was added at a concentration of 10 6 Colony Forming Units (CFU) per gram of dry soil.…”

“…The cultures of Staphylococcus hominis and Kocuria palustris were isolated from the diesel oil contaminated soil of the service station ASP and identified by rDNA 16S sequence (performed by CPQBA/UNICAMP) (Mariano et al, 2007). In treatments 3, 6 and 9, inoculum was prepared as follow: bacteria were grown separately on liquid PCA medium (10 mL), and incubated at 35 o C for 48 h. Cells were harvested by centrifugation (8,000 rpm for 10 min) and the supernatant was discharged.…”

“…For both the soils, the addition of nutrients had a statistically significant positive effect in the biodegradation efficiency (ANOVA analysis, 95% confidence level). Biostimulation with the addition of fertilizers (N and P) has been reported as an important factor to enhance the soil bioremediation (Gallego et al, 2001;Cardona and Iturbe, 2003;Mariano et al, 2007). However, when considering the main focus of this study, i. e. the enhancement of bioremediation by inoculum injection, it had no effect in ASP soil, and in SB soil, the negative influence of the inoculum reduced the effect of the nutrient injection and this treatment obtained a biodegradation efficiency with no significant difference to the control.…”

Biodegradability of commercial and weathered diesel oils

“…The bacteria cultures of Staphylococcus hominis and Kocuria palustris were isolated from the soil of the petrol station where the weathered diesel oil was collected and identified by rDNA 16S sequence (performed by CPQBA/ UNICAMP) (21). The bacterial strain Pseudomonas aeruginosa LBI was isolated by Benincasa et al (5) from a hydrocarbon contaminated area.…”

Monitoramento de indicadores geoquímicos e avaliação de biodegradação em área contaminada com óleo diesel

“…Vol.12 -Nº 3 -jul/set 2007, 296-304 ou natural); a adição de agentes estimulantes como nutrientes, oxigênio e biossurfactantes (bioestimulação); e a inoculação de consórcios microbianos enriquecidos (bioaumento) (Bento et al, 2003;Mariano et al, 2007). O benefício desses processos é a mineralização do poluente, isto é, a transformação em gás carbônico, água e biomassa.…”