Total Petroleum Hydrocarbon Reduction Research Articles

Ozone enhances biodegradability of heavy hydrocarbons in soil

The molecular complexity and the low solubility of petroleum hydrocarbon residuals in weathered soil hinder bioremediation as a clean-up strategy. Pretreatment with advanced oxidation, such as with ozone gas (O3), is a means to transform recalcitrant organics to more biodegradable forms. The efficacy of gas-phase ozone for enhancing the biodegradability of heavy residual petroleum hydrocarbons in weathered soil was tested. Ozonating soil containing ∼1% (w/w) residual petroleum hydrocarbons with a dose of 6 kg ozone/kg initial total petroleum hydrocarbons (TPHs) achieved nearly 50% TPH reduction, simultaneous with a >20-fold increase in soluble chemical oxygen demand, but with a ≤12% loss of total organic carbon. TPH molecules were converted to partly oxidised products, ten of which were identified as n-monocarboxylic acids, which were readily biodegraded, and ozonation resulted in a fourfold increase in 5-d biochemical oxygen demand (BOD5). BOD5 results after ozonation were the same with or without a microbial seed, which suggests that bioaugmentation is likely not necessary after ozonation. Deoxyribonucleic acid sequencing over the time course of the BOD5 tests showed increased diversity and changes in predominant genera, both of which underscore that ozonation made the heavy hydrocarbons readily biodegradable for soil bacteria.

Annexing Marginal Soils for Agricultural Cultivation Using an Organic Source of Fertilizer as a Bioremediation Treatment Option

This study was carried out to ascertain the practicability of using bioremediated, engine-oil-impacted soil for crop cultivation. In this study, bioremediation by land farming and nutrient enhancement was used to treat contaminated soils. In the laboratory, soil samples were homogenized, analyzed, and placed into several reactor vessels including a substrate of poultry droppings and cow dung in various ratios to the contaminated soil. During the first phase of the investigation, contaminated soil without treatment served as a control. The soil matrix was homogenized on a weekly basis, and samples were drawn during the third, fifth, eighth, tenth, and fifteenth weeks for total petroleum hydrocarbon (TPH) reduction and nutrients analysis. The initial concentrations of TPH were diluted upon the addition of the poultry litter and cow dung substrate. Results obtained during the experiment indicate that the amount of nutrients generally decreased as the weeks progressed, and the TPH degradation ranged from 78.27% to 61.84% in the reactor vessels. There was no significant difference (p < .05) in TPH degradation based on the substrate quantities, whereas the TPH reductions in the soil amended with the animal wastes were significantly different from the control sample (soil not amended with animal wastes). In the planting phase, uncontaminated, loamy soil was used as a control (the planting phase control), and the results show that maize planted on the treated soil germinated with no significant difference (p < .05) in the number of leaves and plant heights between the treated samples and the control sample (uncontaminated loamy soil). Analysis of field-scale animal waste requirements for hypothetical TPH contaminated soil covering a certain area shows that inorganic fertilizer application requires lesser quantities with lower costs than using poultry litter and cow dung to supply nutrients to support bioremediation. The study concludes that bioremediation for agricultural purpose is feasible, but it can be better implemented if the astronomical quantities of substrates required for field-scale utilization can be surmounted.

Breakdown of low-level total petroleum hydrocarbons (TPH) in contaminated soil using grasses and willows

ABSTRACTA phytoremediation study targeting low-level total petroleum hydrocarbons (TPH) was conducted using cool- and warm-season grasses and willows (Salix species) grown in pots filled with contaminated sandy soil from the New Haven Rail Yard, CT. Efficiencies of the TPH degradation were assessed in a 90-day experiment using 20–8.7–16.6 N-P-K water-soluble fertilizer and fertilizer with molasses amendments to enhance phytoremediation. Plant biomass, TPH concentrations, and indigenous microbes quantified with colony-forming units (CFU), were assessed at the end of the study. Switchgrass grown with soil amendments produced the highest aboveground biomass. Bacterial CFU's were in orders of magnitude significantly higher in willows with soil amendments compared to vegetated treatments with no amendments. The greatest reduction in TPH occurred in all vegetated treatments with fertilizer (66–75%) and fertilizer/molasses (65–74%), followed sequentially by vegetated treatments without amendments, unvegetated treatments with amendments, and unvegetated treatments with no amendment. Phytoremediation of low-level TPH contamination was most efficient where fertilization was in combination with plant species. The same level of remediation was achievable through the addition of grasses and/or willow combinations without amendment, or by fertilization of sandy soil.

Accumulation of Hydrocarbons by Maize (Zea mays L.) in Remediation of Soils Contaminated with Crude Oil

This study has investigated the use of screened maize for remediation of soil contaminated with crude oil. Pots experiment was carried out for 60 days by transplanting maize seedlings into spiked soils. The results showed that certain amount of crude oil in soil (≤2 147 mg·kg−1) could enhance the production of shoot biomass of maize. Higher concentration (6 373 mg·kg−1) did not significantly inhibit the growth of plant maize (including shoot and root). Analysis of plant shoot by GC-MS showed that low molecular weight polycyclic aromatic hydrocarbons (PAHs) were detected in maize tissues, but PAHs concentration in the plant did not increase with higher concentration of crude oil in soil. The reduction of total petroleum hydrocarbon in planted soil was up to 52.21–72.84%, while that of the corresponding controls was only 25.85–34.22% in two months. In addition, data from physiological and biochemical indexes demonstrated a favorable adaptability of maize to crude oil pollution stress. This study suggested that the use of maize (Zea mays L.) was a good choice for remediation of soil contaminated with petroleum within a certain range of concentrations.

Evaluation of constraints in bioremediation of weathered hydrocarbon-contaminated arid soils through microcosm biopile study

This research investigated the factors influencing bioremediation (biopile) of arid soils contaminated by weathered hydrocarbons. Five soils were thoroughly characterised to determine total petroleum hydrocarbons (TPH), their physicochemical properties and microbial diversity. Identified biopile-limiting factors are to be elevated petroleum hydrocarbon concentrations, high electrical conductivity and the magnitude of the recalcitrant hydrocarbon fraction. To optimise the biopile parameters, microcosm study was conducted which showed significant TPH reduction in three of five soils (BP-1, BP-2 and BP-4) but not in other two (BP-3 and BP-5), where BP-3 had a very high hydrocarbon concentration (123,757 mg kg−1) and BP-5 had a high proportion of recalcitrant hydrocarbons (>70 % of C29). Highest TPH removal (68 %) occurred in soil BP-2 and the lowest (5 %) in soil BP-3 over 56 days. Surfactant (Triton) addition, nutrient amendment or the soil dilution did not improve TPH degradation in soils BP-3 and BP-5. Phylogenetic analysis conducted during the remediation process found that hydrocarbon concentration and hydrocarbon fraction exerted the main effect on bacterial abundance, diversity and assemblage composition. At lower concentrations (~1000–4000 mg kg−1), bacterial diversity and abundance increased significantly, whilst decreased in higher concentrations. Although high TPH content and detection of TPH degraders, TPH biodegradation is limited in soil (BP-5) due to the presence of less soluble hydrocarbon fraction which indicated low TPH bioavailability (~7 %). Biopile could be applied as a technology to remediate three soils (BP-1, BP-2 and BP-4) but further modification of the biopile treatments required for other two soils BP-3 and BP-5.

The effects of oil pollution on Antarctic benthic diatom communities over 5 years

Although considered pristine, Antarctica has not been impervious to hydrocarbon pollution. Antarctica’s history is peppered with oil spills and numerous abandoned waste disposal sites. Both spill events and constant leakages contribute to previous and current sources of pollution into marine sediments. Here we compare the response of the benthic diatom communities over 5years to exposure to a commonly used standard synthetic lubricant oil, an alternative lubricant marketed as more biodegradable, in comparison to a control treatment. Community composition varied significantly over time and between treatments with some high variability within contaminated treatments suggesting community stress. Both lubricants showed evidence of significant effects on community composition after 5years even though total petroleum hydrocarbon reduction reached approximately 80% over this time period. It appears that even after 5years toxicity remains high for both the standard and biodegradable lubricants revealing the temporal scale at which pollutants persist in Antarctica.

Assessment of bioremediation of aliphatic, aromatic, resin, and asphaltene fractions of oil-sludge-contaminated soil

Oil sludge is a viscous material consisting of resin, asphaltene, sand, and water, which is usually formed at the bottom of oil reservoir tanks. Asphaltene and resin contents of oil sludge make it more resistant to biodegradation. Disposal of oil sludge is the main problem of oil industry; discharge of oil sludge into the soil causes damage to the environment. Bioremediation is an efficient, cheap, and environmentally friendly method for oil-sludge treatment. The aim of this study was to investigate the biodegradation of oil-sludge fractions in contaminated soil for a period of 12 months. The oil sludge was mixed with soil with the final concentration of 5 % (w/w), and the nutrients such as phosphate and nitrate salts were added to soil. Finally, reduction of aliphatic, aromatic, resin, and asphaltene was tested. The results showed that the reduction of total petroleum hydrocarbon was 31 ± 5 % during 12 months of the treatment. About 60 ± 8 % of total aliphatic fractions, mainly C14–C22, decreased. Analysis for the detection of two, three, and four rings of polycyclic aromatic hydrocarbons demonstrated about 42 ± 3 % reduction of total aromatic fractions, whereas the resin (6 ± 0.8 %) and asphaltene (4 ± 0.5 %) fractions were slightly biodegraded. In conclusion, biotreatment of oil sludge during 12 months could well reduce aliphatic and aromatic fractions, but more time is needed for resin and asphaltene reduction.

Optimizing photo-Fenton like process for the removal of diesel fuel from the aqueous phase.

BackgroundIn recent years, pollution of soil and groundwater caused by fuel leakage from old underground storage tanks, oil extraction process, refineries, fuel distribution terminals, improper disposal and also spills during transferring has been reported. Diesel fuel has created many problems for water resources. The main objectives of this research were focused on assessing the feasibility of using photo-Fenton like method using nano zero-valent iron (nZVI/UV/H2O2) in removing total petroleum hydrocarbons (TPH) and determining the optimal conditions using Taguchi method.ResultsThe influence of different parameters including the initial concentration of TPH (0.1-1 mg/L), H2O2 concentration (5-20 mmole/L), nZVI concentration (10-100 mg/L), pH (3-9), and reaction time (15-120 min) on TPH reduction rate in diesel fuel were investigated. The variance analysis suggests that the optimal conditions for TPH reduction rate from diesel fuel in the aqueous phase are as follows: the initial TPH concentration equals to 0.7 mg/L, nZVI concentration 20 mg/L, H2O2 concentration equals to 5 mmol/L, pH 3, and the reaction time of 60 min and degree of significance for the study parameters are 7.643, 9.33, 13.318, 15.185 and 6.588%, respectively. The predicted removal rate in the optimal conditions was 95.8% and confirmed by data obtained in this study which was between 95-100%.ConclusionIn conclusion, photo-Fenton like process using nZVI process may enhance the rate of diesel degradation in polluted water and could be used as a pretreatment step for the biological removal of TPH from diesel fuel in the aqueous phase.

Oil Extraction From Oil Sludge and TPH Elimination of Solids/Water by Ozonation

About 1.1 million barrels of oil sludge are generated yearly in Indonesia by many oil and refinery industrial activities. Oil is strongly bound with solid particles in the sludge. Oilin the sludge may range from benzene, phenols to polycyclic aromatic hydrocarbons which are classified as toxic, mutagenic and carcinogenic for human and pollute the environment. Oilextraction is favorable option because of environmental and economical reasons. Oil sludge from an oil fields inSumatra, Indonesia was extracted at low temperature (40–70 °C) resulting in Total Petroleum Hydrocarbon (TPH) around 1–2%. After addition of 10,000 ppm REKLIN G04 surfactant, TPH extraction was improved to 9%. After decantation, effluent water containing ± 15,000 ppm TPH was ozonated for 60 minutes resulting in TPH reduction to ± 5 ppm. After ozonation, TPH of discharge solids was only 7–40 ppm. Fingerprint by gas chromatography showed removal of light fraction of oil after ozonation.

Effect of biologically treated petroleum sludge on seed germination and seedling growth of Vigna unguiculata (L.) Walp. (Fabaceae)

The present investigation was carried out to study the response of different concentrations of treated petroleum sludge on seed germination, root and shoot length and tolerance of Vigna unguiculata (L.) Walp. The biologically treated petroleum sludge with bacterial consortium showed 54.8% reduction in total petroleum hydrocarbons. Treated sludge was utilized with agricultural soil in known concentration for the assessment of growth of V. unguiculata. A remarkable absence of seed germination was observed at higher sludge concentration. The different concentrations of treated petroleum sludge showed severe decline on the length, weight and vigour index of the tested seedlings with increasing sludge concentrations. The results showed that the difference in rate of seed germination was significant among various concentrations. Under environmental stress condition, germination is the most critical phase of life cycle in crop plants. In this present study, the high oil content found to alter the osmotic relation between seed and water and thus reduce the amount of water absorbed. It was concluded that the concentration of nutrients and oil present in the treated sludge were toxic to the plant.

The effects of Fenton process on the removal of petroleum hydrocarbons from oily sludge in Shiraz oil refinery, Iran

BackgroundDue to the high concentrations of total petroleum hydrocarbons (TPH) in oily sludge and their environmental hazards, the concern regarding their effects on health and the environment has increased. The main objective of this research was focused on evaluating the feasibility of using Fenton process in removing TPH in oily sludge from Shiraz oil refinery, Southern Iran.ResultsTo determine optimum conditions, four different parameters were assessed at four different levels using Taguchi method. According to data, the optimum conditions were as follows: the reaction time of 1 hour, H2O2 to sample mass ratio of 15, H2O2 to Fe (II) molar ratio of 10 and pH of 5. The maximum TPH reduction rate was 36.47%. Because of the semi-solid nature of the sample and the hydroxyl radicals mainly generated in the aqueous solution, TPH reduction rate greatly improved by adding water. Ultimately, by adding 40 ml water per gram of the oily sludge under optimized conditions, the reduction rate of 73.07% was achieved.ConclusionsThe results demonstrated that this method can be used as a pre-treatment method for the oily sludge. Moreover, a complementary treatment is necessary to reach the standard limit.

Investigation of Impact Factors on the Treatment of Oily Sludge using a Hybrid Ultrasonic and Fenton's Reaction Process

In this study, a hybrid ultrasonic and Fenton's reaction process (US/Fenton) was applied for oily sludge treatment. The impacts of four different factors on the reduction of total petroleum hydrocarbons (TPH) in oily sludge were investigated. These include the initial sludge content, the molar ratio of hydrogen peroxide to iron (H2O2/Fe2+), the ultrasonic power, and the ultrasonic treatment duration. Taguchi experimental design method was used to arrange laboratory experiments. The results indicated that a TPH reduction rate of up to 88.1% was reached with an initial sludge content of 20 g/L, a H2O2/Fe 2+ molar ratio of 4:1, an ultrasonic treatment time of 5 min, and an ultrasonic power of 60 W. The initial oily sludge content and ultrasonic treatment duration were found to be the most significant factors affecting the US/Fenton treatment of oily sludge.

압축공기 분사시스템을 이용한 유류오염 해안의 효율적 정화 및 이에 따른 미생물군집분석

본 연구의 목표는 압축공기분사시스템을 이용하여 원유로 유출이 된 해안을 정화함에 있어서 그 정화효율성과 정화 전후의 총석유탄화수소(total petroleum hydrocarbon; TPH) 농도 및 미생물군집변화를 관찰함으로써 그 최적 정화과정을 이해하기 위한 기초자료를 얻고자 하는 것이다. 압축공기제트시스템을 2-5회 연속적용 시 오염지의 TPH가 약 66%까지 저감이 된 반면에 대조구인 해수를 펌핑한 경우에는 40% 정도의 저감효과가 관찰이 되었다. 압축공기의 분사 후 PCR-DGGE에 의한 미생물군집분석 결과에서는 유류분해미생물의 군집은 확인이 되지 않았다. 이는 정화에 의한 낮은 TPH 농도(약 100 mg/kg 수준, 탄소원), 처리환경에 내재적인 제한적인 질소 및 인의 농도에 기이한 것으로 판단된다. 따라서 잔여분의 유류는 에어제트시스템을 적용시 제한적 영양염류(질소 및 인 등)를 적절한 방식과 농도로 투여할 경우 거의 완전하게 제거가 가능할 것으로 사료된다. 향후 본 기술은 고농도의 유류 및 유기물로 오염된 다양한 수질환경 및 토양환경의 효율적이고 환경친화적인 정화에 활용이 될 것으로 기대된다. The objectives of this study were to investigate effectiveness of the Compressed Air Jet (CAJ) System for cleaning up shorelines contaminated with crude oils and to examine effects of the system on total petroleum hydrocarbon (TPH) removal and microbial community changes before and after remediation of the oil-contaminated shorelines. These data will lead to better understanding of optimized remediation process. About 66% of TPH reduction was observed when the contaminated site was treated with the CAJ System 2, 3, 4, and 5 times. This treatment system was more efficient than the seawater pumping system under similar treatment conditions (by 40%). By the way, little oil degrader communities were observed despite a potential function of the air jet system to stimulate aerobic oil degraders. The apparent low population density of the oil degraders might be as a result of low concentration of TPH as a carbon source and limiting nutrients such as nitrogen and phosphorus. It was proposed that the CAJ System would contribute significantly to removal of residual oils on the shorelines in combination with addition of these limiting nutrients.

PHYTOREMEDIATION OF CRUDE-OIL CONTAMINATED MANGROVE SOIL BY Rhizophora racemosa

This study examined the phytoremediative potentials of Rhizophora racemosa in remediation of crude-oil contaminated mangrove soil ecosystem. Results revealed that hydrocarbon utilizing bacterial load increased substantially over the ninety days growth period. The highest increase (77.5%) was recorded in acute crude-oil contaminated soil with three R. racemosa seedlings and poultry manure and lowest increase was recorded in acute oil treatment without poultry manure. The total petroleum hydrocarbon (TPH) and heavy metals levels decreased substantially at the end of period of growth. The highest percentage reduction in TPH of 96.16% was recorded in acute crude-oil contaminated soil containing three R racemosa seedlings and poultry manure. The lowest percentage reduction of 38.3% was recorded in acute crude-oil contaminated soil without poultry manure. Generally, mangrove seedlings with acute and chronic treatments showed potentials for phytoremediation of crude-oil contaminated soil, the former demonstrated greater phytoremediation than the later. Seedlings treated with poultry manure showed more remarkable potentials and promptness for phytoremediation of crude-oil contaminated soil than untreated ones. Equally, there was gradual reduction in pH during the ninety-day growth period. Results from this study also indicated that acute contamination of crude-oil has more adverse effect on the mangrove ecosystem than chronic contaminations. The stem height, stem girth (diameter), number of leaves and leaf area (length and width) of the mangrove seedlings, Rhizophora racemosa increased comparably fortnightly in the ninety days growth period. This study has shown that mangrove plants together with microbial actions are efficient and fast in phytoremediation of crude-oil in a mangrove ecosystem. Keyword : Phytoremediation, oil polluted mangrove soil, Rhizophora racemosa .

Bioremediation of Soil Contaminated with Biodiesel and Glycerin - Results of Soil Microbial Adaptation Through Evidence Contaminants Removal

Sources of contamination with Total Petroleum Hydrocarbons (TPH) in soil are related to exploration, production, storage, transportation, distribution and disposal of fuels, such as biodiesel. Therefore, this study examined the ability of bioremediation of soil contaminated with biodiesel and glycerol using mixed culture (C1) from site contaminated by petroleum products. The culture was adapted in two stages of adaptation: in the first stage to the liquid medium and later in contaminated soil contaminated by biodiesel and glycerol, called R01. For adaptation of microorganisms to the contaminated soil, the reactor R01 contained 1.5 kg of soil in which the relationship C: N: P-100 has been corrected: 10:1, as well as pH, humidity and oxygenation of the soil. It was used the technique bioaugmentation with 4 reactors called R1, R2, R3 and R4. In each of these reactors was used a total of 400g of contaminated soil with percentages of 15 %, 20 %, 25 % and 30 % by weight of soil corresponding to fractions removed from R01 source. The same operating procedures employed in R01 were applied in monitoring the 4 reactors for 111 d. The results show that after 111 days there was a reduction of TPH (%): 21, 31, 43 and 51 in reactors.

Polymer Partitioning Approach for Petroleum Hydrocarbon Reduction in a Clay Soil

Soil contamination by crude oil is a major environmental and health hazard. Extraction of the total petroleum hydrocarbons (TPH) sorbed to the clay soil (kaolin) was carried out using synthetic sorbent (Desmopan®) and 2-propanol as a mobilizing agent. The crude oil-loaded polymer beads were bioregenerated in a solid–liquid two-phase partitioning bioreactor (TPPB). A central composite design under response surface methodology was employed for the experimental design and analysis of the results. The independent variables were extraction phase to soil ratio, mobilizing agent to soil ratio, and initial concentration of crude oil in polluted soil. The influences of three independent variables on the TPH reduction efficiency were determined using a statistically significant quadratic model (R 2 = 0.9673). Remediation was more efficient when the mobilizing agent to the soil ratio was equal to 3.00 ml g−1, compared to the higher (4.00 ml g−1) and lower (2.00 ml g−1) levels. The results exhibited that the interaction between the extraction phase ratio and the initial concentration of crude oil in kaolin had significantly influenced the TPH removal. The bioregeneration studies showed a significant reduction (72.07 ± 0.63 %) of low-molecular-weight (two- to three-ring) polycyclic aromatic hydrocarbons and n-alkanes (97.75 ± 0.26 %) present in the crude oil-loaded solid polymers within a 10-day experiment. These findings show that solid polymer extraction followed by bioregeneration of sorbents in a TPPB is applicable to treat crude oil-contaminated kaolin.

Multi-process Bioremediation as an Improved Approach for Petroleum-contaminated Soil Restoration

A multiprocess bioremediation approach was applied to treat petroleum-contaminated soil from Dagang Oilfield, China. The bioremediation processes involved the use of four exogenous microbial strains and six herbage plants screened from a large number of species to remove low levels of total petroleum hydrocarbons (TPH) in contaminated soil. The experimental results indicated that the reduction of TPH increased with the improved community structure from the exogenous petroleum-degrading bacteria by over 35% as compared with that using the indigenous bacterial community. The refreshed microbial consortium was also able to accelerate the reduction of TPH via plant roots (phytoremediation) by over 47%. The TPH reduction rate diminished over time. Molecular biomarker ratios such as Ph/nC17, Pr/nC18 increased during the experiment but the ratio of Pr/Ph decreased. The results suggested that the multi-process bioremediation may significantly shorten the bioremediation duration and can be quite effective for treatment of soils contaminated by lower levels of petroleum.

Application of Ultrasound and Fenton's Reaction Process for the Treatment of Oily Sludge

In this study, three advanced oxidation processes (AOP) were investigated for their capabilities to reduce petroleum hydrocarbons (PHC) in oily sludge. These include ultrasonic treatment alone, Fenton's reaction process alone, and the combination of ultrasound and Fenton's reaction (US/Fenton). Under the experimental conditions, the ultrasonic treatment and Fenton's reaction process achieved a reduction of 22.6% and 13.8% in the total petroleum hydrocarbons (TPH), respectively. However, a TPH reduction of 43.1% was observed for the combined process of ultrasound and Fenton's reaction, indicating that the individual AOP is complementary to one another. As a result, the combined process could be acted as a more effective method to treat oily sludge as compared to the single AOP.

Plant residues — A low cost, effective bioremediation treatment for petrogenic hydrocarbon-contaminated soil

Petrogenic hydrocarbons represent the most commonly reported environmental contaminant in industrialised countries. In terms of remediating petrogenic contaminated hydrocarbons, finding sustainable non-invasive technologies represents an important goal. In this study, the effect of 4 types of plant residues on the bioremediation of aliphatic hydrocarbons was investigated in a 90day greenhouse experiment. The results showed that contaminated soil amended with different plant residues led to statistically significant increases in the utilisation rate of Total Petroleum Hydrocarbon (TPH) relative to control values. The maximum TPH reduction (up to 83% or 6800mgkg−1) occurred in soil mixed with pea straw, compared to a TPH reduction of 57% (4633mgkg−1) in control soil. A positive correlation (0.75) between TPH reduction rate and the population of hydrocarbon-utilising microorganisms was observed; a weaker correlation (0.68) was seen between TPH degradation and bacterial population, confirming that adding plant materials significantly enhanced both hydrocarbonoclastic and general microbial soil activities. Microbial community analysis using Denaturing Gradient Gel Electrophoresis (DGGE) showed that amending the contaminated soil with plant residues (e.g., pea straw) caused changes in the soil microbial structure, as observed using the Shannon diversity index; the diversity index increased in amended treatments, suggesting that microorganisms present on the dead biomass may become important members of the microbial community. In terms of specific hydrocarbonoclastic activity, the number of alkB gene copies in the soil microbial community increased about 300-fold when plant residues were added to contaminated soil. This study has shown that plant residues stimulate TPH degradation in contaminated soil through stimulation and perhaps addition to the pool of hydrocarbon-utilising microorganisms, resulting in a changed microbial structure and increased alkB gene copy numbers. These results suggest that pea straw in particular represents a low cost, effective treatment to enhance the remediation of aliphatic hydrocarbons in contaminated soils.

Monitored natural attenuation of a long-term petroleum hydrocarbon contaminated sites: a case study

This study evaluated the potential of monitored natural attenuation (MNA) as a remedial option for groundwater at a long-term petroleum hydrocarbon contaminated site in Australia. Source characterization revealed that total petroleum hydrocarbons (TPH) as the major contaminant of concern in the smear zone and groundwater. Multiple lines of evidence involving the geochemical parameters, microbiological analysis, data modelling and compound-specific stable carbon isotope analysis all demonstrated natural attenuation of hydrocarbons occurring in the groundwater via intrinsic biodegradation. Groundwater monitoring data by Mann-Kendall trend analysis using properly designed and installed groundwater monitoring wells shows the plume is stable and neither expanding nor shrinking. The reason for stable plume is due to the presence of both active source and natural attenuation on the edge of the plume. Assuming no retardation and no degradation the contaminated plume would have travelled a distance of 1,096 m (best case) to 11,496 m (worst case) in 30 years. However, the plume was extended only up to about 170 m from its source. The results of these investigations provide strong scientific evidence for natural attenuation of TPH in this contaminated aquifer. Therefore, MNA can be applied as a defensible management option for this site following significant reduction of TPH in the source zone.