Samuel E. Agarry

Bioremediation of Soil Artificially Contaminated with Petroleum Hydrocarbon Oil Mixtures: Evaluation of the Use of Animal Manure and Chemical Fertilizer

ABSTRACT The search for cheaper and environmentally friendly options of enhancing petroleum hydrocarbon degradation has continued to elicit research interest. One of such options is the use of animal manure as biostimulating agents. A combination of treatments consisting of the application of poultry manure, piggery manure, goat manure, and chemical fertilizer was evaluated in situ during a period of 4 weeks of remediation. Each treatment contained petroleum hydrocarbon mixture (kerosene, diesel oil, and gasoline mixtures) (10% w/w) in soil as a sole source of carbon and energy. After 4 weeks of remediation, the results showed that poultry manure, piggery manure, goat manure, and NPK (nitrogen, phosphorous, and potash [potassium]) fertilizer exhibited 73%, 63%, 50%, and 39% total petroleum hydrocarbon degradation, respectively. Thus, all the biostimulating treatment strategies showed the ability to enhance petroleum hydrocarbon microbial degradation. However, poultry manure, piggery manure, and goat manure treatments showed greater petroleum hydrocarbon reductions than NPK fertilizer treatment. A first-order kinetic equation was fitted to the biodegradation data and the specific degradation rate constant (k) values obtained showed that the order of effectiveness of these biostimulating strategies in the cleanup of soil contaminated with petroleum hydrocarbon mixtures (mixture of kerosene, diesel oil, and gasoline) is NPK fertilizer < goat manure < piggery manure < poultry manure. Therefore, this present work has indicated that the application of poultry manure, piggery manure, goat manure, and chemical fertilizer could enhance petroleum hydrocarbon degradation with poultry manure, showing a greater effectiveness and thus could be one of the severally sought environmentally friendly ways of remediating natural ecosystem contaminated with crude oil.

Substrate inhibition kinetics of phenol degradation by Pseudomonas fluorescence from steady state and wash-out data

The present study investigated the phenol utilization kinetics of a pure culture of an indigenous Pseudomonas fluorescence under steady state and non-steady state (washout) conditions. Steady states of a continuous culture with an inhibitory substrate was used to estimate kinetic parameters under substrate limitation (chemo stat operation) Pure cultures of an indigenous Pseudomonas fluorescence were grown in continuous culture on phenol as the sole source of carbon and energy at dilution rates of 0.010 - 0.20/h. Using different dilution rates, several steady states were investigated and the specific phenol consumption rates were calculated. In addition, phenol degradation was investigated by increasing the dilution rate above the critical dilution rate (washout cultivation). The results showed that the specific phenol consumption rate increased with increased dilution rate at steady state and phenol degradation by Pseudomonas fluorescence can be described by simple substrate inhibition kinetics under substrate limitation but cannot be described by simple substrate inhibition kinetics under washout cultivation. Fitting of the steady state data from continuous cultivation to various inhibition models resulted in the best fit for Haldane, Yano and Koga (2), Aiba and Teissier kinetic inhibition models. The rsmax value of 0.229 mg/mg/h obtained from the inhibition model equations was comparable to the experimentally calculated rsmax value of 0.246 mg/mg/h obtained under washout cultivation. Therefore, the biokinetic constants evaluated using these models showed good tolerance and growth of the indigenous organism.

Studies on Biodegradation of Kerosene in Soil under Different Bioremediation Strategies

ABSTRACT The effectiveness of bioremediation is often a function of the microbial population and how they can be enriched and maintained in an environment. Strategies for inexpensive in situ bioremediation of soil contaminated with petroleum hydrocarbons include stimulation of the indigenous microorganisms by introduction of nutrients (biostimulation) and/or through inoculation of an enriched mixed microbial culture into soil (bioaugmentation). To demonstrate the potential use of bioremediation in soil contaminated with kerosene, a laboratory study with the objective of evaluating and comparing the effects of bioattenuation, biostimulation, bioaugmentation, and combined biostimulation and bioaugmentation was performed. The present study dealt with the biodegradation of kerosene in soil under different bioremediation treatment strategies: bioattenuation, biostimulation, bioaugmentation, and combined biostimulation and bioaugmentation, respectively. Each treatment strategy contained 10% (w/w) kerosene in soil as a sole source of carbon and energy. After 5 weeks of remediation, the results revealed that bioattenuation, bioaugmentation, biostimulation, and combined biostimulation and bioaugmentation exhibited 44.1%, 67.8%, 83.1%, and 87.3% kerosene degradation, respectively. Also, the total hydrocarbon-degrading bacteria (THDB) count in all the treatments increased with time up till the second week after which it decreased. The highest bacterial growth was observed for combined biostimulation and bioaugmentation treatment strategy. A first-order kinetic model equation was fitted to the biodegradation data to further evaluate the rate of biodegradation and the results showed that the specific degradation rate constant (k) value was comparatively higher for combined biostimulation and bioaugmentation treatment strategy than the values for other treatments. Therefore, value of the kinetic parameter showed that the degree of effectiveness of these bioremediation strategies in the clean up of soil contaminated with kerosene is in the following order: bioattenuation < bioaugmentation < biostimulation < combined biostimulation and bioaugmentation. Conclusively, the present work has defined combined biostimulation and bioaugmentation treatment strategy requirements for kerosene oil degradation and thus opened an avenue for its remediation from contaminated soil.

MODIFIED PLANTAIN PEEL AS CELLULOSE-BASED LOW-COST ADSORBENT FOR THE REMOVAL OF 2,6-DICHLOROPHENOL FROM AQUEOUS SOLUTION: ADSORPTION ISOTHERMS, KINETIC MODELING, AND THERMODYNAMIC STUDIES

In this study, the feasibility of using modified plantain peel to remove 2,6-dichlorophenol from iaqueous solutions was investigated under batch mode. The effects of physical factors such as initial 2,6-dichlorophenol concentration, contact time, biosorbent particle size, biosorbent dosage and temperature on the removal process were evaluated. The results showed that biosorption of 2,6-dichlorophenol was dependent on these factors. The equilibrium biosorption data were analyzed by the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) adsorption isotherm models. The four tested isotherm models provided good fits to the experimental data obtained at 30°C; however, the Freundlich isotherm model provided the best correlation (R2 = 0.9874) of the experimental data. The maximum monolayer biosorption capacity (Q max ) was found to be 14.25 mg/g. The biosorption kinetics data of 2,6-dichlorophenol were analyzed by pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, and liquid film diffusion models. The five kinetic models fitted well to the biosorption kinetic data; however, the pseudo-second-order kinetic model gave the best fit when the biosorption mechanism was controlled by film diffusion. Thermodynamic quantities such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), standard entropy change of biosorption (ΔS°), and activation energy (Ea) were evaluated, and it was found that the biosorption process was spontaneous, feasible, endothermic in nature and of dual nature, physisorption and chemisorption; however, the physisorption process was dominant. Therefore, modified plantain peel has potential for application as an effective bioadsorbent for removal of 2,6-dichlorophenol from aqueous solution.

Kinetic Modelling and Half-Life Study on Enhanced Soil Bioremediation of Bonny Light Crude Oil Amended with Crop and Animal-Derived Organic Wastes

In this study, the potential effects of crop and animal-derived organic wastes as nutrient supplements to biostimulate autochthonous microflora for hydrocarbon biodegradation were investigated. Microcosms containing soil were spiked with weathered Bonny light crude oil (WBLCO) (10 % w/w) and amended with various amounts of groundnut shell, beans shell, melon shell, cassava peels, cow dung and pig dung alone or in combinations. The rates of biodegradation of the crude oil were studied for a remediation period of 42 days under laboratory conditions. The results showed that there was a positive relationship between the rate of petroleum hydrocarbons biodegradation and presence of the crop and animal-derived organic wastes alone or in combination in soil microcosms contaminated with crude oil. The WBLCO biodegradation data fitted well to the first-order kinetic model. The model revealed that WBLCO contaminated-soil microcosms amended with crop and animal-derived organic wastes had higher biodegradation rate constants (k) as well as lower half-life times (t1/2) than soil microcosms amended with NPK fertilizer and unamended soil (natural attenuation) remediation system. The biodegradation rate constant and estimated biostimulation efficiency values showed that among the crop and animal-derived organic wastes used alone and in combinations, pig dung suggest to offer the best biostimulation performance, which was closely followed by the combination of pig dung and cassava peels. The system proposed here is inexpensive, efficient, and environmentally friendly and may thus offer a viable choice for petroleum hydrocarbons-contaminated soil remediation.

Biodegradation of phenol in refinery wastewater by pure cultures of Pseudomonas aeruginosa NCIB 950 and Pseudomonas fluorescence NCIB 3756

The potential of microorganisms to catabolise and metabolise xenobiotic compounds has been recognised as a potentially effective means of toxic and hazardous wastes disposal. Phenol and its derivatives have long been recognised as some of the most persistent chemicals in petroleum refinery wastewaters, with high toxicity even at low concentrations. Biodegradation of these compounds has been recognised as a potential solution for their disposal owing to its cost effectiveness and simplicity. Two species of pseudomonas, P. aeruginosa and P. fluorescence, were studied for their biodegradation potential on phenol present in a refinery wastewater under a batch fermentation process. Phenol was successfully degraded by both species, and there was high positive correlation between phenol biodegradation and microbial growth. The maximum specific growth rate were obtained for both species from the Haldane model. The study revealed the high potential of these local strains, with P. aeruginosa being more effective, and the possibility of using them in bioremediation of petroleum refinery wastewaters.

Biosorption equilibrium, kinetic and thermodynamic modelling of naphthalene removal from aqueous solution onto modified spent tea leaves

The object of this study was to investigate the feasibility of using modified spent tea leaves to remove naphthalene from its aqueous solution under batch mode. The effects on the removal process of physical factors, such as initial naphthalene concentration, contact time, biosorbent dosage, pH and temperature, have been evaluated. The equilibrium biosorption data were analyzed by the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) adsorption isotherm models. These models provided a good fit to the experimental data, but the Langmuir isotherm model provided the best correlation (R 2=0.993) to the experimental data. The biosorption kinetic data of naphthalene were analyzed by pseudo-first-order, pseudo-second-order and intra-particle diffusion and surface mass transfer kinetic models. These four kinetic models fitted the biosorption kinetic data well, but the pseudo-first-order kinetic model gave the best fit. The activation energy (E a ) was found to be 15.89 kJ per mole and the thermodynamic properties of the biosorption process, such as the Gibbs free energy, enthalpy and the entropic change of biosorption, were also evaluated. It was established that the biosorption process was spontaneous, feasible and endothermic in nature.

Box-Behnken design application to study enhanced bioremediation of soil artificially contaminated with spent engine oil using biostimulation strategy

This work studies the biodegradation of spent engine oil in soil using Box-Behnken design under response surface methodology. NPK fertilizer (inorganic nutrient), Tween 80 (nonionic surfactant), and pig manure (organic nutrient) concentrations were used as independent biostimulant variables, while total petroleum hydrocarbon (TPH) and hexavalent chromium (Cr (VI)) reductions as dependent variables (response) in a 42-day remediation period. A statistically significant second-order quadratic regression model for TPH and Cr (VI) removal was obtained. The coefficient of determination (R2 = 0.9995 for TPH and 0.9988 for Cr (VI)) and probability value (P < 0.0001) demonstrated significance for the regression model. Numerical optimization technique based on desirability function was carried out for initial spent engine oil concentration of 10% w/w to optimize the biodegradation process. The optimum values for biostimulation agents to achieve a predicted maximum TPH and Cr (VI) removal of 67.20% and 53.20%, respectively, were found to be as follows: NPK fertilizer, 4.22 g; Tween 80, 10.69 mg/l; and pig manure, 47.76 g. At this optimum point, the observed TPH and Cr (VI) reductions were found to be 66.47% and 52.33%, respectively. The statistical analyses and the closeness of the experimental results and model predictions show the reliability of the regression model, and thus, biostimulation of indigenous microbial density and activity can reduce remediation period of petroleum hydrocarbon and heavy metal-contaminated environment and subsequently the cost of remediation.

Kinetic Modelling and Half-Life Study on Bioremediation of Soil Co-Contaminated with Lubricating Motor Oil and Lead Using Different Bioremediation Strategies

The focus of this study was to investigate the effect of nutrient supplement (urea fertilizer) and microbial species augmentation (mixed culture of Aeromonas, Micrococcus, and Serratia sp.) on biodegradation of lubricating motor oil (LMO) and lead uptake by the autochthonous microorganism in LMO and lead-impacted soil were investigated. The potential inhibitory effects of lead on hydrocarbon utilization were investigated over a wide range of lead concentrations (25–200 mg/kg) owing to the complex co-contamination problem frequently encountered in most sites. Under aerobic conditions, total petroleum hydrocarbons (TPH) removal was 45.3% in the natural attenuation microcosm while a maximum of 72% and 68.2% TPH removal was obtained in biostimulation and bioaugmentation microcosms, respectively. Lead addition, as lead nitrate, to soil samples reduced the number of hydrocarbon degraders in all samples by a wide range (11–52%) depending on concentration and similarly, the metabolic activities were affected as observed in mineralization of LMO (3–60%) in soils amended with various lead concentrations. Moreover, the uptake of lead by the autochthonous microorganisms in the soil reduced with increase in the initial lead concentration. First-order kinetics described the biodegradation of LMO very well. The biodegradation rate constants were 0.015, 0.033, and 0.030 day−1 for LMO degradation in natural attenuation, biostimulation and bioaugmentation treatment microcosms, respectively. The presence of varying initial lead concentration reduced the biodegradation rate constant of LMO degradation in the biostimulation treatment microcosm. Half-life times were 46.2, 21, and 23 days for LMO degradation in natural attenuation, biostimulation and bioaugmentation treatment microcosms, respectively. The half-life time in the biostimulation treatment microcosm was increased with a range between 10.7 and 39.2 days by the presence of different initial lead concentration. The results have promising potential for effective remediation of soils co-contaminated with hydrocarbons and heavy metals.

Anaerobic bioremediation of marine sediment artificially contaminated with anthracene and naphthalene

The bioremediation of marine sediments contaminated with naphthalene and anthracene was studied under anaerobic conditions to investigate the enhancing effect of a biostimulating agent (Tween 80, silicone oil, pig dung and NPK fertilizer) on the rate of degradation. Sediment samples were amended with the biostimulating agent (alone or in combination). The results showed that all the tested agents, applied individually to the sediments, increased the rate of anthracene and naphthalene degradation, with the pig dung having the greatest effect. The biodegradation data were fitted to a pseudo‐first‐order kinetic model, from which the biodegradation rate constant, as a measure of the enhancement of degradation rate by the biostimulators, was estimated. The rate constant values were consistently higher for the sediments treated with individual stimulators, or a combination of them, than for the untreated sediment. The contaminated sediment treated with the combination of Tween 80 and pig dung exhibited the highest biodegradation rate. The results indicated that the effect of various biostimulating agents, in combination or alone, on enhancing the degradation rate of anthracene and naphthalene can be arranged in the following order: Tween 80 + pig dung > silicone oil + pig dung > Tween 80 + NPK fertilizer > silicone oil + NPK fertilizer > pig dung > NPK fertilizer > Tween 80 > silicone oil. The addition of biostimulators increased the biodegradation potential of the intrinsic microbial populations; thus, these results will contribute to the development of new strategies for in situ bioremediation of anoxic sediments contaminated with polycyclic aromatic hydrocarbons (PAHs).