Evaluation of the effects of inorganic and organic fertilizers and activated carbon on bioremediation of soil contaminated with weathered crude oil

The objective of this study was designed to evaluate the effects of nutrients (inorganic NPK fertilizer and organic fertilizer) and adsorptive amendment agents (activated carbon) as well as their interactions on bioremediation of soil contaminated with Weathered Crude Oil (WECO). The organic fertilizer was made up of cattle dungs, pig dungs and poultry droppings mixtures. Box Behnken Design (BBD) of Response Surface Methodology (RSM) with three levels and three factors was used having inorganic NPK fertilizer (3 - 5 g), activated carbon (20 - 40g) and organic fertilizer (30 - 50 g) as independent variables and percentage WECO degradation as dependent variable (response) in a four weeks remediation period. Results of the study showed that WECO removal rate in soil is invariably dependent on the amount of nutrient and adsorptive agents. The optimum amount of nutrient and adsorptive amendment agents obtained to achieve a predicted maximum WECO removal of 66.24% are: inorganic NPK fertilizer, 4.19 g; activated carbon, 35.42 g and organic fertilizer, 48.94 g. At this predicted optimum amount, validation experiment revealed that 65.55% of WECO removal was achieved. Statistical analyses revealed the closeness of the experimental results to model predictions which thus show the reliability of the quadratic regression model. Therefore, organic and inorganic nutrients as well as adsorptive amendment alone and/or in combination enhances soil indigenous microbial density and activity which thereby accentuates petroleum hydrocarbons biodegradation and subsequently reduces the period of bioremediation and remediation cost.Keywords: Activated carbon; Box-Behnken design; Crude oil; Nutrients; Regression mode

Enhanced ex-situ bioremediation of soil contaminated with petroleum refinery waste effluents by biostimulation through electrokinetics and inorganic fertilizer

Ex situ bioremediation is an attractive and often cost-effective technology for the clean-up of organics-contaminated sites; however, it often requires extended treatment time under field conditions. Electrokinetic bioremediation is an emerging technology to remediate organic-contaminated soil. Thus, the objective of this study was to investigate the feasibility and effectiveness of using electrical biostimulation processes to enhance ex-situ bioremediation of soils contaminated with organic pollutants. The effect of different applied voltages (0.33 – 1.0 V/cm) as well as the effect of inorganic (NPK) fertilizer on the electrokinetic bioremediation of soil was evaluated. A bench-scale uniform electrokinetic system was developed for this purpose and tested by using a sandy loam soil spiked with petroleum refinery waste effluent having total organic compound (TOC) as model organic pollutant. The results demonstrated that the application of a low direct current (voltage) could be an effective strategy to accelerate the movement and ex situ biodegradation or removal of TOC in the soil. At the application of 0.33, 0.67 and 1.0 V/cm voltage, electricity biostimulation correspondingly and averagely remove 65.7%, 70% and 73.3% of TOC from soil in only 15 days without nutrient (NPK fertilizer) application; while with nutrient application, electricity biostimulation correspondingly and averagely removed 71.8%, 77.4% and 81.6% of TOC from soil. Thus, bioremediation of soil contaminated with petroleum refinery waste effluents can be enhanced by electrokinetics and the rate of TOC biodegradation or removal relatively increased with increased specific voltage application. The electrokinetic bioremediation of soil can further be enhanced or accelerated with the addition of nutrient in the form of nitrogen, phosphorus and potassium (NPK). Small changes in soil pH and/or moisture were induced by the applied electric field.Keywords: Bioremediation; Electrokinetics; NPK Fertilizer; Refinery Waste Effluents; TOC

Bioelectricity generation and treatment of petroleum refinery effluent by Bacillus cereus and Clostridium butyricum using microbial fuel cell technology

Microbial fuel cells (MFCs) being an emerging technology have been the research focus of increasing interest due to their sustainable capacity for wastewater treatment together with electricity generation. This study investigated the potential use of pure culture Bacillus cereus and Clostridium butyricum as inoculums in MFCs for simultaneous bioelectricity generation and treatment of petroleum refinery effluent. Double-chambered MFCs was used for the study and operated over four-batch cycles for 30 cumulative days but with different external resistances. The influent concentrations of chemical oxygen demand (COD) and total organic compound (TOC) in the petroleum refinery effluent was 970 mg/l (ppm) and 156 g/l, respectively. Experimental results indicated that the MFCs with the use of Bacillus cereus as biocatalyst achieved its maximum COD removal, TOC degradation and coulombic efficiencies of 70%, 88.7% and 19.21%, respectively; while with the use of Clostridium butyricum, it achieved the highest COD removal, TOC degradation and coulombic efficiencies of 54.2%, 68.7% and 17.84%, respectively. A maximum voltage of 450 mV and highest power density of 17066.67 mW/m2 with a maximum current density of 1.270 mA/m2 was obtained in regard to the external resistor of 1000 Ω using Bacillus cereus as biocatalyst. Similarly, using Clostridium butyricum as biocatalyst the maximum voltage of 370 mV and highest power density of 8816.17mW/m2 with a maximum current density of 0.913 mA/m2 was achieved. The study demonstrated that both Bacillus cereus and Clostridium butyricum has strong potentials to be used as inoculums for simultaneous bioelectricity generation and treatment of petroleum refinery effluent in MFCs.Keywords: Microbial fuel cell; Petroleum refinery effluent; Bacillus cereus; Clostridium butyricum; Bioelectricity; Biodegradatio

Statistical optimization and kinetic studies of enhanced bioremediation of crude oil - contaminated marine water using combined adsorption-biostimulation strategy

The objectives of this study were to investigate and evaluate through Taguchi orthogonal experimental design the effects of amendment agents as well as the optimization and kinetics of enhanced bioremediation of crude oil-contaminated marine water using combined adsorption-biostimulation strategy. The amendment agents are organic fertilizer, slow release inorganic NPK fertilizer, commercial activated carbon and Tween 80. Bioremediation of weathered Escravos crude oil (WECO)-contaminated marine water was studied for four weeks in ten plastic buckets open system. The oil-contaminated marine water in nine of the buckets was each amended with the amendment agents according to Taguchi’s (L9) orthogonal array of four factors and three levels and the tenth un-amended bucket served as control (natural bioattenuation). Results showed that the amendment agents had relative significant influence on the enhancement of WECO-marine water bioremediation. The optimum amendment agent conditions were determined as follows: organic fertilizer 30 g, inorganic slow release NPK fertilizer 4 g, activated carbon 30 g, and Tween 80, 1.5 g. Under these optimum conditions, the optimum percentage of crude oil biodegradation achieved was 98.25%. Bioremediation kinetic data of WECO fitted well to the first-order kinetic model. The combined adsorptionbiostimulation strategy (using the amendment agents) resulted in higher biodegradation rate constant, k (0.0443 - 0.1183 day-1) and lower biodegradation half-life,  t1/2 (5.86 – 15.6 days) of the WECO biodegradation than the natural bioattenuation with lower k (0.0144 day-1) and higher t1/2 (48.8 days). Therefore, the amendment agents have effective potential application as a tool for combined adsorption-biostimulation strategy in the remediation of crude oilcontaminated aquatic environment.Keywords: Biodegradation; Bioremediation; Amendment agents; Crude oil; Kinetics; Optimizatio

Statistical Optimization of Process Variables for Osmotic Dehydration of Okra (Abelmoschus esculentus) in Sucrose Solution

The objective of this study was designed to elucidate the effects of temperature, solute concentration, and size diameter and process time on the osmotic dehydration of okras in sucrose solution. Response Surface Methodology (RSM) with Central Composite Rotable Design (CCRD) was used with five levels and four factors (temperature, sucrose concentration, size diameter and process time) as independent variables, while water loss and solute gain as dependent (response) variables. The osmotic dehydration data was well fitted to a second-order quadratic polynomial regression model with high correlation coecient (R2 > 0.90) using the Statistica program (v. 6.08). The quadratic regression models for the water loss and solute gain yielded signicant (p < 0:05) and predictive results. The osmotic dehydration process was optimized for water loss and solutes gain. The predicted optimum conditions to achieve 39. 78 percent water loss and 10.16 percent solute gain were found to be: solute concentration, 49.28(% w/w); solution temperature, 40.79; sam- ple size diameter, 15mm and process time, 4.49hr. At this predicted optimum point, the observed water loss and solute gain were found to be 38.87 and 10.65(g/100g initial sample), respectively.Keywords: okra, optimization, osmotic dehydration, process variables, response surface, sucros

Thin Layer Drying Kinetics of Pineapple: Effect of Blanching Temperature – Time Combination

Drying is an energy intensive unit operation and long drying periods tend to increase the energy requirements for the production of a unit dry product. In this study, the effect of blanching temperature - time combinations treatment conditions on the drying behavior of pineapple slices was investigated. Slices of pineapple were blanched at different temperature-time combinations before being dried in an oven dryer at adry bulb temperature of 70oC. Four thin-layer drying models were fitted to the experimental drying data. The results show that drying rates and drying times were affected by the blanching temperature-time combinations. Drying times increased as blanching temperature-time combinations increased. The predominant drying regime of the blanched pineapple was observed to be in the falling rate period. The logarithmic model best describe the drying behaviour of blanched pineapple slices with goodness of fit (R2 > 0.99). The effective moisture diffusivity of blanched samples decreased with increase in blanching temperature-time combinations. This implied enhanced mass transfer activities of blanched pineapple slices at decreasing blanching temperature-time combinations. Therefore, blanching pretreatment at lower temperature-time combinations in the drying of fruits and vegetables reduces the drying time and energy cost of drying.Keywords: Blanching; drying; drying models; effective diffusivity; pineapple; temperatur

Application of Carbon-Nitrogen Supplementation from Plant and Animal Sources in In-situ Soil Bioremediation of Diesel Oil: Experimental Analysis and Kinetic Modelling

In this study, the potential effects of sawdust, yam peel and mixture of cow dung, goat dung and poultry dung used alone or in combination as amendment/nutrient supplements to biostimulate autochthonous micro?ora for hydrocarbon biodegradation were investigated in microcosms containing soil spiked with diesel oil (10 % w/w). The rates of biodegradation of the diesel oil were studied for 42 days remediation period under laboratory conditions. The results showed that there was a positive relationship between the microbial growth, biodegradation rate and presence of the sawdust, yam peel and the mixture of cow dung, goat dung and poultry dung (alone or in combination) in microcosms simulated diesel oil contaminated soil.  The biodegradation data fitted well to first-order kinetic model. The model revealed that the combination of sawdust, yam peel, cow dung, goat dung and poultry dung elicited higher diesel oil biodegradation with biodegradation rate constant of 0.089 day-1 and half-life of 7.79 days. The system proposed here takes advantage of the organic wastes bulking properties as well as the autochthonous microorganism metabolic activity to efficiently degrade petroleum hydrocarbons. This system is inexpensive, efficient, and environmentally friendly and may thus offer a viable choice for petroleum hydrocarbons-contaminated soil remediation. Keywords: Biodegradation; Biostimulation; Diesel oil; Organic wastes; First-order kinetics; Half-life

Removal of Phenol from Paint Wastewater by Adsorption onto Phosphoric Acid Activated Carbon Produced from Coconut Shell: Isothermal and Kinetic Modelling Studies

The feasibility of using phosphoric acid activated carbon produced from coconut shell to remove phenol from paint wastewater under batch mode was investigated. The results showed that adsorption of phenol was contact time, adsorbent particle size and adsorbent dosage dependent. The batch equilibrium adsorption data were analyzed by two-parameter adsorption isotherm models of Langmuir and Freundlich using the linear regression method. Both isotherm models fitted very well to the equilibrium adsorption data, however, the Freundlich isotherm equation provided the best model to describe the adsorption of phenol onto coconut shell activated carbon. Adsorption capacity of 2.01 mg/g and adsorption intensity of 1.07 was obtained for granular coconut shell activated carbon and corresponding 3.63 mg/g and 1.55 for powdered coconut shell activated carbon at 30 oC. The adsorption kinetic data were fitted to three adsorption kinetic models (pseudo first-order, pseudo second-order and intra-particle diffusion) using the linear regression method. The three kinetic models fitted well to the adsorption kinetic data; however, the pseudo second-order kinetic model gave the best fit and the adsorption mechanism was controlled by film diffusion. Thus, phosphoric acid activated carbon produced from coconut shell has the potential for application as an effective adsorbent for phenol removal from wastewater. Keywords: Activated carbon; Adsorption isotherms; Adsorption kinetics; coconut shell; paint wastewaters

Thin Layer Drying Kinetics and Modelling of Okra (Abelmoschus Esculentus (L.) Moench) Slices under Natural and Forced Convective Air Drying

The effect of sample thickness (10 and 20 mm), method of drying (open sun, solar and hot air drying) and drying air temperature (50, 60 and 70 oC) on the drying characteristics and kinetics of okra slices were investigated. The results showed that sample thickness, method of drying and drying air temperature significantly (P = 0.05) affected the drying rate and thus the drying time. It was observed that okra slices would dry perfectly within 216 – 240 h, 192 -216 h, and 12 – 19 h under open sun, solar and hot air drying, respectively. Irrespective of the drying method, all the samples dried in the falling rate period with no constant rate period. Four thin-layer semi-empirical mathematical drying models (Newton, Page, Henderson and Pabis, and Logarithmic models) were fitted to the experimental drying curves. The models were compared using the coefficient of determination ( ) and the root mean square error (RMSE). The logarithmic model has shown a better fit to the experimental data obtained from the open sun, solar and hot air drying respectively as relatively compared to other tested models. Correlation between the model parameters and the drying air temperature (under hot air drying) to calculate moisture ratio in relation to the drying time were also determined. The transport of water during drying was described by application of Fick’s diffusion model and the effective moisture diffusivity was estimated. The value ranges from 0.253 to 0.901 × 10-10 m2/s for open sun, 0.31 to 1.01 × 10-10 m2/s for solar drying and 3.29 to 14.7 × 10-10 m2/s for hot air drying, respectively. The Arrhenius-type relationship describes the temperature dependence of effective moisture diffusivity and was determined to be 16.74 kJ/mol and 10.39 kJ/mol for 10 and 20 mm sample sizes, respectively. Keywords: Okra; Open sun drying; Solar drying; Hot air drying; Mathematical modelling; Effective moisture diffusivity.

Kinetics of batch microbial degradation of phenols by indigenous binary mixed culture of Pseudomonas aeruginosa and Pseudomonas fluorescence

The potential of various organisms to metabolize organic compounds has been observed to be a potentially effective means in disposing of hazardous and toxic wastes. Phenolic compounds have longbeen recognized as one of the most recalcitrant and persistent organic chemicals in the environment. The bioremediation potential of an indigenous binary mixed culture of Pseudomonas aeruginosa andPseudomonas fluorescence was studied in batch culture using synthetic phenol in water in the concentration range of 100 –500 mg/L as a model limiting substrate. The effect of initial phenol concentration on the degradation process was investigated. Phenol was completely degraded at different cultivation times for the different initial phenol concentrations. Increasing the initial phenol concentration from 100 to 500 mg/L increased the lag phase from 0 to 18 h and correspondinglyprolonged the degradation process from 24 to 96 h. There was decrease in biodegradation rate as initial phenol concentration increased. Fitting data into three different kinetic models (Monod, Haldane, andYano and Koga) showed that the difference in fit between the models was very small and thus statistically insignificant. Thus, the Yano and Koga model has been used to interpret the free cell dataon phenol biodegradation. The kinetic parameters have been estimated up to initial phenol concentration of 500 mg/L. The rsmax decreased, while Ks and Ki increased with higher concentration of phenol. The rsmaxhas been found to be a strong function of initial phenol concentration