Naphthalene and pyrene degradation in contaminated soil as a function of the variation of particle size and percent organic matter

The effect of soil particle size distribution and percent organic matter on the degradation rate of naphthalene and pyrene in a water medium of 7.05 ml/min at 27 ± 2oC in a soil reactor was studied. Analysis of the pattern of disappearance of these polycyclic aromatic hydrocarbons (PAHs) using various particle sizes showed a rapid decline of concentration of the chemicals during initial stages ofbioremediation treatment, followed by a slow reduction rate. The extent of naphthalene and pyrene removal and final concentrations for the period under study differed among the different soil particlesizes. Results show that from an initial 100 mg/l, the concentration of both naphthalene and pyrene decreased in the following sequence clay > silt > fine sand > coarse sand. The degradation of the two PAHs was significantly enhanced by the addition of organic matter to the bulk composite soil. The specific reaction rate constant k was found to increase with decreasing particle size and increase withincreasing % organic matter. For both PAHs, coarse sand had the lowest rate constant while clay had the highest. This implies that degradation was faster in the clay fraction than in the other soil fractions. The correlation coefficients obtained using linear regression method was between 0.734 and 0.996 indicating the reliability of the experimental data

Simulation of the Bioremediation of Polycyclic Aromatic Hydrocarbons (PAHs) in Stirred Reactors

The mathematical solution to a one-dimensional advective-dispersive solute transport model with linear equilibrium sorption and first-order degradation was carried out in this study. Simulation was carried out using MathCad software. The model solution predicted time approximated concentration distribution at varying depths of the selected PAHs (naphthalene, anthracene and pyrene) used in this study at distances. Simulation results showed that the concentrations of naphthalene, anthracene and pyrene within a contact period of 40, 55, and 50 days respectively, decreased in the direction of flow from 200 mg/l at the surface to zero at 9cm subsurface depth within the porous media. The residual concentrations of naphthalene, anthracene and pyrene were found to be 14% (35th day), 44% (50th day) and 29% (45th day) respectively. The simulation results closely fit the data from experiments an indication that the technique significantly provides solution to non-steady state model concerned with contaminant solute transport and degradation

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

Degradation of anthracene: Influence of adsorbents from inorganic activation

The use of rice and melon husks in their raw, carbonized (at 400°C and 600°C) and activated (using 10%, v/v orthophosphoric acid) form to catalyze the degradation of anthracene in sandy soil was investigated. Rice husk carbonized at 600°C and activated was found to be a better adsorbent than melon husk under same condition. After five weeks of degradation experiment the anthracene reduced from an initial concentration of 5000 to 1009.7 and 1200.2 μg/g soil for rice and melon husks, respectively, while the control reduced to 2671.0 μg/g soil. Result of the batch degradation process of anthracene was found to follow first order heterogeneous kinetics with rice husk carbonized at 600°C and activated having the fastest reaction rate constant of 0.0018 h-1 followed by melon husk with 0.0016 h-1 while the control had 0.0009 h-1.The regression coefficients obtained from the analysis of the experimental data used to test the order of reaction were greater than 88% showing a good reliability of the data obtained.Keywords: Degradation, polycyclic aromatic hydrocarbon, anthracene, rice husk, melon hus

Application of adsorbent as a novel technique during biodegradation of a polycyclic aromatic hydrocarbon (anthracene)

The use of an alternative technique as a management strategy for the decontamination of hydrocarbonbased pollution in soil has been advanced in this work. The study investigated the degradation ofanthracene, a three-ringed benzene derivative, in clay soil at ambient conditions under the influence of hydrophilic compound (carbon), thermally activated at temperatures of 300, 500, 700 and 900oC. Thesoil (500 g) was impacted with 1:1 of the contaminant anthracene and activated carbon from groundnut shell in a water medium at a flow rate of 5.0 ml/min. Experimental results revealed that there was asignificant reduction in the level of anthracene in the soil matrix with time. The percentage reduction was found to be directly dependent on the activation temperature. The estimated reaction rate constantwas found to be 0.014/h (control sample without activated carbon) while for the experimental samples, the values ranged from 0.018 - 0.051/h. The study therefore affirms that the presence of activatedcarbon in microbial degradation of anthracene, elicits an enhanced disappearance rate of the hydrocarbon

Predicting the Biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) in Continuous Stirred Tank Reactor by Artificial Neural Network

This study investigates the prediction of biodegradation of polycyclic aromatic hydrocarbons using a mixture of naphthalene; anthracene and pyrene in a continuously stirred tank reactor by an artificial neural network. Artificial neural networks are relatively crude electronic networks of "neurons" whose operations are based on the neural structure of the brain. They process records one at a time, and "learn" by comparing their prediction of the record (which, at the onset, is largely arbitrary) with the known actual record. Experimental data were employed in the design of the feed forward neural networks for modeling the prediction of biodegradation process. Comparatively, results showed that predictions from the feedforward neural network closely fitted the measured values. The degradation pattern was characterized by an exponential decline in the concentrations of the polycyclic aromatic hydrocarbons, and this was followed by a ‘plateau’ concentration signifying the attainment of endpoint of the degradation process.Keywords: Model, Neuron, Feed forward, Training, Input, Hidden and Output layersJournal of the Nigerian Association of Mathematical Physics, Volume 19 (November, 2011), pp 395 – 39

Application of adsorbent as a novel technique during biodegradation of a polycyclic aromatic hydrocarbon (anthracene)

The use of an alternative technique as a management strategy for the decontamination of hydrocarbonbased pollution in soil has been advanced in this work. The study investigated the degradation ofanthracene, a three-ringed benzene derivative, in clay soil at ambient conditions under the influence of hydrophilic compound (carbon), thermally activated at temperatures of 300, 500, 700 and 900oC. Thesoil (500 g) was impacted with 1:1 of the contaminant anthracene and activated carbon from groundnut shell in a water medium at a flow rate of 5.0 ml/min. Experimental results revealed that there was asignificant reduction in the level of anthracene in the soil matrix with time. The percentage reduction was found to be directly dependent on the activation temperature. The estimated reaction rate constantwas found to be 0.014/h (control sample without activated carbon) while for the experimental samples, the values ranged from 0.018 - 0.051/h. The study therefore affirms that the presence of activatedcarbon in microbial degradation of anthracene, elicits an enhanced disappearance rate of the hydrocarbon

Estimation of transport and degradation parameters for naphthalene and anthracene: Influence of mass transfer on kinetics

The method of temporal moment solutions (MOM) for onedimensional convective-dispersive solute transport involving linear equilibrium sorption and first order degradation for time pulse sources has been applied to analyze experimental data from a soil microcosm reactor. Estimation of the pore-water velocity V for a non-reactive solute was aided by the use of only the first normalized moment while the dispersion coefficient D, first-order degradation rate constant λ and the retardation factor R were estimated using both first and second normalized moments. These transport and degradation parameters were compared to those obtained by a transport model using a nonlinear least square curve-fitting program CXTFIT (version 2.0). Results obtained showed that the MOM fits the breakthrough curve with tailing better than the CXTFIT. The initial estimates of these parameters aided the reduction of the dimensionality of the search process of the nonsteady state model. A residual concentration of naphthalene 1.12E-5mg/l, 1.48mg/l, and anthracene 7.67E-4mg/l, 1.61mg/l in the axial and radial directions respectively suggests the preference of naphthalene during the biodegradation process. The surface concentration as depicted using threedimensional plots, showed that there is occlusion of the aromatics (naphthalene and anthracene) within the soil micropores thereby limiting their bioavailability and in the long run increasing their toxicity.Journal of the Nigerian Association of Mathematical Physics, Volume 15 (November, 2009), pp 223 - 23