Bioadsorption of 2,6-Dichlorophenol from Aqueous Solution onto Plantain and Pineapple Peels Mixture Used as Adsorbent: Optimization Studies Based on Taguchi Method, Batch Equilibrium, and Kinetic Modelling

The feasibility of using pineapple/plantain peels mixture to remove 2, 6-dichlorophenol (2,6-DCP) from its aqueous solutions was investigated under batch mode. The effects of factors such as pH, initial 2, 6-DCP concentration, temperature and pineapple/plantain peels adsorbent ratio on the removal process were evaluated. Four factors and three levels according to Taguchi’s (L9) orthogonal array were used to assess and optimize the bioadsorption behaviour of pineapple/plantain peels mixture. Analysis of variance was applied to determine the significant factors that affect bioadsorption.  The levels of significant factors were optimized using Signal to Noise ratio. The results showed that bioadsorption of 2, 6-DCP was dependent on these factors. However, pH was the major factor that affects the percentage (%) removal of 2,6-DCP with its % contribution of 52.23. An optimum parameter combination for the maximum percentage removal of 2,6-DCP was obtained using the analysis of Signal to Noise (S/N) ratio. The best conditions for bioadsorption of 2,6-DCP were determined by the Taguchi method and desirability approach as pH = 7, initial 2,6-DCP concentration of 300 mg/l, temperature 50 °C, and pineapple/plantain adsorbent ratio of 2:1. The equilibrium bioadsorption data were analyzed by Langmuir and Freundlich isotherm models. The Freundlich isotherm model provided the best fit (R2 = 0.9980) to the experimental data. The maximum monolayer bioadsorption capacity ( ) was found to be 76.92 mg/g. The bioadsorption kinetics data of 2, 6-DCP were analyzed by pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The pseudo-second order kinetic model gave the best fit. Therefore, pineapple/plantain peel adsorbent mixture has potential for application as an effective bioadsorbent for 2, 6-DCP removal from aqueous solution. Keywords: Bioadsorption; Bioadsorption isotherms; Kinetics; Pineapple-Plantain peel mixture; 2, 6-Dichlorophenol; Taguchi method

Antagonistic properties of microogranisms associated with cassava (Manihot esculenta, Crantz) products

The antagonistic properties of indigenous microflora from cassava starch, flour and grated cassava were investigated using the conventional streak, novel ring and well diffusion methods. Antagonism was measured by zone of inhibition between the fungal plug and bacterial streak/ring. Bacillus species were more effective to inhibit the growth of Aspergillus niger, A. fumigatus, Fusarium moniliforme and Rhizoctonia sp. Pseudomonas fluorescens, Escherichia coli and Saccharomyces sp. inhibited the growth of A. niger, A. flavus and F. moniliforme. There were considerable variations in inhibitory activity. The zone of inhibition was more apparent in the novel ring method. Percentage inhibition increased to 78% in the Ring method and 62% in streak method after 168 h of incubation. Lactobacillus brevis, L. acidophilus and Bacillus subtilis inhibited the growth of E. coli and Staphylococcus aureus. Inhibition of the pathogenic microorganisms was probably due to the production of organic acids and bacteriocins.African Journal of Biotechnology Vol. 4 (7), pp. 627-632, 200

Modelling the Simultaneous Adsorption and Biodegradation of Aromatic Hydrocarbons onto Non-Carbonized Biological Adsorbent in Batch System

In this study, a modified two-site sorption kinetic numerical model that differentiates between the adsorption and biodegradation quantities of a non-carbonized biological activated adsorbent (NCBAA) was developed and validated. Also, the effects of initial naphthalene and phenol concentrations on the simultaneous adsorption-biodegradation performances of orange and pineapple peel immobilized Pseudomonas aeruginosa NCIB 950 in naphthalene and phenol removal was respectively evaluated. Adsorption-biodegradation model was developed from the modification of a two-site kinetic numerical model by combining the elements of adsorption and biodegradation models and validation of the model carried out through the application of batch adsorption-biodegradation equilibrium and kinetic experimental data. Results showed that the model predictions of the naphthalene and phenol concentrations are in good agreement with the experimental data. For simultaneous adsorption-biodegradation of naphthalene by orange peel immobilized Pseudomonas aeruginosa, adsorption rate coefficient increased with initial naphthalene concentration and biodegradation rate coefficient decreased with increased initial concentration; and for phenol simultaneous adsorption-biodegradation by pineapple peel immobilized Pseudomonas aeruginosa, adsorption rate coefficient decreased with increased initial phenol concentration and biodegradation rate coefficient increased with increased initial phenol concentration. Thus, the adsorption-biodegradation model is a reasonable tool for simulating the adsorption-biodegradation behaviors of aromatic hydrocarbons in NCBAA. Keywords: Bacteria; Simultaneous adsorption-biodegradation; Phenol; Naphthalene; Non-carbonized biological activated adsorbent; Numerical model.

Experimental Optimization of Lead (II) Bioadsorption from Aqueous Solution onto Banana Stalk using Central Composite Design

This study investigated the effect of operating parameters on the bioadsorption process of Pb(II) from its aqueous solution using three Banana Stalk (BS) bioadsorbents [Raw (RBS), Acid Activated (AABS) and Base Activated (BABS) ]. A five-factor, three-level Central Composite Design (CCD) was applied to determine the effects of independent variables (initial metal concentration, contact time, temperature, adsorbent dosage and solution pH) on percentage Pb(II) removal. Response Surface Methodology (RSM) was employed to optimize the parameters in the experiment. AABS had the highest percentage removal (96.13%) from the preliminary experiment and was then used for the optimisation experiment. Data analysis showed that all the variables significantly affected the percentage Pb(II) removal at p < 0.05. The square of the adjusted coefficient of determination for regression model of percentage Pb(II) removal is 0.9355. Optimum percentage removal of 96.41% was obtained using AABS when the Pb(II) concentration, contact time, temperature, dosage and solution pH were 21.83g/mL, 152.21minutes, 50oC, 0.90g and 8.00,  respectively. There absolute error between the experimental and the predicted optimum percentage removal was less than 1%. Keywords: Banana stalk, optimization, bioadsorption, acid, base

COMPARATIVES STUDY ON THE EFFECT OF WET AND DRY SUBSTRATES ON BIOGAS YIELD

The objective of this study is to compare the use ofwetanddry wastes as substrates for anaerobic digestion and its effect on biogas yield.Different quantities of substrates and co-substrates (wet and dried) were weighed and mixed vigorously with corresponding quantity of distilled water to form the fermentation slurry in the digesters; the digesters were operated at 45°C in batch anaerobic digesters for 25 days. The results showed that the average volume of biogas obtained from the dried animal wastes co-digested with dried fruit wastes and wet animal wastes co-digested with wet fruit wastes was found to be 0.2928 kg and 0.0972 kg per day respectively. When the fermentation process was performed with dried animal wastes only and wet animal wastes only the value of the average volume of biogas obtained were calculated to be 0.1508 and 0.0892 kg per day respectively. Thus biogas yield using dried substrates comparatively gave a better biogas yield than wet substrates. In conclusion, the use of dried wastes for biogas production suggests superior energy recovery, saving resources and engineering investment as compared to the use of wet wastes as substrates

Biodegradation of Dichlorovos (Organophosphate Pesticide) in Soil by Bacterial Isolates

Excessive and continuous dispersion of pesticides which are toxic heterogeneous compound in the environment results in environmental pollution with ecological effects that require remediation. This study investigated the potential of microbial isolates to biodegrade or cleans up agricultural soil artificially contaminated with Dichlorvos (2, 2-dichlorovinyldimethylphosphate) pesticide.  A bacterial consortium which degraded Dichlorvos pesticide was isolated from agricultural soil using pour plate method.  This consortium was composed of four pure strains which were characterized based on their morphological and biochemical characteristics.  The strains were presumptively identifies as Proteus vulgaris, Vibrio sp., Serratia sp. and Acinetobacter sp. The consortium and the four bacteria were evaluated in order to discover their ability to biodegrade Dichlorvos pesticide in medium supplied with different nutrients (NH4NO3, KH2PO4 and NPK (20:10:10) fertilizer). The results showed that the bacterial consortium and the four bacteria isolates were able to grow in nutrient medium containing Dichlorvos as the only carbon source.  Moreover, the bacterial consortium was able to remove greater amount of DDP in soil amended with inorganic fertilizer (NPK) than those amended with NH4NO3 and KH2PO4, respectively.  These results indicate that the isolated strains can be used for waste biodegradation or bioremediation of organophosphate pesticide- contaminated soil or water. Keywords: bacteria; biodegradation; dichlorvos; nutrient; organophosphate pesticide

Biosorption Kinetics of vetiveria zizanioides Rhizobacter on Heavy Metals Contaminated Wastewater

The burden of heavy metals pollution in the environment has increased over the last century. Consequently, concerted efforts towards addressing this menace in the environment and subsequently on health has being on the increase. A number of plants and microorganisms are currently being experimented for their potential to uptake heavy metals from both soil and water. However, the kinetics of uptake of heavy metals in wastewater which are necessary for the design of the treatment system have been largely neglected, this paper therefore investigates the kinetics of biosorption of heavy metals in contaminated wastewater using two  microorganism isolated from rhizospheric soil of Vetiveria zizanioides (vetiver) plant.The result of bioaccumulation studies showed that Bacillus cereus showsthe maximum bioaccumulation capacity of 96.75% for Lead, 23% for Cadmium and 16.98% for Zinc while Bacillus subtilis accumulated 95.2% of the Lead, 41.3% of Cadmium and 32.2% of Zinc from solution.Also, the result of kinetic studies revealed that the kinetic data agrees with pseudo-second order kinetic model. Keywords: Biosorption, Heavy metals, Rhizospheric, Wastewater, Vetiveria zizanioides

Evaluation of Microbial Systems for Biotreatment of Textile Waste Effluents in Nigeria: Biodecolourization and Biodegradation of textile Dye

The evaluation of some microbial species for the decolourization and degradation of textile dye has been investigated. Six microbial strains were isolated from soil contaminated with textile waste effluents using the spread plate technique and the isolates were identified as bacterial isolates ( Pseudomonas fluorescence , Pseudomonas nigificans , and Pseudomonas gellucidium ) and fungal isolates ( Aspergillus niger , Proteus morganii and Fusarium compacticum } based on gram staining, morphological and biochemical tests. They were evaluated for their capability to remove colour and degrade dye, reduce chemical oxygen demand (COD) and biological oxygen demand (BOD) levels of textile waste effluents. The results revealed that all the bacterial and fungal isolates have a good potential to remove colour and degrade dye, reduce the COD and BOD levels of the textile waste effluents with percent colour removal, COD and BOD reductions between 39 and 48%, 74 and 97% and 77 and 95%, respectively. Binary mixed culture of Pseudomonas fluorescence and Aspergillus niger was efficiently utilized for the removal of different initial concentration (10, 15, 20, 25 and 30 mg/l) of dye from textile waste effluents. It had a higher percent decolourization than individual isolates. The stirred tank bioreactor was found to be very effective for efficient biotreatment of textile waste effluents

Evaluation of Microbial Systems for Biotreatment of Textile Waste Effluents in Nigeria: Biodecolourization and Biodegradation of textile Dye

The evaluation of some microbial species for the decolourization and degradation of textile dye has been investigated. Six microbial strains were isolated from soil contaminated with textile waste effluents using the spread plate technique and the isolates were identified as bacterial isolates ( Pseudomonas fluorescence , Pseudomonas nigificans , and Pseudomonas gellucidium ) and fungal isolates ( Aspergillus niger , Proteus morganii and Fusarium compacticum } based on gram staining, morphological and biochemical tests. They were evaluated for their capability to remove colour and degrade dye, reduce chemical oxygen demand (COD) and biological oxygen demand (BOD) levels of textile waste effluents. The results revealed that all the bacterial and fungal isolates have a good potential to remove colour and degrade dye, reduce the COD and BOD levels of the textile waste effluents with percent colour removal, COD and BOD reductions between 39 and 48%, 74 and 97% and 77 and 95%, respectively. Binary mixed culture of Pseudomonas fluorescence and Aspergillus niger was efficiently utilized for the removal of different initial concentration (10, 15, 20, 25 and 30 mg/l) of dye from textile waste effluents. It had a higher percent decolourization than individual isolates. The stirred tank bioreactor was found to be very effective for efficient biotreatment of textile waste effluents