Bioremediation and Detoxification of Synthetic Wastewater Containing Triarylmethane Dyes by Aeromonas hydrophila Isolated from Industrial Effluent

Economical and bio-friendly approaches are needed to remediate dye-contaminated wastewater from various industries. In this study, a novel bacterial strain capable of decolorizing triarylmethane dyes was isolated from a textile wastewater treatment plant in Greece. The bacterial isolate was identified as Aeromonas hydrophila and was shown to decolorize three triarylmethane dyes tested within 24 h with color removal in the range of 72% to 96%. Decolorization efficiency of the bacterium was a function of operational parameters (aeration, dye concentration, temperature, and pH) and the optimal operational conditions obtained for decolorization of the dyes were: pH 7-8, 35°C and culture agitation. Effective color removal within 24 h was obtained at a maximum dye concentration of 50 mg/L. Dye decolorization was monitored using a scanning UV/visible spectrophotometer which indicated that decolorization was due to the degradation of dyes into non-colored intermediates. Phytotoxicity studies carried out using Triticum aestivum, Hordeum vulgare, and Lens esculenta revealed the triarylmethane dyes exerted toxic effects on plant growth parameters monitored. However, significant reduction in toxicity was obtained with the decolorized dye metabolites thus, indicating the detoxification of the dyes following degradation by Aeromonas hydrophila

Enterobacterial Repetitive Intergenic Consensus (ERIC) as a tool for genetic characterisation of bacterial isolates in Nigeria

Genetic characterisation as a tool for identification of bacterial isolates in Nigeria has been on the increase in recent years, and the 16s rRNA typing has been a preferred method. Due to cost limitations, there is a need to explore other genetic options. Enterobacterial Repetitive Intergenic Consensus (ERIC) polymerase chain reaction (PCR) analysis is a PCR- only based system which offers the advantage of reduced cost. This study set out to explore the use of ERIC-PCR in genetic characterisation of some selected bacterial isolates from Nigeria and compare it with genetic characterisation using 16s rRNA sequence typing. ERIC-PCR and 16s rRNA typing were carried out on 15 isolates following previously described protocols. Using 16s rRNA typing, thirteen different bacterial species were identified of which majority (85.7%) were Gram negative, with 57.1% belonging to the Enterobacteriaceae family. Using ERIC-PCR, only 13 of the 15 isolates (86.7%) could be typed, resulting in the identification of the 13 different types. ERIC-PCR was able to accurately differentiate between two members of the Proteus species, as well as identify the organisms as similar based on the banding pattern. The results show that ERIC-PCR may play a role as a bacterial identification tool but this role might be more suited to differentiating closely related members of a genus or typing within species rather than general bacterial identification. Keywords: Genetic characterisation, 16s rRNA, ERIC-PCR, Nigeri

NON-NEWTONIAN POWER-LAW FLUID FLOW IN ECCENTRIC ANNULI: CFD SIMULATION AND EXPERIMENTAL STUDY

Numerous publications have addressed the problems inherent to calculating wellbore hydraulics in eccentric annulus. The challenge of theoretical and numerical studies of fluid flow in an eccentric annulus is mainly due to the required coordinate systems. CFD modeling provides an alternative approach of investigating fluid flow in such complex geometries. The CFD technique emerged as a result of the current increase in computer processing speed and available memory. This branch of fluid flow analysis complements experimental and theoretical work, providing economically interesting alternatives through the simulation of real flows and allowing an alternative form for theoretical advances under conditions unavailable experimentally.In this study, results from a series of numerical simulations for the fully developed laminar flow of non-Newtonian power law fluids in eccentric annular geometries, conducted using the computational fluid dynamics (CFD) code FLUENT, are used to investigate the effect of eccentricity, and diameter ratios (ratio of the outer diameter of the inner tubing to the inner diameter of the outer tubing) on axial velocity profiles, the viscosity profile, as well as the axial friction pressure losses. Unlike the uniform velocity profile applicable for every sector in a concentric annulus, the axial velocity profile for an eccentric annulus is altered, with the peak velocities varying with location. A virtual inspection of the velocity profiles in an eccentric annulus shows that the zone of highest shear exists across the narrowing sector of an eccentric annulus; hence this region is noticeably accompanied by a considerable reduction in viscosity.The friction pressure gradients predicted by the CFD simulations were verified by comparing with the published studies and flow data from a field scale experimental data of a fully eccentric annulus. At a constant flow rate, it is confirmed that frictional pressure losses are decreased with increasing eccentricity. Also, fluids with the stronger non-Newtonian property show a slower rate of decrease in pressure drop as eccentricity increases. A good agreement is obtained with the Haciislamoglu et al. correlation, and the results of this study, especially at low values of eccentricity. At very high eccentricities, data from the CFD model yields lower friction pressure compared to Haciislamoglu et al. correlation. A Haciislamoglu et al. type expression is obtained, incorporating the improved data of this study.Next, the results of an experimental study carried out to investigate friction pressure behavior of drag reducing polymer solutions flowing turbulently through an eccentric annulus are presented. The experimental set-up includes 30 ft of 3½-in. x 2 3/8-in., 200 ft of 3½-in. x 1¾-in., 69 ft of 5½-in. x 4-in., and 79 ft of 5-in. x 3½-in. fully eccentric annuli. Data analysis enabled the development of a new correlation using Fanning friction factor, generalized Reynolds number, and diameter ratio, all of which can be easily determined in the field, as independent variables. These new correlations for laminar and turbulent flow of drag reducing polymer solutions present an improvement to existing correlations, and also permit undemanding hydraulic program calculations for varying annular configurations

Production of the lactic acid from mango peel waste – Factorial experiment

AbstractThe production of lactic acid from mango peels using the bio-fermentation method was investigated. The possible relationship between the operational factors, namely process temperature (15 and 35 °C), initial medium pH (4 and 10) and duration of fermentation (3 and 6 days) on lactic acid production as the response was determined using the factorial design. Analysis of the data obtained showed there was a strong significant influence of the operational factors and their interactions on lactic acid production (P < 0.0001) of fermenting microorganisms. The regression model for lactic acid production fitted the data adequately and explained more than 99% of the variation in the response. The results also showed that the maximum production of lactic acid can be achieved at initial medium pH of 10; incubation time of 6 days; and at a temperature of 35 °C. The maximum production of lactic acid was 17.484 g/L. This study highlights the potential of mango peels as a low cost and economically viable fermentation substrate for the production of lactic acid

Decolorization and partial mineralization of a polyazo dye by Bacillus firmus immobilized within tubular polymeric gel

The degradation of C.I. Direct red 80, a polyazo dye, was investigated using Bacillus firmus immobilized by entrapment in tubular polymeric gel. This bacterial strain was able to completely decolorize 50 mg/L of C.I. Direct red 80 under anoxic conditions within 12 h and also degrade the reaction intermediates (aromatic amines) during the subsequent 12 h under aerobic conditions. The tubular gel harboring the immobilized cells consisted of anoxic and aerobic regions integrated in a single unit which was ideal for azo dye degradation studies. Results obtained show that effective dye decolorization (97.8%), chemical oxygen demand (COD) reduction (91.7%) and total aromatic amines removal were obtained in 15 h with the immobilized bacterial cell system whereas for the free cells, a hydraulic residence time of 24 h was required for an equivalent performance in a sequential anoxic and aerobic process. Repeated-batch experiments indicate the immobilized cells could decolorize C.I. Direct red 80 and reduce medium COD in five successive batch runs with enhanced activity obtained after each consecutive run, thus suggesting its stability and potential for repeated use in wastewater treatment. UV–visible spectrophotometry and HPLC analysis were used to confirm the partial mineralization of the dye. Data from this study could be used as a reference for the development of effective industrial scale biotechnological process for the removal of dyes and their metabolites in textile wastewater

Influence of chemical structures on biodegradation of azo dyes by Pseudomonas sp

No Abstract. Global Journal of Environmental Sciences Vol. 5(1) 2006: 19-2

Toxic Effect Of Azo Dyes On Nitrite-N Utilization By Nitrobacter

The toxicity of five azo dyes (toxicants) on Nitrobacter was investigated. The index for toxicity was inhibition of rate of nitrite-N utilization. The rate of nitrite-N utilization decreased with increase in concentration of each toxicant at specific exposure time. However, stimulation of utilization was obtained at low concentrations and short exposure time for two of the dyes. This was attributed to hyperactivity. The median effective concentration50 (EC50) values increased with increase in exposure time for each toxicant. This was attributed to acclimatization and/or detoxification. Inhibition was attributed to any/or all of the following factors: molecular size, impurities in the toxicants and dye content. KEY WORDS: Toxicity, Azo dyes, Nitrobacter, hyperactivity, acclimatization Global Journal of Environmental Sciences Vol.4(1) 2005: 47-5

Economics of gas to liquids technology for monetization of Alaska North Slope Natural gas reserves

Thesis (M.S.) University of Alaska Fairbanks, 2006The proven natural gas reserves of the Alaska North Slope (ANS) have enormous potential as clean-burning energy resources, if they can be effectively and efficiently utilized. These gas resources, exceeding 35 trillion cubic feet (TCF), currently represent a significant proportion of the energy equivalence of proven ANS oil reserves. With ANS located far from potential markets, there is need to evaluate the prospective economics of promising technologies for monetization of these stranded gas reserves. The economics of the chemical conversion of natural gas to synthetic liquid fuels favored by recent advances in FT synthesis techniques, liquid fuel transportation for the Trans Alaskan Pipeline System (TAPS) operations, and increased demand for clean burning diesel fuels, was the main focus of this study. Economic evaluation using Internal Rate of Return (IRR) analysis, Payout Time and the Net Present Value (NPV) to access and compare the economic viability of 3-train and 4-train GTL Projects is performed. Monte-Carlo simulation using the Crystal Ball software was utilized to run sensitivity analysis, incorporating the probabilistic approach, which generated insightful scenarios on the project economics.1. Introduction -- 2. Literature review -- 3. GTL plant layout and economic parameters -- 4. Economic evaluation and analysis -- 5. Discussion of results -- 6. Conclusions and recommendations -- References -- Appendix

Biodegradation of Azo dyes by immobilized and free cells of Pseudomonas sp.under fed-batch conditions

No Abstract. Global Journal of Environmental Sciences Vol. 5(1) 2006: 1-

Quantal Response Of Freshwater Shrimp (Desmocaris trispinosa) To Toxicity Of Azo Dyes

The quantal-response of freshwater shrimp (Desmocaris trispinosa) to the toxicity of five azo dyes was studied. Generally, increase in percentage mortality of the organisms was obtained with increases in concentration of the toxicants and exposure time. The median lethal concentration50 (LC50) and median lethal concentration50 (LC50) values were obtained from the concentration-mortality and time-mortality probit graphs, respectively. Based on the LC50 and LT50 values, the dyes were ranked in order of toxicity: Mordant Black 11>Acid Orange 10>Direct Red 28>Direct Orange 31>Direct Red 23. Differences in quantal effect of the toxicants was attributed to their molecular weight, dye content and/or impaired oxygen transfer through the respiratory apparatus of the organisms due to adsorption of the dye molecules on their gill surface. Evidence of bioaccumulation of the toxicants in guts and tissues of the shrimps was obtained and its implication to human health was discussed. KEY WORDS: Toxicity, azo dyes, Desmocaris trispinosa, quantal response, bioaccumulation Global Journal of Environmental Sciences Vol.4(1) 2005: 41-4