Performance evaluation and kinetic study of fluorene biodegradation in continuous bioreactor using polyurethane foam as packing media

870-878Polycyclic aromatic hydrocarbons (PAHs) are precarious persistent pollutants derived from incomplete combustion of fossil fuel and petroleum products. Due to adverse effects of PAHs on the environment, the wastewater contaminated with PAHs needs to be treated prior to discharge in the water bodies. In the present study, we used immobilized polyurethane foam Pseudomonas pseudoalcaligenes NRSS3 for degradation of fluorene in packed bed bioreactor (PBBR) to stimulate biofilm and possibly enhance removal efficiency. The most affecting process parameters, such as pH, process time and temperature were optimized at batch mode and found to be 7.0, 8.0 days, and 30 °C, respectively. At the optimum condition, the bioreactor was operated in continuous mode up to 45 days and obtained results demonstrate that the maximum removal efficiency (RE) of 91.1% along with 27.3 mg/L day-1 of elimination capacity (EC) were observed. Biodegradation kinetics of fluorene were evaluated by Monod growth and Andrew-Haldane inhibition models and parameters were obtained to be µmax: 0.32 day-1; Ks: 10.8 mg/L by Monod while µmax: 0.47 day-1; Ks: 12.3 mg/L; 27.5 mg/L by Andrews-Haldane

Combination of UV-Fenton oxidation process with biological technique for treatment of polycyclic aromatic hydrocarbons using <em>Pseudomonas pseudoalcaligenes</em> NRSS3 isolated from petroleum contaminated site

460-469Polycyclic aromatic hydrocarbons (PAHs), often from petroleum oil spill, by-product of petroleum refining, incomplete combustion of fossil fuel, leakage in pipeline and underground storage, apart from the effluents of pesticide, dye, pigment, and drug industries, are considered carcinogenic and mutagenic. As the abundance of PAHs in the environment cause adverse effects on humans and ecosystem, the PAHs contamination needs to be monitored and such polluted sites require remediation. Conventional methods available for remediation of PAHs are adsorption, advance oxidation process, electrochemical remediation, solvent extraction, use of synthetic surfactants and photocatalytic remediation. These methods including the alternative Fenton oxidation technology are not only expensive but also produce secondary pollutants. In this study, we evaluated the performance of UV-Fenton-PBBR (Packed bed bioreactor) hybrid system for the treatment of polycyclic aromatic hydrocarbons (naphthalene and fluorene). Pseudomonas pseudoalcaligenes NRSS3 isolated from petroleum contaminated site and immobilized on Sterculia alata was used as packing media in the PBBR. The naphthalene and fluorene were taken as model polycyclic aromatic hydrocarbon (PAHs) with initial concentration of 400 mg/L. The optimum conditions for UV-Fenton oxidation were (pH: 3, Fe2+: 2.5 g/L, H2O2: 1000 mg/L) for naphthalene and (pH: 3, Fe2+: 3.0 g/L, H2O2: 1200 mg/L) for fluorene. The overall maximum removal efficiency of the combined system was found to be 96 and 94.7% for naphthalene and fluorene, respectively. GC-MS analysis confirmed the formation of catechol, 1-napthol, salicylic acid and phthalic anhydride as metabolites during degradation process. Biodegradation kinetics of naphthalene and fluorene were studied using Monod model and kinetics constants were found to be µmax: 0.3057 per day; Ks: 112.87 mg/L for naphthalene and µmax: 0.2921 per day; Ks: 114.75 mg/L for fluorene

Removal of Atrazine by coupling Fenton reaction with bioreactor in series

498-505Atrazine is a commonly used weedicide in agriculture fields. Owing to its long half-life (125 days) and slow-biodegradability, it adds to problematic residues in the environment. It is known to disrupt endocrine and reproductive systems and has potential to damage vital organs such as liver, kidney and heart. While atrazine is banned in European countries, many countries, such as India, China, and the USA it is still in use widely. In atrazine biodegradation, batch bioreactors are most commmon cost effective alternative to conventional methods. However, it has only major limitation of slow rate of degradation. In this work, we explored coupling of UV-Fenton and biological method for atrazine removal and also optimized the process parameters. In the bioreactor, Loofa was used as the packing media on which consortia was immobilized. The performance of coupled system was studied with an initial atrazine concentration of 300 mg/L. Overall, maximum removal efficiency of 93% was achieved for the coupled system. GC-MS analysis of residual treated effluent sample was performed to identify the intermediate compound. Two metabolites biuret and urea were identified which confirmed the degradation of atrazine. The growth kinetic parameters µmax (0.224 per day) and KS (106.64) were calculated using Monod model. The coupling method was found superior than individual chemical and biological methods for treatment of atrazine

Biodegradation of methylene blue dye in a batch and continuous mode using biochar as packing media

Bacterial species for metabolizing dye molecules were isolated from dye rich water bodies. The best microbial species for such an application was selected amongst the isolated bacterial populations by conducting methylene blue (MB) batch degradation studies with the bacterial strains using NaCl-yeast as a nutrient medium. The most suitable bacterial species was Alcaligenes faecalis (A. faecalis) according to 16S rDNA sequencing. Process parameters were optimized and under the optimum conditions (e.g., inoculum size of 3 mL, temperature of 30 °C, 150 ppm, and time of 5 days), 96.2% of MB was removed. Furthermore, the effectiveness for the separation of MB combining bio-film with biochar was measured by a bio-sorption method in a packed bed bioreactor (PBBR) in which microbes was immobilized. The maximum MB removal efficiencies, when tested with 50 ppm dye using batch reactors containing free A. faecalis cells and the same cells immobilized on the biochar surface, were found to be 81.5% and 89.1%, respectively. The PBBR operated in continuous recycle mode at high dye concentration of 500 ppm provided 87.0% removal of MB through second-order kinetics over 10 days. The % removal was found in the order of PBBR>Immobilized batch>Free cell. The standalone biochar batch adsorption of MB can be described well by the pseudo-second order kinetics (R2 ≥0.978), indicating the major contribution of electron exchange-based valence forces in the sorption of MB onto the biochar surface. The Langmuir isotherm suggested a maximum monolayer adsorption capacity of 4.69 mg g−1 at 40 °C which was very close to experimentally calculated value (4.97 mg g−1). Moreover, the Casuarina seed biochar was reusable 5 times