Journal of School of Public Health and

Background and Aim: In this research we isolated the bacterial species degrading polycyclic aromatic hydrocarbons (PAHs) and determined optimal salt concentration for PAH degradation.

Materials and Methods: We used naphthalene and anthracene as the only sources of carbon for isolating PAH-degrading bacteria the main culture medium was ONR7a. The bacteria isolated by this method were used for the study of the effect of salt concentration on PAH degradation.

Results: Pseudomonas is the only PAH-degrading bacterium isolated from the lake's water and sediment. The greatest numbers of naphthalene- and anthracene-degrading bacteria where found in the water and sediment from the Khoshk River (mean counts: 227 and 167 per ml water and 290 and 193 per gram of sediment). The mean counts of naphthalene- and anthracene degrading bacteria in Pol- Fasa River were 107 and 73 per ml water and 157 and 127 per gram sediment, respectively. Values from Nazar Abad River were 27 and 17 /cc water and 43 and 20 / g sediment. In the center of the lake counts were 63 and 33 per ml water and 123 and 73 per gram sediment and in the western part of the lake counts were 30 and 13 /ccl water and 43 and 17 /g sediment.Maharloo lake is located in south-east of Shiraz, 23 km from the city and contains saline water with a mean salt content of 220 g/L. Among the most important pollutants entering the lake are polycyclic aromatic hydrocarbons (PAHs). Our research showed that overall, naphthalene-degrading bacteria are present in greater numbers compared to anthracene-degrading bacteria. The optimal salt concentration for the growth of Pseudomonas spp growth and PAH-degradation is around 6% the rate of degradation increases with time.
Conclusion: Regarding isolation of PAHs degrading bacteria from the lake, it is obvious that part of the degradation is done by bacteria. The main bacterium here is pseudomonas and it is optimally active at a salt concentration of 6%.

Background and Aim: Acrylonitrile (ACN) is widely used as a main raw material in the Acrylonitrile-Butadiene-Styrene (ABS) resin-manufacturing units and other industrial and commercial processes. ACN, due to its toxicity, is not easily decomposed by microorganisms. The discharge of improperly treated ACN-containing wastewater into a natural water body may cause serious environmental problems and severe adverse impact on the aquatic ecology. This study attempts to isolate and identify bacteria which utilize ACN as the sole source of carbon and nitrogen from the activated sludge of petrochemical wastewater treatment system. The performance of the isolated strains in treating different initial ACN concentrations was also investigated under aerobic conditions. In addition, the performance of biodegradation and the metabolic intermediates and end-products in the process were determined.

Materials and Methods: Experiments were conducted with three batch reactors, the volume of each one being 250 mL. The activated sludge samples as a microbial seeding were taken from the return sludge line of the aeration tank of the wastewater treatment facility in Tabriz Petrochemical Complex. Phosphate-buffered medium (PBM) was used to make available minerals and trace elements, and ACN was used as the sole carbon and nitrogen source for microbial growth. R2A medium was used to obtain pure colonies, and to identify the isolated strain, Gram staining and microscopic examination followed by biochemical and physiologic analyses using selective media such as O-F glucose, MacConkey agar, TSI agar, EMB and SS agar, nitrate reduction, gelatin liquefaction, lactose fermentation, oxidase, catalase and SIM were used. In the final stage, the performance of biological systems in degrading different initial concentrations of ACN and its intermediate and end-products were investigated.

Results: The findings indicated that when the ACN concentration was 500 mg/L, the average removal efficiency after 46 and 70 h reached 46% and 98%, respectively. But at an initial concentration of 700 mg/L, the removal efficiency of the ACN in the biological system was 50% after 46 h and 98.6% after 94 h . However, when the ACN concentration was increased to 1000 mg/L, the removal efficiency after 46 and 94 h was only 30% and 40%, respectively, and after 118 h of reaction, the remaining concentration of ACN was about 580 mg/L. Furthermore, the results of isolation and identification experiments revealed that at the optimum operation of the biological system the strain belonging to the gamma group of Proteobacteria as Pseudomonas putida had the best ability to degrade ACN.

Conclusion: Biological processes can degrade ACN and the abilities of different bacterial strains in this degradation vary. The rod-shaped Gram-negative P. putida could easily adapt to ACN concentrations up to 700 mg/L and utiliz ACN and its intermediate- and end-products as a carbon and nitrogen source for growth in the process. Thus, this strain is expected to play an important role in aeration tanks for treating ABS resin-manufacturing wastewater.