ABSTRACT:The ability of native bacteria to utilize diesel fuel as the sole carbon and energy source was investigated in this research. Ten bacterial strains were isolated from the oil refinery field in Tehran, Iran. Two biodegradation experiments were performed in low and high (500 and 10000 ppm, respectively) concentration of diesel fuel for 15 days. Only two isolates were able to efficiently degrade the petroleum hydrocarbons in the first test and degraded 86.67 % and, 80.60 % of diesel fuel, respectively. The secondary experiment was performed to investigate the toxicity effect of diesel fuel at high concentration (10000 ppm). Only one strain was capable to degrade 85.20 % of diesel fuel at the same time (15 days). Phenotype and phylogeny analysis of this strain was characterized and identified as dieseldegrading bacteria, based on gram staining, biochemical tests, 16S rRNA gene sequence analysis. These results indicate that this new strain was Bacillus sp. and could be considered as Bacillus Cereus with 98 % 16 S rRNA gene sequence similarity. The results indicate that native strains have great potential for in situ remediation of diesel-contaminated soils in oil refinery sites.

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The high capital, operational and maintenance costs of municipal wastewater treatment plants in Iran are a concern for the government. Wastewater treatments in natural systems have shown suitable methods for their low cost. The performance of a pilot-scale subsurface constructed wetland with Phragmites australis to treat municipal wastewater has been investigated. The purpose of this study was to determine the surface area requirement per person in an arid region to achieve an acceptable quality in terms of discharge standards. Experiments were carried out in two cells (15 × 10 mxm) with media size ranging from 4-8 mm. One cell was used as blank (unplanted) and the other one was planted. Different hydraulic loading rates ranging from 5 to 20 L/min were used. Minimum land requirement was determined to be 1-2 m2/P.E. to reduce COD (86±4%), BOD5 (90±3%), TSS (89±4%), TN (34±6%), TP (56±5%) and fecal coliform (>99%).

The effectiveness of ozone treatment for improving the biodegradability of recalcitrant pollutants has been proved by investigating the ozonation reaction of Methyl tert-butyl ether (MTBE) a bioresistant gasoline oxygenate. Laboratory scale experiments have been carried out, at room temperature, by bubbling, for 120 min, ozonated air (3.4 ppm min^-1 ) into 3 liter of an alkaline (pH=11.5) aqueous solution (100 mg L^-1) of MTBE. The experimental results indicated that during the ozonation, complete MTBE degradation occurs in 100 min and after this time, ozone consumption goes on very slowly. At the end of the ozonation, after 100 min, the initial value of COD (256 mg O₂ L^-1) is 98 and correspond to a relative removal of about 62%.As for MTBE solution biodegradability expressed as (BOD5)/(COD) ratio, during the first 90 min its value regularly increases from lowest (0.01) up to a maximum of 0.68 that corresponds to an ozone consumption of 1.25 mg per each mg of COD initially present in the solution.The experimental results for determining the rate of MTBE removal due to stripping showed that about 14% of MTBE strips out after an hour of sparging with oxygen gas. The fraction of MTBE oxidized and/or striped increases to about 28% (in pH=7) and 70% (in pH=11.5) with ozonation over the same time period

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The influence of soil organic matter on PCP degradation was studied using the white rot fungus Phanerochaete chrysosporium in shake cultures contaiing syringic and humic acids. Cumulative 14C02 production after 31 days showed that the presence of syringic and humic acids at 1,000 mg/L significantly decreased PCP mineralization (P = 0.05). At a lower concentration of 250 mg/L, these acids did not significantly decrease mineralization compared with controls. Time series of 14C02 production showed that the presence of the acids, especially syringic acid, delayed the onset of mineralization and suppressed the maximum mineralization rate, but extended the lifetime of the mineralization reaction over that of the control. The presence of syringic acid at 1,000 mg/L significantly increased volatilization and partitioning of 14C onto the fungus at the end of 31 days, while an equal amount of humic acid significantly decreased the extent of mineralization and increased partitioning of 14C onto the fungus. The presence of 250 mg/L of each acid did not significantly affect the distribution. These results are evaluated and implications for practical remediation of PCP-contaminated soils are discussed. BACKGROUND