| In recent years, pharmaceuticals and personal care products(PPCPs) which are new trace pollutants have drawn more and more attention because of their potential danger to natural ecological system and human security. In this paper, iopromide and its analogues iomeprol are common iodinated contrast media compounds and they were taken as research object.Fristly, a method for the determination of trace pollutant in wastewater and surface water by solid-phase extraction-high performance liquid chromatography (SPE-HPLC) was developed. The water sample was adjusted to acidity (pH=5) by sulfuric acid, and the trace iopromide and iomeprol were extracted and enriched by HLB solid phase extraction column and eluted with 8mL 100% methanol at a flow rate of 1mL·min-1. After pretreatment, the samples were measured by HPLC with Eclipse XDB C18 column(4.6mm×150mm,5μm), and eluted with a mobile phase of acetonitrile and water (9:91;v:v) at a flowing rate of 0.4 mL·min-1. The detection wavelength was at 242 nm, the column temperature was 25℃, the injection volume was 20μL. The retention times of iomeprol and iopromide were 5.5 minute and 8.1minute-8.8 minute respectively. Standard curve equation of iomeprol was y= 0.008x+0.0291(x was peak area; y was contentration of iomeprol), and R2=0.9999, which showed a good linear relationship. Standard curve equation of iopromide was y= 0.007x+0.0059 (x was peak area:y was contentration of iopromide), and R-=0.9999,which showed a good linear relationship. The recoveries of iomeprol and iopromide by the method were 96.58% and 97.28% respectively, the relative standard deviation of results was not more than 2%. It was concluded that the method was handy and effective with high precision.Secondly, this study has isolated an strain of iopromide-degrading bacteria from the recycling sludge from the secondary sedimentation tank in municipal wastewater treatment plant. Based on the morphology, physiology and phylogenetic analysis of 16S rRNA sequence, the iopromide-degrading bacterium has been identified to be closely related to Pseudomonas putida and was named as Pseudomonas sp.1-24. Its degradation mechanism of the iopromide is co-metabolism. The optimum condition of degrading iopromide was at 30℃, pH 7. Under this condition, strain 1-24 could degrade 30 mg/L iopromide by 99% in liquid mineral salt medium after 5 days, with 5% appropriate inoculation and 200mg/L starch as co-metabolism substrate. Besides, strain 1-24 also could degrade iomeprol by co-metabolism. Iopromide and iomeprol degradation kinetics of strain 1-24 can be explained with the following equations respectively: y=93.057e-0.886x(R2=0.9718):y=35.043e-00927x(R2=0.9229). (x was degradation time,t(d); y was contentration of iopromide or iomeprol c(mg·L-1)).Finally, Adding strain 1-24 and sludge (2500mg/L) with the proportion of 1/1000(v:v) in the aeration tank with 50%(V/V) suspended carrier of suspended carrier A2O process. To some extent, the presence of suspended carrier could prevent the loss of bacteria. At the same time, a control reaction apparatus without strain 1-24 was run. The two reaction apparatuses were run under the same condition:the filling rate of padding in aeration tank was 50%, inner recycling ratio was 200%, the external reflux ratio was 100%, the DO was controlled 3-4mg/L in aerobic tank, in anoxic pond was<0.5mg/L, and in anaerobic tank was<0.2mg/L. The objective was to study the effects of HRT and SRT on the iopromide and iomeprol removal. It was found that the optimal HRT was 10h, the optimal SRT was 10d.Under this condition, the remove rate of iopromide and iomeprol were 27.3%,20% respectively in the control reaction apparatus without strain 1-24. But the remove rate of iopromide and iomeprol were 60%,50.4% respectively in the reaction apparatus with strain I-24, and at the same time, the remove rate of conventional water quality parameters such as CODcr,NH3-N and TP were 94.27%,92.32% and 90.88% respectively.With the comparison of the two reaction apparatuses, it could be concluded that the adding of strain 1-24 only enhanced the iopromide and iomeprol removal but had no effects on the removal rates of other conventional water quality indicators such as CODcr,NH3-N and TP and so on. The results showed that when the dosing quantity of strain 1-24 was 1/1000(v/v), the adding of strain couldn't change the degradation ability of the original processing system in case of conventional water quality indicators. Additionally, analysis of the activities of dehydrogenase of sludge and the DGGE patterns proved that the adding of strain 1-24 had no negative effects on the original system. At the beginning of adding strain 1-24, the activities of dehydrogenase of sludge would change slightly higher, however, after the reactor running for two days, it has returned to the level before. The results of PCR-DGGE showed that there were slight changes in microflora at the beginning of the reactor's start-up, which was not only about the adding strain 1-24, but also because the reactor running was instable caused by new microorganisms added. With the stabilized reactor running, the number of bacteria began to gradually recover. After the reactor ran for 15 days, strain 1-24 still existed in the recover, while the degradation of iopromide, iomeprol and water quality indicators were stable. |
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