| Summary: | 碩士 === 東吳大學 === 微生物學系 === 107 === Benzophenone (BPs) are widely used as pharmaceuticals and personal care products (PPCPs) in our daily life. BPs are identified as interfering with the biological endocrine system in living organisms. When BPs are released into aquatic environment, it can cause a high health risk of an ecological system through bioconcentration and bioaccumulation. The objective in this study is to treat BPs-contained sewage in the sequencing batch reactor (SBR). The experiment was carried out at two stages. First stage was to evaluate the effect of different hydraulic retention time (HRT) at 8, 16 and 48 hrs on the treatment of BPs-contained synthetic sewage in the SBR. This results indicated that the 48hrs HRT treatment had the best remove efficiency. TOC and COD removal rates were measured as 97.04% and 89.44%, respectively. The degradation rate of BPs: benzophenone-1 (BP-1) and benzophenone-3 (BP-3) were measured as 96.80% and 98.04%, respectively. The treatment efficiency of BPs-contained sewage under the aerobic (aeration) and anoxic (idle) operating phases was evaluated in the SBR at HRT=48 hrs. The removal of BP-contained sewage under the aerobic operating phase is better than that under the anoxic operating phase. COD removal rate is measured as 57.19%; BP-1 and BP-3 removal rates were measured as 85.85% and 74.53%, respectively. Changes of extracellular polymeric substances (EPS) in the SBR were measured, higher sludge SV30 is proportional to higher protein (PN) of EPS at longer HRT. Soluble EPS concentration increases with the decreasing HRT. It is inferred that microorganisms of activated sludge release more EPS due to the presence of BPs in the SBR. The microbial population was analyzed and revealed that different HRT affected obviously in the SBR. In Phylum level, the percentage of Proteobacteria was accounted as 31.69% at 8hrs HRT, which is the lowest among different HRT samples; the highest biodiversity of microorganisms was measured at 48 hrs HRT. In the Genus level, the dominant bacterial strains are Sediminibacterium sp. (26.65%) at 8 hrs HRT; Novosphingobium sp. (35.76%) and Coprococcus eutactus (34.50%) at 48 hrs HRT.
The second stage of the experiment is to isolate bacteria that can utilize BPs as a sole carbon source from the SBR. 6 BP-1-biodegrading strains and 5 BP-3-biodegrading strains were isolated. Each of 3 strains with the higher ability of biodegrading BPs were selected for further batch biodegradation experiments. The results showed that BP1-D was the best strain for BP-1 biodegradation, and the pseudo-first-order rate is measured as 0.628 hr-1; BP3-5 was the best strain for BP-3 biodegradation, its pseudo-first-order rate is measured as 0.187 hr-1. Base on the 16S rDNA identification, all of 3 BP-1 strains with the higher ability of biodegrading BP-1 were identified as Pseudomonas sp.; the BP-3 strains was identified as Gordonia sp. (BP3-1), Pseudomonas sp.(BP3-4) and Rhodococcus sp.(BP3-5). Further analysis of biometabolites and their biodegradation pathways, BP-1 will first be biotransformed to (4-hydroxyphenyl) (phenyl) methanone (207 m/z), then decomposed into small-molecular-weight biometabolites, such as 126 m/z metabolite (BP1-A), 151 m/z alcohol-based metabolites (BP-1-D and BP1-F), then hydroquinone. Bacteria strains which decomposed BP-3 will also produce (4-hydroxyphenyl) (phenyl) methanone, but subsequent metabolites differed depending on the microorganisms. BP3-1 produced 137 m/z biometabolites; BP3-5 was identified as toluene (92 m/z). This study is the first time to dealing with the biological treatment of BP-contained sewage. This results will provide a great reference for biological process in treating BPs-contained sewage/wastewater in the future.
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