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This dissertation, Anaerobic Degradation of Toxic and Refractory Aromatics by Dawei, Liang, 梁大為, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Anaerobic Degradation of Toxic and Refractory Aromatics Submitted by LIANG DAWEI for the degree of Doctor of Philosophy at the University of Hong Kong in January 2007 This thesis studies the degradation of phenol and dimethyl phthalate (DMP), two representative toxic and refractory aromatics, in wastewater. Degradation of phenol was conducted under anaerobic condition, whereas degradation of DMP was conducted under both anaerobic and denitrifying conditions. In addition, microbial communities in sludges were characterized using molecular techniques. Over 99% of phenol was degraded in an upflow anaerobic sludge blanket (UASB) reactor at 55C with 40 h of hydraulic retention time (HRT) for a wastewater containing up to 630 mg/L of phenol. The maximum specific methanogenic activity (SMA) of the phenol-degrading sludge was 21.5 mg-CH /(g-VSS-d). A total of 21 operational taxonomy units (OTUs) were found in the sludge, of which 13 (79.6% of population) were affiliated with known thermophilic species. Degradation pathway of phenol for thermophilic sludge was likely via caproate, instead of via benzoate as reported for the mesophilic sludge. The most predominant group in the thermophilic phenol-degrading sludge was a novel uncultured bacteria group TMTG. The population of TMTG was estimated as 3.5-9.9% using quantitative real-time polymerase chain reaction (qRT-PCR) with a TaqMan probe. The standard curve for the qRT-PCR was established using the plasmid containing 16S rDNA of the bacterium TPD-2 in TMTG group. Over 99% of DMP and 93% of COD were effectively removed in a UASB reactor for the wastewater containing 600 mg/L of DMP at 8 h of HRT, 37C. Using DMP as substrate, the maximum SMA was 24 mg-CH /(g-VSS-d). The sludge yield was estimated as 0.08 g-VSS/g-COD. DMP was de-esterified, first to mono-methyl phthalate (MMP) and then phthalic acid (PA), before being de-aromatized. The maximum specific degradation rates (SDRs) of DMP, MMP and PA were 415, 88 and 36 mg/(g-VSS-d), respectively. Anaerobic DMP-degrading granular sludge from the UASB was characterized by electron microscopic (EM) and molecular methods. EM and fluorescence in situ hybridization (FISH) images showed that the granule exhibited layer structure. The skin layer was predominantly Bacteria, whereas the interior was Archaea, the population of which were 895% acetoclastic Methanosaetaceae and 115% hydrogenotrophic Methanomicrobiales. A total of 78 Bacteria clones developed from the sludge were classified into 22 OTUs in 9 divisions, the most abundant of which were LGC (5 OTUs, 51.3% of population) and δ-Proteobacteria (6, 26.9%). Two most abundant OTUs, DMPU-91 (41% of population) and -11 (21%), were likely responsible for DMP de-esterification and PA degradation, respectively. Denitrifying degradation of DMP was found optimum at pH 7-9 and 30-35C by batch experiments. DMP was first degraded to MMP, and then to PA, before complete mineralization. The maximum SDRs for DMP, MMP and PA were 0.32, 0.19 and 0.14 mM/(g-VSS-h), respectively. About 86% of available electron in DMP was utilized for denitrification. The biomass yield was estimated as 0.17 mg/mg-DMP based on electron balance. The denitrifying sludge was mainly composed of α- and β- subdivisions of Proteobacteria. A primer set was designed to amplify the denitrification nirK g

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