In this study, occurrence of the main odorous compounds in different types of source water in China, including rivers, lakes and reservoirs, were investigated by integrating the methods of flavour profile analysis (FPA) and sensory-GC/MS analysis. Simultaneous distillation extraction (SDE) was chosen as the preconcentration technique while the odour-causing compounds were identified with sensory-GC/MS. It was found that MIB, which is mainly produced by some cyanobacteria and actinomycetes, was one of the most widely distributed odour-causing Dimethyl trisulfide might be an important T/O-causing compound in China.
Five powdered activated carbons (PACs), including one fruit-based, one wood-based, and three bituminous coal-based, were selected for the investigation of the effects of surface characteristics of activated carbon on the adsorption of 2-methylisobornel (MIB) and geosmin. Characterization of the carbons was performed using nitrogen adsorption, Fourier transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). All the carbons showed a broad absorption band in the 1300-1000 cm −1 region, which can be assigned to C-O stretching and O-H bending modes of alcoholic, phenolic, and carboxylic groups in FTIR spectra. The contents of O and C on the surfaces of carbons were acquired from the data of XPS analysis. Statistical analyses on the relationship between the adsorption capacities and different carbon surface parameters (O content, C O and C-O chemical group contents, the surface area, different pore volumes, iodine number and methylene blue number) were performed using Spearman rank correlation method. A good linear relationship between the adsorption capacities for MIB and geosmin and the micropore volumes was acquired. Both of iodine number and methylene blue number, the two most often used parameters for the evaluation of activated carbon quality, and other parameters, such as meso and total pore volumes, surface area, O and C-O contents were found to be insignificant in correlation with the adsorption capacities of MIB and geosmin. The volume of micropores could be used as an effective indicator for the selection of PAC for the removal of both MIB and geosmin.
Microbial community structures in biofilms of a clearwell in a drinking water supply system in Beijing, China were examined by clone library, terminal restriction fragment length polymorphism (T-RFLP) and 454 pyrosequencing of the amplified 16S rRNA gene. Six biofilm samples (designated R1–R6) collected from six locations (upper and lower sites of the inlet, middle and outlet) of the clearwell revealed similar bacterial patterns by T-RFLP analysis. With respect to the dominant groups, the phylotypes detected by clone library and T-RFLP generally matched each other. A total of 9,543 reads were obtained from samples located at the lower inlet and the lower outlet sites by pyrosequencing. The bacterial diversity of the two samples was compared at phylum and genus levels. Alphaproteobacteria dominated the communities in both samples and the genus of Sphingomonas constituted 75.1%–99.6% of this phylum. A high level of Sphingomonas sp. was first observed in the drinking water biofilms with 0.6–1.0 mg L−1 of chlorine residual. Disinfectant-resistant microorganisms deserve special attention in drinking water management.This study provides novel insights into the microbial populations in drinking water systems and highlights the important role of Sphingomonas species in biofilm formation.
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