Biodegradation of geosmin in drinking water by novel bacteria isolated from biologically active carbon

Three strains of Gram-negative bacteria capable of removing geosmin from drinking water were isolated from biologically active carbon and identified to be Chryseobacterium sp., Sinorhizobium sp. and Stenotrophomonas sp. based on physio-biochemistry analysis and 16S rRNA gene sequence analysis. Removal efficiencies of 2 mg/L geosmin in mineral salts medium were 84.0%, 80.2% and 74.4% for Chryxeobacterium sp., Sinorhizobium sp. and Stenotrophomonas sp., respectively, while removal efficiencies of 560 ng/L geosmin in filter influent were 84.8%, 82.3% and 82.5%, respectively. The biodegradation of geosmin was determined to be a pseudo first-order reaction, with rate constants at 2 mg/L and 560 ng/L being 0.097 and 0.086 day-1, 0.089 and 0.084 day-1, 0.074 and 0.098 day-1 for the above mentioned degraders, respectively. The biomass of culture in the presence of geosmin was much higher than that in the absence of geosmin.

Biodegradation of 2-methylisoborneol by bacteria enriched from biological activated carbon

One of the most common taste and odour compounds （TOCs） in drinking water is 2-methylisobor- neol （2-MIB） which cannot be readily removed by conventional water treatments. Four bacterial strains for degrading 2-MIB were isolated from the surface of a biological activated carbon filter, and were characterized as Micrococcus spp., Flavobacterium spp., Brevibacterium spp. and Pseudomonas spp. based on 16S rRNA analysis. The removal efficiencies of 2-MIB with initial concentra- tions of 515 ng.L i were 98.4%, 96.3%, 95.0%, and 92.8% for Micrococcus spp., Flavobacterium spp., Brevibacter- ium spp. and Pseudomonas spp., respectively. These removal efficiencies were slightly higher than those with initial concentration at 4.2 mg. L~ （86.1%, 84.4%, 86.7% and 86.0%, respectively）. The kinetic model showed that biodegradation of 2-MIB at an initial dose of 4.2 mg. L1 was a pseudo-first-order reaction, with rate constants of 0.287, 0.277, 0.281, and 0.294d-1, respectively. These degraders decomposed 2-MIB to form 2-methylenebor- nane and 2-methyl-2-bornane as the products.

Mechanisms for simultaneous ozonation of sulfamethoxazole and natural organic matters in secondary effluent from sewage treatment plant

Sulfamethoxazole(SMX)is commonly detected in wastewater and cannot be completely decomposed during conventional treatment processes.Ozone(O_(3))is often used in water treatment.This study explored the influence of natural organic matters(NOM)in secondary effluent of a sewage treatment plant on the ozonation pathways of SMX.The changes in NOM components during ozonation were also analyzed.SMX was primarily degraded by hydrolysis,isoxazole-ring opening,and double-bond addition,whereas hydroxylation was not the principal route given the low maximum abundances of the hydroxylated products,with m/z of 269 and 287.The hydroxylation process occurred mainly through indirect oxidation because the maximum abundances of the products reduced by about 70%after the radical quencher was added,whereas isoxazole-ring opening and double-bond addition processes mainly depended on direct oxidation,which was unaffected by the quencher.NOM mainly affected the degradation of micropollutants by consuming•OH rather than O_(3)molecules,resulting in the 63%–85%decrease in indirect oxidation products.The NOM in the effluent were also degraded simultaneously during ozonation,and the components with larger aromaticity were more likely degraded through direct oxidation.The dependences of the three main components of NOM in the effluent on indirect oxidation followed the sequence:humic-like substances>fluvic-like substance-s>protein-like substances.This study reveals the ozonation mechanism of SMX in secondary effluent and provides a theoretical basis for the control of SMX and its degradation products in actual water treatment.