This study was undertaken to investigate the current contamination status of polyhalogenated aromatic hydrocarbons (PHAHs) in sediments from large reservoirs located in Hebei and Hubei provinces in China. The concentrations of 21 polybrominated biphenyl (PBB) congeners, seven polybrominated diphenyl ether (PBDE) congeners, and 27 polychlorinated biphenyl (PCB) congeners in sediments were measured using the GC-MS/MS technique. Low-brominated PBBs (including 1, 3, 4, 10, 30, 31 and 53) were the most abundant PBB congeners and PBDEs 28, 47 and 99 were the most prevalent PBDE congeners in these samples. Among the three subfamilies of PHAHs, PCBs were the most predominant pollutants detected. The measured levels of PHAHs were compared with recent results reported in the literature and their respective sediment quality guidelines recommended by USEPA. The levels of PHAHs in the present study were generally lower than their respective threshold-effect levels, or were comparable to those reported in relatively uncontaminated freshwaters from other regions. This suggests that, in these reservoirs, toxic biological effects on aquatic biota--due to PHAH contamination of sediments--can be expected to be negligible. Thus, in terms of PHAHs, the sediments in the selected reservoirs are relatively uncontaminated.
This paper studied on the treatment of urban domestic wastewater with Anaerobic MBBR in the tropical and subtropical areas in the South of China. The emphasis focused on the effects of the Hydraulic Retention Time (HRT) and pH value to the CODCrconcentration and the NH3-N concentration of the outflow of the reactor. Moreover, the mechanism of denitrification was also explored. The results showed that the mechanism of denitrification of the reactor was found. When HRT was equal to or more than 8h, NH3-N was reduced mainly in the way of short-cut nitrification and denitrification. When HRT was less than 8h, the reactions of short-cut nitrification and denitrification & anaerobic ammonia oxidation both existed in the reactor.
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