Effect of different carbon sources on purification performance and change of microbial community structure in a novel A2N-MBR process were investigated. The results showed that when fed with acetate, propionate or acetate and propionate mixed (1:1) as carbon sources, the effluent COD, NH4+-N, TN and TP were lower than 30, 5, 15 and 0.5 mg?L–1, respectively. However, taken glucose as carbon source, the TP concentration of effluent reached 2.6 mg?L–1. Process analysis found that the amount of anaerobic phosphorus release would be the key factor to determine the above effectiveness. The acetate was beneficial to the growth of Candidatus Accumulibacter associated with biological phosphorus removal, which was the main cause of high efficiency phosphorus removal in this system. In addition, it could eliminate the Candidatus Competibacter associated with glycogen-accumulating organisms and guarantee high efficiency phosphorus uptake of phosphorus accumulating organisms in the system with acetate as carbon source.
Laboratory experiments were conducted to examine the impact of cadmium (Cd) on survival of Diplostomum sp. cercariae. Freshly emerged cercariae were exposed to Cd solutions at concentrations ranging between 0.2 and 200 microg/l. The mortality patterns and mean survival times (MSTs) of the exposed parasites were determined by the Kaplan-Meier estimator and were compared (Log-Rank test) to corresponding patterns and estimators of the unexposed controls. Cd concentrations >20 microg/l caused statistically significant changes in the mortality pattern of Diplostomum sp. cercariae and reduced MST by at least five hours compared to the control group, where MST was 52 h. The results show that longevity of the free-living Diplostomum sp. cercariae can be reduced by direct exposure to heavy metals. Cd contamination of aquatic habitats thus potentially can have an impact on parasite populations and communities. 相似文献
Most research conducted on the concentration distribution of sediment in the sedimentation tank does not consider the role of the
suction dredge. To analyze concentration distribution more accurately, a suspended sediment transportation model was constructed and
the velocity field in the sedimentation tank was determined based on the influence of the suction dredge. An application model was then
used to analyze the concentration distribution in the sedimentation tank when the suction dredge was fixed, with results showing that
distribution was in accordance with theoretical analysis. The simulated value of the outlet concentration was similar to the experimental
value, and the trends of the isoconcentration distribution curves, as well as the vertical distribution curves of the five monitoring sections
acquired through simulations, were almost the same as curves acquired through experimentation. The di erences between the simulated
values and the experimental values were significant. 相似文献