Respiration adaptation of activated sludge under dissolved oxygen and hypochlorite stressed conditions.

In this work, the relationship between environmental disturbance and the recovery of activated sludge at a low dissolved oxygen of 0.5mg/l or in the presence of sodium hypochlorite of 1-15mg Cl2/gSS/d was examined. When microorganisms entered their physiological adaptation period, a sharp increase in endogenous respiration rate was observed. The activity recovery potential of sludge depended on the ratio of the endogenous respiration rate to the maximum respiration rate. A subsequent decrease in this ratio after a sharp increase indicates that the disturbance was recoverable. An increase in this ratio to a certain value, e.g., 0.35, suggests that the sludge system could not adapt to the new environments and thus was unrecoverable. In addition, the recoveries of sludge respiration and effluent quality were asynchronous, which was impacted by both sludge activity and operating conditions. These results provide a useful approach for the operation of activated sludge systems.

[Analysis of Respirogram Characteristics of Filamentous Bulking Caused by Low Dissolved Oxygen].

The current research on filamentous bulking focuses on the effluent quality and the settling properties but the reports on the microbial physiology under filamentous bulking conditions are seldom. In this study, the variations in the respirogram of microorganisms and affinity coefficient during filamentous bulking were explored in a sequence batch reactor. Low dissolved oxygen, regarded as the typical reason for filamentous bulking, was applied as the stimulation method. The results showed that microorganisms entered the physiological adaptation stage in the early period of low DO. The following properties were observed in the system:① a sudden increase in the endogenous specific oxygen uptake rate (SOURe) of activated sludge, ② an abrupt decrease in the specific oxygen uptake rate (SOURn) of autotrophic bacteria, ③ a rapid increase after a slight decline in the specific oxygen uptake rate (SOURc) of heterotrophic bacteria and a sudden increase in the oxygen affinity coefficient (KO). However, maintaining the low DO levels would deteriorate the effluent quality and sedimentation properties, but the SOURn and SOURc could recover to higher levels after a while and the COD affinity coefficient (KS) and KO would decrease gradually. In low DO conditions, a sufficient hydraulic retention time will benefit the effluent quality from a theoretical point of view. Moreover, microorganisms could adapt to low DO conditions, which verifies the feasibility of "low oxygen aeration theory" from the respiration and kinetic parameters. The results from this study provide a theoretical support for energy savings of sewage treatment plant operations.

Guangsangons F-J, anti-oxidant and anti-inflammatory Diels-Alder type adducts, from Morus macroura Miq.

Five Diels-Alder type adducts, named guangsangons F, G, H, I, and J, along with two known compounds, mulberrofuran J and kuwanon J, were isolated from Morus macroura Miq. Their structures were determined by means of spectroscopic analyses and chemical methods. These compounds were regarded biogenetically as Diels-Alder type adducts of dehydroprenylphenols and chalcone derivatives, and (1)H NMR variable temperature experiments suggested that they all existed as an equilibrium mixture of conformational isomers in solution. Among the isolated new compounds, guangsangons H, I, and J displayed potent antioxidant activities and moderate anti-inflammatory activities.

Bioactive diels-alder type adducts from the stem bark of Morus macroura.

Five new compounds, named guangsangons A (1), B (5), C (6), D (7), and E (8), along with four known compounds, albafuran C (2), kuwanon X (3), kuwanon P (4), and kuwanon Y (9) were isolated from Morus macroura Miq.. Their structures were determined by means of spectroscopic analyses and chemical methods. These compounds were regarded biogenetically as Diels-Al-der type adducts, and 1H-NMR variable temperature experience suggested that they all existed as an equilibrium mixture of conformational isomers in solution. Compounds 1-3 and 5-9 showed good anti-oxidation activity, with the inhibitory rate of malondialdehyde being from 90.1% to 102.7% at a concentration of 10(-4) mol/L and from 70.9% to 88.1% at a concentration of 10(-5) mol/L. Compounds 1, 5, and 7 showed anti-inflammation activity, with the inhibitory rates of release of lysosome enzyme from polymorphonuclear leukocytes of rats being 19.0% (P > 0.05), 57.3% (P < 0.001) and 24.3% (P < 0.05) at concentrations of 10(-5) mol/L, respectively.