[Variations in the active characteristics of sludge during the operation of an aerobic membrane bioreactor and their effects on membrane fouling].

The present work investigated the variations in the active characteristics of sludge during the operation period of an aeration membrane bioreactor, as well as their effects on the fouling of membrane module. Through discharging the excess sludge, the concentration of the mixed liquor was maintained at around 4 000 mg x L(-1) for 75 days, during which the characteristics of sludge were carefully tested every day to reflect its variation. Results indicated the dehydrogenase activity increased with the prolonging operation time. The increased activity of dehydrogenase had two effects on the operation of the bioreactor, one was the enhancement of pollutant removal by the microorganisms, while the other effect was the increase of extracellular polymeric substance (EPS), which led to a deteriorative effect on the membrane fouling. During the operation of the bioreactor, the sludge yield coefficient first increased, and then decreased to a certain degree with obvious decrease in particle size and increase in the amount of EPS, which also enhanced the quality of the effluent. At the same time, protozoon and metazoan were observed in the whole bioreactor at the late operational phase but relatively rare at the initial phase. Analysis of membrane fouling showed that the fouling rate of the membrane module increased during the late operational period, which was attributed to the deposition of fine sludge particles and EPS caused by the decreased particle size of the sludge and the increased amount of EPS.

[Rapid enrichment and cultivation of denitrifying phosphate-removal bacteria and its identification by fluorescence in situ hybridization technology].

The present work focused on a rapid enrichment and cultivation of denitrifying phosphate-removal bacteria (DPB) in a membrane bio-reactor(MBR) by using A2/O anaerobic sludge from a wastewater treatment plant as seed, as well as providing an identification method. In the experiments, sodium acetate was used as the carbon source and a certain amount of nitrate was added to the MBR in the anoxic stage. Results showed that, with the efficient trap of the hollow-fiber membrane module, the proportion of DPB in all the phosphate-accumulating organisms (PAOs) increased from 24% to 93% within 35 days after two-stage's cultivation including anaerobic/aerobic and anaerobic/anoxic, during which the removal efficiency of nitrogen and phosphorus reached more than 90%. The activated sludge was identified by combining a regular method and the fluorescence in situ hybridization (FISH) technique, which demonstrated that Pseudomonas sp. and Rhodocyclus sp. were the dominant bacteria in the used bioreactor.

[Synergistic effects of nano-sized magnetic particles and uncoupler to the characteristics of activated sludge].

For improving the performance and sludge settling property of an activated sludge reduction process with uncoupler, in this investigation, uncoupler and nano-sized magnetic particles were added simultaneously to a sequencing batch reactor for exploring their synergistic effects to the characteristics of activated sludge. The results showed that the volume reduction of sludge reached 41% with single 2,4,5-Trichlorophenol (TCP) Comparing with the control experiment, the biodegradability and settling properties of the activated sludge decreased. Under the actions of TCP combined with nano-sized magnetic particles, the volume reduction of sludge reached 34%, the removal efficiencies of COD, nitrogen, and phosphorus as well as the sludge settling property were not significantly influenced. After 31 d's operation, the dehydrogenase activity was improved by 10%-18% and exhibited an accumulative effect over time. It was observed with an optical microscope that the species and amounts of protozoon and metazoan increased and a compact structure of sludge floc was formed. The results also indicated that using nano-sized magnetic particles and uncoupler could restrict the yield of excess sludge and improve the performance of an activated sludge system.

1,2-Dibenzoyl-hydrazine-dimethyl-formamide (3/1).

The title compound, 3C(14)H(12)N(2)O(2)·C(3)H(7)NO, was synthesized by reaction of benzoyl chloride with hydrazine hydrate under microwave irradition. The asymmetric unit comprises three 1,2-dibenzoyl-hydrazine mol-ecules and one dimethyl-formamide mol-ecule. The 1,2-dibenzoyl-hydrazine mol-ecules are linked by pairs of N-H⋯O hydrogen bonds into chains propagating along [010].