Research On The Microbial Performance And Effects Of C/P Ratio On Phosphorus Removal In A~2/O-MBNR Process

A2/O-MBNR combined process could achieve a good nitrogen removal, butphosphorus removal was not very stable. To further enhance the phosphorus removal andunderstand the mechanism of phosphorus removal in the microbial level and optimizeoperation, this test researched on the relations of intracellular polymers’ content changesand phosphorus accumulating ability, and analyzed the system flora morphology combinedwith biotechnology means. The results were shown as follows：Intracellular PHB was extracted by means of comparing and optimizing, selecting thepre-processing step by three times pure water washed sludge and centrifugal and extractionmethods of NaClO mixed with chloroform. Using UV spectrophotometry analyzed itquantitatively. The digesting method with potassium persulfate and high pressure boilerand the polyphosphate content analyzing by antimony anti-spectrophotometric weredetermined.The two methods were quick, easy and cost-effective, so they were suitable forthe applications of laboratory research and other practices.Under the condition of different C/P ratio, the system had different phosphorusremoval, which achieved the best phosphorus removal in the C/P ratio of36. Contentconversion of intracellular polymers was changed with the change of C/P ratio. PHBcontent variation increased in the anaerobic pond, and reduced in the aerobic pond. In theexperiment, the highest content of PHB was up to160mg/g, and PHB production and CODconsumption, release of phosphorus existed a certain quantitative relationship in theanaerobic pool,△PHBAnaerobic pond/△CODAnaerobic pondwas about0.7-1.1,△PO4^3--PAnaerobic pond/△PHBAnaerobic pondreduced from0.22to0.05with the increase of C/P ratio,which showed that glycogens were dominant under the condition of high C/P ratio；△PO4^3--PAerobic pond/△PHBAerobic pondincreased from0.13to0.76with the decrease of C/Pratio, which showed that glycogens were dominant under the condition of low C/P ratio.Content variation for Phosphorus accumulating bacteria reduced in the anaerobic pond, andincreased in the aerobic pond. Polyphosphate content of the various structures increasedwith the decrease of C/P ratio, the unit sludge at levels ranged from27mg/g to76mg/g；Under the condition of low C/P ratio, there was the presence of denitrifying phosphorusbacteria in the anoxic tank. PHB utilization was higher for phosphate accumulatingbacteria In the aerobic pond than that in the anoxic tank. The ability of phosphorusaccumulating to the microorganism was the best in the C/P ratio of36, the followingindicators could be used to explain this view: Phosphorus uptake rate in the aerobic pond： 95.6%, unit sludge phosphorus uptake:9.97mg/g. The system took place inflation offilamentous fungi in the C/P ratio of46-73, which had a serious impact on the phosphorusremoval, the content of intracellular polymer changed a lot, it could no longer take placethe PHB cyclical content change, the process of aerobic phosphorus uptake disappeared.It could be found by scanning electron microscopy to the sludge that the anaerobicpond contained the fulfilling of spherical bacteria, a small amount of short bacilli, as wellas the cell nest of sludge; The dominant bacteria in the hypoxia pool were0.5-1μmStaphylococcus aureus and about1.5μm corynebacterium; There were more microbialspecies in the aerobic tank, about3μm long bacilli,1.5μm corynebacterium, ellipticalcoccus, and a lot of coral large cell clusters in together. Using fluorescence in situ-hybridization method for the detection that there were phosphorus accumulating bacteriaassociated with Rhodocyclus in the system. Phosphorus accumulating bacteria present inthe sludge dispersedly. The content of the aerobic pool was more than Anaerobic tank andanoxic tank, but the overall had less difference.It could be found that the anaerobic pond was dominated by Proteobacteria and theaerobic pool was dominated by Proteobacteria and Bacteroidetes with the method of PCR-Sequencing. Microbial species in anaerobic pond and aerobic pond were very rich,although there were differences about species categories and community structure in thetwo ponds, they were in the dynamic balance.