The Study Of Enhanced Biological Phosphorous Removal And Denitrfying Phosphorous Uptake

Nitrogen and phosphorous are the main pollutants that cause eutrophication of water body. Biological denitrification, phosphorous removal and simultaneous nitrogen and phosphorous removal are the main techniques for removing nitrogen and phosphorous in water body. The formation of biological phosphorous removal granular sludge, the effect of influent COD load on enhanced biological phosphorous removal and the process of phosphorous removal granular sludge induced to denitrifying phosphorous uptake granular sludge were studied. The results showed as follows:(1) Phosphorus removal granular sludge was cultivated through shortening the settling time gradually in alternate anaerobic and aerobic condition with sodium acetate as substrate and flocculent sludge as inoculated sludge. After running for 26 days, the concentration of effluent phosphorous was below lmg/L, the maximum concentration of phosphorous released in anaerobic stage was 87.1mg/L, the maximum velocity of releasing phosphorous was 51.8mgP/gVSS·h, the maximum velocity of absorbing phosphorous was 39.7mgP/gVSS·h. The diameter of the granular sludge was 0.5-1.5mm, the highest settling velocity was 20m/h, the moisture content was 94%, and the SVI was 20-30mL/g. The total quantity of phosphorous in the sludge was 8.1-11.8%.(2) The influent COD load and C/P were the main factors that affected the stability of enhanced biological phosphorous removal. When C/P was less than 30, the concentration of phosphorous released in anaerobic stage increased with the C/P. The higher-concentration of phosphorous was released in anaerobic stage, the more quantity of phosphorous was absorbed in aerobic stage. The positive effect of removing phosphorous can be achieved while C/P between 20 and 30. The sludge bulking caused by multiplication of sphaerotilus, the outflow of PAOs because of bad precipitation as well as decreasing efficiency of phosphorous removal appeared when the COD load was too high. Regulating the concentration of COD at the end of anaerobic stage was very important for the stability of the system.(3)The DNPAOs granular sludge was successfully induced after adding nitrate to EBPR granular sludge in SBR at the end of anaerobic stage. The ability of denitrifying phosphorous accumulation was increased after induced, then the concentration of nitrate in anoxic stage was improved from 6mg/L to 12mg/L, and the quantity of the phosphorous absorbed in anoxic stage in the whole system increased from 36.3% to 69.6% . The ratio of DNPAOs to the total PAOs increased from 16.2% to 77.2% after induced. The quantity of absorbed phosphorous for consuming 1 mg nitrogen in anoxic stage was 2.38mg.