Study On Shortcut Nitrification- Denitrification And Denitrifying Phosphorus Removal In A Two-sludge SBR System

The eutrophication of water environment has drawn increasing attention because of the excess emissions of nitrogen and phosphorus,as one of the most environmental problems human concerns. It becomes a hot point that development of an efficient, energy-saving new nitrogen and phosphorus removal technology, as the inadequate of treatment capacity of low-carbon sources sewage by conventional biological nutrient and phosphorous removal technology .This paper focused on the research of new shortcut nitrification-denitrification and denitrifying phosphorus new techniques and A2NSBR system was improved by cultivation of denitrifying phosphate accumulating bacteria with nitrite as electron acceptor in the A2-SBR1 and hanging biofilm in N-SBR2, formation biofilm two-sludge SBR system to be used for treatment of small-town Sewage.The results shows that shortcut nitrification-denitrification could be achieved in a biofilm in N-SBR2 by controlling dissolved oxygen (DO) concentration around 1.0mgO2/L during 60 days stable operations after the biofilm in N-SBR2 was successfully linked. The research on the factors of affecting nitrite accumulation shows that 28±1℃, NO2--N accumulation rate at pH 7.5 ~ 8.5 is higher than at pH 6.5 ~ 7.5. The changes of pH affect the accumulation of nitrite, but after several cycles of recovery, still obtain a stable shortcut nitrification- denitrification efficiency. Compared with C/N of 6 ~ 8, C/N of 3~ 5 is more conducive to the accumulation of nitrite. In addition, the study found that the biofilm N-SBR2 system can not achieve shortcut nitrification by higher dissolved oxygen concentration (2.5mg / L) continuous aeration mode.Using three-stage progressive increasing nitrite concentration, it realized using high concentration of nitrite as electron acceptor for denitrifying phosphorus removal. It also found that the domestication of phosphate accumulating bacteria via nitrite can use both nitrate and nitrite as electron acceptor for denitrifying phosphorus removal, but the net P uptake 22.5mg/L with nitrate as electron acceptors was higher than the net P uptake 18.9mg/L with nitrite as electron acceptors, however the rate of nitrate consumption, only 70%-80%, was less than the rate of nitrite consumption, which was more than 80%.The simulated sewage was treated in the biofilm two-sludge SBR. It shows that the system has a good operational stability and nitrogen, phosphorus removal. When the influent of COD and C/N were 200~250mg/L and 3~6, the effluent concentration of COD,TN,TP were reduced to below 20mg / L, 5.0mg / L and 0.5mg / L, and average removal rates were 94.9 %, 81.2% and 89.5%, to meet "Municipal Wastewater Treatment Plant Pollutant Emission Standards" GB18918-2002 Grade A standard emission standards.