Study on the Nitrosation Denitrifying Phoshporus Removal Process and Molecular Microbiology
|School||Beijing University of Technology|
|Keywords||Nitrosation denitrifying phosphorus removal(NDPR) Electron acceptors Nitrite nitrogen Nitrosation denitrifying phosphate-accumulating organisms(NDPAOs) Molecular microbiology|
The flinty situation of lacking water resources and deteriorated water environment was analyzed in the paper. Water eutrophication was becoming more serious little by little, and the efficiency of removing nitrogen and phosphorus in the wastewater treatment plant was low, and there was controdiction between nitrogen removal and phosphorus removal. The evolvement of electron acceptors of biological phosphorus removal and the process development were expaciated, then the wastewater treatment process of nitrosation denitrifying phosphorus removal （NDPR） was put forward. Three systems including SBR nitrosation, SBR NDPR and continuous flow two-sludge NDPR were established on the basis of this conception. Long time research on the system of removing nitrogen and phosphorus were going along, and microbiology and molecular microbiology about nitrosation denitrifying phosphate-accumulating organisms（NDPAOs）were investigated.The SBR nitrosation experimental equipment was established firstly, by which some main factors impacting on the system such as DO, temperature and pH value were investigated. DO was a key one among these factors. In the activated sluge system, the effect of nitrosation was good while DO was 0.5-1.0mg/L, the efficiency of ammonia nitrogen removal was 98.3% and nitrosation rate was 80%. In SBBR system, the effect of nitrosation was good while DO was 1.5mg/L, the efficiency of ammonia nitrogen removal was 95.9% and nitrosation rate was 95.38%. When temperature was 25-30℃, nitrosation rate was above 95%. When temperature was below 17℃, nitrosation rate was below 50%. The most appropriate pH value in mid-temperature was 7.5-8.0.The SBR denitrifying phosphorus removal system was investigated at the same time. The system included two styles according to the electron acceptors, nitrate and nitrite. The consumption rate of nitrite was greater than that of nitrate, the removal rate of nitrite was more than 90%, while nitrate was 72%-91%. The most appropriate temperature toward nitrate and nitrite were 28℃and 30℃, respectively. The removal ratio of TP was 81% when the concentration of nitrite nitrogen was 30mg/L. The most appropriate ratio between NO3--N and NO2--N was 30/20, phosphate removal rate was 90.12%, the greatest phosphorus uptake rate was 0.271 mg/L·min,and even phosphorus uptake rate was 0.167 mg/L·min at this ratio.Some important factors on NDPR such as temperature, pH, COD concentration, carbon source species and sludge age were investigated. The most appropriate temperature of removing TP was 31℃. The best removal effect of TP appeared when pH was 7.4-7.8 and COD was140mg/L. Sodium acetate was in favor of NDPR by contrast with glucose as carbon source. The removal rate of TP and COD was 78% and 91% at 32d sludge age, respectively.The NDPR system was started successfully and in function steadily. COD, TP and TN were removed well, the removal rate of COD and TP were 80% and 74.13%, respectively, and TN concentration in effluent was 13.76mg/L. Amonia nitrogen was converted to NOx--N （nitrate and nitrite） in nitrosation tank, in which nitrite was more, and nitrosation rate reached 83.94%. NOx--N was removed as electron acceptors in anoxic tank by NDPAOs, the even and greatest removal rate of nitrate was 79.64% and 93.43%, respectively, while nitrite 82.86% and 91%. At the same time, NDPAOs took up phosphorus in wastewater excessively using PHB as electron donator, the even removal rate of TP was 70.96%. COD, TN and TP got greatest removal when the carbon nitrogen ratio was 4-5, and their removal rate was 88.51%, 76.85% and 75.00%, respectively.NDPAOs in the continuous flow two-sludge NDPR system were separated, cultured and identified with the method of integrating physiological and biochemical technique with molecular biological gene sequencing technique. The separated bacteria belonged to Klebsiella, Bacillus, Enterobacter, Moraxella, Staphylococcus, Paracoccus and Pantoea. The enriched pure bacteria were tested with nitrosation denitrifying phosphorus removal experiment, and their abilities of removing nitrogen and phosphorus were ascertained. The descending sequence of the ability of phosphorus uptake was Bacillus, Klebsiella, Staphylococcus, Paracoccus, Moraxella, Pantoea and Enterobacter.