Research On Interaction Of Aerobic Nitrifying And Phosphorus Uptake And Characteristics At The Aerobic In SBR

Under the aerobic condition, oxidation of organic, nitrifying and phosphorus accumulating occur simultaneously and often interacted with each other in SBR. In urban domestic sewage treatment , good effect of nitrogen removal and phosphorus removal can not often occur simutaneously because of above reasons, therefore, it is necessary to reaserch the biological characteristics of nitrifying bacteria and PAOs and the interaction of the both two. There are multiple factors effecting on nitrifying and phosphorus accumulating ,for example, SRT, temperature, pH, C/N, and poison and so on. As for unitary nitrogen removal process or phosphorus removal process, SRT is often not same in actual operation. The temprature of urban sewage arranged because of seasonal replacement , which influenced the biological characteristics of nitrifying bacteria and PAOs, and their distribution proportion was effected by C/N. So effect of above four factors influencing on nitrifying and phosphorus accumulating were studied during the experimental.The experiment results were shown as follow:(1) Under the condition of high sludge loading, mutual inhibitation between phosphorus-accumulating bacteria and nitrobacteria existed, and heterotrophic bacteria was prior to autotrophic bacteria in occupying substrate and dissolved oxygen at the aerobic. When it run accordance with Aerobic-anaerobic Process, predominant phosphorus-accumulating bacteria was prior to nitrobacteria in occupying substrate and dissolved oxygen. With the increase of dissolved oxygen, rate of phosphorus accumulating was improved quickly, hower, nitrification was not fast at the fist aerobic. When N_S=0.51kgCOD/(kg.MLSS.d), 23% of the ammonia nitrogen was removed at the time 0～60min,hower 77% was removed at the time 60～180min. Nitrification and phosphorus accumulating did not process simultaneously at a certain distant and initial decrease of ammonia nitrogen resulted from assimilation.(2) Under the conditon that when concentration of COD was 300mg/L, concentration of NH₄⁺-N was 35mg/L and concentration of PO₄³-P was 5mg/L, stable and better effectivness of ammonia nitrogen removal and phosphorus removal can be realized simutaneously even though SRT=3d, and more than 96 percent removal of ammonia nitrogen was realized . From testing contrast analysis up on SRT=3d, 5d and 7d, when SRT=5d, the synchronization between nitrifying and phosphorus accumulating was better.(3) Temprature and SRT were main factors having effecting on nitrifying and phosphorus accumulating. Compared with temprature, effect on nitrifying from SRT was relatively small, when SRT was equal to three, more than 96 percent removal rate of ammonia nitrogen can be realized . Maybe it was caused by lower MLSS, because this can improve the transmission rates of dissolved oxygen and utilization ratios, so it decreased the competition for dissolved oxygen.(4) In the four different temperature experiments, it was found that tht satisfied effect of ammonia nitrogen removal and phosphorus removal can be acquired simutaneously, 97.8% and 95.1% respectively. When temperatue was beyond 25 centigrade, PAOs was sensitive to temperature, so the remvoal of phosphorus and sludge settling decreased significantly, because PAOs was likely to cold environment. At a certain temperature range, removal efficency of phosphorus was proportional to temperature. Comprehensive analysis showed that keeping the temperature range from 15 to 200℃was benefical to the removal of phosphorus and ammonia nitrogen.(5) According to the experimental data, when temperature was different, the influence of nitrate nitrogen effecting on phosphorus removal was also different, and it was proportional to temperature. Under the condition of 25-30℃, effect of nitrate nitrogen having influence on phosphorus removal was enhanced, but when temperature was under 20℃, the effect was not obvious. Maybe it was because that the optimum of denitrifying bacteria was 20-40℃, and when temperature was beyond 20℃, denitrification and competition for carbon were strengthened, so the process of release phosphorus was influenced.(6) Under the experiment of different temperature, there was a correlation between compactness of sluge and phosphorus removal. It was that phosphorus removal was proportional to compactness of sluge to some extent. (7) Under the condition of different carton-nitrogen ratio, with the increasing of C/N, ammonia nitrogen removal did not decrease significantly, and when the ratio of carbon and nitrogen was 10, the removal rate was lowest, which was 98.1%. It is believed that the increase of the ratio , result in excessive propagation of heterotrophic bacteria, so nitrobacteria was at a disadvantageous state in competition for dissolved oxygen, but it was found that only ample dissolved oxygen and suitable temperature were supplied, the effect of the ratio of carbon and nitrogen influencing on nitrification can be decreased to some extent.