Research On Carbon Source Effective Utilization And Mechanism In A₂N System

The low C/N proportion of urban sewage has become a common problem to the wastewater treatment process, and how to efficiently use the carbon source of the sewage itself become the main subject of the current sewage nitrogen and phosphorus removal technologies. In this paper, by adding the pre-anoxic to the A2N two sewage system to deeply study the sludge absorption of the carbon source in the anaerobic phase and the release of carbon source in the anoxic phase, finally the author found the way of the efficient utilization of the carbon source, as well as the efficient removal effect of nitrogen and phosphorus by the means of changing the content of the small organic molecules which are easily degradated.The results show that:(1) In the anaerobic part of A-A2N system, the more carbon source is adsorbed and synthesized, the more efficient carbon source is used. This study shows that quality of carbon source which adsorbed by the activated sludge accounted for29.81%of the total carbon source consumption. The quality of carbon source synthesized into PHB by DPBs accounted for53.34%of the total carbon source consumption, respectively.(2) In the anoxic phase of the A-A2N system, the complete release of the extracellular carbon source provided enough carbon source which is used for the denitrifying phosphorus removal. This study found the quality of the carbon source which is released from the anoxic phase accounted for77.67%of the total absorbed sludge carbon source.(3) In A-A2N system, the carbon usage of pre-anoxic part, anaerobic part, biological film nitration part, anoxic part, post-aeration part is11.71%,1.99%,11.26%,58.41%,16.63%.(4) For A-A2N process, the longer the raw sewage was fermented, the more were easily degradable organic molecules in the raw sewage, the more PHB would be synthesized from carbon source in raw water,and so the higher the PHB conversion rate was,thus more amount of PHB was used for denitrifying phosphorus removal in the anoxic stage.(5) In A-A2N process,the longer the raw sewage was fermented,the better the system performed,with low value of nitrogen and phosphorus in the emission,much lower than the Level A emission standard of GB18918-2002.(6) The VFA concentration in raw sewage showed a good correlation with the removal rate of COD、TN、TP in A-A2N processa, as follows:ηCOD=0.0005ΔFFA2-0.0113ΔVFA+84.89(R2=0.9985);ηTN=0.0878ΔVFA+70215(R2=0.9802);ηTP=0.1891ΔVFA+81.353(R2=0.9821)。This study found the process and mechanism of carbon source adsorp/release, and the utilization characteristics in each part of the A-A2N system, finds out the method of the sewage using itself carbon source effectively.