Study On Carbon-Release Mechanism And Application Of Recycled Liquid In Anoxic/Oxic Process

A method is put forward by our research group and applied in the traditional A/O process,which utilized hydrocyclone to disrupt sludge flocs in nitrification mixed return liquor and release organic substance as the complementary carbon source for denitrification.It can enhance denitrification reaction and improve the denitrification efficiency,and it also can accomplish the cryptic growth and reduce the productivity of excess sludge.The cone angle is one of the most important structure parameters,which apparently has a important influence on the disruption effect of sludge in carbon-release hydrocyclone.CFD numerical simulation and test are both carried on to research the effect of carbon-release hydrocyclone in A/O process in this essay.Two kind of different structural hydrocyclone are firstly designed in this essay,with same nominal diameter 35mm and different cone angle 8° and 20°.Then,CFD is adopted to simulate the three dimensional flow field distribution law in carbon-release hydrocyclone with two different cone angle under the conditions of inlet velocity=lm/s?3m/s?5m/s and 7m/s,the effect of cone angle on the flow field of carbon-release hydrocyclone are analysed,especially for tangential velocity.Discrete Phase Model(DPM)is adopted to simulate the movement tracks of sludge floc particles in carbon-release hydrocyclone,and the effect of cone angle on the movement of sludge floc particle are analysed.Finally,the comparison experiment is carried on to test the application effect of the two kind of different structural carbon-release hydrocyclone in A/O process,the main tested projects include sludge reduction?advanced nitrogen removal and effluent quality.The major results are as follows:(1)The disruption and carbon-release process of sludge floc particulates are couply affected by 3 dimentional flow field and pressure field in carbon-release hydrocyclone,which mainly happens at the zones near the center and wall of carbon-release hydrocyclone.Sludge floc particulates are suffered from strong shear stress at these zones and have high revolution speed and rotational velocity,which are caused by tangential velocity.Sludge floc particulate are transported from weak shear and low swirling speed zones to strong shear and high swirling speed zones by radial velocity.The backmixing of some sludge floc particulate is caused by axial velocity,so the residence time is prolonged.sludge floc particulates are squeezed for the vast pressure gradient at the centeral zone.Sludge floc particulates are also suffered from impulse stress for different scale turbulent vortexes.(2)The average overflow and underflow SCOD,Polysaccharide,Protein concentrationsof carbon-release hydrocyclone 0=8°were improved 10.5 mg/L and 12.5 mg/L,6.2mg/L and 7.6mg/L,2.59mg/L and 2.90mg/L than the inlet,and the average overflow and underflowSCOD,Polysaccharide,Protein concentrations of carbon-release hydrocyclone 0=20°were improved 9.7 mg/L and 11.1 mg/L,4.9mg/L and 5.9mg/L,1.83mg/L and 2.06mg/L than the inlet.(3)The average TN removal efficiency of AOH8°and AOH20°were respectively improved 21%and 15%.The average observed biomass yields(Yobs)of AOH8°and AOH20°were respectively decreased 0.110mgMLSS/mgCOD and 0.086mgMLSS/mgCOD than A/O.The total excess sludge productions of AOH8°and AOH20°were decreased 3521 g TSS and 3050 gTSS than A/O.