Excess Sludge Sorting And Utilization By A Mini-Hydrocyclone

The activated sludge process is one of the core technologies for wastewater treatment in the past 100 years,and the recycling of excess sludge is a research hotspot in related fields at home and abroad.As a general-puirpose separation device,the hydrocyclone cannot directly separate substances with small difference in density due to the influence of turbulent diffusion However,atfter the internal complex flow field treatment,it is possible to sort out the inferior sludge.lThis paper proposed a method for sorting external excess sludge by a hydrocyclone,combining with carbon releasing by hydrocyclone and density sorting,to improve sludge settleability and biochemical efficiency.The major conclusions are as follows:(1)A hydrocyclone separator with a nominal diameter of 10 mm was designed.After theoretically calculating by computational fluid dynamics,we found that the rate at which the particles rotate inside the hydrocyclone reached the order of 103 rad/s.The centrifugal force generated by high-speed rotation made the sludge floc EPS break,releasing the organic carbon source;Most of the released organic matter flowed out from the underflow of the hydrocyclone,so the denitrification rate of the sludge at the underflow was increased by 50%.(2)The dense component of the sludge floc moved downward in the axial direction under the action of the swirling flow field,and moved outward in the radial direction,moved downward along the wall of the cone section,and was discharged from the underflow port.Thus,an external vortex flow field was formed;the light component moved toward the central axis,and an upwardly moving inner vortex was formed at the center of the axis,and then discharged through the overflow port.The SVI of the sludge at the bottom flow was reduced by 10.4%after treatment;the SVI of the sludge at the overflow was 46.1%higher than that before treatment.(3)The SBR process side line experiment with hydrocyclone was designed.the new SBR process was superior to the traditional SBR process in sludge performance and effluent quality.Under the sorting of the cyclone field,the sludge particle size became smaller and denser,the SVI was reduced by 6.1%.The respiration rate and denitrification rate of the sludge were increased by 11.1%and 6.4%,respectively,and the sludge activity was enhanced.In terms of effluent quality,the removal rates of SCOD,NH4-N and TN in new SBR process were increased by 6.9,8.4 and 8.9 percentage points respectively,and the effluent SS decreased by 6.1%.