| The optimal design and operation control, involving complicated hydraulics and biochemical process, of wastewater biologic treatment project is the frontier research field of current international water science and technology, but, because of ambiguity realization to hydrokinetics and efficiency of complex reactor of wastewater biological treatment, the research in the term of coupling reaction kinetics with hydrokinetics has not get substantial progress. This paper focused on Carrousel oxidation ditch, developed a new local un-contact measuring method of multiphase district flow field, carried out model experiment in laboratory and measuring in field, studied solid-liquid turbulence and biologic reaction kinetics in the oxidation ditch, and did research on the numerical stimulation of multiphase turbulence reaction kinetics, with the main research results as follows:①A new velocity measurement system of multiphase flow digital particle image was developed, used in velocity field measurement of 2-dimention and 3-dimention multiphase flow in the reactor of complicate fluid, overcoming weakness of traditional contact point measuring method which can not get the synchronous flow information in the whole field.②The PIV velocity measurement system improved on the acquire information arithmetic of traditional PIV system, increasing the calculation velocity of image manipulation of system by using standardized correlation coefficient as measuring degree and by optimizing search region; multiphase flow was identified, demarcated and calibrated by math-morphology theory, gray scale weighted calibrating method and particle diameter matching method.③The PIV technique was applied to measure the 1-phase or 2-phase flow in 2-dimention or 3-dimention whole-flow-field velocity of Carrousel oxidation ditch reactor. The result show that: the flow rate of solid was generally smaller than the liquid; longitudinal and vertical flow distribution were the mainly determinative factors of hydraulic characteristic in the reactor; the position of sludge sediment were primarily depended on lateral and vertical velocity; the sludge sediment was the results of lateral and vertical velocity together with liquid energy.④The flow field of oxidation ditch under alternate aeration condition was actually measured, the results show: opening two aerators, the outside ditch was the dangerous areas to easily deposit; the comparatively high kinetic energy of inner ditch contributed to components mixture, preventing sludge deposition; three aerators operated increased the outside ditch velocity by more than 10%, yet, not much changing flow structures of inner ditch; at the beginning of open-stop stage, the velocity changing speed was reduced with the distance to the aerators increased; the time needed to shift from open-stop aeration to stable operation condition for the whole outside ditch accounted for 40%⑤Water quality in the oxidation ditch was measured in the field, the results show: velocity was positive correlated to dissolved oxygen, negative correlated to MLSS; velocity was an essential factor which influenced mixing of dissolved components, so increasing local velocity near the inlet would be helpful to reduce the distance and time for uniform distribution of inflow components.⑥Sediment characteristics of sludge of different particle diameters under water turbulence condition was studied by PIV velocity measurement system, getting the relation between under static state condition sludge sedimentation velocity and particle diameter of sludge, and setting up the under turbulence state condition sludge sedimentation velocity model.⑦The under turbulence state condition sludge sedimentation model was coupled with 2-phase turbulence mixture model, separating movements of 2 phases in vertical direction; computational fluent software"Fluent"was utilized to stimulate sewage-sludge 2 phases velocities in oxidation ditch of industrial-scale sewage plant, demonstrating that 2-phase flow mixture model to some extent was able to display mixture flow field and sludge distribution⑧Liquid-solid 2-phase turbulence mixture model of Carrousel oxidation ditch was coupled with Activated Sludge Model NO.2 (ASM2), building liquid-solid 2-phase turbulence reaction kinetics model of Carrousel oxidation ditch, compiling corresponding solving program, simultaneously stimulating and studying the space-time distribution of liquid-solid 2-phase 3-demention velocity field and water quality concentration.⑨Using liquid-solid 2-phase turbulence reaction dynamics model of Carrousel oxidation ditch to optimize the operation of oxidation ditch in wastewater treatment plant, the results show that opening underwater propellers at the existing main channels of oxidation ditch would improve the velocity field distribution on the curve, reducing impacts of inflow fluctuate to the operation of the ditch, preventing negative effects brought by sludge deposition at this area.
|
PDF Full Text Request