Aeration Of The Two-phase Flow Of Oxygen Mass Transfer Study

Activated sludge treatment is one of the most widely used methods in thewastewater treatment field at present. The oxygen transfer efficiency in theaeration tank, which is the key reactor of the activated sludge treatmentsystem, has immediate relations with the cost and efficiency of the wastewatertreatment. Based on the achievements of other scholars and the observationresults of the two-phase flow experiment, this paper aimed at establishing thecomprehensive oxygen transfer equation, which includes the two-phase flowfactors. Thus provided theoretical basis for the rational designing, accessingand controlling of the aeration tank operation.Three parts were studied in this paper:experimental study of the aerationtwo phase flow, oxygen transfer study of the aeration sector in the fine-bubbleblast diffusion aeration tank, study of the microbiological respiration effecton the oxygen transfer coeffcient of aeration. The main methods and resultsof the study are listed as follows:Experimental equipment was designed accord with the aim of the wholeproject, then the experimental study about the gas-liquid two-phase flow wascarried out. The bubble generation, movement, coalescence and rupture instill clean water were discussed preliminarily through the analyses of theexperimental results, which provided the basis for the following studiesThe actual operation of the aeration sector in the fine-bubble blastdiffusion aeration tank was studied. Some simplifications and hypotheseswere made, and based on which the clean water oxygen transfer equation offine bubble blast aeration system was obtained. This equation combined thetwo-phase flow factors with the oxygen transfer rate, thus laid a foundationfor the theoretical study of the aeration tank operation and provided methodsfor the comparison of different aeration systems under various operationconditions.Based on the study of the factors, which affect the transfer coeffcient,the adsorption of the microorganism on the two-phase flow interface werediscussed thoroughly through tl1e analyses of the mixture of the sewage,activated sludge, etc. Then it was obtained that the adsorption is accord withthe hypotheses of the Langmuir Adsorption Isotherm. The experimentalresults of Anand was used to study the respiration effect of the aerophilicmicroorganisms -- adsorbed on the gas liquid interface -- on the oxygentransfer coeffcient in activated sludge wastewater treatment system. Thestudy showed that the relation between the oxygen transfer coeffcient and theoxygen uptake rate per dried weight of the mixed liquid in the aeration tank isa1so accord with the Langmuir Adsorption Isotherm.Through the analyses of the aeration tank operation and the derivation ofthe equations, both of the oxygen transfer rate equation and the enhancementrate equation of the oxygen transfer coefficient were interpreted from an angleof physics.