Mass Transfer Mechanism Of Hybrid Biofilm Bioreactor And Experimental Research

Biofilm wastewater treatment is the research hot spot of biological wastewater treatment process today. At present, the technology has been widely applied in the recovery of city-life sewage and industrial wastewater purification. The primary factor which decides reactor’s performance and efficiency is the formation and inner mass transfer process characters of biofilm whether for aerobic biofilm reactor or in anaerobic biofilm reactor. Substrate mass transfer efficiency from bulk liquid to biofilm and inner biofilm will affect reactor’s performance and efficiency ultimately. Therefore, these researches on the correlations among environmental factors, biofilm structure and substrate mass transfer inner biofilm are the basis and prerequisite of enhancing biofilm reactor performances.Based on the above research purposes, this paper’s main researches content include the following aspects.(1) Set up an external loop airlift bioreactor of2.3L and launched anaerobic ammonium oxidation (abbreviate to Anammox) process successfully, researched on the performance of the reactor. Aerated continuously, and the maximum removal quantity nitrite and total nitrogen was476.5mg(N)·L-1and663.1mg(N)·L-1separately, average removal efficiency reached up to75%and93%. After30days operation under HRT=24h, total nitrogen loading rate was1.01kg(N)·m-3day-1, corresponding total nitrogen removal rate was0.75kg(N)·m-3·day-1. By changing HRT, this paper investigated the ability of strong shock resistance and stability of the ALR.(2) Launched CANON process in ALR successfully. When influent substrate just contained ammonium sulfate((NH4)2SO4), aerated air and limited concentration of dissolved oxygen of bulk liquid, proportionate relationship between nitrite nitrogen and ammonia nitrogen consumption was0.136:1, and this value got close to average stoichiometric relationship of CANON process. There were much NOB survival in the reactor and CANON appeared and ammonium sulfate removal rate was75%.(3) Set up a biofilm mass transfer model which included diffusion, convection and reaction terms. By the model, caculated mass transfer process and microbial growth process inner biofilm. Researched on the effect of related environmental factors on these both process. Orthogonal analysis result showed that diffusion coefficient was the primary factor and got the optimal model parameters. Tested oxygen concentration along with the depth of biofilm using PA2000oxygen microelectrode and found model data agreed well with experimental result.(4) Coupled N-S equation and Brinkman percolation equation with mass transfer equation inner biofilm, researched on the effect of bulk liquid flow on the seepage velocity field and on the effect of mass transfer in porous biofilm. At the same time, researched on diffusion mass transfer and convection mass transfer inner anisotropic biofilm and also researched on the effect of biofilm thickness on the flow boundary layer and mass transfer resistance from bulk liquid to biofilm.