| A comprehensive study of micro-expansion up-flow biological activated carbonprocess （MEUF-BAC）was investigated, including characteristics and mechanismof organic matter removal, microbial activity and its influential factors,microbiological characteristics, biodegradation kinetics model and full-scaleapplication. The main results were obtained as the below:1. The influence of particle size of granular active carbon (GAC) in up-flowBAC process was studied, and micro-expansion up-flow biological activated carbonprocess was proposed. It was observed that the particle size of GAC, temperatureand operation time were the main factor controlling the expansion rate. The model ofexpansion rate was established. During the absorption phase, in the removal oforganic matter was mainly controlled by the mass transfer rate. However, during thebiodegradation phase, the removal of organic matter was mainly controlled by thebiodegradation rate. Comprehensively considering the removal of organic matter,GAC layer expansion and the cost of the GAC filter due to the footprint and height,it was recommended that the optimal expansion rate was set at10%~30%when thehydraulic loading maintained at10~14m/h.2. The operation parameters of MEUF-BAC were studied. According to theraw water quality, the optimal pre-ozonation dose was proposed2mg/L and fed inthree stages with ratio of3:1:1. Because of the expansion of carbon layer, theimpacting of the variation of hydraulic loading to the empty bed contact time (EBCT)was mitigated. When the hydraulic loading maintained at7.6m/h~13.4m/h, theimpacting of the hydraulic loading to the removal efficiencies of organics (CODMn,DOC and UV254) were not appreciable, which was in consistency with thesteady-state film mechanisms. When the water temperature maintained13oC~34oC,the variation of temperature did not dramatically affect the organics removal byMEUF-BAC as well.3. A comparison of organics removal by MEUF-BAC and down-flow BAC was performed. During the adsorption phase, the down-flow BAC had higherremoval efficiency than MEUF-BAC did. In contrary, during the biodegradationphase, MEUF-BAC obtained higher organics removal efficiency than down-flowBAC did. The organics removal in CODMn, DOC and UV254by MEUF-BAC was12%,7%and6%higher than those by down-flow BAC respectively, becauseMEUF-BAC had more biomass and more even distribution in whole GAC bed. Themajor phylum was Proteobacteria in effluent and BAC bed.4. The full-scale MEUF-BAC was designed, constructed and operated basedon this study. The MEUF-BAC was recommended to located before the rapid sandfiltration, which could maintained the chemical and microbiological safety offinished water. |
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