Research And Application Of Internal-circulation Moving Bed Biofilm Reactor

The moving bed biofilm reactor(MBBR) is a new biofilm reactor with many distinct advantages. It has been received considerable attention for academic and application aims, and there are many efforts focused on the study and exploiting of the structure and operation manner of MBBR. In this work, the structure of traditional moving bed biofilm reactor was improved and the internal-circulation moving bed biofilm reactor(ICMBBR) was exploited, so that the efficiency of the reactor was improved. The test demonstrates that the internal-circulation moving bed biofilm reactor is a high efficient reactor and is capable of removing organic matter and nitrogen simultaneously.The circulation state in the reactor were shown to relate with the gas flow rate, the gap between the inner canister and the bottom of reactor and the liquid height above the inner canister. After all the factors were taken into account, 60mm and 120mm was recommended for the gap between the inner canister and the bottom of reactor and the liquid height above the inner canister. 1 to 2 was suggested for the ratio of the raising area to down-coming area. With increase of the carrier adding rate, oxygen transfer coefficient gradually became larger and circulation rate reduced, 35% was suggested for the carrier adding rate.(1) ICMBBR has a well removing organic carbon efficiency. The removal efficienciey of COD is up to 90% and the ability of resistance to impact load is strong, with the carrier adding rate of 35%, the influent COD of 200～700mg/L, hydraulic residence time(HRT) of 6h and COD volume loading of 1.0～3.0 kgCOD/m³Â·d.(2) The aerobic environment and anoxic environment of the biofilm on carrier are benefit for the performance of simultaneous nitrification and denitrification in the reactor. The average removal effficieneies of NH₄⁺-N and TN could up to 98% and 93% respectively, in the condition of HRT 6h, DO 2.0mg/L and C/N 25.(3) The state of circulation is modest in ICMBBR, which makes a favorable mass transfer efficiency and controls the thickness of the biofilm efficiently, so that the biofilm always keep a high microbial activity. Compared with other biofilm reactors, the biomass in ICMBBR was low, the high efficiency resulted from the high microbial activity.(4) The average removal efficiency of COD and nitrogen of ICMBBR was better than that of MBBR from the results of the compared tests.