| Membrane bioreactor (MBR) and bioferric process of conventional activated sludge system have their own advantages. This dissertation combined theseadvantages and formed a kind of novel MBR process-Bioferric MBR. Bycomparison with bioferric MBR and MBR under three kinds of operating conditions, their removal effect, mixed liquor characteristic and membrane fouling were investigated systematically in synthetic dyeing wastewater (Reactive Brilliant Blue KN-R) treatment. Under the foundation of fully manifested the relations of operation conditions, microbial metabolic characteristics & operational performance, the relative mechanisms were studied and the following results have been obtained:By removal effect analyses of COD, BOD5, NH3-N & dyestuffs density etc. of two system's supernatant and effluent, biofferic MBR had better results than conventional MBR's. These removal effect rate are 1.73%, 0.68%, 0.92% and 13.94% which is higher than conventional MBR.By analyses of two system's mixed liquor characteristic, such as SS, VSS, SV30, SV1, sludge loading & particle size of sludge etc., results demonstrated that iron hydroxide addition can improve the structure of sludge & sedimentation characteristic, enlarge particle size 2.8 times also (especially these submicro particles, 7.5 times), enhance SS and reduce sludge loading.Studying removal effect & microbial activity under the influence of Fe, results showed that it can improve removal effect with increasing concentration below 5% and deteriorate removal effect for restrain the microbial activity as concentration over 5%. So we obtained a operating experience of biofferic MBR, Lower ratio & higher concentration will be better and the practical means is to increase SRT or to decrease HRT.The experiments of influence of Fe on microbial dehydrogenase activity andSOUR demonstrated that influences laws of two systems were contrary opposite. With increasing concentration of Fe, it can improve the dehydrogenase activity and restrainSOUR.The variation of transfer membrane pressures showed that increasing of flux & MLSS accelerated the membrane fouling with decreasing of HRT (from 15h to 9h) & of increasing SRT (from 20d to 50d).The total resistance of third operation conditions were 9 times & 5times more than the first one. Moreover, the most important is bioferric MBR has obviously advantage on reducing fouling and its total resistance was just only 1/2-1/5 of conventional MBR's.Mechanisms of membrane fouling was studied by investigating the properties of membrane dead-end filtration, resistance -in-series & scanning microscope photos. Cake on membrane surface of bioferric MBR was thinner, the total resistance was one third of conventional MBR's and polarization layer resistance, external resistance & internal resistance decreased 78% ,77% & 67% than conventional MBR's. These results demonstrated that iron hydroxide addition can efficiently reduce fouling.Then relative mechanisms were discussed in detail.By experiments of flux recover efficiency after washing cleaning, physical washing & alkali washing had higher efficiency for conventional MBR because the fouling substance were mainly organic materials such as microorganism sludge & microbial metabolis microbial products etc; On the other hand, alkali washing & acid washing have higher efficiency for bioferric MBR because the fouling substanceswere not only sludge & microbial metabolis but also inorganic materials-iron ion& its compound.
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