Study On The Treatment Of Wastewater From Polyester Fabric Alkali-peeling Process By Hydrolysis-acidification/Hybrid Membrane Bioreactor With Suspended Carriers

Now the polyester fabric alkali-peeling process wastewater (PAP-wastewater) is one kind of the popular textile industrial wastewater in China due to the high concentration of terephthalic acid (TA) and the poorly biodegradable polyester oligomer and chemical promoters. The treatment of PAP-wastewater by hydrolysis-acidification/ hybrid membrane bioreactor (HMBR), as well as the membrane fouling control and operational performance of HMBR, was investigated in this dissertation. The following results have been obtained:The biodegradation of TA on aerobic and anoxic condition, as well as the impact of ethylene glycol (EG) on the biodegradation of TA, was researched. It was found that TA was not toxic to the TA degrading cultures on the aerobic condition, whether the concentration of TA was high or low. There was a lag phase prior to degradation of TA and EG when TA and EG were fed as sole carbon source. Furthermore, the lag period of EG was longer than TA. However, once the cultures were acclimated, TA and EG started to be degraded rapidly. Although EG didn't inhibit the aerobic primary biodegradation of TA, it inhibited the aerobic ultimate biodegradation of TA. EG inhibited the anoxic biodegradation of TA, but TA was consumed at the same rate as in the experiments performed with TA as sole carbon source after complete consumption of EG It can be concluded that TA is easily degradable on aerobic condition and more difficult to be degraded on anaerobic condition and hardly degradable on anoxic condition, while EG is easily degraded on aerobic, anoxic and anaerobic condition.The result showed that the biosorption and desorption of TA by unadapted aerobic and facultative sludge could be characterized by Freundlich isotherm. Two Freundlich equations, q=8.6170C_e^0.4207 and q=4.0764C_e^0.5405, were established to describe the biosorption of TA by unadapted aerobic and facultative sludge, respectively. So q=9.4723Ce03271 and q= 4.2353 Ce03688 for desorption of aerobic and facultative sludge, respectively. The maximum biosorptive uptakes of TA by aerobic and facultative sludge were 39.06, 31.45mgTA.gSS"1, respectively. The difference between biosortion and desortion Freudlich constants suggested that biosorption of TA was an partly irreversible process. In bioreactor the removal of TA by activated sludge was due to biodegradation rather than biosorption.The experiment demonstrated that the hydrolysis-acidification/ HMBR process was an economically attractive alternative for the treatment of PAP-wastewater. The effluent COD average 55.9mg/L and the following results were obtained at HRT =(9.0+7.2)h: t)Cod=96% and tita>99% for the total system, r|CoD<10% and TyrA<5% for hydrolysis-acidification bioreactor, t|cod>94% and t|Ta>98% for HMBR. The hydrolysis-acidification pretreatment improved the biodegradability of PAP-wastewater. The impact of volumetric loading rate (Uv) was slightly on the performance of hydrolysis-acidification bioreactor, but largely on HMBR. The effluent COD was below 80 mg/L and ticod averaged 95% for HMBR when Uv of HMBR was below egCOD.I/'.d"1.The observations revealed that suspended carriers played an important role in governing the filtration conditions and decreasing fouling resistance. The results indicated that the cake resistance of HMBR decreased by 86%, the critical flux increased by about 20% and the rate of membrane fouling decreased by 70% in comparison with MBR. The effects of the membrane flux (J), sludge concentration (X) and carriers volume (C) on the increasing rate of the transmembrane pressure were in decreasing order: C99% for the total system. It should be noted that the relative contributions of hydrolysis-acidificationbioreactor and HMBR to the total removal rate were 29.8*^ 67%.