Application Of A/O-type Sequencing Batch MBR To Dye-containing Textile Wastewater

Combined physical process with biological technology with excellent effluent quality, membrane bioreactor technology (MBR) is facing new opportunities. At the same time, due to membrane cutoff of both refractory organic macromolecules and exclusive microorganisms, MBR performance treating refractory organic wastewater overmatches the traditional process. There have shown a good corresponding point between treatment of textile wastewater and MBR technology. With the sustainalbe development of MBR technology and the rapid popularization of cleaner production concept in textile industry, it will have a good prospect durign the treatment of textile wastewater. In this study, the optimum operation conditions are determined by investigating the effect of key operating factors on MBR performance. In the meantime, the effect of EPS content and its components on sludge properties, the changes of membrane flux and dye adsorption mechanism are investigated. It will be of significance for its practical application. The main research content and results are as follows.(1) The influence of organic loading rate on performance and membrane fouling of A/O-type sequencing batch MBR is investigated. The results show that A-phase effectively improves B/C ratio of synthetic textile wastewater. And, the lower the wastewater B/C ratio, the more the treatment efficiency. A/O-type sequencing batch MBR has strong resistance to loading shock. The average removals of COD, ammonia nitrogen and color are more than 92.3%, 92.7% and 95.0%, respectively. And, their concentrationsin effluent are less than 60 mg/L, 7 mg/L and 40. Compared with continuous operation, the membrane fouling also was greatly alleviated.(2) The influence of aeration intensity on operating performance and the content of extracellular polymeric substances of A/O-type sequencing batch MBR is stueies. High aeration intensity will ease pollutants in the membrane adhesion and delay the membrane fouling, and can lead to fragmentation of sludge flocs and production and accumulation of EPS, thus the deterioration of membrane fouling. The influence of aeration intensity on the operation characteristics of MBR is highly complex.(3) The influence of HRT on operating characteristics and sludge properties of A/O-type sequencing batch MBR is examined. In different HRT, effluent quality indicators of COD and color are good and stable. Btoh the total removal of COD and color are more than 95%. However, the removal rate of ammonia nitrogen firstly increased and then decreased. And when the HRT is 24 h, the removal of ammonia nitrogen reached the maximum for 96.4%. The SVI in reactor is in the range of 50-70 mL/gSS. Membrane flux increases with the extension of HRT.(4) The feasibility of A/O-type sequencing batch MBR treating textile wastewater is finally probed. When the organic loading rate is 3.22 kgCOD/(m3·d), aeration intensity is 0.15 m3/h and HRT is 24 h, effluent concentration of COD, ammonia nitrogen and color are 32.2-46.0 mg/L, 0.13-0.22 mg/L and 21-28, respectively. Effluent quality meets the standard ruled in DB32/1072-2007. The color of wastewater is mainly removed through degradation and conversion during A-phase. COD and ammonia nitrogen are removed through O-phase of MBR. The advantages of MBR in the degradation of refractory organic pollutants and color removal are fully expressed and enhanced due to A-phase pretreatment and sequencing-batch mode. Compared with continuous operation, the membrane fouling also is greatly alleviated.